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Anesthesia for Electroconvulsive Therapy in Obese Patients

2002; Lippincott Williams & Wilkins; Volume: 94; Issue: 2 Linguagem: Inglês

10.1097/00000539-200202000-00024

1526-7598

Andrew G. Kadar, Caleb Ing, Paul F. White, Cynthia A. Wakefield, Barry Alan Kramer, Kerri Clark,

Thyroid and Parathyroid Surgery

Obese outpatients undergoing electroconvulsive therapy (ECT) pose a special dilemma for many anesthesiologists. Studies have reported that obese patients have delayed gastric emptying (1,2) and are therefore at increased risk for aspiration of gastric contents. In a recent review on anesthesia for ECT, Folk et al. (3) suggested that aspiration prophylaxis should be considered for obese patients. However, if rigorous “full stomach” precautions were to be used (4), these patients would also be subjected to a rapid induction with cricoid pressure for tracheal intubation three times per week for 2–4 wk, and subsequently for maintenance ECT treatments on a less frequent basis. The risks and complications associated with performing a series of tracheal intubations on an obese patient need to be weighed against the rare possibility of aspiration. Repeated laryngoscopy and intubation procedures can cause throat pain, swelling and even bleeding secondary to airway trauma (5). Mandøe et al. (6) reported a 60% incidence of sore throat after tracheal intubation. In the Framingham heart study (7), obese subjects were found to have an incidence of hypertension 10 times more frequent than the general (nonobese) population. Because laryngoscopy and intubation are commonly associated with an increase in both heart rate and blood pressure, this procedure may place these patients at an increased risk for cardiovascular complications during and after the ECT treatment. Although the overall risk of aspiration during anesthesia is very small (1 in >2,000 cases), Olsson et al. (8) found that 83% of the cases involved patients with one or more risk factors for aspiration (e.g., delayed gastric emptying, obesity). Based on the data published in this article, the incidence of aspiration in the subpopulation with preexisting risk factors (e.g., obesity) could not be accurately determined. Furthermore, these data were obtained from the medical records of patients undergoing surgical procedures of widely varying lengths. Because ECT is a very short procedure, requiring only a transient period of unconsciousness during which the airway reflexes are compromised, the period of time during which the patient might be “at risk” for aspiration is very brief. Therefore, one could argue that the risk:benefit ratio does not favor routine aspiration prophylaxis or tracheal intubation of obese patients undergoing ECT treatments. We evaluated the collective experiences in managing obese patients undergoing ECT at two major medical centers (Cedars-Sinai Medical Center in Los Angeles and Zale Lipshy University Hospital in Dallas) with extensive experience in performing these procedures (Table 1). At both of these centers, anesthesiologists have elected not to administer aspiration prophylaxis or to tracheally intubate obese patients undergoing routine ECT treatments. Over a period from June 1999 through August 2001, 50 obese patients were anesthetized for a total of 660 ECT treatments. All of these patients met the criteria for obesity as defined by a body weight exceeding their ideal body weight (IBW) by over 45 kg, by weighing more than twice their IBW, and/or by a body-mass index (BMI) greater than 29 (9). The International Obesity Task Force provides a detailed classification system for the severity of obesity based on the BMI (kg/m2): Class I obesity (30–34.9), Class II obesity (35–39.9), and Class III (morbid) obesity (≥40) (10).Table 1: Demographic and Anesthetic Characteristics of Obese Patients Undergoing Electroconvulsive Therapy (ECT) at Cedars-Sinai Medical Center in Los Angeles and Zale Lipshy University Hospital in DallasAll of these patients were fasted overnight and breathed 100% oxygen using a face mask before induction of anesthesia with methohexital 60–120 mg IV. After loss of consciousness, succinylcholine, 40–120 mg IV, was administered for muscle relaxation. Ventilation was assisted using positive pressure with a face mask until the patient was able to resume adequate spontaneous respirations. The ECT procedures were performed in the supine position with their upper body elevated 15–30 degrees. All patients recovered without any adverse incidents and were discharged from the recovery area within one hour after completing the ECT treatment. There were no cases of aspiration (as assessed clinically) in over 650 consecutive general anesthetics for ECT in this obese population, including 97 consecutive procedures in 9 morbidly obese (Class III) patients. According to the “Rule of Three”(11), if the occurrence of gastric aspiration in obese ECT patients is considered to be a Bernoulli random variable with an unknown probability (P) and no aspiration events have occurred in “n” independent events (e.g., general anesthetics), a “quick-and-ready” approximation to the upper 95% confidence bound for “P” is 3/n (12). Based on the number of cases performed at our two institutions (n = 658), this analysis would suggest that the risk of aspiration in this obese ECT patient population would be <5 in 1,000. Although some institutions routinely administer prophylaxis to patients with any risk factors for prophylaxis using Bicitra, H2-receptor antagonists (e.g., ranitidine) and/or metoclopramide, there are no data to support this common practice. Interestingly, administration of Bicitra before induction of anesthesia may actually increase the risk of aspiration by increasing residual gastric volume. The H2-blocking drugs require a minimum of 60–90 min to exert a significant effect on gastric acid production, and therefore would be of little (if any) value in the largely outpatient population undergoing ECT. On the basis of this extensive experience at two different major medical centers in the United States, we suggest that it is an acceptable clinical practice to anesthetize obese patients for ECT without full-stomach (“aspiration”) precautions. Given the infrequent incidence of aspiration in patients receiving general anesthesia for elective surgical procedures, continued vigilance in this ECT patient population is recommended. However, it would appear to be unnecessary, and potentially even harmful, to subject these patients to aspiration prophylaxis and tracheal intubation because of “theoretical” (or medicolegal) concerns regarding their risk of aspiration during ECT procedures.