Conscious Sedation and General Anesthesia Techniques ... Section of Anesthesia, University of Southern California, School of Dentistry, Los Angeles, CA.
Conscious Sedation and General Anesthesia Techniques and Drugs used in Dentistry Stanley F. Malamed Section of Anesthesia, University of Southern California, School of Dentistry, Los Angeles, CA
The dental profession has a variety of routes of administration available to it through which medications may be given to aid in the management of a patient's pain, fear, and anxiety toward dentistry. This paper will review briefly the most commonly used routes of administration and agents which are most frequently employed, stressing the advantages and disadvantages of each, and attempt to place each technique into an overall spectrum of pain and anxiety control. I must start by first defining several oft misunderstood terms: conscious sedation, deep sedation, and general anesthesia. Sedation describes a depressed level of consciousness, which may vary from light to deep. At light levels, termed conscious sedation, the patient retains the ability he or she had before sedation to independently maintain an airway and respond appropriately to verbal command. The patient may have amnesia, and protective reflexes are normal or minimally altered. In deep sedation, some depression of protective reflexes occurs, and although more difficult, it is still possible to arouse the patient. General anesthesia describes a controlled state of unconsciousness, accompanied by partial or complete loss of protective reflexes, including the inability to independently maintain an airway or respond purposefully to verbal command. With these definitions in mind, it must also be remembered that the drugs employed to produce these effects are central nervous system (CNS) depressants which produce a progressive dose-related continuum of effects from light sedation potentially through general anesthesia. All techniques of drug administration have advantages and disadvantages, as do all of the medications which are employed to reach these levels of altered consciousness. There is no technique of drug administration, nor is there any medication which is entirely free of risk. Therefore, the benefits to be gained through the use of a drug or technique must always be weighed against the potential risk to the patient receiving these drugs and techniques. In all situations the most controllable technique which will accomplish the desired therapeutic goals should be selected. If possible, as is often the case, a nondrug 176
technique of sedation should be selected. These techniques, such as iatrosedation and hypnosis, maintain an important role in the overall management of patients' dental fears and anxieties. The oral route of drug administration is probably the simplest to employ. The doctor prescribes a drug to the patient to be taken about 1 hour prior to the start of dental treatment. Easy to do, well accepted by most patients, inexpensive, and relatively safe, the oral route has several significant disadvantages including: slow onset of action, inability to titrate proper dose, and inability to readily lighten or deepen clinical effect. Yet, when employed rationally for the relief of preoperative anxiety, the oral route is an extremely valuable adjunct to other techniques. For the adult patient, the most highly recommended group of drugs for the relief of mild to moderate anxiety today is the benzodiazepines. Included in this group of agents are diazepam (Valium) and chlordiazepoxide (Librium). Other more recent additions to this group which are especially valuable for adult patients are: flurazepam (Dalmane) and triazolam (Halcion) for nighttime sedation and management of moderate anxiety, and oxazepam (Serax) for preoperative anxiety control. In the pediatric population there remains a group of drugs used either singly or in various combinations which retain a valuable place in the antianxiety armamentarium: chloral hydrate, promethazine (Phenergan), and hydroxyzine (Atarax, Vistaril). Unfortunately, the oral route is not controllable enough to safely permit the more profound levels of sedation required for the management of the extremely fearful patient, especially the pediatric patient. In order to achieve success in this area the pediatric dentist (as well as a few dentists treating adults) employ parenteral drug administration techniques, either intramuscular (IM) or submucosal (SM) injections. Most drugs are absorbed more reliably and more rapidly via these routes than following oral administration, however the onset of action (approximately 10 minutes) is too slow to permit accurate titration to be accomplished, and the duration of action is too long to permit the patient to be discharged from the office unescorted. ANESTHESIA PROGRESS
Rarely indicated for use in adult patient, other more controllable techniques are available, the IM and SM routes are reserved almost exclusively for the uncooperative pediatric patient, and therein lies a problem. The drugs most often employed via these routes to quiet the unmanageable child are those which produce a greater degree of CNS depression: the narcotic agonists. These agents, which include meperidine (Demerol) and alphaprodine (Nisentil) usually do a very good job at providing clinically acceptable levels of sedation (as well as providing varying degrees of analgesia). Unfortunately, hand in hand with the sedative properties of these drugs is observed a dose-related respiratory depression. Lack of adequate monitoring of the pediatric patient during sedation (i.e., precordial stethoscope, pulse oximeter) has led to too many serious morbidities and mortalities and to significant legal repercussions. Goodson and Moore presented an excellent, yet chilling recounting