Anesthetic Considerations for Bariatric Surgery

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 of incisional hernia and wound infection (8,15). There are also smaller postoperative pain medication requirements, less pain intensity during mobilization, and improved pulmonary function. Complications after RYGB include anastomotic leak, gastric pouch outlet obstruction, jejunostomy obstruction, deep vein thrombosis (DVT), pulmonary embolism (PE), respiratory failure, gastrointestinal (GI) bleeding, and wound infection. Late complications include prolonged nausea and vomiting, cholelithiasis, ventral hernia, anemia, and protein-calorie malnutrition. Nguyen et al. (15) discovered, in a prospective, randomized study, that these complications are more common after open RYGB than after laparoscopic RYGB, except for late anastomotic stricture, which was significantly more common after the laparoscopic approach. The more frequent leak rate with laparoscopic RYGB was thought to be related to the learning curve. RYGB induces an undesirable “dumping syndrome” if the patient ingests a high-sugar liquid meal (17), with potential side effects of iron and vitamin B12 malabsorption. Dumping syndrome consists of early postprandial abdominal and vasomotor symptoms resulting from fluid shifts and release of vasoactive neurotransmitters (the pathophysiology of which is peripheral) and splanchnic vasodilation, coupled with a relative hypovolemia, leading to diarrhea and abdominal cramps. It occurs in approximately 10% of patients postgastric bypass surgery. Late dumping symptoms are due to reactive hypoglycemia, which results from an exaggerated insulin and glucagon-like peptide 1 release. Symptoms can be relieved with dietary modifications to minimize the ingestion of simple carbohydrates and to exclude fluid intake during ingestion of the solid portion of the meal. Severe cases may respond to agents such as pectin and guar (plant polysaccharide bulking agents that increase the viscosity of intraluminal contents) or to acarbose, an α-glucosidase inhibitor that blunts the rapid absorption of glucose (18,19). Octreotide, a somatostatin analog that alters gut transit and impairs the release of vasoactive mediators, may also be useful in patients refractory to all other therapy (18). It acts through its inhibitory effects on insulin and gut hormone release, a delay of intestinal transit time, and inhibition of food-induced circulatory changes (19). The AGB (Fig. 2), recently approved by the Food and Drug Administration for use in the United States, is the newest gastric restrictive operation and is usually placed by a minimally invasive laparoscopic approach. It consists of an adjustable inflatable band placed around the proximal stomach to limit oral intake (8). It is a less dynamic operation than RYGB and has a learning curve of 30 operations. Up to 50% ± 28% average excess weight loss has been reported with AGB at 2-yr follow-up, with a complication rate of 19% and a mortality rate of 0.4%(20,21). Band erosion and erosive esophagitis were reported by Westling et al. (22) to be the most common complications requiring repeat surgery over 3 yr. Other complications include herniation of the stomach upward inside of the band and band migration from overfilling (23). In a series of 250 laparoscopic AGB patients by Nehoda et al. (24), the most significant complications were early pouch dilations occurring in the first week; however, the most common complications were disconnections at the portal site between the tube and reservoir. Specific contraindications to AGB include inflammatory diseases of the GI tract (such as severe esophagitis, gastric or duodenal ulcers, or specific inflammation, such as Crohn’s disease), upper GI bleeding (such as esophageal or gastric varices), portal hypertension, congenital or acquired anomalies of the GI tract (e.g., atresias or stenoses), intraoperative gastric injury (e.g., gastric perforation at or near the location of the intended band placement), liver cirrhosis, chronic pancreatitis, and allergy to the materials used to make the band.Figure 2: Adjustable gastric banding. A, Proximal pouch. B, Adjustable band. C, Needle access port through which saline is injected or removed to vary the size of the adjustable band.Medical Therapy for Obesity Approved indications for drug treatment include a BMI of ≥30 kg/m2 or a BMI from 27 and 29.9 kg/m2 in conjunction with an obesity-related medical complication. The combination of phentermine and fenfluramine (Phen-Fen) was the most popular treatment for obesity until it became associated with valvular heart disease and pulmonary hypertension. As a result of this, Phen-Fen is no longer approved by the Food and Drug Administration and should never be used for this purpose. Sibutramine and orlistat are newer antiobesity medications approved for long-term use. Sibutramine inhibits the reuptake of norepinephrine, serotonin, and dopamine, thereby causing anorexia. These mechanisms act synergistically to increase satiety after the onset of eating rather than reduce appetite It the release of serotonin, fenfluramine and which increase the release of in and also the thereby