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AMBULATORY ANESTHESIA

Anesthesia for Electroconvulsive Therapy in Obese Patients

Andrew G. Kadar, MD^*, Caleb H. Ing, MS, Paul F. White, PhD, MD, Cynthia A. Wakefield, MS, Barry A. Kramer, MD, and Kerri Clark, RN

Departments of *Anesthesiology and Pain Management and Psychiatry, Cedars Sinai Medical Center, Los Angeles, California; and the Department of Anesthesiology and Pain Management, the University of Texas Southwestern Medical Center at Dallas, Dallas, Texas

Address correspondence to Dr. Paul White, Professor and Holder of the Margaret Milam McDermott Distinguished Chair in Anesthesiology, Department of Anesthesiology & Pain Management, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390-9068. Address e-mail to paul.white{at}utsouthwestern.edu

	Abstract

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IMPLICATIONS: Obese patients have successfully undergone over 650 consecutive uncomplicated ECT treatments without any special precautions at two major U.S. medical centers.

	Introduction

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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).

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.

	Acknowledgments

 
The medical students (CHI and CAW) received summer research stipends from University of Texas Southwestern Medical Center at Dallas, Dallas, TX.

	References

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6. Mandøe H, Nikolajsen L, Lintrup U, et al. Sore throat after endotracheal intubation. Anesth Analg 1992; 74: 897–900.[Abstract/Free Full Text]
7. Hubert HB, Feinleib M, McNamera PM, et al. Obesity as an independent risk factor for cardiovascular disease; a 26-year follow-up of participants in the Framingham Heart Study. Circulation 1983; 67: 968–77.[Abstract/Free Full Text]
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