of 14 cases of morbidity or mortality associated with pediatric sedation.' As these techniques (IM, SM) of sedation are employed primarily as a means of avoiding the need for general anesthesia and hospitalization, very specific guidelines for their employment are necessary. The American Academy of Pediatric Dentistry last year passed such guidelines which address these problems. (See Creedon RL, this volume.) Perhaps one means of accomplishing the goal of moderate to profound sedation required in certain of our patients might be through the use of some of the newer narcotic agonist/antagonist agents which provide levels of CNS depression and analgesia similar to the narcotic agonisits (meperidine, fentanyl, morphine, alphaprodine), but which appear to have a ceiling effect on the degree of respiratory depression produced. Further research in this area is warranted. Inhalation sedation utilizing nitrous oxide (N20) and oxygen (02) provides the dentist with the most controllable conscious sedation technique available. Currently used by about 38% of practicing dentists in the United States, this technique is the most nearly ideal of all. Rapid onset of action, pleasant smell, titratable, easily deepened or lightened, and allowing a rapid, and in most cases, complete recovery, permitting the patient to be discharged from the office unescorted with no restrictions upon their activities, nitrous oxide is not a panacea. It is a weak anesthetic agent and not all patients will be adequately sedated within the parameters permitted by the current generation of sedation units. Complications associated with the use of inhalation sedation are few and are usually associated with a technique of administration which deviates from that recommended. Although the safety of nitrous oxide is unparalleled, there are several concerns which must be considered: the question of chronic exposure to low levels of N20 by members of the dental staff, particularly females; the ever-present problem of recreational abuse of N20 by members of the dental profession, JULY/AUGUST 1986
leading to peripheral sensory neuropathy; and allegations against dentists by female patients of sexual improprieties during the administration of inhalation sedation. In spite of this, inhalation sedation with N20/02 remains the most frequently used technique of sedation in dental practice today, a position it well deserves. Second only to inhalation sedation in the degree of control maintained by the doctor is the intravenous route of administration. Drugs administered intravenously provide a rapid onset of action and welldefined durations of action, permitting the doctor to select the appropriate technique for a given dental procedure. Titration is easily accomplished and provides an important safety feature of IV sedation. Where titration is adhered to, problems with IV sedation simply will not develop. Recent years have seen the introduction of regulations imposed by state legislatures or dental boards which mandate definite levels of education and office preparation for this technique (and in most instances IM and SM too). These requirements are certainly justified because of the number of instances in which untrained individuals have produced morbidity and death. Several techniques form the backbone of IV sedation practice: diazepam (Valium) and the Jorgensen technique (pentobarbital, meperidine, scopolamine). As the doctor receives increased training other agents may be included: the narcotics, such as meperidine, with diazepam in certain procedures. Recent developments include the introduction of the narcotic agonist/antagonists butorphanol (Stadol) and nalbuphine (Nubain), and the watersoluble benzodiazepine, midazolam (Versed). A benzodiazepine antagonist should be available within a few years, joining naloxone as an important member of the antidotal therapy group of drugs. General anesthesia, the controlled state of unconsciousness, is required by that small percentage of the dental population which is unable, for whatever the reason, to receive dental treatment with any of the above techniques. Three forms of general anesthesia are employed today in dental practice: outpatient (light) general anesthesia-using ultrashort-acting barbiturates such as methohexital (Brevital) and thiopental (Pentothal), for procedures usually not exceeding 20 to 30 minutes; general anesthesia in a day-surgery center (i.e., Surgicenter) enabling the patient to avoid hospitalization and its costs and inconveniences, yet permitting the patient and doctor the advantages of the operating room environment. Longer procedures, as in periodontal surgery, extensive restorative dentistry, and full mouth dentistry in unmanageable children, can be accomplished in a much less stressful, more controlled environment. These first two types of general anesthesia are available for the healthy (ASA I and I1) patient. For the increasing number of patients with pre-existing medical problems, hospitalization with medical evaluation with dentistry under sedation or general anesthesia 177
in the operating room followed by an appropriately long convalescent period is increasingly available and recommended. Newer agents and techniques of general anesthesia are becoming available. An entire new generation of inhalation anesthetics (enflurane, isoflurane), muscle relaxants, and narcotics is available to increase the safety to the patient during general anesthesia. In conclusion, the dental profession has at its disposal a spectrum of techniques and drugs for use in
the management of pain, fear, and anxiety. Not all techniques are recommended for all patients and all procedures. The education of the dental professional in the use of these techniques and drugs is the primary source of increased safety to the dental patient.
