US Pharm. 2009;34(12):HS-2-HS-10.
Obesity is a chronic condition characterized by an extreme accumulation of fat that exceeds the body's skeletal and physical standards.1 It is insidious, with symptoms slowly becoming evident over a prolonged period of time. Morbid (clinically severe) obesity, which involves an increased risk of coexisting disease, is defined as having at least 100 lb. of excess weight, being 20% or more above ideal body weight, or having a body-mass index (BMI) of 35 kg/m2 or higher.2,3 (BMI, a measure of body fat based on height and weight, is calculated as weight [kg]/height [m]2.3,4) At this stage, obesity becomes a health risk and treatment options must be contemplated.5 Weight-loss, or bariatric, surgery is considered for the morbidly obese patient when all conventional therapy--including behavioral modification, diet therapy, exercise, and medication--has failed.
Obesity: Epidemiology and Screening
In the last 20 years, there has been a dramatic increase in the prevalence of obesity in the United States.2 In 1991, no state had an obesity rate higher than 20%.4 According to 2008 statistics, obesity prevalence in adults increased in 37 states, with Mississippi having the highest rate (31.7%) and Colorado having the lowest rate (18.4%). In every state except Colorado, more than 20% of adults are obese.4
In 1994, according to the National Health and Nutrition Examination Survey III, approximately 55% of U.S. adults (about 97 million) were obese.6 In 2007, it was estimated that about 66% of adults are overweight or obese; 16% of children and adolescents are overweight and 34% are at risk for becoming overweight.7 The prevalence of severe obesity in the U.S. between 1999 and 2002 was greater in women than in men.8 In the U.S., approximately 280,000 deaths are attributed to obesity, which will soon exceed smoking as the primary preventable cause of death.9
Surgical Treatment Options
Introduced in the 1950s, bariatric surgery currently offers the best method of producing sustained weight loss in morbidly obese individuals.10 A consensus statement by the American Society for Metabolic and Bariatric Surgery (ASMBS) concluded that bariatric surgery is the most effective treatment for morbid obesity and that it can result in improvement or complete resolution of obesity comorbidities.11-13 In 2002, 63,000 bariatric surgeries were performed in the U.S.; in 2006, an estimated 177,600 patients underwent the procedure, according to the ASMBS. Fewer than 1% of individuals who meet the criteria for weight-loss surgery actually undergo the procedure. It is advisable for severely obese patients to have surgery early to prevent the development of other medical conditions, such as diabetes and hypertension.14
Three types of bariatric surgery exist (TABLE 1). Restrictive surgery limits food intake by making the stomach smaller. Malabsorptive surgery hinders calorie absorption by shortening the duodenum and/or altering where the duodenum connects to the stomach, thereby limiting the amount of food digested or absorbed. The third type of surgery is a combination of the first two. Restrictive procedures, which are performed least often, result in the most significant weight loss by reducing the amount of food eaten and slowing the speed of gastric emptying.15
The mechanism by which weight loss occurs after bariatric surgery is most likely an interplay between mechanical effects of the surgery and neurohormonal feedback loops involved in body-weight homeostasis.16,17 The amount of weight loss that occurs is a valuable method of evaluating the efficacy of bariatric surgical procedures.18 Generally, laparoscopic Roux-en-Y gastric bypass (RGB) has better outcomes than other procedures with regard to a greater percentage of weight loss and a more controlled diet with avoidance of fatty foods.18,19
Combined Restrictive/Malabsorptive Surgery: RGB, the most frequently performed type of bariatric surgery since the 1960s, is the most successful combined procedure. Today, most bypass surgeries are performed using limited-access (laparoscopic) techniques rather than open (traditional) surgery, which has a longer recovery period. Laparoscopic surgery uses several small incisions, called ports, for inserting surgical instruments and a telescope.
First, a small pouch is created by separating the stomach into two sections. Both the pouch and the unused portion of stomach are closed with staples or a band. The small intestine, which produces digestive enzymes necessary for the breakdown and absorption of fats and proteins, is reconnected to the pouch, bypassing the duodenum, jejunum, and all but the last section of ileum. Because much of the small intestine is bypassed and the amount of food exposed to digestive enzymes is limited, very few fat and protein calories are absorbed; as a result, malabsorption occurs.
Initially, this procedure results in the greatest percentage of weight loss (about 61% of excess body weight), with a maintenance loss of about 50% to 60%.13 A 3-year follow-up study found that laparoscopic gastric bypass was as effective as open bypass with respect to weight loss and improvements in comorbidities and quality of life.20 The operation takes about 4 hours and involves a hospital stay of 3 to 5 days. Lower fasting and postprandial proinsulin concentrations have been observed after gastric bypass surgery in patients with diabetes.21
Combined surgery is more difficult to perform than restrictive surgery. Negative effects of the procedure include vomiting, second surgery, leakage of the Y connection between the pouch and the duodenum, and gallstone development. The bypassed portion of the stomach is difficult to see on radiographs. A reaction known as dumping syndrome occurs when the contents of the stomach move too quickly through the small intestine, resulting in nausea, weakness, sweating, and diarrhea soon after eating and in extreme weakness after sweets are consumed.22 Pregnancy should be avoided until the weight loss has been achieved and the patient's weight is considered to be stable.
