Shocking postoperative visits - Wiley Online Library

1 downloads 0 Views 1MB Size Report
occur when anaesthesia is deep enough. .... adsorbed onto the surface of a pre-used laryngeal ..... earlier had revealed bilateral air entry and chest ..... Central nerve blockade in patients receiving ...... anesthetic spread to the cervical plexus.
Anaesthesia, 2001, 56, pages 799±820 ................................................................................................................................................................................................................................................

Correspondence Teaching methods

Bernice McCarthy notes that trainees ask the following questions [1]. Why am I learning? What will I learn? How will I learn it? What if I don't agree, can't learn, and don't like it? Educators must help find the answers to these questions. A registrar-teaching programme should provide the means to learn the knowledge, skills and attitudes necessary for trainees to pass their exams and become successful anaesthetists. Many believe the best way to organise a programme is through dialogue between trainers and trainees [2, 3]. The resulting synthesis provides an environment for adult learning that is both enjoyable and achieves its stated goals as well as constructing a `built in' improvement cycle. Many institutions have implemented teaching programmes developed through dialogue but few or no data exist in the United Kingdom on how changes from a caring but one-sided registrar training programme to a programme synthesised from the input of trainees and trainers affects outcome. We were presented with an opportunity to measure attitudinal changes between groups of our registrars during a reorganisation of the teaching programme for Specialist Registrars in anaesthesia, which was undertaken over the course of two successive 3month modules with different groups of trainees in paediatric anaesthesia in the Northwest Region. The first module followed the pattern that had been used for many years. The second module included changes in design based on

criticism from registrars. Records were kept of tutorial attendance during the two modules and an identical questionnaire was given to trainees at the end of each module. The Mann±Whitney test (p , 0.05) was used to test statistical significance. The new programme was based on the assumption that increased motivation would be the key to improved learning [3]. This would come from trainees having a larger part to play in the content and presentation of tutorials and teaching. The following changes were added: mutually agreed objectives, registrar presentation at each tutorial, practice exams to be marked by postFellowship registrars, contribution of papers to a departmental file, 6-week review of trainees' progress by trainer and completion of feed-back forms by both trainers and trainees at the end of the module. Questionnaire response rates were similar for the two groups. Module 1: 12/17 (70%), Module 2: 13/16 (81%). Changes in the organisation of the teaching coincided with statistically significant improvements in attendance at tutorials and improved perception of the usefulness of tutorials, handouts, presentations and exam practice. Selfassessment of clinical skills, confidence and enjoyment of the module were not affected significantly. Overall, no assessed categories were graded as worse in the second module. Improvements came in categories most affected by tutorials. Tutorials are more easily controlled environments and were targeted for change. These improvements are likely due to the

increased input from trainees and more enthusiastic teaching that arises from a motivated energised atmosphere. Although continued subjective evaluation and objective testing of knowledge retention would be desirable to substantiate the claimed improvements, these results provide support to those programmes that have instituted similar changes and stimulus to those considering them. A programme based on mutually agreed objectives, explicit content and defined process with built in assessment and flexibility answers McCarthy's questions and provides potential for improvement too dramatic to allow a return to the previous organisation. J. C. Sanders Manchester, UK E-mail: [email protected]

References

1 McCarthy B. About Learning. Wauconda, IL: About Learning Inc., 1996. 2 Knowles M. The Adult Learner. A Neglected Species. 3rd edn. Houston, TX: Gulf Publishing Co., 1984. 3 Keller JM. Motivational Design of Instruction. In: Reigeluth CM, ed. Instructional- design Theories, Models, Vol. 1. Hillsdale, NJ: Lawrence Erlbaum Associates, 1983: 383±436. Anaesthesia and hair fashion

We read with great interest the letter describing problems with intubation resulting from an elaborate `pom-pom'

All correspondence should be addressed to Professor M. Harmer, Editor of Anaesthesia, Department of Anaesthetics, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, UK. Letters (two copies) must be typewritten on one side of the paper only and double spaced with wide margins. Copy should be prepared in the usual style and format of the Correspondence section. Authors must follow the advice about references and other matters contained in the Notice to Contributors to Anaesthesia printed at the back of each issue. The degree and diplomas of each author must be given in a covering letter personally signed by all the authors. Correspondence presented in any other style or format may be the subject of considerable delay and may be returned to the author for revision. If the letter comments on a published article in Anaesthesia, please send three copies; otherwise two copies of your letter will suffice.

q 2001 Blackwell Science Ltd

799

Correspondence Anaesthesia, 2001, 56, pages 799±820 ................................................................................................................................................................................................................................................

hairstyle in an African woman in Zimbabwe (Chikungwa. Anaesthesia 2000; 55: 305), as well as the letter addressing similar problems encountered in an Afro-Caribbean community in the United Kingdom (Ashley & Marshall.Anaesthesia 2000;55: 834). We have encountered very similar problems and agree with the authors that these otherwise beautiful hairstyles can convert an easy airway into a difficult one. However, our management solution to the problem is different from that described, respectively, by Chikungwa (two head rings or a small pillow under the patient's head) and Ashley and Marshall (dropping the head section of the operating table). We recently described a case of a patient who presented for an emergency Caesarean section with an elaborate occipital hairpiece that was covered by a hospital hat and resulted in unexpected difficult intubation [1]. A 23-year-old gravida 2 para 1 African American female was admitted for an emergency Caesarean section. Her pre-operative airway examination was perfectly normal. The patient refused regional anaesthesia. Rapid sequence induction of anaesthesia was performed in a standard manner. The head was thought to be in a reasonable `sniff ' position. Laryngoscopy revealed a Grade IV view. In re-evaluating the position, it was discovered that an elaborate occipital hairpiece (Fig. 1)

would not permit full extension of the head on the neck. Positive pressure ventilation was easily instituted. A shoulder roll 3 inches in diameter was placed under the patient's shoulders. Laryngoscopy then revealed a Grade I view and tracheal intubation was easily accomplished. Elaborate hairpieces used to be worn only on formal occasions. However, we think there is a recent trend wherein African American women in the United States are increasingly wearing them even in the absence of a formal indication. These hairpieces are firmly tied to the native hair and their quick removal in an emergency is difficult. Additionally, hospital head covers may mask the problem. Our airway evaluation now includes examination of the hair formation. A shoulder roll seems an effective and simple method to manage a bulky mass of occipital hair by providing extra space for head extension and proper alignment of oral, pharyngeal and laryngeal axes. Subsequent to this case, we have encountered preoperatively two more patients with similar hairpieces; shoulder rolls were used and no airway problems were experienced. In summary, these cases should serve as a warning that the increasing popularity of elaborate hair fashions will require increasing vigilance on the part of the anaesthetist.

Figure 1 Model with a hairpiece very similar to the one actually worn by our patient.

800

K. M. Kuczkowski J. L. Benumof University of California San Diego, San Diego, CA 92103±8812, USA E-mail: [email protected]

References

1 Kuczkowski KM, Benumof JL. Elaborate hairpiece as a cause of unexpected difficult intubation. American Journal of Anesthesiology 2001; in press. Use of the laryngeal mask is not contraindicated for laparoscopic cholecystectomy

We question the premises on which Asai bases his opinion that use of the laryngeal mask airway is contraindicated during laparoscopic cholecystectomy (Asai. Anaesthesia 2001; 56: 187). His opinion that tracheal intubation is mandatory for laparoscopic surgery, or that the laryngeal mask airway is contraindicated, could equally be applied to gynaecological laparoscopy. The popularity of the laryngeal mask airway in gynaecological laparoscopy, despite the head-down position that might be expected to facilitate passive regurgitation, stands in sharp contrast to the rarity of reported pulmonary aspiration [1, 2]. This suggests that the danger is more apparent than real. Asai quoted one case report from 10 years ago to justify his concern of `high risk' of pulmonary aspiration [3]. No large-scale randomised study has compared the incidence of clinically significant pulmonary aspiration between tracheal intubation and laryngeal mask, but the incidence appears to be similar (1 in 5±10 000) in the general population of healthy patients undergoing elective surgery [1, 4, 5]. Pulmonary aspiration has not been reported in studies that compare efficacy and safety of these methods of airway management for laparoscopic cholecystectomy [6, 7]. Active vomiting under inadequate depth of anaesthesia can force gastric contents past and into the laryngeal mask airway to reach the pharynx and

q 2001 Blackwell Science Ltd

Anaesthesia, 2001, 56, pages 799±820 Correspondence ................................................................................................................................................................................................................................................

lungs. However, passive regurgitation occurs at baseline intragastric pressure of 9±15 mmHg [8], which is less than the pressure needed to bypass a correctly placed laryngeal mask airway [9]. Distension of the abdomen by gas insufflation does not increase the risk of regurgitation unless the patient has an incompetent lower oesophageal sphincter. Rather, it causes a reflex increase in the tone and therefore the barrier pressure of the lower oesophageal sphincter [10]. Cholangiogram dye is emetogenic and, unless gastric suction is used following intra-operative cholangiography, `regurgitation' (active vomiting) of bile-stained gastric fluid is common during emergence from anaesthesia when anaesthesia is light. We have not seen vomiting during the surgical procedure for which we maintain anaesthesia at 1.0±1.5 MAC. Georgiou's concern in his case report [11] about inflation of the stomach is relevant if the laryngeal mask airway is not the correct size, or if it is incorrectly positioned and causes airway obstruction. We found that gastric distension was not a problem when we used the laryngeal mask airway for airway management with positive pressure ventilation during laparoscopic cholecystectomy [7]. We randomised 104 healthy, non-obese patients with no history of gastro-oesophageal reflux to tracheal intubation or laryngeal mask airway. The surgeons, who were blinded to the airway device, scored the size of the stomach 0±10 at entry of the laparoscope and before its removal at the end of surgery. The degree of change in stomach size was similar in both groups, and the surgeon only requested deflation of the stomach in one patient ± in the intubation group! J. R. Maltby M. T. Beriault N. C. Watson Foothills Medical Centre, Calgary AB T2N 2T9, Canada E-mail: [email protected]

References

1 Verghese C, Brimacombe Jr. Survey of

q 2001 Blackwell Science Ltd

laryngeal mask airway usage in 11,910 patients: safety and efficacy for conventional and nonconventional usage. Anesthesia and Analgesia 1996; 82: 129±33. 2 Malins AF, Cooper GM. Laparoscopy and the laryngeal mask airway. British Journal of Anaesthesia 1994; 73: 121. 3 Griffin RM, Hatcher IS. Aspiration pneumonia and the laryngeal mask airway. Anaesthesia 1990; 45: 1039±40. 4 Warner MA, Warner ME, Weber JG. Clinical significance of pulmonary aspiration during the preoperative period. Anesthesiology 1993; 78: 56±62. 5 Brimacombe JR, Berry A. The incidence of aspiration associated with the laryngeal mask airway: a meta-analysis of published literature. Journal of Clinical Anesthesia 1995; 7: 297±305. 6 Dolbneva EL, Buniatian AA. The Problem of airtightness during the use of a laryngeal mask under conditions of carboperitoneum and muscle relaxation. Anesteziologiya I Reanimatologiya 1997; 5: 68±77. 7 Maltby JR, Beriault MT, Watson NC, Fick GH. Gastric distension and ventilation during laparoscopic cholecystecomy: LMA-Classic vs. tracheal intubation. Canadian Journal of Anaesthesia 2000; 47: 622±6. 8 Link JF, Warrian WG, Wankling WJ. Responses of the gastroesophageal junctional zone to increases in abdominal pressure. Canadian Journal of Surgery 1966; 9: 32±8. 9 Keller C, Brimacombe JR. Water flow between the upper esophagus and pharynx in fresh cadavers. Canadian Journal of Anaesthesia 1999; 46: 1064±6. 10Jones MJ, Mitchell RW, Hindocha N. Effect of increased intra-abdominal pressure during laparoscopy on the lower esophageal sphincter. Anesthesia and Analgesia 1989; 68: 63±5. 11Georgiou L, Bousoula M, Spetsaki M. Combined thoracic epidural and general anaesthesia with laryngeal mask airway for laparoscopic cholecystectomy in a patient with myasthenia gravis. Anaesthesia 2000; 55: 821±2.

