Phaeochromocytoma diagnosed during labour

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British Journal of Anaesthesia 87 (2): 288±94 (2001)

Correspondence Phaeochromocytoma diagnosed during labour EditorÐWe were interested to read the article by Strachan and colleagues1 as we have recently managed a similar case of phaeochromocytoma undiagnosed antenatally, during labour and subsequently in the intensive care unit.2 Despite the paucity of data about this rare endocrine emergency during pregnancy we would like to challenge certain aspects of the overall management. The presumptive and fortuitous diagnosis of phaeochromocytoma during labour was made on the basis of a single hypertensive reading and glucose intolerance; the latter is not unusual in a patient diagnosed with gestational diabetes. We believe that hypertension in labour associated with headache is pre-eclampsia until proven otherwise and should be treated accordingly, i.e. epidural, magnesium, hydralazine. Alpha-blocking drugs do not routinely form part of the armamentarium of the management of pre-eclampsia. But magnesium has been found to be a useful adjunct in the management of both severe pre-eclampsia and phaeochromocytoma due to its calcium antagonist action. Calcium plays a fundamental role in stimulus response coupling of catecholamine release from the adrenal medulla and adrenergic nerve terminals.3 Every labour suite in the UK should have ready access to magnesium and possess guidelines on how and when to administer the drug. Harper and colleagues report4 that an unrecognized phaeochromocytoma may be potentially fatal as hypertensive crises may be precipitated by vaginal delivery, the mechanical effects of the gravid uterus, uterine contractions and even vigorous fetal movements. Hence from the maternal standpoint, in the presence of a functioning epidural during a labour punctuated with high blood pressure readings, we are surprised that the decision to proceed with a vaginal delivery was taken; a view supported by Schenker and Grant5 who believe labour and vaginal delivery should be avoided in such cases. Fetal hypoxia and death may also occur during these hypertensive crises. Phaeochromocytoma is the great mimic. In retrospect, the clues were present: headache, gestational diabetes, and hypertension. The key to a better prognosis is early diagnosis and therefore despite our difference of opinion we congratulate the authors on their prompt consideration of such a rare diagnosis in pregnancy and the successful outcome. A. S. Bullough M. Watters Department of Anaesthesia Princess Margaret Hospital Swindon, UK 1 Strachan AN, Claydon P, Caunt JA. Phaeochromocytoma diagnosed during labour. Br J Anaesth 2000; 85: 635±7 2 Bullough AS, Karadia S, Watters M. Phaeochromocytoma: An unusual cause of hypertension in pregnancy. Anaesthesia (in press) 3 Fawcett WJ, Huxby EJ, Male DA. Magnesium: Physiology and pharmacology. Br J Anaesth 1999; 83: 302±20 4 Harper MA, Murnaghan GA, Kennedy L, Hadden DR, Atkinson AB. Phaeochromocytoma in pregnancy. Five cases and a review of the literature. Br J Obs Gynaecol 1989; 96: 594±606 5 Schenker JG, Grant M. Phaeochromocytoma in pregnancy. Anaesthesia 1983; 38: 654±58

EditorÐStrachan and colleagues are to be congratulated on their diagnosis and management of a phaeochromocytoma during

labour.1 However, we were disappointed that magnesium was not mentioned as a possible treatment in the discussion. Magnesium has a well established place in the management of both non-pregnant and pregnant patients with phaeochromocytoma,2 3 where it has a marked anti-adrenergic effect and is effective in reducing catecholamine concentrations.2 It has a number of different mechanisms of action, in particular inhibition of catecholamine release, as well as vasodilation and a reduction in the incidence of cardiac arrhythmias.4 The anti-adrenergic effect is particularly desirable in a labouring patient as catecholamine surges may produce gross haemodynamic changes in the mother and severely compromise placental perfusion. Although a tocolytic, magnesium does not prolong or affect the duration of labour (although it may necessitate a higher dose of oxytocin).5 Whilst we accept that a and b blockade are important in the management of phaeochromocytoma in pregnancy (although the latter may cause fetal bradycardia), as well as the judicious use of an epidural, magnesium should be considered. The rarity of the condition will always prevent large studies, but magnesium is a safe drug with increasing usage. In particular, with its established place in the treatment of eclampsia, magnesium should be familiar to all obstetric anaesthetists, thus making it an ideal agent for the control of hypertension in these patients.6 W. J. Fawcett C. L. Edkins Guildford Surrey, UK 1 Strachan AN, Claydon P, Caunt JA. Phaeochromocytoma diagnosed during labour. Br J Anaesth 2000; 85: 635±7 2 James MFM. Use of magnesium sulphate in the anaesthetic management of phaeochromocytoma: a review of 17 anaesthetics. Br J Anaesth 1989; 62: 616±23 3 James MFM, Huddle KR, Owen AD, van der Veen BW. Use of magnesium sulphate in the anaesthetic management of phaeochromocytoma in pregnancy. Can J Anaesth 1988; 35: 178±82 4 Fawcett WJ, Haxby EJ, Male DA. Magnesium: physiology and pharmacology. Br J Anaesth 1999; 83: 302±20 5 Witlin AG, Friedman SA, Sibai BM. The effect of magnesium sulfate therapy on the duration of labor in women with mild preeclampsia at term: a randomized, double-blind, placebo-controlled trial. Am J Obstet Gynecol 1997; 176: 623±7 6 James MFM. Magnesium in obstetric anaesthesia. Int J Obstet Anesth 1998; 7: 115±23

EditorÐThank you for the opportunity to respond to the points raised by Bullough and Watters, and Fawcett and Edkins in our case report. We agree that hypertension during pregnancy (and labour) associated with headache is pre-eclampsia until proven otherwise. Pre-eclampsia is a syndrome of pregnancy including hypertension and proteinuria. Our patient never had measured hypertension or proteinuria antenatally. The sudden unexplained extreme rise and fall of blood pressure in our patient is not a recognized feature of pre-eclampsia appearing in labour. In retrospect, we were not surprised about her normal antenatal blood pressure readings. She had not had blood pressure measured during an attack before. In non-pregnant patients with phaeochromocytoma, 30% of patients have normal blood pressure between attacks.1 We agree that magnesium sulphate could be a possible alternative treatment option. It has an established role in obstetrics

Ó The Board of Management and Trustees of the British Journal of Anaesthesia 2001