Combined surgery is more likely to result in long-term nutritional deficiencies, so it is important to monitor patients. Deficiencies of the fat-soluble vitamins (A, D, E, and K) and calcium, zinc, and selenium are common after gastric bypass.23 There is an increased incidence of anemia owing to decreased levels of iron, vitamin B12, and folic acid.24 Patients should take a supplemental multivitamin containing B12 and folic acid.
Purely Restrictive Surgery: Approved by the FDA in June 2001 for patients over 18 years of age, laparoscopic adjustable gastric band surgery (LAGBS) is a minimally invasive procedure for the severely obese that, unlike gastric bypass surgery, offers the advantages of being adjustable and reversible (band can be removed). LAGBS seems to be increasing in popularity in the U.S.25 This type of surgery is easier to perform and has a lower complication rate than malabsorptive surgery. The surgery, which usually takes about 1 hour, is done on an outpatient basis or involves an overnight stay.
After small incisions are made, a laparoscope is used to visualize placement and to suture an adjustable/inflatable hollow silicone gastric band around the top 5% of the stomach, creating a small upper pouch and a large lower pouch. No staples are used. The band is connected to a port that is placed subcutaneously in the stomach via small incisions; the port can be accessed to inflate or deflate the balloon in the band, which changes the size of the band accordingly. The diameter of the band obstructs or restricts the passage of food. The band is inflated or adjusted by adding saline to or removing it from the port. As the patient eats, the upper pouch fills and the patient feels full sooner. The pouch initially can hold only about 1 oz. of food, but later expands to hold up to 3 oz. The normal digestive process is not altered. Most patients return to normal activities within a few weeks.22
Postsurgical instructions include a liquid diet for about 2 weeks, followed by soft foods and then solid foods. It is highly recommended that the patient follow a personalized nutrition plan and exercise program. Within the first 2 years, there is a weight loss of about 50% to 60%.26 LABGS is also safe and effective as reoperative surgery in obese patients who require additional weight loss after previous bariatric surgery.27
Weight loss is not as dramatic as with restrictive/malabsorptive surgery, and some patients regain weight quickly. Vomiting results from poor chewing, rapid eating, exceeding pouch capacity, or drinking shortly after eating; repeated vomiting may cause the pouch to stretch, enabling weight gain.28 Because adjustments involve needle puncture of the access port, there is an increased chance of infection. The procedure is contraindicated in patients with Crohn's disease, large hiatal hernia, or a history of gastric ulcers.
Vertical banded gastroplasty (VBG) uses both a band and staples to create a small stomach pouch that empties into the lower pouch. Once the most common restrictive operation, VBG is not often used today because long-term weight loss is minimal.
Purely Malabsorptive Surgery:
In biliopancreatic bypass with duodenal switch, the stomach is reduced and the small pouch that remains is connected directly to the end of the ileum, thus bypassing the duodenum and jejunum entirely. This procedure is performed infrequently because of the high risk of nutritional deficiencies.
Criteria for Surgery
The patient-selection guidelines for bariatric surgery developed by the National Institutes of Health (NIH) are listed in TABLE 2. A candidate for weight-loss surgery must meet these criteria.29 The risk of death if a patient does not undergo the surgery may outweigh the risks from possible complications of the procedure.
In 2007, a survey of 1,343 U.S. bariatric surgeons was published. A questionnaire examining clinical predictors of patient selection was mailed to participants. The survey concluded that the influences of patient age, gender, insurance status, social support, and functional status on the decision to operate were mitigated by comorbidities and BMI.30
The patient must be prepared to make significant lifestyle changes after having bariatric surgery. These include proper diet, physical activity, and health care practices necessary for any surgical weight-loss system to work.