A reply

My main concern is not the possible increase in intragastric pressure or gastric insufflation during laparoscopic cholecystectomy. What concerns me most is the increase in gastric contents during surgery, due to duodenogastric reflux of bile and contrast medium. Professor Maltby and colleagues state that `regurgitation (active vomiting) of bile-stained gastric fluid is common during emergence from anaesthesia' and claim that vomiting would not occur when anaesthesia is deep enough. I fully agree with this. I argue that this common occurrence of regurgitation during emergence from anaesthesia is the very reason why I believe that the trachea should be intubated to prevent pulmonary aspiration in patients undergoing laparoscopic cholecystectomy. My next major concern is regurgitation of bile. As Professor Maltby states, the patient undergoing laparoscopic cholecystectomy may often regurgitate bile-stained fluid, particularly during emergence from anaesthesia [1]. In addition, patients with gallstones may have frequent regurgitation even when they are awake [2]. When aspirated, bile damages the lungs much more seriously than gastric acid does [3, 4]. Therefore, a greater precaution is required to prevent aspiration of bile than that of acid. The estimated incidence of pulmonary aspiration for which intensive care is required after the use of the laryngeal mask in the general population is between 1 : 9000 and 1 : 250 000 [5]. To show that the incidence is no greater than this in patients undergoing laparoscopic cholecystectomy, between 30 000 and 750 000 patients would be required [6]. The number of patients (53 patients) that Professor Maltby and colleagues studied [7] is far less than these figures. In fact, when 95% confidence limits are calculated from their results, the incidence of pulmonary aspiration during the use of the laryngeal mask can be as high as 7% [6]. Therefore, there have been no convincing studies to support their claim. If there are no studies, one should judge indications and contraindications of

801

Correspondence Anaesthesia, 2001, 56, pages 799±820 ................................................................................................................................................................................................................................................

each technique based on anecdotal reports and theoretical risks. Professor Maltby and colleagues claim that I only cited one case report [8] from 10 years ago to justify my concern. In fact, I cited two [8, 9], and several anaesthetists stated through their experiences that the patient undergoing laparoscopic cholecystectomy is at increased risk of pulmonary aspiration [10±12]. In contrast, I do not find any major advantages (that improve clinical outcome) of the use of the laryngeal mask over tracheal intubation in this group of patients. Therefore, it is reasonable to conclude that theoretical risks of the use of the laryngeal mask outweigh the advantages of its use in the circumstances, and I maintain my claim that the laryngeal mask is contraindicated in patients undergoing laparoscopic cholecystectomy. T. Asai Kansai Medical University, Moriguchi City, Osaka, 570±8507, Japan E-mail: [email protected]

References

1 Doyle MT, Twomey CF, Owens TM, McShane AJ. Gastroesophageal reflux and tracheal contamination during laparoscopic cholecystectomy and diagnostic gynecological laparoscopy. Anesthesia and Analgesia 1998; 86: 624±8. 2 Earlam RJ, Thomas M. The clinical significance of gallstone and their radiological investigation. British Journal of Surgery 1978; 65: 164±7. 3 Porembka DT, Kier A, Sehlhorst S, Boyce S, Orlowski JP, Davis K. The pathophysiologic changes following bile aspiration in a porcine lung model. Chest 1993; 104: 919±24. 4 Brown ES. Aspiration and lung surfactant. Anesthesia and Analgesia 1967; 46: 665±72. 5 Brimacombe J, Berry A. Aspiration and the laryngeal mask airway ± a survey of Australian intensive care units. Anaesthesia and Intensive Care 1992; 20: 534±5. 6 Altman DG. Practical Statistics for Medical

802

Research. London: Chapman & Hall, 1991. 7 Maltby JR, Beriault MT, Watson NC, Fick GH. Gastric distension and ventilation during laparoscopic cholecystectomy: LMA-Classic vs. tracheal intubation. Canadian Journal of Anaesthesia 2000; 47: 622±6. 8 Griffin RM, Hatcher IS. Aspiration pneumonia and the laryngeal mask airway. Anaesthesia 1990; 45: 1039±40. 9 Brain AI. The laryngeal mask and the oesophagus. Anaesthesia 1991; 46: 701±2. 10Pearce AW, Heath ML. Aspiration pneumonia and the laryngeal mask airway. Anaesthesia 1991; 46: 592. 11Riddle PL. Aspiration pneumonia and the laryngeal mask airway. Anaesthesia 1991; 46: 418. 12Philpott B. Aspiration pneumonia and the laryngeal mask airway. Anaesthesia 1991; 46: 418. Malignant hyperpyrexia and the laryngeal mask airway

Recently, we had occasion to anaesthetise a patient, who was susceptible to malignant hyperpyrexia, for the incision and drainage of a peri-anal abscess. She was a fit and healthy 19-year-old with no significant past medical history. She was well starved and we proposed to induce her with fentanyl 1±2 mg.kg2l, propofol 2 mg.kg2l and maintain anaesthesia with a propofol infusion. We had decided to let her breathe spontaneously on a laryngeal mask. However, on consideration, it was unclear whether the techniques used for cleaning laryngeal mask airways were sufficient to ensure that no volatile agent remained adsorbed onto the surface of a pre-used laryngeal mask. A discussion with Intavent followed and the company was also unsure as to whether normal cleaning would completely remove any traces of volatile agents from a laryngeal mask airway. A review of the literature shows that flushing silicone tubing with oxygen for over 1 h does not remove volatile agents and that normal decontamination procedures of rubber and silicone products reduce volatile anaesthetics to a

variable extent [1]. Further review (Medline) has been unable to discover any cases of malignant hyperpyrexia triggered by the re-use of a laryngeal mask. We felt that to use a pre-used laryngeal mask would expose our patient to an unquantifiable, but unnecessary risk. Therefore, we used a disposable laryngeal mask airway in addition to the usual fresh breathing system and a vapour-free machine. The patient was anaesthetised without any ill effects. C. M. Danbury K. Torlot Queen Alexandra Hospital, Portsmouth PO6 3LY, UK

Reference

1 Gilly H, Weindlmayr-Goettel M, Koberl G, Steinbereithner K. Anaesthetic uptake and washout characteristics of patient circuit tubing with special regard to current decontamination techniques. Acta Anaesthesiologica Scandinavica 1992; 36: 621±7.

Why KY?

Dr Tackley reports the obstruction of a lubricated tracheal tube with a flexible clear membrane said to be `like a lump of glue' (Tackley. Anaesthesia 2001; 56: 279±81). An independent tester commissioned by Mallinckrodt Medical, the tube's manufacturer, compared this lump with a KY lubricant and stated `It would seem likely that the contaminant involved in this complaint was a lubricant, e.g. KY Jelly'. A simple observational experiment of our own confirms that a lump of KY when exposed to air becomes like a lump of glue. In this case, lubricant is at least circumstantially implicated in this tracheal tube obstruction. Tackley also states that the intentionally applied lubricant interfered with the tube's inspection. Tubes for orotracheal intubation are often lubricated prior to use as a matter of routine, based on

q 2001 Blackwell Science Ltd

Anaesthesia, 2001, 56, pages 799±820 Correspondence ................................................................................................................................................................................................................................................

tradition. We do not advocate this practice because: 1 we are not aware of any evidence that lubrication makes intubation easier; 2 water-soluble products such as KY jelly do not reduce the incidence of postoperative sore throat [1]; 3 some lubricants such as lidocaine jelly [2] or hydrocortisone [3] increase postoperative sore throat; 4 as Dr Tackley's letter demonstrates, lubricants may result in tube obstruction and may interfere with inspection. We agree with Drs Sprague and Moffett that `there is nothing to be gained by lubricating oral tracheal tubes' [4] and we therefore ask `Why KY?' A. Badrakumar D. R. Ball P. D. Jefferson Dumfries and Galloway Royal Infirmary, Dumfries DG1 4AP, UK

References

1 Stock MC, Downs JB. Lubrication of tracheal tubes to prevent sore throat from intubation. Anesthesiology 1982; 57: 418±20. 2 Loeser EA, Stanley TH, Jordan W, Machin R. Post-operative sore throat influence of tracheal tube lubrication versus cuff design. Canadian Anaesthetists Society Journal 1980; 27: 156±8. 3 Stride PC. Post operative sore throat: topical hydrocortisone. Anaesthesia 1990; 45: 968±71. 4 Sprague NE, Moffett SP. Oral tracheal tubes. Is lubrication necessary? Today's Anaesthetist 1989; 4: 140±2. Another problem with reusable tubes

I would like to report yet another case of a faulty tube leading to a critical incident. This case involves a 47-year-old woman admitted to the ITU with acute pancreatitis. She was anticipated to be a difficult intubation principally because of her high body mass index, short neck and full set of teeth. She proved to be impossible to intubate with a standard

q 2001 Blackwell Science Ltd

Figure 2

rapid sequence induction and bougie due to a very oedematous, erythematous epiglottis and, as anticipated, difficulty visualising her cords. An intubating laryngeal mask was inserted and she was oxygenated adequately with this. She was then intubated with the accompanying reinforced tracheal tube that was passed over a fibreoptic bronchoscope inserted through the laryngeal mask. After an initial period of uncomplicated ventilation, she was noted to have a persistent positional leak around the tracheal tube. The leak did not respond to further inflation of the cuff but was improved by changing her head position. The leak, however, became more significant with loss of ventilating volume and ultimately the tube had to be changed as a semi-urgent procedure. This was achieved by using a McCoy laryngoscope. On removal of the old tube it was noted that the cuff inflated asymmetrically (Fig. 2) and this was no doubt the reason for the positional problem with ventilation. We have previously encountered this problem in theatres when using a reinforced tube. The damage to the cuff appears to occur when these reusable tubes are sterilised. The tubes are laid on a flat metal surface that is heated in the sterilisation process and, as a result, the cuff becomes damaged at the point of contact with the plate.

This case illustrates two points. Firstly, that it is important to check the cuff of any tube prior to use even in an urgent situation to ensure that it does inflate symmetrically. The second is that care must be taken where tubes are reused to avoid damage in the sterilisation process. In view of the difficulty in intubating this woman, a potentially dangerous tube change was required because of failure on both these counts. It seems sensible at a time when reusable equipment is being questioned, the added risk of damage to these tubes should add weight to the argument for keeping them as single use only, regardless of the cost. K. C. Hames R. Fernandes Wexham Park Hospital, Slough SL2 4HL, UK

A reply

We are grateful to Drs Hames and Fernandes for reminding readers that it is important to check the cuff of any reusable tracheal tube prior to use with the intubating laryngeal mask, to ensure that it inflates symmetrically. We do not, however, recommend use of any tube other than that which we supply, which is designed specifically for use with the ILMAw. This tube may normally be

803

Correspondence Anaesthesia, 2001, 56, pages 799±820 ................................................................................................................................................................................................................................................

reused up to 10 times, as specified in the product literature. The instructions for sterilisation include advice to `wrap the tube in a lint-free sterilisation wrapper'. If this advice is followed, standard autoclave temperatures should not normally rise high enough to cause damage to the cuff. No part of the tube should be allowed to contact a surface whose temperature rises above 134 8C. It appears the tracheal tube in question was not supplied by us, so we are unable to comment further, apart from suggesting that the authors' experience illustrates the importance of using the tube recommended by the manufacturer, if it is desired to intubate the trachea using the ILMAw as a guide. B. H. Goodman Intavent Ltd, Reading RG8 8ER, UK E-mail: [email protected] Reliability of Mallampati classification in upper airway pathology

I read with great interest the article on the use of a new device to facilitate awake oral fibreoptic intubation (OteroCarrasco et al. Anaesthesia 2001; 56: 277±9). I was delighted to know the various uses of the `safe bite' that the authors described. I wish to congratulate them for the excellent description of its use during awake oral fibreoptic intubation (a challenge for any anaesthetist!). However, I wish to raise a point on the method of airway assessment, which the authors used for prediction of difficult airway. In the original article published by Mallampati et al. [1], they state that the Mallampati classification would not be a reliable indicator for patients with pathology in the upper airway. The case presented by OteroCarrasco et al. had major airway pathology. The patient had a non-Hodgkin's lymphoma involving the region around the airway, had undergone radiotherapy of the tumour (probably very close to the airway) and was scheduled for right total maxillectomy. As a trainee, I am

804

confused over the reliability of the Mallampati classification in such circumstances and I would be grateful to the authors if they could clarify my query. M. V. Krishnakar Good Hope Hospital, Sutton Coldfield B75 7RR, UK

Reference

1 Mallampati SR, Gatt SP, Gugino LD, et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Canadian Anaesthetists Society Journal 1985; 32: 429±34. A reply

We are grateful for the opportunity to reply to Dr Krishnakar's letter. Indeed, oral awake fibreoptic intubation is a challenge to any anaesthetist and we are pleased to report that our patient underwent awake fibreoptic intubation with the `Safe Bite' on three more occasions. Dr Krishnakar is quite right in pointing out the limitation of the Mallampati classification in predicting a difficult intubation in patients with upper airway pathology. We wish to reassure him that this was not the only basis of performing awake oral intubation in our patient and that other factors including previous radiotherapy and limited mouth opening were of more significance. J. Otero-Carrasco M. T. Popat The John Radcliffe, Oxford OX3 9 DU, UK A sticky edge

Sterile impermeable paper drapes with adhesive edges have recently replaced traditional cotton drapes in our operating theatre department. We have witnessed a number of serious critical incidents associated with this change. The most serious of which is described below. A healthy 57-year-old woman was anaesthetised for wide local excision of a breast lump with an axillary clearance.