Correspondence

though its use in the treatment of pre-eclampsia is still under debate in the United Kingdom.2 We opted to use the epidural and alpha blockade to control blood pressure. Alpha blockade has been used for the management of the vast majority of pregnant patients with phaeochromocytoma recorded in the medical literature with proven reduction in infant and maternal mortality.3 Magnesium has been used as an alternative to alpha blockade in a small number of reported patients who had been stabilized with alpha blockade pre-operatively. Additional therapy was occasionally needed and magnesium failed to block the catecholamine release in all patients.4 Magnesium has not been shown to be superior to alpha blockade as yet, but we agree that it should be considered as an option. We used alpha blockade because of the reasons outlined above and because of our familiarity with this regimen with non-pregnant patients with phaeochromocytoma. The decision as to the mode of delivery was not easy as both vaginal delivery and Caesarean section had major risks. Resection of the tumour in an unprepared patient at Caesarean section would be dangerous. Thus Caesarean section seemed to have no obvious bene®ts over vaginal delivery, both allowing only the delivery of the baby. As we stated in our report the evidence from the literature after 1980 for one form of delivery over the other was inconclusive for this situation. We had the probability of a short second stage of delivery. After much debate with all concerned, including the patient's wish for a normal delivery, we committed ourselves to a trial of labour, but were prepared to change our plans if necessary. With so few patients diagnosed in active labour it will be dif®cult to scienti®cally answer this debate, but recent practice seems to have moved to allow some patients diagnosed as having a phaeochromocytoma to have a trial of labour. One institution elected to delivery vaginally four of eight patients diagnosed during pregnancy without loss of mother or baby.5 Finally, we would like to agree with Bullough and Watters that early diagnosis is the key to better prognosis and thus we must be watchful for the great mimicÐphaeochromocytoma!

in several settings of cerebral injury (such as head injury and stroke), its value in cardiac surgery remains uncertain. Despite numerous investigations (including our own), the distinct lack of a consistent relationship between S100 and cerebral outcome after cardiac surgery is puzzling. Although late elevation (occurring 24 h or more after surgery) may have a stronger relationship to cerebral outcome, the short term elevations (occurring within the ®rst few hours after surgery) may entirely be due to extracranial contamination. If one accepts that S100 is present in mediastinal tissue and, therefore, in cardiotomy blood returned to the circulation,2 then a link between S100 elevation and cerebral outcome begins to emerge. Cerebral outcome after cardiac surgery has been shown to be related to intra-operative cerebral microembolic load as quanti®ed by transcranial Doppler (TCD).3 We have previously shown that elevations in S100 after cardiac surgery are related to the number of TCD emboli.4 Subsequent to this latter investigation, however, it has been shown that cardiotomy blood itself is a signi®cant source of cerebral microemboli.5 Therefore, if neurological outcome is related to cerebral microemboli, and use of the cardiotomy suction increases microembolic load, and the cardiotomy blood contains S100, then the relationship between S100 and cerebral outcome, although most likely erroneous, becomes entirely plausible. We believe that having a reliable marker for cerebral injury will be of use, possibly for its early diagnosis, particularly when pharmacological neuroprotectants become available, but also in the investigation of neuroprotectants using the marker as an intermediate endpoint in phase II clinical trials. Reducing marker levels (whatever that marker may be) by a drug may be the `proof of principle' that the drug developer needs in order to go forward with a larger, and more expensive de®nitive trial where a clinical outcome is sought. At present, however, we do not believe that there is any current value in S100 as a marker of cerebral injury following cardiac surgery.

A. N. Strachan P. Claydon J. A. Caunt Northern General Hospital Shef®eld UK

H. P. Grocott Department of Anesthesiology Duke University Medical Center Durham North Carolina USA

1 Desmonts JM, Marty J. Anaesthetic management of patients with Phaeochromocytama. Br J Anaesth 1984; 56: 781±9 2 Fawcett WJ, Haxby EJ, Male DA. Magnesium: physiology and pharmacology. Br J Anaesth 1999; 83: 302±20 3 Harper MA, Murnaghan GA, Kennedy L, Hadden DR, Atkinson AB. Phaeochromocytoma in pregnancy. Five cases and a review of the literature. Br J Obstet Gynaecol 1989; 96: 594±606 4 James MFM. Use of magnesium sulphate in the anaesthetic management of phaeochromocytoma: a review of 17 anaesthetics. Br J Anaesth 1989; 62: 616±23 5 Freier DT, Thompson NW. Phaeochromocytoma and pregnancy: The epitome of high risk. Surgery 1993; 114: 1148±52

J. E. Arrowsmith Department of Anaesthesia Papworth Hospital Cambridge UK 1 Shaaban Ali M, Harmer M, Vaughan R. Serum S100 protein as a marker of cerebral damage during cardiac surgery. Br J Anaesth 2000; 85: 287±98 2 Anderson RE, Hansson LO, Liska J, Settergren G, Vaage J. The effect of cardiotomy suction on the brain injury marker S100b after cardiopulmonary bypass. Ann Thorac Surg 2000; 69: 847±50 3 Pugsley W, Klinger L, Paschalis C, Treasure T, Harrison M, Newman S. The impact of microemboli during cardiopulmonary bypass on neuropsychological functioning. Stroke 1994; 25: 1393±9 4 Grocott HP, Croughwell ND, Amory DW, White WD, Kirchner JL, Newman MF. Cerebral emboli and serum S100b during cardiac operations. Ann Thorac Surg 1998; 65: 1645±9 5 Brooker RF, Brown WR, Moody DM, et al. Cardiotomy suction: a major source of brain lipid emboli during cardiopulmonary bypass. Ann Thorac Surg 1998; 65: 1651±5

Serum S100 protein as a marker of cerebral damage during cardiac surgery EditorÐWe read with interest the review of serum S100 protein by Shaaban Ali and colleagues.1 While we wholeheartedly agree with their premise, that identi®cation of a serum marker to assist in the diagnosis of cerebral injury after cardiac surgery is potentially useful, we take issue with their choice of S100 itself. Accepting that elevations of serum S100 levels have been shown to be of some signi®cance in diagnostic and prognostic decisions

EditorÐWe welcome the opportunity to respond to the letter of Grocott and Arrowsmith. The points they raise with regard to extracranial sources of S100b protein are valid, but some