Considerations in Adolescents and Older Adults
Bariatric surgery is an option for obese adolescents. However, emotional and physical long-term effects of the surgery on the adolescent patient should be considered. Although weight-loss surgery can yield outstanding improvements in comorbid conditions in adults, it is not clear whether similar improvements occur in adolescents.31 Bariatric surgery has not been a common therapy in adolescents, largely because the long-term effects (e.g., nutritional deficiencies) are unknown. Within the last few years, many hospitals have been conducting FDA-approved studies of LABGS. Currently, only gastric bypass surgery is approved for patients under 18 years of age.32
Bariatric surgery should be considered for an adolescent only after the patient has unsuccessfully tried to lose weight for least 6 months. The candidate should have a BMI of 40 or more, be at least 13 years old (girls) or 15 years old (boys), and have serious comorbid conditions.32
Bariatric surgery in adults aged 60 years and older is effective. However, older patients may develop more pre- and postoperative problems and achieve less weight loss than younger patients.33
Complications, Risks, and Adverse Effects
Negative effects of bariatric surgery may be classified into true complications associated with the operation and adverse effects related to alterations in upper-gastrointestinal (GI) anatomy (TABLE 3).34
Nausea and vomiting are common adverse effects. The patient can minimize their occurrence by eating a meal without interruption, chewing meticulously, never drinking with meals, and waiting 2 hours after consuming solid food before drinking.34
The prevention of secondary complications of morbid obesity is an important goal of management. In the majority of cases, the results of surgery outweigh the risks, and the consensus is that surgery is the most effective treatment for severe obesity.35 However, successful postsurgical weight loss does not preclude complications, and questions persist regarding efficacy and safety.1,34,35 In 2006, approximately 40% of patients who underwent bariatric surgery developed complications within 6 months.36,37
Mortality from bariatric surgery is relatively rare.38 The mortality rate differs according to the type of surgical procedure: 0.15% for VBG and 0.54% for gastric bypass.38 The most common cause of death is pulmonary embolism.38
A recent study documented a 30-day mortality rate of 0.9% postsurgery and a 6.4% mortality rate at 5 years. Mortality increased substantially with age (>65 years), and coronary heart disease was the leading cause of death overall.39 Another study found that rates of hospitalization doubled in the first 3 years after gastric bypass surgery and that many admissions were directly related to the procedure, including ventral hernia repair and gastric revision (e.g., surgery for staple-line failure).40
Assessment of the risks of weight-loss surgery should include operative, perioperative, and long-term complications. The rate of complications in the early postoperative period (wound infection; leaking from stomach into abdominal cavity [peritonitis]; leaking from staple lines or from Y connection; saline solution leaking from port; stomal stenosis; marginal ulcers; constipation; staple-line dehiscence; pulmonary problems; deep thrombophlebitis) may be as high as 10% or more.41 In fewer than 1% of patients, splenectomy may be necessary to control operative bleeding. Sometimes a second operation may be necessary, which increases mortality and morbidity rates.
A recent study found that patients who undergo LAGBS may have lower short-term morbidity than those treated with RGB, but reoperation rates may be higher among LAGBS patients.42
Postoperative Drug-Absorption Alterations
Considering the changes made to the upper GI-tract anatomy in bariatric surgery, specific nutritional and absorptive side effects should be expected and managed appropriately to avoid complications and decreased drug efficacy.43 All weight-loss procedures reduce the size and surface area of the stomach, which decreases the amount of drug absorption and increases transit time; this causes the drug to remain in contact with the GI mucosal lining longer. Patients should not take drugs with the potential to cause ulcers (nonsteroidal anti-inflammatories, aspirin, oral bisphosphonates).44 Alternative analgesics (e.g., acetaminophen, narcotics) and osteoporosis agents (e.g., calcitonin nasal spray) should be recommended.43 RGB bypasses a major portion of the small intestine, reducing the surface area for drug absorption. Therefore, a drug's route of administration, formulation (liquid vs. tablet/capsule), or dosage must be altered.43
Drugs with long absorptive phases that remain in the intestine for extended periods are likely to exhibit decreased bioavailability in bypass-surgery patients. For that reason, products with prolonged dissolution times, such as extended-release formulations, should be avoided in this group.43
Iron must be absorbed in the ferrous state in the acidic stomach, but because bypass patients have reduced acid production, iron must be taken with vitamin C. This acidifies the stomach contents, allowing for better absorption.43,45 The small stomach pouch created during the bypass procedure produces less gastric acid and hydrochloric acid; this may reduce the absorption of calcium carbonate, but the citrate salt is unaffected.43
Drugs that may potentially cause decreased absorption in these patients include enalapril and ketoconazole, for which an alternative agent should be prescribed. With ramipril, metoprolol, metformin, olanzapine, quetiapine, ramipril, simvastatin, and zolpidem, the patient should be monitored for reduced drug efficacy.43
Conclusion and Future Trends
The growing epidemic of overweight and obesity is a serious health problem in the U.S., with more than 5 million Americans having a BMI exceeding 35.46 Severe obesity is a chronic condition that is difficult to treat, and weight loss can be hard to maintain. There are many different approaches to weight management; bariatric surgery should be considered only when all other methods have failed.
Surgery can result in profound weight loss in adults, which in turn may spur a significant improvement in comorbid conditions. Methods of bariatric surgery have improved over the past 25 years, but questions about safety and efficacy remain. Although concerns exist regarding bariatric procedures in adolescents, surgery is gaining acceptance as a treatment option in this population. Preoperatively, it is essential to stress to the bariatric surgical candidate the importance of healthy eating and exercise behaviors.47
In 2003, the National Institute of Diabetes and Digestive and Kidney Diseases of the NIH formed a partnership with researchers called the Longitudinal Assessment of Bariatric Surgery. The goal of this consortium is to plan and conduct studies that will lead to a better understanding of bariatric surgery and its impact on the health and well-being of patients with extreme obesity.
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