Following induction with propofol and fentanyl, the patient developed a degree of laryngeal spasm which terminated after a brief period. A laryngeal mask airway was placed and anaesthesia maintained using a mixture of nitrous oxide and isoflurane in oxygen. During transfer of the patient from the trolley to the operating table, the patient again developed laryngeal spasm. She was therefore paralysed, intubated and ventilated before the start of surgery. Correct tracheal tube position was confirmed by direct visualisation at laryngoscopy. A normal end-tidal CO2 trace was seen and adequate ventilation of both lungs was confirmed by auscultation. The tube was secured in position using a cotton tie. The patient was cleaned and then draped with impermeable paper drapes with an adhesive border (Cal-Med Adhesive Paper Drape, Caledonian Medical Ltd, Strathclyde, Scotland). The initial period of surgery was uneventful. However, after about 5 min, there was collapse of the circle reservoir bag and loss of the end-tidal CO2 trace on the capnograph. The reservoir bag failed to inflate despite immediately increasing the fresh gas flow, and manual ventilation was impossible using the circuit. As manoeuvres were being carried out to identify the source of a presumed disconnection, the `scrub' nurse commented that the abdomen was beginning to distend. Accidental extubation of the trachea was suspected. As laryngoscopy was performed, it was noticed that the adhesive edge of a surgical drape was stuck onto the tube; the tube tip was in the oropharynx. The cuff was deflated and the trachea reintubated. The drapes were then repositioned and prevented from coming into contact with the tube. The patient underwent a brief period of desaturation during this episode but came to no harm. Since discussing this case with our colleagues, we have heard of a number of cases where a drape edge has been seen stuck to the tracheal tube or catheter mount. There have also been instances where a peripheral cannula has become dislodged when drapes unintentionally stuck onto the cannula

q 2001 Blackwell Science Ltd

Anaesthesia, 2001, 56, pages 799±820 Correspondence ................................................................................................................................................................................................................................................

and cost benefits from using these drapes. However, these examples remind us that small changes to a system can cause unrecognised hazards. When drapes with long sticky borders are used, extra vigilance is required. G. Hilditch J. Crawford D. McLaughlin Western Infirmary, Glasgow G11 6NT, UK Hypothermia and rapid, cold, peritoneal crystalloid infusion

Figure 3 Tracheal tube stuck onto sticky

edge of drape supporting 12 lb.

dressing, or giving set, have been removed at the end of surgery. This unintentional extubation was caused by the adhesive edge of a drape extending beyond the field of surgery and sticking onto the tracheal tube. Examination of these drapes showed the sticky border to have excellent adhesive properties. To illustrate this, a tracheal tube was pushed onto the sticky border of a drape, held vertically, and orthopaedic weights suspended from the tube. Figure 3 shows 12 lb suspended from a tube in such an arrangement. These drapes come in various sizes and the adhesive border extends the full length of the drape. In most cases, this length far exceeds the length of surgical field leading to the dangers described above. We hesitate to suggest that such tremendous stickiness might be useful for securing tracheal tubes in the first place. However, we would be concerned that damage to the facial skin might occur. There may be microbiological, health

q 2001 Blackwell Science Ltd

Hypothermia and resultant electrocardiographic changes during surgery are well documented [1±5]. However, sudden precipitous drops in core body temperature in the operating room are rare. We cared for a healthy 32-year-old female who presented as an outpatient for laparoscopic ovarian cystectomy. Our patient received intravenous midazolam 2 mg in the pre-operative holding area. General anaesthesia was induced using propofol and narcotics. The neuromuscular blocking agent rocuronium facilitated placement of a 7.0-mm tracheal tube and this agent was used throughout the case. Maintenance of the anaesthetic consisted of air, oxygen, desflurane and narcotics. We also used standard ASA monitoring, a convective warming device, a heat and moisture exchanger, 2 l.min21 fresh gas flow, and fluids administered at a slow rate. Temperature was measured via an oesophageal stethoscope with an incorporated thermocouple. Induction of anaesthesia and the first hour of anaesthetic maintenance were uneventful. The surgeon then encountered bleeding of the omentum and requested normal saline for irrigation. Two litres of normal saline were infused through a laparoscopic port over a period of 3± 4 min. The patient's temperature at the beginning of irrigation was 35.7 8C and within 1 min of the initiation of irrigation the patient's body temperature began to decline. By the fourth minute of irrigation the oesophageal probe read 33.3 8C. At this time the Twaves of the electrocardiogram became

inverted, but no Osborne waves were evident and there was no change in rhythm. The patient remained haemodynamically stable. The anaesthesiologist alerted the surgeon and inquired of the nursing staff as to where the normal saline was procured. The nursing staff indicated that the irrigant was taken from reserves stored at room temperature, not from the usual warm fluid storage. Further measures taken by the anaesthesiology staff to correct the patient's thermal disturbance included warming of the intravenous fluids and raising the operating room temperature. The inverted T-waves became isoelectric at 33.8 8C and upright (normal repolarisation pattern) at 34.1 8C. Approximately 75 min passed before a core body temperature of 35 8C was achieved. The patient emerged from anaesthesia without difficulty and in the post anaesthesia care unit she had a temperature of 35.2 8C. A normal electrocardiogram was documented postoperatively (a pre-operative electrocardiogram was neither indicated nor obtained). The patient was discharged home the same day. Hypothermia during anaesthesia is the most common peri-operative temperature disturbance [6, 7]. Usually it is due to a cold surgical environment combined with thermoregulatory impairment secondary to administration of an anaesthetic [8]. Laparoscopies and laparotomies generally do not differ as to core body temperatures at the end of a case [9, 10]. Surgeons have traditionally been able to test the warmth of fluid empirically with their gloved hands. In the case of laparoscopy, the irrigant is not routinely instilled over the surgeon's hand, thus a critical check point has been eliminated. We offer several suggestions to avoid similar problems in the future: (1) the surgeon may empirically run some of the fluid over his/her hands, (2) temperature trend indicator strips may be applied to the fluid irrigation bags, (3) skin temperature probes may be applied to the fluid irrigation bags, (4) the irrigation may be warmed in a fluid warmer (as in some genitourinary cases) [11] and (5) staff procuring the irrigant can ensure that they remove it from a warm storage

805

Correspondence Anaesthesia, 2001, 56, pages 799±820 ................................................................................................................................................................................................................................................

source. This last point may need to involve system changes and education to avoid knowledge-based errors. Hypothermia remains, for the most part, a preventable thermal disturbance in which proper planning and vigilance remain the cornerstones of prevention. T. J. Papadimos E. Fowler Medical College of Ohio, Toledo, OH 43614, USA

References

1 Sessler DI. Perioperative thermoregulation and heat balance. Annals of the New York Academy of Science 1997; 813: 757±77. 2 Sessler DI, Ponte J. Shivering during epidural anesthesia. Anesthesiology 1990; 72: 816±21. 3 Sessler DI, Olofsson CI, Rubinstein EH. The thermoregulatory threshold in humans during halothane anesthesia. Anesthesiology 1988; 68: 836±42. 4 Sessler DI, Rubinstein E, Efer EIII. Core temperature changes during N2O fentanyl and halothane/O2 Anesthesia. Anesthesiology 1987; 67: 137±9. 5 Weinberg AD, Hypothermia. Annals of Emergency Medicine 1993; 22: 370±7. 6 Morris RH. Operating room temperature and the anesthetized patient. Archives of Surgery 1971; 102: 95±7. 7 Vaughn MS, Vaughn RW, Cork RC. Postoperative hypothermia in adults: relationship to age, anesthesia, and shivering to rewarming. Anesthesia and Analgesia 1981; 60: 746±51. 8 Holdcroft A, Hall GM. Redistribution of body heat during anesthesia. Anaesthesia 1979; 34: 758±64. 9 Stewart BT, Stitz RW, Tuch MM et al. Hypothermia in open and laparoscopic colorectal surgery. Diseases of the Colon and Rectum 1999; 42: 1292±5. 10Luck AJ, Moyes D, Maddern GJ et al. Core temperature changes during open and laparoscopic colorectal surgery. Surgical Endoscopy 1999; 13: 480±3. 11Monga M, Comeaux B, Roberts JA. Effect of irrigating fluid on perioperative temperature regulation

806

during transurethral prostatectomy. European Urology 1996; 29: 26±8. Pulse oximeter aided diagnosis of fluid extravasation

Apart from measurement of haemoglobin oxygen saturation and heart rate, pulse oximeters have been useful in other situations such as diagnosis of leftsided aortic arch, judging the adequacy of revascularisation and safe patient positioning [1±3]. I would like to report an instance where the presence of pulse oximetry enabled early diagnosis of extravasation of fluid from a peripheral venous cannula. There have been no similar reports in the literature before. A 39-year-old man was admitted to the intensive care unit post resuscitation following cardiac arrest secondary to hanging. He was sedated, paralysed and on controlled mechanical ventilation with 30% inspired oxygen concentration. He was haemodynamically stable. Routine clinical examination about 2 h earlier had revealed bilateral air entry and chest clear to auscultation with no added breath sounds. The patient had become polyuric in the past 6 h with an average urine output of 250 ml.h21. He was being given additional 0.9% saline supplementation at a rate of 200 ml.h21 using a fluid pump through an 18 G venous cannula in the left hand. Although the cannula had been in situ for more than 24 h, it was not used for injection of any drugs or other fluids due to the presence of a quad lumen central venous cannula. The pulse oximeter probe was in the left ring finger displaying an oxygen saturation of 98% with a good waveform. The monitor suddenly alarmed, displaying an oxygen saturation of 87%. There was no change in the haemodynamic variables or the ventilatory mechanics. The waveform was still present although it was significantly damped. When the probe position was checked, it was found that the hand was swollen and the digits were congested. The probe was repositioned onto the right hand and the saturation returned to normal. The extravasation of fluid

was immediately apparent and the infusion was stopped. The limb was placed in a non-dependent position. Even though the arterial waveform from the left radial artery cannula was normal, the cannula was resited in a different limb. Further clinical course was uneventful. Undiagnosed extravasation from a peripheral venous cannula is uncommon in intensive care units. Nevertheless, the combination of an unconscious patient, extremities hidden under the drapes and an apparently free flowing infusion can lead to a missed diagnosis. This becomes especially dangerous if the rate of fluid infusion is relatively high and the cannula is in `infrequent' use. Fortunately, in this patient, no drugs were administered. It is likely that the extravasation would have been diagnosed at a much later time but for the low oximetry reading. Decreased blood flow and venous congestion have been considered among the various sources of error in pulse oximetry [4, 5]. It has been shown that pulse oximeters are very sensitive and they may display a pulse waveform even when the blood pressure is too low to provide adequate blood flow. A low reading of oxygen saturation may occur due to oxygen consumption by the finger from the pulsating but stagnant arterial blood [6]. A combination of the above factors may have led to the low oxygen saturation reading in this case leading to detection of fluid extravasation. S. Kannan City Hospital, Birmingham B18 1QH, UK E-mail:[email protected]

References

1 Gupta S, Varma M, Chari P. Right sided aortic arch ± diagnosis by pulse oximetry. Anaesthesia 1993; 48: 1108±9. 2 Ryan CA. Detection of pulsus paradoxus by pulse oximetry. American Journal of Diseases of Childhood 1988; 142: 481±2. 3 Herschman ZJ, Levy MI, Frost EA,

q 2001 Blackwell Science Ltd

Anaesthesia, 2001, 56, pages 799±820 Correspondence ................................................................................................................................................................................................................................................