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consideration of the time-scale of S100b protein needs to be taken into account. The biological half-life of S100b protein is less than 1 h.1 Therefore, to avoid extracerebral contamination of S100b samples, proper sampling times should be selected (~2 h after cardiotomy suction or autotransfusion).2 In our review, we explained that the early release of S100b after cardiopulmonary bypass (CPB) is associated with different preand peri-operative events and it is dif®cult to determine the exact cause of its release. In addition, the level of S100b protein at which stroke or any cerebral complication can be diagnosed is not entirely clear. Furthermore, the patterns of S100b protein give little or no information about the anatomical distribution of cerebral injury or its functional impact.3 We agree that neurological and neurophysiological examinations should be considered as the gold standards in assessment of perfusion techniques and neuroprotective drugs. However, S100b protein warrants continuing consideration as an early indicator of cerebral injury, if extracerebral sources are eliminated. In particular, it can be measured at a time when other diagnostic techniques (e.g. neurological and neuropsychological examinations, CT scan, MRI) may not be suitable or are not able to detect such injuries.3 Secondary or late release pattern of S100b protein (15±48 h) in the post-operative period is a sign of further neurological injury,4±6 unless there is ongoing autotransfusion from chest tubes.2 Georgiadis and coworkers found that S100b protein levels at 24 h after CPB surgery have a sensitivity and speci®city of approximately 90% and 97.4%, respectively, in identifying or excluding patients with or without cerebral injury.6 Interestingly, Herrmann and colleagues showed that the most signi®cant time window in which S100b may have a predictive value for diagnosis of neurophysiological and neuropsychiatric impairments is between 6 and 30 h after surgery.7 Moreover, Abdul-Khaliq and colleagues found higher serum concentrations up to 22.5 mg litre±1 at 24 h after CPB in children who had seizures after cardiac surgery.8 These studies6±8 support the importance of the late release pattern of S100b protein in early detection of brain injury in children and adults after CPB. We believe that with proper identi®cation of extracerebral sources, and with better sampling times, S100b protein may be used to differentiate between the bene®ts and adverse effects of different perfusion strategies and neuroprotective drugs. M. Shaaban Ali M. Harmer R. S. Vaughan University of Wales College of Medicine Cardiff UK 1 JoÈnsson H, Johnsson P, Alling C, BaÈckstroÈm M, Bergh C, Blomquist S. S100 b after coronary artery surgery: release pattern, source of contamination, and relation to neuropsychological outcome. Ann Thorac Surg 1999; 68: 2202±8 2 Shaaban Ali M, Vaughan RS, Harmer M. Reply to the editor. Br J Anaesth 2000; 85: 936±7 3 Shaaban Ali M, Harmer M, Vaughan R. Serum S100 protein as a marker of cerebral damage during cardiac surgery. Br J Anaesth 2000; 85: 287±98 4 JoÈnsson H, Johnsson P, Alling C, Westaby S, Blomquist S. Signi®cance of serum S100 release after coronary artery bypass grafting. Ann Thorac Surg 1998; 65: 1639±44 5 Blomquist S, Johnsson P, Luhrs C, Malmkvist G, Solem JO, Alling C, Stahl E. The appearance of S100 protein in serum during and immediately after cardiopulmonary bypass surgery: A possible marker for cerebral injury. J Cardiothorac Vasc Anesth 1997; 11: 699±703 6 Georgiadis D, Berger A, Kowatschev E, et al. Predictive value of S100b and neurospeci®c enolase serum levels for adverse neurologic outcome after cardiac surgery. J Thorac Cardiovasc Surg 2000; 119: 138±47

7 Herrmann M, Ebert AD, Galazky I, et al. Neurobehavioral outcome prediction after cardiac surgery. Role of neurobiochemical markers of damage to neuronal and glial brain tissue. Stroke 2000; 31: 645±50 8 Abdul-Khaliq H, Alexi-Meskhishvili V, Lange PE. Letter to the editor. J Thorac Cardiovasc Surg 1999; 117: 843±44

The carina as a landmark in central venous catheter placement EditorÐThe paper by Schuster and colleagues1 is valuable in de®ning the anatomical relationship of the pericardium to the carina, and by inference to the carina as seen on x-ray. We agree that the ideal placement of a central venous catheter (CVC) tip is in the superior vena cava (SVC) above the pericardial re¯ection. However, the statement that `in all cases, the pericardial sac ends below the level of the carina' applies only to their sample and not necessarily to the underlying population. Their conclusions should be based on estimates of the variability between individuals. We would not be surprised if the carina was occasionally below the pericardial re¯ection in the wider population, but we would like to know how often we might expect it. They report the carina to pericardial distance as a mean, SEM and range. If a normal distribution is assumed (with n = 34 and SEM = 0.1) then the standard deviation of their sample is about 0.6 cm. With this assumption we would expect 95% of the population to fall within the range of ±0.7 cm to +1.5 cm; the negative sign indicating that the carina is below the pericardial re¯ection. It is likely, from the range given (0±2.1 cm) and from anatomical considerations, that the distribution is skewed to the right. If this were the case, the carina would be inferior to the pericardial re¯ection less often than we have assumed. It would be of interest to know whether their results can be transformed to approximate a normal distribution to allow prediction of the chances of the carina lying lower than the pericardial re¯ection. Thus further information would be useful before we rely on this landmark for judging the tip position of CVCs. J. M. Crawford W. G. Hilditch L. C. Chee M. Higney Department of Anaesthesia Western In®rmary Glasgow UK 1 Schuster M, Nave H, Piepenbrock S, Pabst R, Panning B. The carina as a landmark in central venous catheter placement. Br J Anaesth 2000; 85: 192±4

EditorÐWe agree with Crawford and colleagues that further investigations in a larger experimental group would be helpful for a more reliable de®nition of a landmark for central venous catheter placement. Thus, we are planning to investigate more corpses in this aspect. Furthermore, we are interested in any anatomical changes in the elderly compared with younger adults, or in adolescents and children. M. Schuster H. Nave S. Piepenbrock R. Pabst B. Panning Hannover Germany

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Safe placement of central venous catheters EditorÐI welcome the advice given by both groups of authors regarding the placement of central venous catheters.1 2 The articles highlight concerns surrounding the risks of perforation of the cardiac chambers and great veins resulting from poorly positioned catheters and suggest various sites for correct catheter tip placement. I feel both groups have failed to mention one simple and practical problem. Many central venous catheters are inserted by junior doctors who, particularly those from specialities outside of anaesthesia, ®nd it necessary to insert the entire length of the catheter, irrespective of the route of insertion. As many hospitals only stock 20 cm catheters as standard, this will inevitably give rise to some of the complications outlined in the articles. If hospitals were to make 15 cm catheters more widely available, this would overcome two particular problems. First, that of catheter tip position. By using shorter catheters, the likelihood of the tip lying in an unsatisfactory position must be less, although we must not detract from trying to achieve the ideal (whatever position that might be). Second, a shorter catheter alleviates the frustrating need to create ingenious loops of redundant catheter around the insertion site. I have not found the clip-on ®xation devices to be particularly helpful, and it is not uncommon for patients or staff to hook a digit under the loop and inadvertently remove the catheter. In addition, it is well recognized that poor ®xation allows excessive mobility at the insertion siteÐthis increases the risk of perforation by the catheter tip and development of infection at the skin site. I feel we need to alert hospitals and doctors to provide and use the correct tools for the job. Most manufacturers will supply 15 cm central venous catheters. The 20 cm catheters are unnecessary for the great majority of patients and yet we persist in using them. J. M. Cupitt Department of Anaesthesia Manchester Royal In®rmary Manchester, UK 1 Fletcher SJ, Bodenham AR. Safe placement of central venous catheters: where should the tip of the catheter lie? Br J Anaesth 2000; 85: 188±91 2 Schuster M, Nave H, Piepenbrock S, Pabst R, Panning R. The carina as a landmark in central venous catheter placement. Br J Anaesth 2000; 85: 192±4