Reference 1. Moore PA and Goodson JM: Risk appraisal of narcotic sedation for children. Anesth Prog 32:129-139, 1985.
Preoperative Assessment of Patients for Conscious Sedation and General Anesthesia John A. Yagiela, D.D.S., Ph.D. Anesthesia and Pain Control Section, UCLA School of Dentistry, Los Angeles, California It is an axiom of medical practice that one should never treat a stranger. In dentistry, nowhere does this admonition apply more strongly than to the use of drugs for sedation and anesthesia. A single case report will illustrate this point. A 52-year-old Hispanic female presented for the extraction of several teeth (Allen GD, personal communication). The dentist's medical history of the patient indicated that she had been hospitalized at age 38 for six weeks and that a blood transfusion had been contemplated. Few other details were provided in the chart. There was also no indication that the weight of this frail women had been determined. The patient was given atropine sulfate 0.3 mg, menadiol sodium diphosphate (Synkayvite, 5 mg), and methohexital sodium 150 mg intravenously. An unknown amount of 2% lidocaine with 1:100,000 epinephrine was injected intraorally. The patient immediately became pulseless. Cardiopulmonary resuscitation (CPR) was initiated, and the patient was intubated. A pulse was re-established, and the patient began to make some respiratory efforts. The patient was transported to the hospital; intermittent CPR was performed en route. On admission, she was found to have a blood pressure of 80/69 and spontaneous cardiac activity. Stat laboratory studies indicated anemia with a hemoglobin of 8.8 g/dl and a hematocrit of 27.8%. There was also a 1 +glucosuria. The patient's hospital course was stormy; she suffered two additional arrests in the first week. Subsequent testing of the patient's plasma electrolyte and hormonal concentrations eventually established the diagnosis of Sheehan's syndrome (postdelivery hypopituitarism). Failure by the dentist to fully explore the patient's past medical background, to adjust the anesthetic regimen to her physical 178
status, and to perform a simple blood screening test all contributed to the anesthetic emergency. (As a postscript to this case, the patient died two weeks after discharge from the hospital because of a failure to take her posterior pituitary extract as prescribed.) The preoperative evaluation should prepare the dentist to manage the patient in a safe and effective manner and help the patient to receive the treatment under optimal conditions. Four goals of the preoperative evaluation can be identified: (1) establishing the need for anesthetic intervention, (2) assessing the physical and mental status of the patient, (3) selection of the anesthetic regimen, and (4) patient education and preparation.
Need for Anesthetic Intervention In a manner analogous to the determination of a patient's chief complaint, the dentist should establish the main reason or need for anesthetic intervention. Major indications include patient anxiety, stressful procedures, lack of patient cooperation, and problems associated with local anesthesia. Of these, patient anxiety is the most common reason for employing sedative techniques in dentistry. Some patients may volunteer that they are anxious; others may hide their fears, only to have them revealed durng attempted treatment. Studies have shown that dentists tend to underestimate patients' apprehension.1 Recognizing this, some clinicians and researchers have used questionnaires as measures of patient anxiety.2 While this approach holds promise, no one has as yet successfully based drug selection on such measures. Stressful surgical procedures generate anxiety in most individuals. Fortunately, clinicians are usually adept at gauging the stress of an anticipated treatANESTHESIA PROGRESS