Goldiner PL. Pulse oximetry during shoulder arthroscopy. Anesthesiology 1986; 65: 565. 4 Vegfors M, Lindberg LG, Lennmarken C. The influence of changes in blood flow on the accuracy of pulse oximetry in humans. Acta Anaesthesiologica Scandinavica 1992; 36: 346±9. 5 Skacel M, O'Hare E, Harrison D. Invalid information from the ear probe of a pulse oximeter in tricuspid incompetence. Anaesthesia and Intensive Care 1990; 18: 270. 6 Severinghaus JW, Spellman MJ. Pulse oximeter failure thresholds in hypotension and vasoconstriction. Anesthesiology 1990; 73: 532±7.

Pulse oximetry from a haemofiltration line

During an evening intensive care handover, W.F.S.S. observed a difference in blood colours between the in and out tubing of a haemofitration unit being used. A project to compare blood gases in the lines was proposed when N.S. suggested that the clear tubing and the pulsatile flow of blood fulfilled the requirement for saturation monitoring. A Viamed pulse oximeter finger probe put on the line taking haemofiltered blood from Prisma Hospal unit back to the patient gave a waveform, a rate of 45 min21 and a saturation of 71% (Fig. 4). The saturation signal deteriorated further down the line from the pump. Blood gases from the same line were: pH 7.31, Po2 5.8 kPa, Pco2 5.1 kPa, BE26 and saturation 70.87%. Blood gases from the line coming towards the filter were: pH 7.26, Po2 5.6, Pco2 4.9, BE29 and saturation 75.67%.

Figure 4

q 2001 Blackwell Science Ltd

Figure 4 shows that there are tiny 250-min21 waves caused by blood pump rotation. Superimposed on these are deeper waves with a rate of 45 min21. The cause of these regular deeper waves is the dialysate fluid pump that adds fluid to the haemofiltered blood at a rate of 45 min21. We are not sure what use can be made of the above finding but it made us think hard about the principles involved in saturation measurement. N. Sharma W. F. S. Sellers Kettering General Hospital, Kettering NN16 8UZ, UK Acute epiglottitis, sevoflurane and HIB vaccination

The substantial decline in the incidence of childhood epiglottitis is a result of the Haemophilus influenza type B (HIB) vaccination programme. We present a case of acute epiglottitis in a fully vaccinated 6-year-old girl. She was admitted to the accident and emergency (A & E) Department at 4.00 a.m. with a classical history of short duration. She was sitting upright, tachypnoeic and unable to swallow. She had marked inspiratory and expiratory stridor. Her temperature was 39.1 8C and she had a reduced level of consciousness. Previously fit and well, her vaccination status was up-to-date including three doses of HIB vaccine. She was quickly transferred to the anaesthetic room. Anaesthesia was induced in the sitting position using incremental concentrations of sevoflurane to 6% in oxygen; 4% halothane was subsequently used to achieve an adequate depth of anaesthesia for intubation.

Induction of anaesthesia was uneventful; she did not cough or hold her breath. Direct laryngoscopy demonstrated a red, grossly swollen epiglottis. The trachea was intubated without difficulty using an oral 5.5-mm tracheal tube, which was replaced by a nasal tube a few minutes later. An intravenous cannula was inserted and cefotaxime commenced. She remained intubated in PICU for 48 h, was uneventfully extubated and transferred to a medical ward. Her throat and blood cultures were positive for HIB. We wish to emphasise two points in this short case history: 1 Sevoflurane appears to be a safe and effective anaesthetic agent for induction in adult patients with acute epiglottitis [1, 2]. It has a more rapid onset of action and is better tolerated than halothane. However, sevoflurane has a more pronounced ventilatory depressant effect than other anaesthetic vapours. There appears to be a single reference to its use in a child with the condition [3]. In our experience, combining the rapid onset of action of sevoflurane with subsequent early substitution of halothane as a maintenance agent allowed a smooth and rapid induction without respiratory depression. 2 Haemophilus influenza type B is the most frequent causative agent of acute epiglottitis in children (95.2%) [5]. HIB vaccination has been extremely successful; however, there is evidence that 27% of cases of acute epiglottitis in children in the USA are due to vaccine failure [6]. We believe this to be one of very few cases of acute epiglottitis following HIB vaccination in the United Kingdom [7]. Clinicians must still have a high index of suspicion of acute epiglottitis when presented with a fully vaccinated child with stridor. I. Sobolev N. Plunkett I. Barker Sheffield Children Hospital, Sheffield S10 2TH, UK

807

Correspondence Anaesthesia, 2001, 56, pages 799±820 ................................................................................................................................................................................................................................................

References

1 Spalding MB, Ala-Kokko TI. The use of inhaled sevoflurane for endotracheal intubation in epiglottitis. Anesthesiology 1998; 89: 1025±6. 2 Youngs PJ. Sevoflurane induction and acute epiglottitis. Anaesthesia 1999; 54: 301. 3 Milligan K. Sevoflurane induction in acute epiglottitis. Anaesthesia 1997; 52: 810. 4 Vernon DD, Sarnaik AP. Acute epiglottitis in children: a conservative approach to diagnosis and management. Critical Care Medicine 1986; 14: 23±5. 5 Midwinter KI, Hodgson D, Yardley M. Paediatric epiglottitis: the influence of the Haemophilus influenzae b vaccine, a ten-year review in the Sheffield Region. Clinical Otolaryngology 1999; 24: 447±8. 6 Kessler A, Wetmore RF, Marsh RR. Childhood epiglottitis in recent years. International Journal of Pediatric Otolinolaryngology 1993; 25: 155±62. 7 Wagle A, Jones RM. Acute epiglottitis despite vaccination with haemophilus influenzae type B vaccine. Paediatric Anaesthesia 1999; 9: 549±50.

Anaesthesia in pyruvate dehydrogenase deficiency

A male infant was born at 41 weeks' gestation with a birth weight of 2.31 kg and good Apgar scores. Aged 10 days he became hypoglycaemic, acidotic and peripherally shut down. He was treated with fluid resuscitation, antibiotics and was discharged from a peripheral hospital. At 4 weeks of age he presented to the same hospital with poor feeding, rapid breathing and poor weight gain. Clinically, he was acidotic, tachypnoeic with deep sighing respiration and a pH of 7.1. Despite symptomatic treatment with sodium bicarbonate, he remained acidotic and was transferred to this hospital. Systemic examination revealed some dysmorphism with flat nasal bridge, a long indistinct philtrum, thin upper lip, high arched palate and glandular hypospadias. His parents were first cousins and there is no history of any similar illness

808

in the family. A provisional diagnosis of lactic acidosis was made. Extensive enzyme studies following skin and muscle biopsy revealed very low levels of pyruvate dehydrogenase. He was treated with sodium bicarbonate and oral dichloro-acetate, which is an activator of pyruvate dehydrogenase. DNA studies for the coding region of the PDH E1 alpha sub unit revealed a single base substitution at position 809 but, unfortunately, this substitution did not change the amino acid sequence. Activity of pyruvate dehydrogenase remained low. MR scan revealed agenesis of the corpus callosum with severe frontal lobe dysplasia. Auditory evoked responses showed significant hearing impairment on the right and the left. Following treatment, he made some developmental progress. However, he remains generally hypotonic, unable to sit and has poor head control. Feeding gastrotomy was performed under general anaesthesia at the age of 4 months. He presented for MAGPI hypospadias repair at the age of 11 months with a weight of 11.2 kg. He was fed at 5 am for a morning list. He was induced with sevoflurane 8% by mask. After venous cannulation, he was paralysed with 6 mg of atracurium and his trachea was intubated with a 4.5-mm orotracheal tube. Caudal epidural was performed with 9 ml of bupivacaine 0.25% with 15 mg clonidine. He was given 10% dextrose intravenously throughout the operation. Blood glucose concentration was maintained. He was ventilated throughout with nitrous oxide, oxygen and sevoflurane to an end-tidal MAC concentration. Care was taken to avoid hypothermia and the temperature was maintained between 36.8 and 37.1 8C. Monitoring included ECG, noninvasive blood pressure, pulse oximetery, core temperature, anaesthetic agent concentration and airway pressure. Duration of the procedure was 90 min. He had good pain relief with caudal epidural, which was later supplemented with paracetamol. Gastrostomy feeds were started once he was fully awake and the dextrose infusion was stopped. The pyruvate dehydrogenase complex

(PDHC) catalyses the oxidation of pyruvate to acetyl coA, which enters the tricarboxylic acid cycle for ATP production. The complex comprises five components. Deficiency of any of these components is associated with syndromes varying from a benign condition of intermittent ataxia to a devastating condition of congenital lactic acidosis, failure to thrive, developmental delay, generalised hypotonia and death in early infancy [1]. A distinctive facial dysmorphism has been described in some patients with PDHC deficiency. About half of the children presenting with primary congenital lactic acidosis never get a biochemical diagnosis of their presumed enzyme deficit and are treated symptomatically with bicarbonate. Management of anaesthesia includes avoidance of events that could contribute to lactic acidosis such as hypothermia or decreased cardiac output. The selection of drugs for induction and maintenance of anaesthesia is influenced by possible drug-induced inhibitory effects on gluconeogenesis, which could enhance coexisting metabolic acidosis. The use of lactate-containing intravenous fluids is questionable, as they could increase the plasma lactate levels. The use of opioids has been recommended, but respiratory depression in the postoperative period is a disadvantage. Overall, anaesthetic experience is too limited to make any recommendation as to the optimal selection of drugs for anaesthesia [2]. In summary, this child presented with congenital lactic acidosis, developmental delay, dysmorphism, generalised hypotonia and central nervous system dysfunction. This child has pyruvate dehydrogenase deficiency, although the exact biochemical lesion had not been isolated. He was given dichloro-acetate to activate the enzyme. Infusion of 10% dextrose was suggested by our metabolic consultant in order to increase the enzyme product and decrease conversion to lactate which may be exacerbated by long periods of starvation. Caudal epidural not only provided good analgesia during the intra-operative and immediate postoperative period, but also helped in avoiding opioids and

q 2001 Blackwell Science Ltd

Anaesthesia, 2001, 56, pages 799±820 Correspondence ................................................................................................................................................................................................................................................

their side-effects. Meticulous care was taken to avoid hypothermia by using a warming mattress, warm air blower and fluid warmer. D. Acharya O. R. Dearlove Royal Manchester Children's Hospital, Manchester M27 4HA, UK

References

1 Devivo DC, Dimauro S. Hereditory and acquired types of Myopathy. In: Mcmillan JA, DeAngelis CD, Feigin RD, Warshaw JB, eds. Oski's Paediatrics ± Principles and Practice. Philadelphia: Lippincott Williams & Wilkins, 1999: 1971±87. 2 Dierdorf SF, McNiece WL. Anaesthesia and pyruvate dehydrogenase deficiency. Canadian Anaesthesia Society Journal 1983; 30: 413±6. Sotos' syndrome ¼ a rare challenge?