EditorÐWe would concur with Dr Cupitt's comments on the availability and use of 15 cm central venous catheters. It is important, however, that catheter selection is appropriate to the proposed route of insertion. For instance, the tip of a 15 cm catheter fully inserted via the left internal jugular approach might abut the wall of the superior vena cava (SVC) and be at high risk of perforation, whereas a similarly inserted 20 cm catheter would pass down the SVC such that the tip is coaxial with the vessel. This raises the wider issue of training in central venous catheterization and the question of whether occasional practice is justi®able. Two logical conclusions might be for anaesthetists to play a greater role in hospital-wide training in vascular access or that anaesthetists should provide all central venous access. Clearly, both options would have huge implications for the workload of anaesthetic departments. S. J. Fletcher A. R. Bodenham General Intensive Care Unit Leeds General In®rmary Leeds, UK

Dif®cult intubation in a patient with benign masseteric muscle hypertrophy EditorÐI wish to report a case of benign masseteric hypertrophy in a patient who presented as a day case for routine dental surgery and who was predicted to be a dif®cult intubation requiring awake ®breoptic intubation. Benign masseteric hypertrophy is a rare condition, usually of unknown aetiology, in which there is unilateral or bilateral hypertrophy of the masseter muscle. This case illustrates that the condition may produce dif®cult conditions for tracheal intubation. A 46-yr-old Caucasian, male patient was scheduled for an extraction of the lower right wisdom tooth under general anaesthesia. Anaesthetic assessment revealed a ®t male with no signi®cant past medical history, although his ®rst words were `Doctor, you are going to have problems with me!' His dentist had warned him that his airway was potentially dif®cult for the anaesthetist. He had benign masseteric hypertrophy with extremely limited mouth opening causing problems in eating; he had to cut food into very small pieces to ®t into his mouth. He was a non-smoker, on no medication and had no allergies. Physical examination was unremarkable, except for his airway. Routine pre-operative assessment showed limited mouth opening of 1±1.5c cm which was a grade IV in Mallampati's modi®ed classi®cation.1 2 The surgical team thought local anaesthesia was not an option as access would be dif®cult, and it was assumed that some relaxation would occur under general anaesthesia. The patient was fully informed of the problems relating to his case and that the safest option was to proceed with an awake ®breoptic intubation. This technique was explained to him in detail. The patient was co-operative and agreed to the procedure. He was unpremedicated and in the anaesthetic room, standard monitoring was commenced (ECG, pulse oximetry, and non-invasive blood pressure). Intravenous access was obtained and glycopyrronium 0.2 mg was given as an antisialogogue. Sedation was given in increments to a total of midazolam 2 mg and fentanyl 20 mg intravenously. Topical anaesthesia of the nasal passages was achieved using a combination of 1.0 ml of topical 4% lidocaine (diluted to 2% with 0.9% saline), injected into each nostril. Into the left nostril three cotton buds impregnated in 5% cocaine was also inserted for 10 min. For the oral cavity, 5 ml of 2% lidocaine gel were given and the patient was asked to move it around in his mouth for two min and then to swallow it. The procedure was then repeated. A cricothyroid puncture was performed using a 22 G cannula inserted through the cricothyroid membrane. Injection of 1.5 ml of a mixture containing 3 ml of topical 4% lidocaine (diluted up to 5 ml with 0.9% saline) was performed at the end of a deep inspiration, and repeated once. After checking for adequate anaesthesia, a 6.5 mm internal diameter reinforced tracheal tube was inserted under ®breoscopic guidance through the left nostril without problems. On con®rmation of tracheal placement using the capnograph, anaesthesia was induced with an intravenous bolus of propofol 2.5 mg kg±1, vecuronium 0.1 mg kg±1 was given and anaesthesia was maintained with oxygen in air and iso¯urane 1±2%. Direct laryngoscopy was performed at this point. The mouth opening had not improved; laryngoscopy was very dif®cult being a grade 3 in Cormack and Lehane's classi®cation3 with a downward pointing epiglottis. For analgesia, fentanyl 100 mg, and morphine 5 mg were given with diclofenac 100 mg administered rectally. Consent had been obtained pre-operatively for the suppository. Surgical access to the tooth proved extremely dif®cult but enough mouth opening was achieved for the tooth to be removed. Local in®ltration with 5 ml of 0.5% bupivacaine was done by the surgeon to help with post-operative pain relief. Residual muscle relaxation was reversed after 50 min with neostigmine 2.5 mg and glycopyrronium 0.5 mg and the patient was fully awake within 10 min, still

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with the tracheal tube in place. He was extubated and sent to recovery without any further problems. Post-operatively, he was advised to join the Medic-Alert scheme, and always to warn anaesthetists of this problem. Three weeks later, the patient was reviewed in the surgical clinic with no problems except for limited mouth opening that was unchanged. Masseteric muscle hypertrophy is a clinical condition in which there is an increase in the size of the cells and an overall enlargement of the muscle itself. The condition usually occurs in late adolescence and is more common in males than females.4 The aetiology of the condition is unexplained. The acquired enlargement represents work hypertrophy, most frequently following clenching, bruxing during sleep, and constant gum chewing. It is often associated with dental wearing. A congenital variety also exists, but it is far less common.4 5 7 The main complaint is of an unwanted cosmetic appearance due to facial asymmetry (unilateral) or too broad a face (bilateral), the so-called `masseteric look'.4 5 Some individuals also complain of pain, usually of a mild nature, or some limitation of mouth opening.5 The diagnosis of this condition is based on awareness of the existence of this pathology, the clinical and radiographic ®ndings, and exclusion of more serious pathology.6 Our patient had the typical `masseteric look' (Fig. 1) of this condition, but the clinical complaints were atypical. He did not have any cosmetic complaint nor any pain or discomfort. The main problem was of severe limitation of mouth opening which made simple tasks such as eating very laborious (Fig. 1b). The mild discomfort was associated with repeated in¯ammation of his infected wisdom tooth. The main issue for anaesthesia was the severe limitation of mouth opening. A literature search did not reveal any previously reported cases of severely limited mouth opening with dif®cult intubation in patients with masseteric muscle hypertrophy. We thought that the limitation of mouth opening may be due to a degree of trismus caused by in¯ammation of the repeatedly infected tooth. However, general anaesthesia and muscle relaxation failed to produce any improvement. Post-operatively, the patient had the same limitation of mouth opening and was still a grade IV on the modi®ed Mallampati's classi®cation. The severe

