Metabolic Syndrome

The clustering of a group of defined metabolic and physical abnormalities is now referred to as the metabolic syndrome. Patients with metabolic syndrome commonly have abdominal obesity, reduced levels of high-density lipoprotein (HDL), hyperinsulinemia, glucose intolerance, hypertension, and other characteristic features as listed in Box 58.1 . Specific criteria for diagnosing metabolic syndrome are included in Table 58.4 . The diagnosis requires that at least three of the following be present: abdominal obesity, elevated fasting glucose, hypertension, low HDLs, and hypertriglyceridemia. Weight gain with visceral obesity is a major predictor of the metabolic syndrome. The clinical approach uses waist circumference, rather than BMI, to define the adipose mass component contributing to the metabolic syndrome since BMI has been shown to be a relatively insensitive indicator of the risk for obesity-associated metabolic and cardiovascular diseases. Waist circumference, but not BMI, reflects abdominal subcutaneous adipose tissue as well as abdominal visceral adipose tissue and is therefore a better index of central, or truncal, fat mass.

In the United States, approximately 34% of the adult population have metabolic syndrome. Of these, more than 83% meet the criterion of abdominal obesity. The incidence of metabolic syndrome increases with age, with more than 40% of the U.S. population affected by the age of 60 years. Men are affected more commonly than women, and Hispanics and South Asians appear to be particularly susceptible. Its frequency is lower in African American men than in Caucasians. Metabolic syndrome may result from use of some commonly prescribed drugs, including corticosteroid, antidepressant, and antipsychotic agents. Protease inhibitors used to treat human immunodeficiency virus (HIV) infection can induce metabolic syndrome secondary to insulin resistance.

Patients with metabolic syndrome have an increased risk for cardiovascular disease events and are at increased risk for all-cause mortality. Metabolic syndrome increases the risk of type 2 diabetes, which itself is an important risk factor for atherosclerotic disease and may be considered as a coronary heart disease equivalent. Metabolic syndrome is also associated with a variety of other conditions, such as polycystic ovary syndrome, nonalcoholic fatty liver disease, gallstones, sleep disturbances, sexual impotence, and numerous forms of cancer including breast, endometrial, pancreatic, colon, and liver cancer, as detailed in Table 58.3 . In multiple trials involving nearly 1900 patients, morbidly obese individuals had much greater weight loss following bariatric surgery than after nonsurgical therapy, with amelioration of most of the diseases associated with morbid obesity in a year’s time. Metabolic syndrome is resolved by bariatric surgery in over 95% of patients who achieve the expected weight loss, making it clear that bariatric surgery is a metabolic intervention and not simply a weight management procedure.

Inflammatory processes appear to play an important role in the metabolic syndrome. Adipose tissue has two major functions: storage and release of energy-rich fatty acids and secretion of proteins required for endocrine and autocrine regulation of energy metabolism. Adipocytes exert their metabolic effects by release of free fatty acids, whose release is enhanced by the presence of catecholamines, release of glucocorticoids, increased beta-receptor agonist activity, and reduction of lipid storage mediated by insulin. Visceral adipose tissue has been identified as an important source of proinflammatory cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), as well as antiinflammatory cytokines such as adiponectin. Increased levels of proinflammatory cytokines likely contribute to the etiology of insulin resistance primarily by obstructing insulin signaling and contributing to downregulation of peroxisomal proliferator-activated receptor-γ, which are fundamentally important regulators of adipocyte differentiation and control. Additionally, insulin resistance may promote inflammation through diminution of insulin’s antiinflammatory effects. Lastly, oxidative stress is increased with obesity, primarily as a result of excessive intake of macronutrients and a concomitant increase in metabolic rate. These factors may also contribute to the inflammatory response noted with obesity.

Native immune responses act aberrantly in obese individuals. Natural killer (NK) cell cytotoxic activity is depressed with obesity, as are plasma levels of cytokines such as IL-12, IL-18, and interferon-γ known to regulate NK cell function. Other cytokines (primarily IL-6 and TNF-α) and adipokines (leptin, adiponectin, adipose-derived resistin) are two additional major groups of inflammatory proteins produced and released by adipose and adipose-associated tissue. Both serum and adipose tissue obtained from obese subjects consistently have elevated levels of IL-6 and TNF-α, and circulating levels of IL-6 are consistently increased in individuals having either type 2 diabetes or impaired glucose tolerance. Proteins such as leptin and adiponectin, which are produced primarily by adipocytes, are classified as adipokines. Although leptin is primarily involved in appetite control, its immunologic effects include protection of T lymphocytes from apoptosis and regulation of T-cell activation and proliferation. Reduced leptin levels may increase appetite and slow metabolism, but may also increase susceptibility to the toxicity of proinflammatory stimuli, such as endotoxin and TNF-α. Elevated leptin levels are proinflammatory, and this likely plays an important role in the progression of heart disease and diabetes, especially in obese patients. Serum levels of adiponectin correlate with insulin sensitivity and do not rise in obesity. Significantly reduced adiponectin levels are found in patients having type 2 diabetes. Adiponectin reduces both TNF-α production and activity. It also inhibits IL-6 production. Resistin, an adipokine that induces insulin resistance, is induced by endotoxin and cytokines. Resistin acts at the cellular level to upregulate production of proinflammatory cytokines, most likely through the nuclear factor κB (NFκB) pathway. Resistin appears to present a molecular link among metabolic signaling, inflammatory processes, and the development of cardiovascular disease. Resistin levels have been associated with inflammatory markers apparently independent of BMI in humans.