We would like to report the case of a child with Sotos' syndrome who presented for emergency orthopaedic surgery. This report adds to the documented anaesthetic management [1, 2] of this very rare syndrome, first described by Sotos in 1964. A 13-year-old girl, weighing 55 kg and approximately 165 cm tall, presented one evening for emergency surgery. She had fallen and fractured her right tibia 5 h earlier and was listed for an emergency manipulation under anaesthesia by the orthopaedic surgeons who suspected vascular compromise. She had eaten 3 h prior to falling over so was assumed to have a full stomach. With regards to her Sotos' syndrome her mother reports two main problems: learning difficulties and muscle weakness necessitating use of a wheelchair for long distances. The fact that the patient had undergone general anaesthesia within the past 1±2 years with no problems was reassuring. On examination, she showed some of the typical features of Sotos' syndrome including macrocephaly with a prominent

q 2001 Blackwell Science Ltd

forehead, dolichocephaly and down slanting palpebral fissures. She had a tall stature with long arms and was mentally retarded. Cardiac abnormalities, e.g. mitral valve prolapse, can also occur in Sotos' syndrome; however, our patient had a normal heart. We also noted a high arched palate, markedly receding jaw (not typical of Sotos' syndrome), a reduced thyro-mental distance and crowded teeth. Mallampati score was difficult to determine, as the patient was uncooperative. Information on Sotos' syndrome was sought from the departmental library and the Internet. We found almost nothing about the practical aspects of anaesthetic management. Most of the references found were regarding medical and genetic aspects of the syndrome [3]. The usual pre-operative preparation along with a `difficult intubation trolley' were made available. No premedication was given except topical local anaesthetic cream, amethocaine 4%. Once the patient was in the anaesthetic room, intravenous access was established. The mother distracted the child and provided invaluable help. A modified rapid sequence was performed. The patient was pre-oxygenated and anaesthesia was induced with thiopental 300 mg followed by bag and mask ventilation. Suxamethonium 100 mg was administered once the patency of the airway had been confirmed. The intubation turned out to be surprisingly straightforward ± Grade 1 laryngoscopy and a size 7 tracheal tube used to secure an airway. The patient was maintained on sevoflurane, oxygen and air. As the procedure was only expected to last a few minutes, no further muscle relaxant was given. She had a total of 75 mg fentanyl, 100 mg rectal diclofenac and ondansetron 4 mg. She was extubated awake with no complications. Other options were considered with regards to the anaesthetic management. Firstly, an inhalational induction with sevoflurane or halothane. We were concerned that the patient had a full stomach with the risk of vomiting/ regurgitation, potential aspiration and consequent loss of the airway. Alternatively, regional anaesthesia was an

option. As the child was 13 and mentally retarded, this would have been very difficult even under sedation. The response to sedation is also not always predictable possibly making the patient even more agitated. Despite the fact that this patient with Sotos' syndrome did not create any significant anaesthetic problems, we felt it was useful to document our experience. We hope that by doing so we would add to the limited published work of the anaesthesia management for this rare syndrome. This case, along with other rare cases that present for anaesthesia and surgery, poses a serious problem of availability of information relevant to anaesthesia. Often these cases present themselves out of hours so the need for easy access to relevant information is crucial. An anaesthetic web site listing these uncommon diseases and giving advice on their management could be life saving in an emergency situation. We wonder whether this could be a project for the Association of Anaesthetists to embark upon? A. Varvinski F. J. McGill V. Judd I. Hodzovic Royal Gwent Hospital, Newport NP20 2UB, UK E-mail: [email protected]

References

1 Suresh D. Posterior Spinal fusion in Sotos' syndrome. British Journal of Anaesthesia 1991; 66: 728±32. 2 Jones J, Lachlan D, Kester B. Anaesthesia for a child with Sotos' syndrome. Anaesthesia and Intensive Care 1991; 19: 298±306. 3 Opitz JM, Weaver DW, Reynolds JF Jr. The Syndromes of Sotos and Weaver. Reports and Review. American Journal of Medical Genetics 1998; 79: 294±304. Misplaced central venous catheter

A 41-kg 14-year-old girl with chronic renal failure was referred to our unit for renal transplantation. She had recently

809

Correspondence Anaesthesia, 2001, 56, pages 799±820 ................................................................................................................................................................................................................................................

Figure 5

had a veno-venous haemodialysis catheter inserted at another hospital. Our paediatricians were unable to aspirate blood freely from this catheter, so a chest X-ray was taken. The catheter was seen to pass inferior to the middle third of the left clavicle and to lie with its tip against the left side of the mediastinum. It was thought that this was most unlikely to lie in a central vein other than an anomalous one such as a left superior vena cava. Twenty millilitres of Niopam 300 was injected into the line. The contrast was seen to flow away into a natural space, so an erect PA chest X-ray was taken (Fig. 5). This shows the contrast collected in the subpulmonary part of the left pleural space (arrow). No pneumothorax is seen. The line was not removed pre-operatively because of concern that if intra-operative heparinisation was required (to aid graft patency) bleeding might be a problem. We were also concerned about precipitating a pneumothorax. The line was spigoted off and labelled `do not use'. The renal transplant was uneventfully carried out under general anaesthesia according to our hospital protocol. Postoperatively the transplanted kidney functioned well. Several days later the misplaced catheter was removed in the operating theatre under general anaesthesia. A chest X-ray taken 2 h later

810

showed a large left-sided pneumothorax. An intercostal drain was inserted under general anaesthesia. A chest X-ray taken later that evening showed that the lung had partially reexpanded. Full expansion required the application of negative pressure to the drain. The patient was discharged home 26 days after her transplant. Misplaced vascular catheters are newsworthy items at present [1]. They may cause the unfortunate doctor to become involved with the General Medical Council. In view of the current `one-strike-and-you-are-out' phase that regulation of the medical profession is going through, we must take meticulous care both with our own vascular catheters and those inserted by others. J. Kenningham O. Dearlove B. Wilson Royal Manchester Childrens' Hospital, Manchester, UK

Reference

1 Roberts P. Health chiefs act on baby deaths. Manchester Evening New, 17th October, 2000. Operating theatre exsanguinators pose a low risk for transmission of infection

There is increasing concern regarding transmission of infection in hospitals. The cost of a hospital-acquired infections can run into several thousands of pounds per patient [1]. We regularly use Esmarch bandages and black rubber Rhys exsanguinators, which are applied prior to tourniquet inflation for orthopaedic and plastic surgery procedures. An open wound is wrapped in plastic bags prior to placement of the exsanguinator. It became apparent that as these exsanguinators were used on repeated patients and cleaned between by washing with a Hibiscrub solution, they may be a source of infection. We decided to send swabs from all seven of our exsanguinators to microbiology for routine culture.

All four Esmarch bandages showed no bacterial growth. One out of our three Rhys exsanguinators grew a coagulase-negative staphylococcus. This is a non-pathogenic skin commensal. Obviously, our numbers are small, but the low incidence of positive culture was reassuring. However, the growth from the black rubber exsanguinator may be due to the fact that it is more difficult to clean adequately, and shows that there is no room for complacency in the cleaning of such pieces of equipment. P. Chan G. P. Ashcroft K. A. W. Cranfield Aberdeen Royal Infirmary, Aberdeen AB25 2ZN, UK

Reference

1 Kim T, Oh PI, Simor AE. The economic impact of methicilIinresistant Staphylococcus aureus in Canadian hospitals. Infection Control and Hospital Epidemiology 2001; 22: 99±104. An unexpected and preventable cause of failed epidural analgesia

A recent case that occurred following the failure of a previously functioning epidural infusion has highlighted the importance of checking infusion devices after the refilling of syringes in pumps fitted with seating clamps. A 63-year-old ASA I man underwent a lower midline approach laparotomy for the removal of an acutely inflamed appendix. Methods of postoperative analgesia were discussed and the patient agreed to continuous epidural infusion analgesia. After induction of anaesthesia, an epidural catheter was sited uneventfully at the L223 interspace and good intra-operative analgesia was obtained with 13 ml of bupivacaine 0.5% in divided doses. The patient awoke pain free having received no intra-operative opiates and a continuous epidural infusion of bupivacaine 0.1% 1 fentanyl 2 mg.ml21 was started at 10 ml.h21.

q 2001 Blackwell Science Ltd

Anaesthesia, 2001, 56, pages 799±820 Correspondence ................................................................................................................................................................................................................................................

The epidural infusion system in this hospital consists of a 250-ml pharmacyprepared reservoir bag containing 250 ml bupivacaine 0.1% with fentanyl 2 mg.ml21 attached by a three-way tap to a 60-ml Luer lock BD Plastipack syringe in a Graseby infusion pump. The epidural line is also attached to the three-way tap and fitted with a filter and an antisyphon valve. The patient remained pain free until 16 h postoperatively when he complained of worsening pain around the incision. On checking the syringe it was noted that the contents label attached to the syringe was wet and a large crack was present where the clamp had been allowed to snap shut. Epidural solution was leaking through this fault Consequently, since refilling the syringe 90 min earlier the persistent leak had led to failure of analgesia. The syringe was replaced with another and epidural analgesia successfully reinstated. We assume the fault was caused by repeated snapping shut of the seating clamp onto the syringe with consequent crack propagation. This highlights the importance of visual checks and the care required when delivering analgesia, insulin or vaso-active drugs from syringes fitted with such clamps if under delivery and solution contamination are to be avoided. B. J. Prater C. Timberlake Bromley Hospital, Bromley BR2 9AJ, UK E-mail: [email protected] Epidural haematoma and timing of heparin prophylaxis

Central nerve blockade in patients receiving anticoagulants carries the risk of vertebral canal haematoma [1]. Other risk factors include technical difficulty, multiple bloody punctures and epidural catheter removal [2]. We report the case of 31-year-old woman with Crohn's disease who had an unusual presentation of a vertebral canal haematoma and abscess after removal of an epidural catheter. The patient was scheduled for bowel

q 2001 Blackwell Science Ltd

Figure 6

resection and her only medication was prednisolone 10 mg daily. On the morning of surgery, unfractionated heparin (5000 iu) was administered. A thoracic epidural catheter was inserted prior to surgery and following induction of anaesthesia. On the sixth postoperative day, the epidural catheter was removed. Accurate documentation of the time of catheter removal and the time of heparin administration was not available. Within a few hours of the catheter being removed, the patient experienced severe suprapubic pain. The diagnosis of a resolving paralytic ileus was made and the patient was treated with pethidine, diclofenac and hyoscine. She was apyrexial. She was discharged home on the ninth postoperative day, only to be readmitted that evening with headache, vomiting, pyrexia and dehydration. Two days later, the patient developed severe intractable back pain at the epidural site but full neurological examination revealed no abnormalities. The neurosurgeons were unable to make a diagnosis due to a lack of neurological signs.

On the twelfth postoperative day, a consultant anaesthetist, previously not involved with the patient's management, reviewed the patient and suggested the possibility of an epidural haematoma. It was confirmed by MRI scan (Figs 6 & 7) after transfer to the regional neurosurgical centre. The patient underwent thoracic laminectomy, evacuation of haematoma and drainage of an epidural abscess. The patient was finally discharged 1 month after her original laparotomy. Following surgery, she developed backache and suffered from emotional distress. This case is unusual because the patient did not show the `typical' signs of muscle weakness, sensory deficit, and bladder or bowel dysfunction. The other unusual feature was the late presentation of severe back pain 11 days after epidural insertion and 5 days after removal of the epidural catheter. The suprapubic abdominal pain was probably radicular back pain radiating around the abdomen but misinterpreted as abdominal colic. Only severe back pain above the

811

Correspondence Anaesthesia, 2001, 56, pages 799±820 ................................................................................................................................................................................................................................................