limitation of mouth opening was an intrinsic characteristic of his masseteric muscle hypertrophy syndrome. L. F. Jimenez Princess of Wales Hospital Bridgend Wales 1 Mallampati SR, Gatt SP, Gugino LD, Desai SP, Waraksa B, Freiberger D, Lin PL. A clinical sign to predict dif®cult intubation: a prospective study. Can Anaesth Soc J 1985; 32: 429±34 2 Samsoon GLT, Young JRB. Dif®cult tracheal intubation: a retrospective study. Anaesthesia 1987; 42: 487±90 3 Cormack RS, Lehane J. Dif®cult tracheal intubation in obstetrics. Anaesthesia 1984; 39: 110-5±11 4 Rosa RA, Kotkin HC. That acquired masseteric look. J Dent Child 1996; 63: 105±7 5 Roncevic R. Masseter muscle hypertrophy: aetiology and therapy. J Max-Fac Surg 1986; 14: 344±8 6 Addante RR. Masseter muscle hypertrophy: report of case and literature review. J Oral Maxillofac Surg 1994; 52: 1199±202 7 Mandel L, Tharakan M. Treatment of unilateral masseteric hypertrophy with botulinum toxin: case report. J Oral Maxillofac Surg 1999; 57: 1017±19

Internal jugular venous cannulation complicated by J-tip guide wire entrapment EditorÐWe report an unusual complication of internal jugular venous cannulation with a J-tip guide wire. A 62-yr-old female patient was admitted to the coronary care unit after an episode of central chest pain and dizziness. Acute myocardial infarction was diagnosed. She had a past medical history of rheumatoid arthritis, osteoporosis and kyphoscoliosis of the thoracic spine with chronic obstructive pulmonary disease. She was hypotensive on admission with a blood pressure of 85/51 mm Hg, and oliguric. Central venous

Fig 1 The patient's limited mouth opening (B) compared with the closed state (A), is apparent.

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introduction of an excessive length of guide wire during placement of central venous catheters through the internal jugular vein can result in rare but signi®cant complications. In most cases, 18 cm should be considered the upper limit of safe guide wire length to be introduced in adults.4 M. Mastan P. R. Clothier B. Ousta U. Deulkar Tameside General Hospital Ashton-Under-Lyne Lancashire, UK 1 Wang LP, Einarsson E. A complication of subclavian vein catheterisation. Extravascular knotting of a guidewire. Acta Anaesthesiol Scand 1987; 31: 187±8 2 Wang HE, Sweeney TA. Subclavian central venous catheterization complicated by guidewire looping and entrapment. J Emerg Med 1999; 17: 721±4 3 Kjeldsen L. Transvenous misplacement and loop formation of spring guide wire. Anaesthesia 1987; 42: 216±7 4 Andrews RT, Bova DA, Venbrux AC. How much guide wire is too much? Direct measurement of the distance from subclavian and internal jugular vein access sites to the superior vena cava±atrial junction during central venous catheter placement. Crit Care Med 2000; 28: 138±42

Fig 1 Close up view of entrapped guide wire.

cannulation of the right internal jugular vein was planned by an experienced physician. A pre-packaged Seldinger-type triple lumen kit (Hydrocath-Becton Dickinson critical care system plc Ltd) was used. It consisted of a catheter 7Fr/2.4 3 200 mm (16G:18G:18G), a J-tip guide wire 0.9 3 700 mm, introducers 1.4 3 70 mm, and 1.7 3 70 mm, and a dilator (8Fr). The procedure was explained to the patient by the doctor. Under aseptic conditions and after con®rming the landmarks, the physician inserted the introducer needle and achieved good venous return. The guide wire was inserted with minimal resistance up to 25 cm. The triple lumen catheter was then inserted, but the guide wire could not be removed despite several attempts with gentle traction. A portable chest x-ray was obtained and revealed looping of the guide wire (Fig. 1). A consultant surgeon was called and the patient was taken to the operating theatre for surgical removal of the looped guide wire. Exploration showed that the guide wire had passed through the anterior wall of the internal jugular vein into the extravascular space, and coiled up in the sternocleidomastoid muscle and subcutaneous tissue. The guide wire was removed uneventfully. The placement of central venous catheters is a technically challenging procedure with known risks and complications. The majority of the complications are preventable if adequate precautions are taken. Complications may involve inserting the needle, the guide wire, the dilator, or the catheter. The performing physician's skill also plays an important role. Although catheter looping and knotting are well recognized as complications of central venous catheterization, there are few reports of guide wire looping, knotting or entrapment.1 2 In the case report by Wang and Sweeney, a straight and relatively stiff solid core guide wire without a J-tip may have been an aggravating factor in causing guide wire looping and entrapment.2 But Kjeldsen reported a case of transvenous misplacement and loop formation of a relatively ¯exible spring guide wire. The author suggested that occlusion due to thrombosis in the vessel wall might explain the ease with which the soft end of the wire had pierced the vessel.3 In this report, we hypothesize that the guide wire, after entering the internal jugular vein, might have pierced the wall of the vein and gained access to the extravascular space. Altered landmarks due to kyphoscoliosis might have contributed to the complication described. Wang and Sweeney suggested that `if a J-tip guide wire is not used, particular attention should be given to the risk of the guide wire lodging against or perforating the vessel wall'.2 The