causing These in mechanisms of may have been no of causing valvular the of to with fenfluramine and generally The most frequent effects of treatment include and Sibutramine also in and blood by a of and induces a small increase in heart rate of blood with weight loss, this effect on blood as as is A that of with with of with of initial results in weight loss after approximately 6 mo that is for at least 1 is a of a from that inhibits It and absorption of dietary by in the GI decrease in to the weight loss GI by are the most A decrease in of and has been in approximately of patients with orlistat an average weight loss of with in the group at the of 1 In orlistat has been as a of in and but a has been proven effect may increase orlistat the absorption of vitamin orlistat and to 10% weight with for up to There is a of and on between or orlistat and should be of the side effects of these and effects on body and and liver are common in the but is usually Up to 90% of obese patients show of the with of more than 50% of In a of obese patients for bariatric of which was severe and in to of obese patients without of liver disease have increased liver is the most frequent in the obese reduction in body weight, improves by In a of patients gastric banding increased liver increased by by and by surgery. and to normal after surgery in all the patients in to the of weight reduction after gastric banding. and that in without liver disease, a weight reduction of and of liver recently obese patients intraoperative liver at the of RYGB an rate of with approximately to severe and these and no has been found between liver and the of the liver to of is increased in obesity of increased blood and rate et al. the of obesity on and in and and found that the and effective were increased in with of the of hypertension. et al. up to a increase in in obese this may be an important to the most in these patients Other have also shown in in obese with should on to the obese and the Patients for bariatric surgery should be for hypertension, pulmonary hypertension, of failure, and heart of as increased heart pulmonary and be difficult to The most common symptoms of pulmonary include and which an inability to increase during of with is the most useful of pulmonary may of such as and The the pulmonary artery the more the may show of disease and of pulmonary to pulmonary of and other that may pulmonary may be they and decrease pulmonary With severe pulmonary hypertension, and may be and access and should be during the and the of invasive should be with the blood and for and of and from postoperative Patients for repeat bariatric surgery may the or after the initial the should be with changes in these long-term include vitamin and is in patients with vitamin in patients up with postoperative With rapid weight loss, patients may also be and should be if patient has been or if the patient is vitamin can to an with a normal of of and the of a vitamin such as can be used to the coagulopathy be for surgery or bleeding and It is that the except insulin and oral be until the of surgery. is important of increased risk of postoperative wound infection. of wound infection after gastric for obesity are approximately and after GI surgery are A of open bariatric surgery the infection rate of restrictive procedures vertical gastroplasty, and as that of combination procedures and was Other have wound infection of after open gastric bypass In a prospective, randomized study, Nguyen et al. (15) found that open RYGB an approximately 10 more frequent incidence of wound infection with the laparoscopic approach. The increased incidence of wound infection is due to longer generally longer operative of obesity, from in and inability of to infection however, also by for the laparoscopic approach. and and should be during are for and they or no respiratory can also be in small for during the with (e.g., and (e.g., and (e.g., reduce gastric or thereby the risk and complications of Morbid obesity is a major risk for from postoperative surgery and 12 until the patient was reduced the risk of low weight have in of injected of of for use in the of in patients bariatric surgery. et al. found that 40 12 rather than 30 12 of in a incidence of postoperative complications without an increase in bleeding In the study, et al. of for in patients RYGB and found that the smaller once is safe and and has as the in is currently in the United Studies have shown that is to the once for In a of of the for Bariatric for was the most of by and other In combination with of on the or to and designed or may be for safe for bariatric surgery. have a weight limit of approximately but of up to with a to the are or into Bariatric surgical patients are to the during they should be to the The use of a is also are in and that are with of The patient is on the which is around the and a is to a inside the which to the they It is to that all materials used to are care should be to and are more common in this in the super obese and the and have been reported may be by of the thereby the of the The upper are most by of the to the side may be by prolonged from the injury may if the and has been associated with