Anesthetic Considerations for Bariatric Surgery

Abstract

According to the National Institutes of Health, obesity is a major health problem with clearly established health implications, including an increased risk for coronary artery disease, hypertension, dyslipidemia, diabetes mellitus, gallbladder disease, degenerative joint disease, obstructive sleep apnea, and socioeconomic and psychosocial impairment (1). The risk of developing one or more of these obesity-related conditions is based on body mass index (BMI), with 25–30 kg/m2 being low risk and >40 kg/m2 being very high risk (2). The prevalence of obesity in the 18- to 29-yr-old group increased from 12% in 1991 to 18.9% in 1999 (3). Bariatric surgery encompasses a variety of surgical weight loss procedures used to treat morbid obesity. Obesity is clinically expressed in terms of BMI or Quetelet’s index (4), which is derived by dividing weight by the square of height to estimate the degree of obesity. Thus, BMI = body weight (kg)/height2 (m2). Morbid obesity is a BMI more than 35 kg/m2, and super morbid obesity is BMI more than 55 kg/m2. The indications for surgical treatment of severe obesity, as outlined in the 1991 National Institutes of Health Consensus Development Conference Panel, include an absolute BMI more than 40 kg/m2 or BMI more than 35 kg/m2 in combination with life-threatening cardiopulmonary problems or severe diabetes mellitus (1). Patients seeking surgical weight loss must have proven attempts at medically supervised weight loss. Documentation of loss of <5% to 10% excess body weight or weight gain after at least 6 mo of diet modification, exercise, and medical therapy or nonimprovement in comorbid conditions during this period indicates failure. Studies have shown that weight loss of 5%–10% of initial body weight improves glucose intolerance and Type II diabetes, hypertension, and dyslipidemia (5–7). The average expenditure is approximately $7000 per year per patient on weight loss programs and equipment. Unfortunately, long-term weight loss is the exception, and most patients regain weight, sometimes more than they initially lost. Surgical Treatment of Obesity Surgical approaches designed to treat obesity can be classified as malabsorptive or restrictive (8,9). Malabsorptive procedures, which include jejuno-ileal bypass and biliopancreatic bypass, are rarely used at present. Restrictive procedures include the vertical banded gastroplasty (VBG) and gastric banding, including adjustable gastric banding (AGB). RYGB, the “gold standard” of bariatric operations, combines gastric restriction with a minimal degree of malabsorption. VBG, AGB, and RYGB can all be performed laparoscopically (10,11). At our institution, laparoscopic Roux-en-Y gastric bypass (RYGB) is routinely performed on patients weighing <160 kg without other contraindications to laparoscopy, including uncorrected coagulopathy and inability to tolerate laparotomy. Technical considerations and instrumentation technology currently make laparoscopic bariatric surgery difficult in patients weighing >180 kg (8,12). Gastric restriction, or gastroplasty, separates the stomach into a small upper pouch (15–30 mL), which restricts food intake. This pouch communicates with the remainder of the stomach through a narrow channel, or stoma. RYGB (Fig. 1), the most commonly performed bariatric procedure in the United States, involves anastomosing the proximal gastric pouch to a segment of the proximal jejunum, bypassing most of the stomach and the entire duodenum. It is the most effective bariatric procedure to produce safe short-term and long-term weight loss in severely obese patients (13). With RYGB, patients lose an average of 50%–60% of excess body weight and show a decrease in BMI of approximately 10 kg/m2 during the first 12 to 24 postoperative months. To the health care provider, the effect of weight loss on associated weight-related comorbidity is more important than absolute weight loss. Studies have shown that Type II diabetes resolves in up to 90% of patients (14).Figure 1: Roux-en-Y gastric bypass. A, A 15- to 30-mL gastric pouch with connected jejunal limb. B, Site of jejuno-jejunostomy.The variables used to measure surgical outcome include operative time, length of skin incision, estimated blood loss, number of patients requiring intensive care unit stay, length of hospital stay, early and late (>30 days) complications, early (<30 days) reoperation, and weight loss. Using these variables, Nguyen et al. (15) found that, with the exception of length of operative time, laparoscopic RYGB was generally associated with better outcomes and cost-effectiveness than open RYGB. The rate of anastomotic leakage is also slightly more frequent with the laparoscopic approach (8), but it becomes comparable once the learning curve has been mastered (approximately 70 cases) (16). Other advantages of the laparoscopic procedure include reduced hospital stay, more rapid return to normal activity, improved cosmesis, and a marked reduction in the incidence