A handmade device for dif®cult intubation EditorÐWe read with interest the case report by Tashayod1 describing two cases of dif®cult intubation managed by a handmade cuffed pharyngeal tube (CPT). We attempted to construct the device using the components and technique described and found it not only dif®cult to make but also, and more importantly, unreliable in cuff in¯ation. We fully appreciate the issues of cost and availability of the equipment designed to manage the dif®cult airway and/or intubation but wonder if we would feel comfortable relying on the CPT in such circumstances. Having ascertained the potential design faults, we would like to raise the issue of its use in the two cases of dif®cult airway/ intubation. Whilst again acknowledging differing techniques, in the discussion it is stated that `when a dif®cult airway is suspected spontaneous respiration should be maintained', and yet this principle is not followed in either case. The technique of intravenous induction with muscle relaxation in these particular patients is potentially dangerous and despite the success in maintaining an airway perhaps some fundamentally safer techniques should have been mentioned, albeit brie¯y, in a journal read by trainers and trainees alike. S. Carroll E. J. Williams Department of Anaesthesia St. George's Hospital London UK 1 Tashayod ME. Two cases of dif®cult intubation managed by a handmade device. Br J Anaesth 2000; 85: 626±8

EditorÐTashayod1 describes a novel `hand-made' airway aid (the cuffed pharyngeal tube, CPT) which it is claimed is readily constructed with available materials (a tracheal tube and surgical glove) and of use for the patient with a dif®cult airway and/or

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Correspondence

intubation. It may indeed be the case that this device has a role in airway management, although probably very similar to the laryngeal mask airway (LMA²), and will certainly require extensive validation. Of more immediate concern are the techniques of airway management outlined in the two case reportsÐI believe the management strategies were wrong and, especially in the ®rst patient, were probably dangerous. Case 1 was a large, muscular athlete of 116 kg. He had a `bushy beard' and was graded a Mallampati 4 prior to anaesthesia. He also had a known history of dif®cult intubation. After induction of anaesthesia and administration of a muscle relaxant, the patient was found not only dif®cult to mask ventilate but had an `immobile' jaw and `head extension was impossible'. Laryngoscopy was a grade 3 to 4 and as part of the planned procedure (for which the author had consent) the CPT was used as the airway of choice. This patient showed multiple warning signs of a dif®cult intubation from his general build to more formal assessment and inability to perform laryngoscopy must have been almost certain.2 Furthermore, there would be a strong suggestion of dif®cult mask ventilation and therefore a technique of inducing anaesthesia and administering a muscle relaxant risks both being unable to intubate and losing the airway. To rely on an experimental device with no robust ®eld testing in elective cases (let alone a dif®cult airway) must be questioned and having lost the patient's airway in this manner what was the next option? `Plan A doesn't kill people, it is the lack of plan B'. In case 1, plan A was highly questionable and I cannot see where plan B would come from. Case 2 must also be examined critically (as the author does during the discussion) where a patient in cervical `halo' traction for surgical cervical fusion was induced and given succinylcholine 100 mg. Laryngoscopy `was dif®cult' and a further dose of muscle relaxant (pancuronium 6 mg) was given to facilitate further attempts at laryngoscopy (unsuccessfully) and then the CPT was used successfully. Again a dif®cult airway must have been expected in this patient3 but I fail to see the rationale behind the use of a longacting relaxant when an optimal dose of succinylcholine failed to provide the required conditions. Pancuronium, in any dose, would not have improved the view, increased the risk of losing the airway irreversibly, and must have encouraged repeated laryngoscopy risking airway trauma and hypoxaemia. I would hold that there was one optimal management of both these dif®cult airwaysÐand it is neither a new nor original technique. Both these patients should have had awake ®breoptic intubations, with no relaxant given until the airway is secure. It is hard to argue otherwise (with the possible exception of a spontaneously breathing gas induction)Ðand one should have strongly considered a regional technique for Case 1, who was to have hand surgery. The use of a non-validated `home made' airway in cases of anticipated dif®culty cannot be justi®ed and

²

raises serious questions over how informed the Case 1 `consent' must have been. Guidelines over airway management are readily available4 5 and have widespread supportÐit is disappointing to see clinicians exploring dubious and probably dangerous techniques for no clear reason or bene®t. C. Morris Craigavon UK 1 Tashayod ME. Two cases of dif®cult intubation managed by a handmade device. Br J Anaesth 2000; 85: 626±8 2 Cobley M, Vaughan RS. Recognition and management of dif®cult airway problems. Br J Anaesth 1992; 68: 90±7 3 Crosby ET, Lui A. The adult cervical spine: implications for airway management. Can J Anaesth 1990; 37: 77±93 4 American Society of Anesthesiologists. Practice Guidelines for Management of the Dif®cult Airway. Anesthesiology 1993; 78: 597±602 5 Benumof JL. Management of the dif®cult airway. Anesthesiology 1996; 84: 1087±1110

EditorÐI appreciate the concerns of Carroll and Williams, and Morris regarding my recent case report. I was delighted to learn that the principle of the CPT has not been criticized. I agree with the authors that the construction of the CPT with its asymmetric cuff is sophisticated. When the project started I had much dif®culty in obtaining the desired con®guration. But it was worthwhile in order to make a cost-free, hand-free, and ef®cient adjunct to manage `The expected cases of dif®cult intubation'. Surprisingly, the CPT has proved to be effective even when its con®guration is not ideal; its pharyngeal ring is useful in management of the dif®cult airway. I hope that the CPT will be produced commercially in the near future. In regard to our anaesthetic technique, we do not have the privilege of working with the newer intravenous and inhalational drugs available in some countries. However, in our ®rst case I do not think that repeated administration of intravenous agents with close control of the state of consciousness and two injections of gallamine 40 mg would stop spontaneous respiration in a 116 kg muscular man. The use of a large dose of relaxant in the second case was, in retrospect, inappropriate. This case was included as it represents a case of `unexpected dif®cult intubation' where the ease of insertion, ef®ciency and ready availability of the CPT promises a new option. M. E. Tashayod Mehr General Hospital Zartosht Street Tehran Iran

LMAq is the property of Intavent Limited.

