Gastric Bypass

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CHAPTER 9 Gastric Bypass

Robert T. Lewis, Noel N. Williams

Case Study

A 42-year-old female presents to a surgeon’s office requesting a gastric bypass operation. She weighs 290 pounds and is 5 feet 4 inches tall (body mass index, 49.8). She reports a history of hypercholesterolemia, hypertriglyceridemia, degenerative joint disease, gastroesophogeal reflux disease, hypertension, and obstructive sleep apnea requiring the use of a continuous positive airway pressure (CPAP) machine at night. She has been overweight since childhood and has attempted multiple diet programs throughout her life, many with good short-term results; however, she has repeatedly regained the lost weight. She is unable to exercise consistently because of joint pain.

Her physical examination is significant for central obesity and mild hypertension. Her fasting serum glucose level is 110 mg/dL, consistent with prediabetes.

Body mass index (BMI) = weight (kg)/height (m)2

BACKGROUND

Obesity is the most prevalent health problem in developed countries worldwide. More than 60% of all Americans are overweight, more than 30% are obese, and more than 4% are severely obese. Obesity and associated comorbidities cost the United States more than $150 billion annually and are responsible for more than 280,000 annual deaths. The rate of childhood and teenage obesity has nearly doubled in less than a decade, resulting in the earlier onset of associated comorbidities. Bariatric surgery is the only treatment for morbid obesity with proven efficacy and results in the loss of 50% to 70% of excess weight in nearly all individuals. In contrast, dietary modification results in long-term weight loss in fewer than 3% of patients. Perhaps more importantly, bariatric surgery is associated with decreased mortality rates and improved control or resolution of diabetes, hypertension, hyperlipidemia, and obstructive sleep apnea in a majority of patients. The most common bariatric procedures performed in the United States are the Roux-en-Y gastric bypass (RYGB) and the adjustable gastric band. The RYGB works through two mechanisms: (1) gastric restriction and (2) reduction of the functional absorptive capacity of the small bowel. The gastric band works through the former mechanism only.

Overweight: Body mass index (BMI) = 25–30

Obese: BMI > 30

Severely obese: BMI > 40 or patient > 100 lb above ideal weight

INDICATIONS FOR SURGERY

Obesity: The specific indications for bariatric surgery continue to evolve. The National Institutes of Health issued a consensus statement in 1991 that established guidelines for identifying patients for whom the benefits of surgery outweigh the associated risks (Box 9-1). Importantly, patients weighing more than 600 pounds exceed the maximum weight capacity of many operating tables and may require staged therapy (including dietary modification) before a definitive surgery.

BOX 9-1

National Institutes of Health Eligibility Criteria for Weight Loss Surgery

• Body mass index (BMI) > 40 or BMI > 35 with comorbid conditions
• Failed medical therapy
• Informed in detail about the procedure and its risks
• Motivated and psychiatrically stable
• Able to tolerate surgery with acceptable medical risk

Data from Buchwald H: Consensus Conference Panel: Consensus conference statement: Bariatric surgery for morbid obesity: Health implications for patients, health professionals, and third-party payers. Surg Obes Relat Dis 1:371–381, 2005.

PREOPERATIVE EVALUATION

A thorough preoperative assessment aimed at identifying modifiable risk factors is mandatory before bariatric surgery.

I. Cardiovascular: A preoperative electrocardiogram should be obtained for men older than 40 years, women older than 50 years, or patients with known coronary artery disease, diabetes mellitus, hypertension, obstructive sleep apnea, or arrhythmias. Patients with multiple cardiac risk factors should also undergo stress testing when possible. Unfortunately, this is not always feasible because most patients cannot tolerate even moderate exercise and thallium stress testing is inaccurate in patients with a BMI of more than 30. When available, transesophageal dobutamine stress echocardiogram is often the optimal study. In patients found to be at moderate or high cardiovascular risk, perioperative β-blockade may be recommended, although no study has yet demonstrated a benefit in this population.
II. Pulmonary: Between 40% and 80% of patients undergoing bariatric surgery have obstructive sleep apnea. Generally, patients should undergo preoperative sleep studies. If obstructive sleep apnea is shown, 4 weeks of CPAP or bilevel positive airway pressure (biPAP) is required before surgery. Long-standing OSA or reactive airway disease (also associated with obesity) can lead to pulmonary hypertension, which substantially increases operative risk. Systolic pulmonary artery pressures of greater than 50 mm Hg are a contraindication to surgery.
III. Psychiatric: More than 50% of candidates for bariatric surgery take psychotropic medication, most often for depression. The presence of inadequately treated psychiatric conditions has been correlated with inadequate weight loss and dissatisfaction after surgery. A structured interview with a psychologist or psychiatrist using a validated questionnaire, such as the Weight and Lifestyle Inventory or the Beck Depression Inventory, is recommended.
IV. Gastrointestinal: Nonalcoholic steatohepatitis (NASH) and cirrhosis are present in 40% and 2% of the severely obese population, respectively. Hepatic compromise is a contraindication to surgery, and liver function tests should, therefore, be obtained for all surgical candidates. Because of the high rate of postoperative cholelithiasis, some surgeons advocate screening for gallstones with a right upper quadrant ultrasound and, if the study is positive, removal of the gallbladder at the time of bariatric surgery.
V. Educational: Bariatric surgery results in the loss of 60% of excess body weight in most individuals, but requires extensive lifestyle changes postoperatively. Many patients have unrealistic expectations and require preoperative education. Postoperative referral to a support group may also be beneficial.

Does your patient have obesity-related comorbidities?

COMPONENTS OF THE PROCEDURE AND APPLIED ANATOMY

Preoperative Considerations

I. Sequential compression devices should be applied before the induction of anesthesia to prevent deep vein thrombosis (DVT). Some centers advocate preoperative treatment with subcutaneous heparin as well.
II. More than 50% of obese patients have gastroesophageal reflux disease. Supine positioning increases intra-abdominal pressure and the risk of aspiration during intubation. Intubation with the head of the table elevated at 15 degrees to 20 degrees is often preferred to decrease this risk.
III. Prophylactic antibiotics are administered before skin incision.
IV. A urinary catheter is placed to allow for continuous urine output monitoring.
V. A nasogastric tube is inserted to decompress the stomach.

Patient Positioning and Preparation

I. The patient is placed in the supine position with the arms extended. Pressure points are padded to prevent necrosis. Additionally, buttresses are constructed under the arms to minimize the amount of traction placed on the torso and to decrease the risk of brachial plexopathies.
II. The sterile preparation should extend to the nipples superiorly, to the pubis inferiorly, and to the posterior axillary lines laterally.
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