Damage to the conus medullaris following spinal anaesthesia: 1

Figure 7

epidural site alerted the anaesthetist, and MRI scan confirmed the vertebral canal haematoma. It is unknown whether insertion or removal of the epidural catheter contributed to the formation of the vertebral canal haematoma. It has been recommended that for epidural catheter insertion there should be at least 4 h delay after administration of unfractionated heparin. When removing a catheter, there should be at least 1 h delay before the subsequent dose of heparin [2, 4]. The insertion of the epidural was within 4 h of heparin but we could not ascertain the relationship between catheter removal and heparin administration. The time scale of the vertebral canal haematoma would make it more likely to be related to removal of the catheter. This case stresses the importance of accurate documentation of the exact time of heparin administration, epidural catheter insertion or removal, and regular neurological assessment. I also recommend adherence to published European guidelines [3, 4] through the

812

implementation of departmental protocols for use of regional anaesthesia and thromboprophylaxis. V. PaÂnek University Hospital of Wales, Cardiff CF14 4XN, UK

References

1 Horlocker TT, Wedel DJ. Neuraxial block and low-molecular weight heparin: balancing Perioperative analgesia and Thromboprophylaxis. Regional Anesthesia and Pain Medicine 1998; 23 (Suppl. 2): 164±77. 2 Vandermeulen EP, Van Aken H, Vermylen J. Anticoagulants and Spinal ± Epidural Anesthesia. Anesthesia and Analgesia 1994; 79: 1165±77. 3 Vandermeulen EP. Is anticoagulation and central neural blockade a safe combination? Current Opinion in Anaesthesia 1999; 12: 539±43. 4 Wildsmith JA, McClure JH. Anticoagulant drugs and central nerve blockade. Anaesthesia 1991; 46: 613±4.

Professor Reynolds' seven closed-case reports of iatrogenic injury to the spinal cord remind us of the tragic history of subarachnoid anaesthesia, and how fragile a hold this powerful technique has in contemporary anaesthetic practice (Reynolds. Anaesthesia 2001; 56: 238± 47). Needle injury to the spinal cord during induction of subarachnoid block may occur in the best of hands, using standard textbook technique [1]. Therefore, the question arises: how can the safety of standard technique be improved upon? The answer to this is quite simple: adopt the loss-of-resistance-to-negative-pressure test (LORT), preferably with a Whitacre type pencil-point needle [2]. The LORT has a long and respectable history from the days of diagnostic cisternal puncture via the atlanto-occipital membrane, when it was used as an appropriate manoeuvre to avoid accidental needle trauma to the underlying hindbrain. Strangely, our specialty seems to have forgotten this simple technique that performs two essential functions when adapted to the more demanding anatomic constraints of spinal subarachnoid anaesthesia. First, it provides safety to an underlying spinal cord by signalling the precise moment to halt advance of the spinal needle. Second, the transmitted negative pressure collapses the subdural space, ensuring that the entire dose of any injected medication will enter the subarachnoid space, and none will become accidentally sequestered in the subdural space as a result of the needle point pushing the pia-arachnoid membrane inwards, away from the overlying dura mater. Technical success requires that two essential details be observed. A very firm, clenched-fist grip is required on the needle hub, while the dorsum of the hand is braced against the patient's back so that advance of the spinal needle can be halted in a fraction of a millimetre at the instant when cerebrospinal fluid (CSF) squirts back into the vacuum of the `seeking' negativepressure syringe. After the needle has been advanced 2±3 cm into the tissues,

q 2001 Blackwell Science Ltd

Anaesthesia, 2001, 56, pages 799±820 Correspondence ................................................................................................................................................................................................................................................

the stilette is removed, the `seeking' glass syringe is attached and its plunger withdrawn between thumb and middle finger while the index finger exerts counter pressure against the rim of the syringe barrel to create a negative pressure of approximately 600 mmHg. This transmitted vacuum effectively clamps the pia-arachnoid membrane onto the overlying dura at the moment of dural puncture and obliterates the potential subdural space, while the process of confirming free reflux of CSF through 27- or 29-gauge needles is speeded up dramatically as CSF gushes back into the monitoring vacuum syringe on the instant of entering the subarachnoid space [2]. Mastery of this simple hydraulic manoeuvre provides optimal security against accidental injury to an underlying spinal cord, while at the same time increasing the probability that the entire dose of spinal medication will be delivered into the subarachnoid space, and that none will become accidentally sequestered in the subdural space. Given these advantages of precision and safety, the question arises: Why is this simple and clinically effective technique not being taught and practised as the preferred, standard routine for safe performance of subarachnoid puncture and spinal anaesthesia in contemporary practice? P. R. Bromage PO Box 420, Vermont 05471, USA

References

1 Greaves JG. Serious spinal cord injury due to haematomyelia caused by spinal anaesthesia in a patient treated with low-dose heparin. Anaesthesia 1997; 52: 150±4. 2 Bromage PR, van Zundert A, Van Steenberge AL, et al. A-loss-ofresistance-to-negative-pressure test for subarachnoid puncture with narrowgauge needles. Regional Anesthesia. 1993; 18: 155±61.

q 2001 Blackwell Science Ltd

Damage to the conus medullaris following spinal anaesthesia: 2

We read with interest the recent case report describing damage to the conus medullaris following spinal anaesthesia (Reynolds. Anaesthesia 2001; 56: 238± 47). Atraumatic (pencil-point) needles have at least 1 mm of blind tip beyond the hole and thus a tendency to insert further into the subarachnoid space than is necessary with a bevelled needle [1]. As Dr Reynolds states, this can only partly account for the cluster of the conus medullaris injuries following combined spinal±epidural (CSE) or pencil-point needles. We would like to suggest further explanations. It is well known that during spinal anaesthesia bevelled needles are deflected more than pencil-point needles, and that the degree of deflection is correlated with gauge and depth of insertion [2±4]. Bevelled spinal needles are deflected in the opposite direction to its bevel. In contrast, pencil-point needle deflect mainly in the direction of the distal side port because of increased `drag' induced by the irregularity of the side port or, if present, the tip bend made at the area of weakness (level of side port) [4]. When spinal and epidural needles are assembled during the CSE technique, the spinal needle emerges at a deflected angle of 4±58 [5] or approximately 108 [6] from the long axis of the epidural needle because of the bent tip of the Tuohy needle. Tuohy needles are also deflected to the bevel (end-hole) side by the curved tip [3]. During CSE block, the spinal needle deflects further to the bevel side of the Tuohy needle than the simply assembled state because the shaft of the Tuohy needle makes a curved route to the epidural space. The variation in conus position follows a normal distribution with the peak incidence at the lower third of the body of L1 with a range from the middle third of T12 to the upper third of L3 bodies [7]. During attempts at spinal anaesthesia at L2/L3, the more cephalad the needle tip is directed, the higher the probability of needle trauma. Even during the midline approach, a slight cephalad angulation

is generally recommended. In Dr Reynolds' report, all the cases were women, six obstetric patients and one obese patient. It is clear that their interspinous spaces could not be widened as much as the general population, because such patients cannot flex their hips fully even in the lateral decubitus position [8]. The paramedian approach, which needs a longer and more cephalad path to the subarachnoid space, may be favoured when the interspinous space is not sufficiently wide or to minimise the risk of postdural puncture headache in high-risk groups such as parturients. While performing a spinal or CSE block with the bevel orientated cephalad, bevelled spinal needles direct more caudad than the axis of insertion into the skin. In contrast, CSE or pencilpoint spinal needles course more cephalad. Because the clinical use of Tuffier's line requires palpation through a variable amount of subcutaneous fat, high placement is especially likely in obese patients [9]. Term parturients with preeclampsia and generalised oedema might have the same tendency. When performing spinal anaesthesia with isobaric bupivacaine, injection at a high lumbar space produces a higher spread of analgesia [10]. The temptation to use a lesser amount of `potentially neurotoxic' spinal anaesthetic drug may force the anaesthetist to choose the L2/L3 interspace. These arguments may help to explain some incidences of spinal cord damage incurred during CSE or spinal anaesthesia attempted at the L2/L3 interspace. As Dr Reynolds states, however, the main reasons for the conus medullaris injuries following spinal or CSE anaesthesia are an error of identification of the correct intervertebral space from surface markings, and a failure to remember that the conus may extend as low as L3. J-H. Bahk H. Ko Seoul National University Hospital, Seoul 110±744, South Korea E-mail: [email protected]

813

Correspondence Anaesthesia, 2001, 56, pages 799±820 ................................................................................................................................................................................................................................................

References

1 Collier CB, Turner MA. Are pencil point needles safe for subarachnoid block? Anaesthesia 1998; 53: 411±12. 2 Drummond GB, Scott DHT. Deflection of spinal needles by the bevel. Anaesthesia 1980; 35: 854±7. 3 Baumgarten RK. Importance of the needle bevel during spinal and epidural anesthesia. Regional Anesthesia 1995; 20: 234±8. 4 Sitzman BT, Uncles DR. The effects of needle type, gauge, and tip bend on spinal needle deflection. Anesthesia and Analgesia 1996; 82: 297±301. 5 Eldor J. Spinal needle deflection in the combined spinal-epidural technique. Anesthesia and Analgesia 1996; 83: 663. 6 Westbrook JL, Donald F, Carrie LES. An evaluation of a combined spinal / epidural needle set utilising a 26-gauge, pencil point spinal needle for Caesarean section. Anaesthesia 1992; 47: 990±2. 7 Saifuddin A, Burnett SJD, White J. The variation of position of the conus medullaris in an adult population: a magnetic resonance imaging study. Spine 1998; 23: 1452±6. 8 Fisher A, Lupu L, Gurevitz B, et al. Hip flexion and lumbar puncture: a radiological study. Anaesthesia 2001; 56: 262±6. 9 Moore DC. Factors influencing spinal anesthesia. Regional Anesthesia 1982; 7: 20±5. 10Tuominen M, Taivainen T, Rosenberg PH. Spread of spinal anaesthesia with plain 0.5% bupivacaine: Influence of the vertebral interspace used for injection. British Journal of Anaesthesia 1989; 62: 358±61. Damage to the conus medullaris following spinal anaesthesia: 3

We read with great interest the case report (Reynolds. Anaesthesia 2001; 56: 238±47) detailing injuries sustained to the conus medullaris following spinal or combined spinal±epidural anaesthesia using atraumatic spinal needles. Highlighting these cases gives the obstetric anaesthetist and those using this technique for other surgical procedures cause for concern. An interesting

814

additional piece of information not indicated by the author in the article is the overall time span within which these cases occurred and the number of spinal or combined spinal±epidural procedures carried out which generated these findings. An indication of the incidence of neurological injury as a direct result of the anatomical variations or anomalies described would provide colleagues with a realistic evaluation of the problem. B. S. Grewal J. Tarpey Warwick Hospital, Warwick CV34 SBW, UK A reply

I thank all those who have expressed an interest in my report of seven cases of conus damage following spinal anaesthesia (Reynolds. Anaesthesia 2001; 56: 238±47). Drs Grewal and Tarpey pose an important question: `What is the incidence of this complication?' The cases I described occurred between 1991 and 1998, in different parts of the country. Not only is the numerator a random figure, it is also impossible to derive a denominator from such scattered cases in order to calculate the frequency. In the same issue as my report, Dr Parry described two very similar cases that occurred in a single hospital over a period of 18 months [1]. The total numbers of spinal and CSE procedures conducted in Watford General Hospital would hardly provide a realistic denominator for these two cases. The incidence depends on local practice and teaching, as I know Dr Parry would agree. A reliable indication of incidence can only be derived from prospective surveys. It may be hoped that the survey of neurological sequelae of regional blockade being conducted by the National Obstetric Anaesthesia Database (NOAD) may be able to provide such a figure. In the meantime, a rough estimate of incidence may be calculated from the results of a retrospective national survey of neurological sequelae of spinals and CSEs that we published in

2000 [2]. The 222 units responding to the questionnaire between them conducted 12 254 CSEs and 29 698 spinals over the period in question, and altogether there were 56 cases of mild to moderate neurological damage; nine were of obstetric origin, 18 anaesthetic and 29 uncertain. The majority were short-lived paraesthesiae. There were, however, two cases specifically of damage to the conus medullaris, one following CSE and one spinal anaesthesia. These were two of the seven described in more detail in my recent report. This therefore gives an approximate incidence of conus damage of 1 : 20 000 procedures. I would like to think that in years to come, when everyone has remembered that there is a difference in the safe level if insertion between spinals and epidurals, this incidence will be much reduced. F. Reynolds St Thomas' Hospital, London, UK

References

1 Parry H. Spinal cord damage. Anaesthesia 2001; 56: 290. 2 Holloway J, Seed PT, O'Sullivan G, Reynolds F. Paraesthesiae and nerve damage following combined spinal epidural and spinal anaesthesia. International Journal of Obstetric Anesthesia 2000; 9: 151±5. Pressure sores: blame the mobile epidural!