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British Journal of Anaesthesia 87 (2): 295±7 (2001)

Book Reviews The Brain and Cardiac Surgery. Causes of Neurological Complications and their Prevention. Stanton P. Newman and Michael J.G. Harrison with David A. Stump, Peter Smith and Ken Taylor (editors). Published by Harwood Academic Publishers. Pp. 343; indexed; illustrated. Price £70. ISBN 90-5702-476-4. This is a timely book which discusses all forms of neurological damage following cardiac surgery. It is a multi-author volume with over 40 contributors from the UK and USA, the majority of whom are well-known experts in their ®elds. The principal editors are internationally renowned for their investigation into cerebral complications following cardiac surgery. The text covers, in 17 chapters, the main topics of: the nature of the problem, monitoring and mechanisms of cerebral injury, surgical and anaesthetic practice, and special problems. This ®nal section contains chapters discussing cerebral damage relating to heart transplantation and paediatric cardiac surgery. The latter chapter by Richard Jonas of Boston Children's Hospital describes succinctly seminal work carried out at that institution which has helped de®ne the causes of neurological injury during cardiopulmonary bypass in children, thereby improving their intraoperative management. Each chapter in the book is designed to be read independently. As a result there is considerable overlap of material between some chapters. This can be regarded as a bene®t to the reader in a reference book of this calibre, because more than one viewpoint is expressed on dif®cult or controversial topics. It is dif®cult to pick out highlights from this book as the chapters are of a uniformly high standard and profusely referenced. The introductory chapters by the main editors Stanton Newman and Michael Harrison, however, are very well constructed and easy to read. I particularly enjoyed the section on peripheral nerve damage in chapter 2 as this is a subject largely neglected in the context of neurological damage following cardiac surgery. The chapter on neuropsychological outcome puts a dif®cult subject into perspective and explains the evaluation and the methodological issues surrounding these assessments in a straightforward and understandable manner. Topical subjects covered extensively in the book include embolic damage, acidbase management in adults and children, over-heating of the brain and the pre-operative risk assessment of patients. In general I have few criticisms of the book. It does not contain a great deal of material covering `off-pump' cardiac surgery and the hazards of blood and platelet transfusion in the context of cerebral damage. This is perhaps not surprising, in view of the gestation period of a book of this nature, as `off-pump' cardiac surgery is still in its infancy and there is little detailed information regarding its effects on the brain. This book will be of interest to all those involved with patients undergoing cardiopulmonary bypass, particularly as cerebral injury remains a major cause of death and disability following cardiac surgery. It should be available in the library of all cardiac units and accessible to both cardiac surgeons and anaesthetists in training. At the listed price, this well-produced book is good value for an individual consultant cardiac surgeon and anaesthetist to buy for their personal use. It will save the endless hours searching the past literature and provide a sound basis for an understanding of future publications on the subject of brain injury in cardiac surgery. J. Gothard London

Regional Analgesia in Obstetrics: A Millennium Update. Felicity Reynolds (editor). Published by Springer-Verlag, London. Pp. 395; indexed; illustrated. Price £50. ISBN 1852332808. Soon after the formation of the Obstetric Anaesthetists Association 30 years ago, Andrew Dougherty hosted a meeting at Kingston-upon-Thames where a group of obstetric anaesthetists met to extol the virtues of epidural analgesia for labour pain. The late Professor Utting reported the proceedings in the following terms: `it would have been a brave man who had mistakenly got up and shouted that epidural analgesia was bunk; one could only pray that his end would be mercifully swift'. Since then regional anaesthesia in obstetrics has come of age and in this book, the fourth in a series of 10 yearly reviews, Professor Reynolds has called upon an impressive group of luminaries to produce a most scholarly and scienti®c text. In the ®rst section of the book contributors from many parts of the world provide a fascinating and rather disturbing insight into the varied obstetric and anaesthetist practices prevailing in their respective countries with the ability to pay, in many cases, seemingly the most important determinant of the quality and type of care. The large remainder of the book has a very strong British ¯avour in which new techniques, drugs, indications, and complications together with research methods, medical legal aspects, and issues of consent are fully discussed. With few exceptions the chapters are models of clarity, brevity and authority; none more so than those contributed by the editor herself. Most are strongly evidence-based with abundant relevant and up-to-date references but where such evidence is lacking very sensible and clinically sound recommendations are offered. The quality of editing is very high. Tables which are always adjacent to the relevant text are widely used making complex data easily understood. There is surprisingly little repetition, and I was proud to discover one printing mistake. This book is a testament to the high standard of obstetric anaesthesia in the UK with its maternal mortality at an almost irreducible low. The vast majority of procedures are now performed under regional anaesthesia for which there appears to be very few contraindications; fears of long-term backache and neurological damage have proven unfounded. We are reminded, however, that accidental dural puncture remains a serious problem, that epidural analgesia for labour still requires expert and attentive midwifery management, and that Tuf®ers line must be respected when using atraumatic spinal needles, if conus damage is to be avoided. The quality of contributions to this ®ne book is a ®tting tribute to the editor's own enormous scienti®c and practical contribution to the specialty. No self-respecting obstetric anaesthetist should be without it. R.G. Wilkes Liverpool Problems in Anesthesia, volume 12 number 2, April 2000. J.M. Neal, M.F. Mulroy and S.S. Liu (editors). Published by Lippincott, Williams and Wilkins, London. Pp. 232; indexed; illustrated. Price US$63. ISSN 0889-4698. Problems in Anesthesia is a quarterly American publication under the editorship of Drs Fleisher and Prough. It has ten chapters written by a total of 19 authors on various aspects of regional anaesthesia. It aims to centre around controversies, dif®culties and state of the art developments of the craft. Being a slim book, it

Ó The Board of Management and Trustees of the British Journal of Anaesthesia 2001

Book Reviews

carries easily and every word of it can be read in not many sittings. The ®rst three chapters are about upper limb, lower limb, and neuraxial blockade respectively and each gives a discourse on standard techniques and their problems. There is repetition of various topics and even then, authority is lacking in the answers to some questions. An example is the use of vasoconstrictors in local anaesthetic solutions. Perhaps this might have been better dealt with as a speci®c chapter or section on its own with a comprehensive literature reviewÐthe reader is left with no clear message about the question of bene®t or risk using vasoconstrictor additives. This reviewer was puzzled by the title choice of chapters four and ®ve: `Regional Anesthesia for Ambulatory Surgery' and `Of®ce Based Regional Anesthesia'. There is no clear de®nition or differentiation of these in the text and a considerable overlap occurs. Surely they would have been better united as one chapter. Specialized practice within regional anaesthesia is covered in separate chapters on `Acute Pain Management' and `Obstetric Anesthesia'. The former concentrates on neuraxial opioids with and without the addition of a long-acting local anaesthetic. It touches on multimodal techniques for pain control and accelerated recovery regimens designed to minimize GI paresis and promote early voluntary musculoskeletal activity. The obstetric chapter con®nes itself to the possible link between neuraxial blockade and maternal fever and neonatal sepsis. Also discussed in this chapter are combined spinal epidural techniques and, as a separate section, how to deal with the morbidly obese parturient. Obesity is a more frequent phenomenon in North American medicine than elsewhere. The last three chapters delve into `Outcome and Effectiveness', `Neurologic Complications' and `Toxicity of Agents'. In Neurologic Complications there is a section on the hazards of low molecular weight heparin. It would have been helpful to specify and reference the `European experience on the treatment (with LMWH) of patients undergoing spinal and epidural blocks'. There is minimal reference throughout the book to the literature outwith North America nor many references later than 1997. Discussion on sterility and asepsis in the performance of neuraxial blocks would have bene®ted from reference to worldwide publications on these issuesÐin particular the wearing of face masks. There is no discussion on skin preparation. The controversy of regional anaesthetic techniques performed on anaesthetized or heavily sedated patients is debated in the context of North American rather than world literature. The reader is left without a clear message on the fundamental issue of risk versus bene®t in the practice of regional anaesthesia which is disappointing in a text compiled by invited experts. A previous review in the series concluded `this is not a textbook for the trainee, neither is it a comprehensive reference book for the practising anaesthetist'. The same is true here though in fairness, for some of the problems, there are as yet no satisfactory answers and the editors have at least attempted to communicate the questions. The preface states that the monograph `aims to provide a state of the art view of regional anesthesia and analgesia'. Though I think this has been partly achieved in an elegant production, there are some points of view which would stimulate debate outwith North America. It is an interesting read for anyone who practises regional anaesthesia. I. Levack Dundee Sex, Gender and Pain. R.B. Fillingim (editor). Published by IASP Press, Seattle. Pp. 393; indexed. ISBN 0-931092-35-3. This excellent book is another in the series from the International Association for the Study of Pain (IASP) Press on Progress in

