Weight loss surgery has been found to be effective in carefully selected patients (Maggard et al., 2005). In the United States, approximately 220,000 bariatric surgeries were performed in 2008. As noted earlier, candidates for bariatric surgery should have a BMI of more than 35 kg/m2 and obesity-related complications. Before considering surgery, patients should have a strong attempt to achieve weight loss through conservative means, including diet, exercise, and behavioral modification. For the patient considering surgery, it is important to work with a team experienced in the different aspects of bariatric surgery and weight loss, including a psychologist or psychiatrist, registered dietitian, physician nutrition specialist (if available), and experienced surgeon. Patients should be well informed of the life-changing nature of the surgery, as well as potential complications.
The complications and degree of weight loss differ depending on the surgical approach. Current procedures are classified as being malabsorptive or restrictive, or a combination, in their mechanism of reducing calorie absorption (Box 36-2). The first surgical procedure to be widely used was the jejunoileal bypass, a malabsorptive approach in which most of the small bowel is bypassed by connecting the proximal with the distal small bowel. Side effects, including steat-orrhea, electrolyte imbalance, and hepatic and renal injury, led to this approach being abandoned.
Current malabsorptive procedures include biliopancreatic diversion with or without duodenal switch. The duodenal switch refers to the portion of the small intestine that is transected. The biliopancreatic diversion is similar to the jejuno-ileal bypass in that much of the small intestine is bypassed. However, the bypassed small intestine continues to supply bile and pancreatic enzymes, preventing some of the most severe complications of the jejunoileal bypass. Nutrient deficiencies are still much more common than with restrictive procedures. Both types of biliopancreatic diversion include a limited partial gastrectomy, with the pylorus being maintained in the duodenal switch.
In general, restrictive procedures tend to result in less dramatic weight loss than malabsorptive procedures. The
Box 36-2 Types of Bariatric Surgical Procedures
Jejunoileal bypass Biliopancreatic diversion
Malabsorptive and Restrictive
Roux-en-Y gastric bypass, by far the most widely used procedure, works predominantly by restricting caloric intake, but it may also have a component of malabsorption, depending on the length of the bypassed intestine (Fig. 36-2). Most of the stomach is transected with this procedure. The small intestine is also transected, and the distal limb is attached to the stomach remnant. The bypassed stomach is attached to the remaining intact intestine through the proximal limb of the transected small intestine. The vertical-banded gastroplasty is also a restrictive procedure, but weight loss is less than with the Roux-en-Y gastric bypass. Restrictive procedures cause more vomiting but overall have fewer side effects related to persistent diarrhea and malabsorption of nutrients than malabsorptive procedures. Malabsorptive procedures may be more appropriate when a greater degree of weight loss is desired, but the patient should be aware of the increased side effects.
The adjustable gastric band is a purely restrictive procedure, usually placed laparoscopically, and its use is increasing. A band is placed around the upper portion of the stomach (Fig. 36-3). Part of the stomach is sutured over the band to help keep it in place. This band contains fluid that can be infused through a port just under the skin. By infusing fluid in the port, the band can be tightened or loosened. Adjustments in the fluid are often necessary as people lose weight because the band may loosen.
One of the side effects with the Roux-en-Y gastric bypass is dumping syndrome, which occurs when high-osmolality foods such as ice cream or soda are consumed and presented immediately to the small bowel through the remnant stomach. Symptoms include cramping, diarrhea, malaise, and sweating, and therefore this can be a deterrent to consuming these generally high-calorie foods. However, because the anatomy is intact with the gastric band, dumping syndrome does not occur. In fact, liquid foods such as ice cream and soda may slide more easily through the band, and therefore greater behavioral changes are required to decrease consumption of these foods with a gastric band compared to the Roux-en-Y gastric bypass. This is one reason why weight loss is not as great with the band compared to the bypass.
Perioperative risks increase with bariatric procedures because of the patient population and type of surgery, but overall mortality is under 1%. All currently used procedures can be performed laparoscopically, which is more technically difficult but associated with faster recovery.
During the immediate postoperative period, it can be anticipated that pharmacotherapy for weight-related conditions will quickly be reduced. Insulin dosing will usually need to
be decreased immediately. Patients taking oral hypoglycemics preoperatively may be better controlled on a sliding scale of short-acting insulin in planning for a decreased postoperative need for medications. Similarly, antihypertensive and other medications may need to be reevaluated. Immediate-release agents may be better suited to the patient after a malabsorp-tive procedure than sustained-release types, because altered gastrointestinal absorption can be anticipated.
Long-term management of surgical patients requires supplementation with vitamins and minerals. Vitamin B12 deficiency is common. Clinical practice at Mayo Clinic is to treat all bariatric surgery patients with 2 multivitamins (starting with chewable form), daily calcium supplementation (carbonate or citrate), vitamin D (1000-2000 U daily), and 1 mL (1000 ^/mL) of subcutaneous cyanocobalamin (vitamin B12) monthly. Ferritin levels should be monitored and iron deficiency treated, as necessary. The altered ability to absorb medications will persist, and serum drug concentrations may need to be performed more frequently.
The Swedish Obese Subjects (SOS) study reported on extremely obese patients treated by bariatric surgery or conventional nonsurgical approaches over 10 years (Sjostrom et al., 2004). Peak weight loss occurred at 6 months in the control group (1% of baseline weight) and at 1 year in the surgical groups. At 1 year, weight loss was 38% for gastric bypass, 27% for vertical-banded gastroplasty, and 21% for those undergoing gastric banding. By 10 years, percentage weight loss from baseline fell to 25%, 16%, and 13%, respectively, for the three procedures, compared with 1.6% weight gain in the control group. Improvement in hypertension, T2DM, and dyslipidemia was greater in the surgical group than the control group at 2 and 10 years. Improvement in hypercho-lesterolemia did not differ between the groups. Reduction in the incidence of T2DM and hypertriglyceridemia was greater in the surgical patients than the control group at 2 and 10 years. The incidence of hypertension and hypercholesterol-emia did not differ between the groups.
The complete reference list is available online at www.expertconsult.com.
Institute for Clinical Systems Improvement; evidence-based guidelines on prevention and management of obesity. www.cdc.gov/obesity
Compilation of current statistics and overview of obesity. www.cdc.gov/obesity/causes/economics.html
Diet and exercise together with behavioral modification can improve short-term outcomes, though long-term effectiveness is lacking (Shepherd, 2003) (SOR: A).
Both sibutramine and orlistat may achieve modest additional weight loss when added to diet and physical activity in patients who are appropriate candidates for pharmacotherapy (Rucker et al., 2007) (SOR: A).
Gastric bypass is more effective than vertical-banded gastroplasty for weight loss and is associated with fewer revisions but more side effects (Everson et al., 2004) (SOR: A).
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