increased A by et al. such an of patients with in series a BMI kg/m2, with of the The and degree to which a is should be that and can be with the and in this A degree of that results in the segment is It is a from injury of with to months. of the with of and other There is loss of at the injury site and with of and of on the for the of and to is the are of the with of all It a for of this with the of with patient and and injury may in this most with and changes during The most used for this is such as can the changes of is increased with increased The degree of its effects on return and There is a to in At an is an increase in from a reduction in splanchnic of with a increase in and however, blunts this of the occurs at an with return from the body and at an blood and blood can be reduced by and with an increased risk of thrombosis weight on the during causing a reduction in and of surgical and in the upper may the et al. the effect of morbid obesity, and body and on respiratory and during In however, they body to have significant effect on respiratory during reported that, was by increased body weight, respiratory were by obesity and but with body have in which of the and from a tube to be into a and may be by of restriction of from that to of to the of the of can and which can be by complications that should be in include and should be used for the super obese with severe cardiopulmonary disease and for with of the blood of severe of the upper or of can be increased if a small for the is used with that a of of the upper the entire should be used and blood can be from the or with blood in in which occurs with blood use in cases in which access be are for cardiopulmonary for is postoperative which can be in this patient and is more performed in the and of should be for the of a difficult and a with surgical should be A or the and can for an exaggerated from The of this as is to the patient that the of the is at a than the to and et al. used a to the between the of and patient that of a in a patient with a 1 than that of patient are the of the patient with a the of a was approximately with a with a at This as the of such as and show significant in of for obese relative to have or no in with obesity. to this include and which are but which have no between degree of and in obese absolute between obese and and should be on the of body weight 1: of with or can be on the of body weight more body mass These are of an obese increase in body weight can be to an increase in to the estimated of medications is to include the can be in this The of are is for but this is in of such as or has been as the of in this patient of its more rapid and with for use during bariatric surgery and of its more rapid incidence of nausea and vomiting, of and early from the and small and make a during bariatric but high in the obese its use. 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The of stomach which is early after gastric was by this et al. recently the of postoperative for patients as of the RYGB between use and the incidence of major anastomotic the risk of anastomotic injury from by a for bariatric patients may deep of and a for abdominal may patients to with early and has been by to postoperative is in this A on the use of in postoperative pulmonary complications to its use during or upper abdominal surgery the 1 reported that deep and were more effective than no treatment in postoperative pulmonary complications after upper abdominal surgery use of laparoscopic for bariatric procedures results in less postoperative pulmonary the for Patients with a of severe sleep may in the intensive care unit prolonged obstructive is a are The pain from an open bariatric surgical procedure can be the are a safe and effective of postoperative in these are also a advantages of in the of bariatric surgery include of improved and of intestinal have been to a in the incidence of and with and however, been as of A at after gastric bypass surgery and found that it postoperative pain with side effects and no of the patients were to oral intake on the postoperative and were by the postoperative on found advantages over in a of and the of postoperative has been used for postoperative after open with and a small incidence of bariatric surgery induces less postoperative pain and is less to with pulmonary laparoscopic bariatric patients with wound and such as In a of patients effective postoperative to was by of or et al. also the of in obese patients RYGB surgery and found that it without effects on blood heart or respiratory function. Patients can be to liquid oral on the first postoperative after has anastomotic or as as they can tolerate with oral or may be but chronic should be of gastric after bariatric Bariatric surgery is a safe and in the of obese patients treatment have been of these patients should into the specific problems associated with obesity and surgery. of medical therapy is at with a loss of 5%–10% body weight at 6 mo to 1 with up to of gastric restriction and bypass or simple gastric restriction have and mortality of and with the most common complications and being respiratory in from to and mortality have been as less frequent (8).