Research and Pain Management. It ful®ls the mission statement of the organization in that it provides a timely, high quality, low cost publication about a current pain problem. During the 1990s, there has been increased interest in the in¯uence of sex and gender on pain. There have been National Institute of Health initiatives and conferences about this important topic. There is now an IASP special interest group on sex, gender and pain. Roger Fillingim who is a recognized expert in the ®eld edits this book. The text brings together basic scientists and clinicians who explore the mechanisms and clinical importance of sex and gender differences in pain. There is something in this book to interest everyone. The text asks as many questions as it answers and gives many ideas for future research. The multi-factorial nature of the in¯uence of sex and gender on pain is a recurrent theme, which involves the interaction of biological and psychological factors. This book is divided into four parts. Section I covers basic considerations for sex, gender and pain research. It has four chapters with a good mix of laboratory-based and biopsychosocial topics. Section II, on sex-related differences in experimental pain responses, has seven very good chapters covering diverse areas. The chapters on visceral pain by Maria Giamberardino, and sexrelated analgesic responses by Christine Miaskowski and colleagues were particularly good. Section III covers sex-related factors in clinical pain conditions. It has six chapters covering epidemiology, headache, ®bromyalgia, TMJ pain, IBS, and female genital pain. The ®nal section IV was a single chapter by Karen Berkley on male versus female pain. This provided an excellent summary of current knowledge and ideas for the future. This book is a must have for all departments and individuals involved in the study and management of pain. It supports the notion that men may be from Mars and women may be from Venus after all! K.H. Simpson Leeds Hypertext Book of Pulmonary Artery Catheterization, on CDROM. D.A. Pybus. Published by D.A. Pybus, Kogarah, Australia. Price Aus$50. Dr Pybus and two colleagues, cardiac anaesthetists from Sydney, Australia, have created an excellent resource for anyone involved with pulmonary artery (PA) catheters. Much of the information is relevant to central venous catheters as well. In some ways the title of the CD-ROM is misleading, because not only is the text comprehensive and extremely well referenced, but they also include both a simulator that allows users to experience the problems and pitfalls of insert PA catheters and an interactive model of cardiorespiratory physiology. Although aimed primarily at those new to the subject, there is much for even the advanced practitioner. The CD-ROM is compatible with Windows 98, Windows NT 4.0 and Windows 2000. The author states that it may run on Windows 95, but we have experienced problems when trying to do so. The hypertext format allows users to navigate easily through the 40 text chapters, as with a conventional book, but in addition provides links to over 100 illustrations, four computer videos and over 300 references. Placing the pointer over a reference number causes the reference to `pop up', whilst clicking on a ®gure reference opens the picture in a new window. Speci®c keywords are highlighted; clicking on these takes the reader to a relevant chapter or page of further discussion. Navigation through the book is by `point and click' and by means of forward, back and `retrace' buttons. 15 MB of hard drive space is required, with the videos running direct from the CD drive. At present the book runs in a speci®c hypertext window; however the author is planning a web-browser based version, which should be more familiar to the internet literate.

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Book Reviews

The hypertext book covers all aspects of PA catheter usage, with detailed descriptions of insertion techniques using pictures from the `sectioned human' projects and video clips. The depth of the work is evidenced by the inclusion of such details as a description of the pressure waveform should the catheter enter the coronary sinus. There is also a page listing the cognitive skills that are deemed necessary for the use of PA catheters, which will be of use to those designing teaching programmes. The authors explore the controversy surrounding the use of PA catheters and include a section on evidence-based practice. The discussion is comprehensive and well referenced though the authors' (understandable) bias in favour of PA catheters is obvious, particularly when they address the `pros' and `cons' of the PA catheter compared with other forms of haemodynamic monitoring. The chapter on complications is wide-ranging and upto-date. The authors go beyond the insertion techniques and complications, exploring cardiorespiratory physiology and pharmacology. This is where the computer simulation comes into its own. The user manipulates a virtual PA catheter by means of buttons controlling balloon in¯ation and catheter advancement. `Real time' ECG and pressure waveforms react appropriately. Although the graphics are not state of the art, they are realistic enough to give one that sinking feeling when an arrhythmia occurs. At this point, the de®brillate button becomes useful! The model is intelligent and prompts users when errors are being made; for

example, withdrawing the catheter with the balloon in¯ated. To complement the physiological information, another window reveals the path of the PA catheter superimposed on a chest radiograph. The model can simulate not just the normal patient but also pathological states such as pulmonary hypertension and acute myocardial infarction. The user can adjust the propensity to arrhythmias during insertion. The cardiorespiratory model permits an exploration of oxygen delivery and consumption, for example the degree of shunt can be altered and the effect on arterial oxygenation seen. In addition, there is an interactive model of the haemoglobin dissociation curve which permits the effect of changes in pH and PaCO2, for example, to be studied. Overall, we have no hesitation in recommending this CD-ROM to individuals and institutions. Learning resources such as this probably represent the future of medical education and one can foresee a time when their use would be required before trainees are allowed to carry out procedures in real life. What might be useful would be the purchase of `institutional licenses' where a larger fee would permit copies to be made and allow widespread usage within a department, single copies are likely to be `borrowed' and never seen again! Up-to-date information on this product can be found at www.manbit.com S.J. Fletcher A.R. Bodenham Leeds

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