There have been a number of recent reports of pressure sores occurring in both obstetric and non-obstetric patients receiving `low-dose' epidural infusions [1±4]. A number of reasons have been postulated for this: quality of bed and incontinence pads; moisture from amniotic fluid, disinfectant and meconium; general health, age and weight; sensory deficit; and immobility from motor block. The cause is likely to be multifactorial but we believe the drive to minimise motor block may be a contributory factor.

q 2001 Blackwell Science Ltd

Anaesthesia, 2001, 56, pages 799±820 Correspondence ................................................................................................................................................................................................................................................

In our obstetric unit in the last year there have been four cases of pressure sores occurring in parturients receiving epidurals for analgesia in labour. During this time, in an attempt to minimise motor block, the use of `low-dose' bupivacaine and fentanyl mixtures by continuous infusions was routine. Our four cases with pressure sores all received infusions of bupivacaine 0.1% and fentanyl 2 mg.ml21 at 14 ml.h21. The staff of this unit have not seen this complication with many years experience of intermittent top-ups with bupivacaine 0.25±0.5%. It seems counter-intuitive to blame this phenomenon on the use of techniques designed to minimise somatic sensory and motor block. However, patients with obvious motor deficit receive assistance to move from midwives. In contrast, patients who appear mobile but having some muscle weakness are encouraged to move unassisted and, being unable to support their weight, may slide themselves up the bed. Moving in this way may increase shearing forces on the tissues. We would like to raise two further points: 1 As the pressure sore rate in our unit is now higher than the dural puncture rate, should we inform patients of it when obtaining consent? 2 Is it time, given the recent number of case reports, for a prospective study to look into this unfortunate complication? V. C. Linnett F. McMenemie J. Duggan Wansbeck General Hospital, Ashington NE63 9JJ, UK E-mail: [email protected]

References

1 Offori E, Popham P. Decubitus ulcers after instituting epidural analgesia for pain relief in labour. Anaesthesia 2000; 55: 194. 2 Alexander R. Pressure sore following low-dose epidural infusion. Anaesthesia 2000; 55: 709. 3 Newton H, Mitchell MD. Pressure ulcers during labour: the effect of

q 2001 Blackwell Science Ltd

Figure 8

epidural analgesia. Anaesthesia 2000; 55: 1140. 4 Sellers WFS. Pressure sores and epidurals ± blame the sheets? Anaesthesia 2000; 56: 394.

Combined spinal-epidural as an alternative method of anaesthesia for a sigmoidcolectomy

We would like to report the case of an 82-year-old woman who required a sigmoid colectomy for carcinoma of the rectum. She is an ex-smoker, living in a nursing home, with a past medical history of congestive cardiac failure, hypertension, chronic obstructive airways disease and osteoporosis. The osteoporosis contributed to severe kyphosis (Fig. 8) leaving her with poor lung function (Table 1). Her exercise tolerance was 10±20 m with a Zimmer frame and she required four pillows for orthopnoea. Special investigations showed mild mitral regurgitation with left ventricular hypertrophy on echocardiograph; small bilateral effusions on chest X-ray and an arterial

blood gas showing type 1 respiratory failure. We were concerned that a general anaesthetic would contribute to further respiratory failure requiring prolonged intensive care management and ventilation. After discussion with patient and family we opted for a combined spinal± epidural technique. Using an aseptic technique, we used a needle through needle technique (27 g/ 16 g-touhy) at L223 interspace. The spinal injection was 3 ml of bupivacaine 0.5% with fentanyl 25 mg. The epidural comprised a mixture of 15 ml of lidocaine 1%, and 15 ml of bupivacaine 0.25% over a period of 3 h, which was give in boluses of 5 ml. An arterial cannula was inserted into a radial artery for accurate blood pressure and blood gas monitoring. The patient was positioned head up with three pillows and a break in the table and received oxygen Table 1 pefr fev1 fev/fvc

60 l 0.5 l ±

22% of predicted 42% of predicted 71% of predicted

815

Correspondence Anaesthesia, 2001, 56, pages 799±820 ................................................................................................................................................................................................................................................

Table 2 Intra-op.

pH PaCO2; mmHg PaO2 Hct

09:00

09:45

10:30

11:29

7.4 56 238 32

7.21 70 305 33

7.19 76 295 31

7.32 49 178 29

5 l.min21 through a Hudson mask. The surgeons could access the surgical field but there was an understanding that if the splenic flexure needed to be mobilised we would have no alternative than to change to a general anaesthetic. The procedure lasted 2.5 h and the patient received 1 l of colloid and 1.5 l of crystalloid. The blood loss was approximately 700 ml. Although arterial blood gasses showed an increasing respiratory acidosis, it had corrected itself on arrival in intensive care (Table 2). The patient stayed in intensive care for 2 days receiving 2 units of blood and was mobilizing around the surgical ward with her Zimmer frame by day 5. She was discharged from hospital a fortnight later. We undertook a literature search and accessed one case [1] that drew some comparison to our case. A patient with severe multiple sclerosis had a sigmoid colectomy for a volvulus and received a spinal anaesthetic with a spinal catheter; diamorphine was used via this catheter postoperatively with a similar favourable outcome as ours. Although a sigmoid colectomy is synonymous with a general anaesthetic, with the possibility of an epidural for intra- and postoperative analgesia, we would like to put forward this case as an alternative technique to the above mentioned operation. G. Morton I. Bowler Llandough Hospital, Cardiff, UK

Reference

1 Leigh J, Fearnley SJ, Lupprian KG. Intrathecal diamorphine during

816

Post-op.

laparotomy in a patient with advanced multiple sclerosis. Anaesthesia 1990; 43: 640±2. Predicting caudal epidural analgesia using nerve stimulation

I read with great interest recent correspondence (Singh & Khan.Anaesthesia 2000;55: 830±1) wherein they describe use of a peripheral nerve stimulator for predicting caudal epidural analgesia and conclude that `the peripheral nerve stimulator, where available, may be used for judging correct placement of local anaesthetic in the caudal space'. While I thank the authors for quoting my paper, which describes the successful use of nerve stimulators to locate the correct placement of the epidural catheter, I think it is worth drawing attention to the fact that I have conducted a similar study, using peripheral nerve stimulator to confirm the proper caudal needle placement, in 1997 and published the result in 1999 [1]. Nevertheless, I am pleased to learn that similar findings and conclusions were made independently by Drs Singh and Khan. In clinical practice, spinal cord stimulation technique for the treatment of chronic pain and electrical stimulation methods for localizing peripheral nerves have been used for decades. However, electrical stimulation has never been described to identify entry into the epidural space until my recent clinical trials [2±7]. A positive motor response to low current electrical stimulation (1±10 mA) confirms proper epidural location. A negative motor response

suggests placement outside the epidural space. Based on our previous study in identifying the caudal space [1], the sensitivity and specificity of the nerve stimulation technique were both 100%. These findings were better than those of Drs Singh and Khan's. The likely reason was that we used an insulated needle to conduct electricity effectively to the tip of the needle. When using a peripheral nerve stimulator to localise a nerve, it is generally agreed that insulated needles are more precise. In Drs Singh and Khan's study, two patients (13.3%) reported only positive sensory sensations with no motor response despite reaching 20 mA current stimulation, even though both developed adequate analgesia after injection of local anaesthetic. This may have been due to the use of an uninsulated needle leading to diffuse leaking of electricity. Thus, I recommend using an insulated needle when performing the nerve stimulation technique. B. C. H. Tsui University of Alberta Hospital, Edmonton, Alberta, Canada T6G 2B7

References

1 Tsui BCH, Tarkkila P, Gupta S, Kearney R. Confirmation of caudal needle using nerve stimulation. Anesthesiology 1999; 91: 374±8. 2 Tsui BCH, Gupta S, Finucane B. Confirmation of epidural catheter placement using nerve stimulation. Canadian Journal of Anaesthesia 1998; 45: 640±4. 3 Tsui BCH, Gupta S, Finucane B. Detection of subarachnoid and intravascular epidural catheter placement. Canadian Journal of Anaesthesia 1999; 46: 675±8. 4 Tsui BCH, Seal R, Entwistle L. Thoracic epidural analgesia via the caudal approach using nerve stimulation in an infant with CATCH22. Canadian Journal of Anaesthesia 1999; 46: 1138±42. 5 Tsui BCH, Gupta S, Finucane B. Determination of epidural catheter placement using nerve stimulation in

q 2001 Blackwell Science Ltd

Anaesthesia, 2001, 56, pages 799±820 Correspondence ................................................................................................................................................................................................................................................

obstetric patients. Regional Anesthesia and Pain Medicine 1999; 24: 17±23. 6 Tsui BCH, Gupta S, Finucane B. Detection of subdural placement of epidural catheter using nerve stimulation. Canadian Journal of Anaesthesia 2000; 47: 471±3. 7 Tsui BCH, Guenther C, Emery D, Finucane B. Determination epidural catheter location using nerve stimulation with radiological confirmation. Regional Anesthesia and Pain Medicine 2000; 25: 306±9. Vertical infraclavicular block and myasthenia gravis

We read with interest the case report regarding the use of a vertical infraclavicular block in a patient with myasthenia gravis (Sinha et al. Anaesthesia 2001; 56: 165±8). While we agree that the use of regional anaesthesia is imperative in a patient who is symptomatic with myasthenia gravis, the infraclavicular approach to the brachial plexus is not without risk in patients with respiratory compromise. Kilka et al. studied 175 patients and reported no pneumothoraces, while Mehrkens et al. reported four cases of pneumothoraces from 800 patients using the vertical infraclavicular approach [1, 2]. These were due to the puncture site being either too medial or too deep. A newer lateral approach to the infraclavicular block described by Kapral et al. uses the coracoid rather than the acromion process as a landmark [3]. The stimulating needle is inserted along the sagittal plane until contact is made with the coracoid process. It is then withdrawn 2±3 mm and redirected under the coracoid process until contact with the brachial plexus is made. This block has a high success rate and uses an approach that minimises the risk of pleural puncture. The authors also state that the axillary brachial plexus block is best for surgery of the forearm and hand, but the axillary approach to the brachial plexus is well described as suitable for elbow surgery, particularly if a multiple injection technique is used [4].

q 2001 Blackwell Science Ltd

Finally, we would like to question why the patient received only 20 ml of lidocaine 2% with 1 : 400 000 epinephrine. The normal volume used for brachial plexus blockade is between 30 and 40 ml using a combination of long- and short-acting agents [1±5]. Fortunately, this patient did not require an open reduction. If this had been the case, however, a combination of drugs and larger volumes could have proved beneficial for both intra-operative anaesthesia and postoperative analgesia. A. M. Troy B. Kinirons University College Hospital, Galway, Ireland

References

1 Kilka HG, Geiger P, Mehrkens H-H. Die infraclaviculaÈre Blockade des Plexus brachialis. Anesthesist 1995; 44: 339±44. 2 Mehrkens H-H, Geiger PK. Continuous brachial plexus blockade via the vertical infraclavicular approach. Anaesthesia 1998; 53 (Suppl. 2): 19±20. 3 Kapral S, Jandrasits O, Schabernig C et al. Lateral infraclavicular plexus block vs. axillary block for hand and forearm surgery. Acta Anaesthesiologica Scandinavica. 1999; 43: 1047±52. 4 Karaca P, Hadzic A, Vloka JD. Specific nerve blocks: an update. Current Opinion in Anaesthesiology 2000; 13: 549±55. 5 Lanz E, Theiss D, Jankovic D. The extent of blockade following various techniques of brachial plexus blockade. Anesthesia and Analgesia 1983; 62: 55±8. A reply

