6 Pregnancy and Weight Loss Surgery
Chapter 6 / Pregnancy and Weight Loss Surgery 83
The band is connected, via a thin flexible tube, to an access port placed underneath the skin on the abdominal wall. By injecting or withdrawing saline from the access port, the band can be tightened or loosened and the amount of restriction adjusted. Unlike the RYGB, the AGB is a purely restrictive operation.
Vertical banded gastroplasty, also known as VBG or “stomach stapling,” was at one time the most common bariatric operation, but has lost favor recently due to its poor long-term results [8]. Like the adjustable gastric band, the VBG is a purely restrictive operation that works by decreasing the volume of food that a patient can eat at one sitting. Unlike the gastric band, the VBG cannot be adjusted. VBG is now an uncommon operation.
One of the most recently developed bariatric operations is the sleeve gastrectomy (SG), a more modern variant of the VBG (Fig. 6.3) [9]. In this technically straightfor-ward operation, the entire left side of the stomach is surgically removed, resulting in a small, banana-shaped stomach. For superobese patients in whom a complex operation like the RYGB may present excessive technical difficulty, the SG can be used as the first component of a two-staged approach. The SG will result in a weight loss of 50 kg or more, after which the patient can be safely taken to the operating room for conversion to a more definitive operation like the RYGB [10]. SG without a second stage may also be used as a purely restrictive procedure.
The least common and most complex bariatric operation performed in the United States is the biliopancreatic diversion with duodenal switch (BPD-DS, Fig. 6.4) [11].
The BPD-DS consists of a SG combined with the bypass of a substantial portion of the small intestine. The first portion of the duodenum is divided and reconnected to the Fig. 6.2. Diagram of the adjustable gastric band. (Image ©2005 Daniel M. Herron, reprinted with permission)
distal 250 cm of small intestine. Additionally, bile and pancreatic secretions are diverted to the distal ileum. The BPD-DS results in moderate volume restriction and significant malabsorption. While providing the best long-term weight loss of any bariatric opera-tion, the BPD-DS causes the most nutritional disturbance.
6.4 WEIGHT LOSS AFTER SURGERY AND POSTOPERATIVE RECOMMENDATIONS FOR PREGNANCY
The rate of weight loss after surgery varies with the type of procedure. A large meta-analysis of surgical interventions for weight loss reported a mean weight loss regardless of operation of 61.2% [12]. Specifically, excess body weight loss was 47.5% for patients who underwent AGB, 61.6% for those who underwent RYGB, and 70.1% for those who had BPD-DS.
Fig. 6.3. Diagram of the sleeve gastrectomy.
(Image ©2005 Daniel M. Herron, reprinted with permission)
Fig. 6.4. Diagram of the biliopancreatic diver-sion with duodenal switch (BDP-DA). (Image
©2005 Daniel M. Herron, reprinted with permission)
Chapter 6 / Pregnancy and Weight Loss Surgery 85 With the RYGB and BPD-DS, the most rapid weight loss occurs during the first 3 weeks after surgery, when patients typically lose 1 lb per day or more. The rate of weight loss gradually decreases until weight stabilizes, about 12 to 18 months after surgery [13]. Weight loss after AGB occurs at a slower rate, but may continue for 2 to 3 years after surgery. Most bariatric surgeons recommend that female patients avoid pregnancy for a period of 18 months or more after their operation or until their weight has stabilized.
6.5 NUTRITION DEFICIENCIES AFTER WEIGHT LOSS SURGERY Deficiencies in vitamins and other nutrients are common after bariatric surgery, par-ticularly with RYGB and BPD-DS, since these operations result in decreased intestinal surface area and bypass the duodenum (Fig. 6.5). Since BPD-DS results in more sig-nificant malabsorption than does RYGB, there are more nutrient deficiencies reported among BPD-DS patients. Although not as prevalent, nutritional deficiencies have also been reported after AGB and SG, primarily because of decreased food intake and the avoidance of certain nutrient-rich foods because of individual intolerances.
In order to better understand what the postoperative nutrition needs are for pregnant women who have had bariatric surgery, it is important to first understand the nutri-tional deficiencies that commonly accompany these procedures. The main deficiencies reported among postoperative patients are protein, iron, vitamin B12, folate, calcium, vitamin D, and fat-soluble vitamins [15]. Below is a brief review of studies that have been carried out as well as the assessments that are recommended as a check for nutrient deficiencies following bariatric surgery.
· Protein. In a prospective randomized study of patients with a BMI greater than 50 kg/m2, 13% of the patients who underwent distal RYGB experienced protein deficiency 2 years after surgery [16]. Protein deficiency occurred more frequently after BPD-DS than RYGB due to the more severe malabsorption caused by this operation. It is recommended that total serum protein and albumin be assessed on a regular basis after bariatric surgery to measure protein stores, typically 3, 6, and 12 months after surgery, then annually.
· Iron. In a study of RYGB patients before surgery and up to 5 years after the procedure, iron deficiency was identified in 26% of patients preoperatively, in 39% at 4 years postop-eratively, and in 25% of those 5 years postoperatively [17]. The anatomic changes result-ing from RYGB reduce the exposure of iron-containresult-ing food to the acidic environment in the stomach, which is required for the release of iron from protein and conversion into its absorbable ferrous form [18]. It is recommended that hemoglobin, hematocrit, iron, ferritin, and total iron binding capacity be evaluated for diagnosis of iron deficiency or anemia.
· Vitamin B12(cobalamin) and folate. Deficiencies of vitamin B12 and folate are common in bariatric surgery patients. Halverson studied patients 1 year after RYGB and found 33%
of patients had a vitamin B12 deficiency, and 63% had a folate deficiency [19]. As with iron digestion after RYGB, the absence of an acidic environment prevents the release of vitamin B12 from food [17]. In addition, intrinsic factor (IF), secreted from parietal cells of the stomach, is responsible for the absorption of vitamin B12. Therefore, after bariatric surgery, inadequate IF secretion or function is a possible mechanism for vitamin B12 defi-ciency [20]. It is recommended that vitamin B12 and folate be assessed regularly. Blood levels of >300 pg/ml for B12 are considered normal.
· Calcium and vitamin D. Calcium and vitamin D are usually assessed together since vitamin D promotes the intestinal absorption of calcium. Brolin et al. found a 10% incidence of calcium deficiency and 51% incidence of vitamin D deficiency in patients who had distal RYGB [16]. Parathyroid hormone (PTH) levels may be a more sensitive indicator of calcium deficiency [18]. If PTH is elevated, then calcium deficiency is presumed. As for vitamin D, it is important to check 25(OH) vitamin D levels rather than 1,25(OH)2 vitamin D. Although the normal range of vitamin D is variable depending on the lab, it is usually recommended that serum 25(OH) vitamin D to be >20 ng/ml.
Salivary amylase
MOUTH ESOPHAGUS
STOMACH
DUODENUM
JEJUNUM Intestinal brush
border enzymes
ILEUM
COLON Gastric juice
Pancreatic juice
• pepsin
• HCI
• bicarbonate
• enzymes Bile
alcohol
iron CI−, SO4−
Na+, K4+ calcium magnesium zinc
glucose, galactose, fructose vitamin C
thiamin water soluble vitamins riboflavin
pyridoxine folic acid protein
vitamins A, D, E, K fat
cholesterol
bile salts and vitamin B12
vitamin K formed by bacterial action H2O
Fig. 6.5. Sites of absorption of nutrients within the gastrointestinal tract. (Adapted from: Mahan and Escott-Stump: Krause’s Food, Nutrition and Diet Therapy, 9/e, p 13, ©1996, with permis-sion from Elsevier)