We are grateful to Drs Troy and Kinirons for their interest in our case report and for their comments. The choice of approach to the brachial plexus in a patient who needs elbow surgery, but who has minimal ventilatory reserve, is a difficult one. The incidence of phrenic nerve paralysis approaches 100% with techniques aimed at the upper reaches of the brachial plexus [1], decreasing progressively with techniques that aim at lower

portions of the plexus. Anaesthetic efficacy for elbow surgery also varies with different approaches to the brachial plexus, being relatively low with singleinjection techniques in the distal axilla, increasing as one approaches a target area between the coracoid process and the first rib, and then decreasing again above this level, as the lower roots and trunks of the plexus are often missed by blocks such as the interscalene or subclavian perivascular. Variations in technique that may encourage local anaesthetic spread to this `coracocostal' area (the part of the plexus that can provide anaesthesia of the entire upper limb) have been described: distal pressure and high volume with an axillary approach [2, 3], proximal pressure and high volume with an interscalene approach [4]. As an increased volume of injectate will most likely result in an increase in both proximal and distal spread (even with digital pressure [5]), and if it is accepted that the mechanism of phrenic block is the proximal passage of local anaesthetic within the plexus sheath to the cervical roots, logical choices for anaesthesia in the described circumstances include a distal plexus block with a high volume or an accurately placed `coraco-costal' block with a lower volume. The solutions suggested by your correspondents (multiple injection technique at the axilla or a coracoid-level block) are also wholly acceptable. However, the technique used in a particular situation depends not only on the anatomy, the techniques and the patient, it also depends upon the skills and experience of the operator. We were not experienced in coracoid-level blocks and had had unsuccessful experiences of singleshot axillary blocks for elbow surgery in the awake patient. We therefore chose a technique with which we were becoming increasingly familiar and which targeted the appropriate area of the brachial plexus: the vertical infraclavicular block. We chose a volume of 20 ml of local anaesthetic solution for two reasons: firstly, in order to minimise the proximal spread of local anaesthetic, and thus, we hoped, to reduce the chances of phrenic nerve paralysis; second, it is

817

Correspondence Anaesthesia, 2001, 56, pages 799±820 ................................................................................................................................................................................................................................................

our contention that 20 ml of local anaesthetic is all that is needed to produce arm, as opposed to arm and shoulder, anaesthesia at a plexus level behind or close to the clavicle. This view is supported by Winnie's demonstrations of the relationship between injection volume and extent of anaesthesia in upper limb blocks [6]. W. Harrop-Griffiths A. Sinha K. Ahmad St Mary's Hospital, London W2 1NY, UK E-mail: [email protected]

References

1 Urmey WF, Talts KH, Sharrock NE. One hundred per cent incidence of hemidiaphragmatic paresis associated with interscalene brachial plexus anesthesia as diagnosed by ultrasonography. Anesthesia and Analgesia 1991; 72: 498±503. 2 Eriksson E, Skarby H-G. A simplified method of axillary block. Nordisk Medicin 1962; 68: 1325±7. 3 Winnie AP. Plexus Anaesthesia: Perivascular Techniques of Brachial Plexus Block. Philadelphia: W.B. Saunders, 1983: 183±6. 4 Winnie AP. Plexus Anaesthesia: Perivascular Techniques of Brachial Plexus Block. Philadelphia: W.B. Saunders, 1983: 138±40. 5 Urmey WF, Grossi P, Sharrock NE, Stanton J, Gloeggler PJ. Digital pressure is clinically ineffective in preventing anesthetic spread to the cervical plexus. Anesthesia and Analgesia 1996; 83: 366± 70. 6 Winnie AP. Plexus Anaesthesia: Perivascular Techniques of Brachial Plexus Block. Philadelphia: W.B. Saunders, 1983: 164±6. Adrenaline 0.5%?

Astra 10-ml vials of bupivacaine with epinephrine (adrenaline) are labelled `Marcain with adrenaline 0.5%'. This is inaccurate in that 0.5% refers to the concentration of bupivacaine and not epinephrine. The actual concentration

818

of both drugs neither appears on the ampoule nor on the covering container. Only on the box is the correct concentration of both drugs indicated, i.e. Bupivacaine hydrochloride anhydrous 5 mg.ml21 and Adrenaline Tartrate Ph. Eur. 10 mg.ml21. This does not meet standard labelling requirements for containers and packages of medicinal products for human use. These standards require a statement of the active ingredients of the product expressed qualitatively and quantitatively per dosage unit or according to the form of administration for a given volume or weight, using the common names of the ingredients [1]. We feel that the concentration of both drugs printed on the box should also appear on the ampoule and that failure to do so would constitute a medical hazard. M. Keohane S. R. Luney The Royal Hospitals, Belfast BT12 6BA, UK

Reference

1 Anon. Medicines control agency guidance for the Pharmaceutical Industry on the labelling and leaflets regulations. September, 1993. A reply

AstraZeneca are grateful for the opportunity to reply to the letter by Drs Keohane and Luney. In response to customer feedback, such as the above, AstraZeneca have amended the labelling of Marcain with Adrenaline to show the actual concentration of both the bupivacaine and the epinephrine. The new label text is: Marcainw 0.25% with Adrenaline (5 mg.ml21) (1 : 200 000), Marcainw 0.5% with Adrenaline (5 mg.ml21) (1:200 000) This wording will appear on the vial and the outer packaging of the product. In addition, the wording `Adrenaline (5 mg.ml21) (1 : 200 000)' is written in red on the outer packaging and on the vial. Please be reassured that the formulations of the products have not changed. We expect that stock with the new

labelling will be provided to the market by June 2001. AstraZeneca hope that this amendment will alleviate the labelling problems highlighted to us by our customers and ensure reliable and convenient handling of Marcain with Adrenaline for customers. J. McKenna Medical Information Manager, AstraZeneca, Kings Langley WD4 8DH, UK Safety, cost and predrawn emergency drugs.

We were interested to read the recent discussion concerning the predrawing of `emergency' drugs in the obstetric theatre (Cupitt & Dunkley. Anaesthesia 2000; 55: 721. Calow. Anaesthesia 2000; 55: 1226±7) and the call for the experiences of others. We have recently published a national survey of the attitudes and practices of New Zealand anaesthetists with regard to emergency drugs [1]. The results demonstrate no uniformity of opinion or practice in New Zealand and indicate that many factors influence which drugs, if any, are predrawn before a case. Eighty-four per cent of respondents reported that their institution had no policy regarding the predrawing of emergency drugs in their workplace. The most common drugs to be predrawn were succinylcholine, atropine, syntocinon, ephedrine and metaraminol. Twenty-six per cent of respondents reported routinely predrawing such drugs, the majority indicating that they did this to avoid delay and to be prepared ± some adding that assistants were too slow in drawing-up during emergencies. Thirty-seven per cent of anaesthetists reported having experienced delay, and 30% errors, while drawing up a drug at the time of a crisis. A number of respondents indicated that the absence of predrawn emergency drugs increased the anaesthetist's stress level even if the patient's outcome was not affected by delay in administering a required drug. Contrary to the widely held view that emergency drugs are rarely used, 86% of respondents had used such drugs in the

q 2001 Blackwell Science Ltd

Anaesthesia, 2001, 56, pages 799±820 Correspondence ................................................................................................................................................................................................................................................

Figure 9

previous year, and 29% had required them more than five times [1]. There is a significant cost in preparing and discarding syringes on a daily basis. Extending their shelf life is certainly the simplest way to decrease this cost, and it may be relatively straightforward to achieve a shelf life of a week or more. A recent US study investigated microbial contamination in over 700 syringes of six common emergency drugs drawn up in an obstetric theatre under routine clinical conditions [2]. The syringes were covered with clean towels and stored in theatre, unrefrigerated, next to the anaesthetic machine; no microbial contamination was found in any syringe after 8 days. However, consideration is also needed of drug stability, and of the possibility of chemical or particulate contamination from the syringe materials. Adequate quality control probably does require the formal procedures of a

Figure 10

q 2001 Blackwell Science Ltd

hospital pharmacy or licensed pharmaceutical manufacturer, which in many cases would permit shelf lives of several months to be attained ± more than offsetting any additional costs. Given proper quality control, the advantages of presenting drugs in a prefilled format are several, and go well beyond the emergency situation. The use of such syringes may well be one method of reducing the very worrying problem of drug administration error [3]. It is well known that the legibility of labels on many ampoules is poor, and that ampoules containing quite different drugs may closely resemble each other, creating what psychologist and systems expert, James Reason, has called a latent error [4, 5] (Fig. 9). In this way, one of the authors recently committed a drug administration error by mistakenly substituting the two leftmost ampoules in Fig. 9. Pre-filled

syringes replace the error-prone, complex task by which an anaesthetist places several different drugs into individual syringes, with the much safer, production-line process by which a manufacturer prepares a large number of syringes containing the same drug [6]. The standard of user-applied labelling of drugs drawn up in theatre is typically variable and idiosyncratic, often little better than the labelling on ampoules and, at times, frankly dangerous [7]. Standard production methods would virtually guarantee the accuracy of labelling and would facilitate the use of highly legible, printed labels, incorporating the drug-class specific, international colour-codes for anaesthetic drugs. We have adopted such prefilled syringes at Green Lane Hospital (for some 10 drugs) as part of a systematic approach to the reduction of drug administration error (Fig. 10) [3]. In the case of emergency drugs, prefilled syringes could be presented in easily recognizable tamper-evident packs. The contents of these packs could be determined by departmental policy and could be speciality specific. Packs could be available from a different drawer of the anaesthetic trolley, thus physically separated from drugs commonly used during uneventful anaesthesia. Such physical separation and effective labelling would surely assist in reducing the incidence of syringe-swap errors. There would be some extra cost, at least initially, in the adoption of this approach. However, there is a substantial cost associated with iatrogenic harm, and recent calls for greater patient safety by the US Institute of Medicine [8] reflect a growing public intolerance of error in healthcare. At the least, the additional expenditure involved with providing emergency drugs in prefilled syringes would be minimal and, as Calow suggests, would be very likely to reduce risk to the patient. In addition, our data suggest the provision of prefilled emergency drugs would also reduce stress for the anaesthetist [1]. The cost involved would be greatly reduced by economies of scale. Therefore, we believe the time is long overdue for pharmaceutical companies to move towards abandoning poorly

819

Correspondence Anaesthesia, 2001, 56, pages 799±820 ................................................................................................................................................................................................................................................

labelled and time-wasting ampoules as obsolete, and to provide all injectable drugs in prefilled syringes clearly labelled according to internationally agreed standards. C. S. Webster A. F. Merry Green Lane Hospital, Auckland, New Zealand E-mail: [email protected]

3

4

C. M. Ducat Middlemore Hospital, Auckland, New Zealand

5

References

7

1 Ducat CM, Merry AF, Webster CS. Attitudes and practices of New Zealand anaesthetists with regard to emergency drugs. Anaesthesia and Intensive Care 2000; 28: 692±7. 2 Driver RP, Snyder IS, North FP, Fife

820

6

8

TJ. Sterility of anesthetic and resuscitative drug syringes used in the obstetric operating room. Anesthesia and Analgesia 1998; 86: 994±7. Webster C, Merry A, Larsson L, McGrath K. A complex-systems approach to safer drug administration in anaesthesia. Journal of Clinical Monitoring and Computing 2000; 16: 150±1. Reason J. Human Error. New York: Cambridge University Press, 1990. Webster CS. Human psychology applies to doctors too. Anaesthesia 2000; 55: 929±30. Perrow C. Normal Accidents ± Living with High Risk Technologies. New York: Basic Books, 1984. Webster CS, Merry AF. British syringe label `standards' are an accident waiting to happen. Anaesthesia 2000; 55: 618. Institute of Medicine. To Err Is Human: Building a Safer Health System. Washington, DC: National Academy Press, 2000.

Shocking postoperative visits

Recently, there has been a great deal of debate about the role of the anaesthetist within the NHS. Whilst writing some teaching material about the complications of anaesthesia, my computer's spell checker suggested that `oliguria' and `tryptase' should be replaced by `lingerie' and `striptease', respectively. Could it be that there are secret plans afoot to revolutionise the emphasis of our pre- and postoperative visits? Would this be entirely appropriate with the rising incidence of patients with ischaemic heart disease? D. W. Wheeler Addenbrooke's Hospital, Cambridge CB2 2QQ, UK E-mail: [email protected]

q 2001 Blackwell Science Ltd