An understanding of the role of NFκB in insulin resistance is required to fully appreciate the links between obesity and inflammation. Both free fatty acids and TNF-α act via intracellular inflammatory cascade pathways to arrest insulin signaling. This process is mediated by activation of transcription factors present within the cell cytoplasm. Following their translocation to the nucleus, they eventually bind to transcription factors regulating the inflammatory process. The cytoplasm also contains NFκB, another transcription factor whose activation is implicated in a number of diseases, including diabetes. NFκB is also induced by hypoxia, and it increases production of proinflammatory cytokines TNF-α and IL-6, both of which are frequently increased in patients with OSA syndrome. Therefore inflammation provides the common linkage underlying the association between obesity, metabolic syndrome, and OSA.

Obstructive Sleep Apnea—Hypopnea Syndrome

OSA is a condition characterized by recurrent episodes of partial or complete upper airway collapse occurring during sleep. An obstructive apneic event is defined universally as the complete cessation of airflow during breathing lasting 10 seconds or longer despite maintenance of neuromuscular ventilatory effort. The definition of an obstructive hypopneic event however may vary depending on the criteria being used for scoring. The Centers for Medicare and Medicaid Services (CMS) defines a hypopneic event as the partial reduction of airflow of 30% or more lasting at least 10 seconds, accompanied by a decrease of at least 4% in the oxygen saturation (SpO ₂ ) as opposed to the American Academy of Sleep Medicine (AASM), which accepts a 3% drop in SpO ₂ or a terminal cortical arousal. Additionally, the AASM recommends scoring a third type of respiratory event in which flow limitation is detected and is associated with a cortical arousal. These events are designated respiratory effort related arousals (RERAs).

The diagnosis of OSA can only be made in patients who undergo polysomnography, or a home sleep study. Results of polysomnography are reported as the apnea-hypopnea index (AHI), which is derived from the total number of apneas and hypopneas divided by the total sleep time or the respiratory disturbance index (RDI) which includes RERA. A normal lower limit for AHI has not yet been defined in an epidemiologic study of healthy subjects. Most sleep centers commonly use an AHI between 5 and 10 events per hour as a normal limit. The severity of obstructive sleep apnea/hypopnea syndrome (OSAHS) is arbitrarily defined, but recommendations for disease classification are as follows :

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  Mild Disease: AHI of 5 to 15 events per hour

  
  
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  Moderate Disease: AHI of 15 to 30 events per hour

  
  
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  Severe Disease: AHI of greater than 30 events per hour

Due to the risks of developing systemic and pulmonary hypertension, left ventricular hypertrophy, cardiac arrhythmias, cognitive impairment, persistent daytime somnolence, and other factors, treatment is recommended for patients with either moderate or severe disease. Treatment partly depends on the severity of the sleep-disordered breathing, but the consensus view is that patients with moderate or severe disease should be treated with continuous positive airway pressure (CPAP) during sleep. Other conservative treatment measures may include weight loss, avoidance of alcohol prior to bedtime, and sleeping on one’s side.

Numerous studies have confirmed that obesity is the greatest risk factor for OSAHS, with about 70% of patients (up to 80% of males and up to 50% of females) with OSAHS being obese. Severe sleep apnea disease is more common in men until women reach the age of menopause, and a strong negative correlation between the AHI and minimum SpO ₂ has been observed. Importantly, the diagnosis of OSAHS may be missed until the patient presents for surgery. In one study of 170 patients presenting for surgery, only 15% had already been diagnosed with sleep apnea, but on preoperative testing, 76% were found to have OSAHS. A STOP-Bang questionnaire ( Box 58.2 ) can be used to screen patients for OSA, with a score of 5 to 8 identifying patients at risk for moderate to severe disease. We believe it is important for obese patients presenting for bariatric surgery to undergo preoperative polysomnography testing for OSAHS. Preoperative diagnosis and appropriate interventional management can have the following benefits: less postoperative sleep deprivation, improved response to analgesic and anesthetic drugs, and normalization of cardiovascular disturbances.

Anatomically, obese patients with OSAHS typically have increased amounts of adipose tissue deposited into oral and pharyngeal tissues including the uvula, tonsils, tonsillar pillars, tongue, aryepiglottic folds, and lateral pharyngeal walls. An inverse relationship exists between the degree of obesity and pharyngeal area. Deposition of fat in the lateral walls decreases the size of the airway and changes the shape of the oropharynx into an ellipse with a short transverse and long anteroposterior axis. This configuration can contribute to both the development and severity of airway obstruction and can also increase the expectation that it will be more difficult to maintain airway patency during mask ventilation and to perform direct laryngoscopy for endotracheal intubation with general anesthesia. Neuromuscular blockade should be fully reversed prior to extubation, and low tidal volumes or lung protective ventilation should be employed.

Additionally, airway obstruction following extubation is likely to be complicated by the use of opiate and sedative drugs needed for postoperative pain management because these drugs tend to decrease pharyngeal dilator tone and increase the likelihood of upper airway collapse.

OSA also plays an important role in inflammation and the metabolic syndrome. The hypopneic and apneic events that occur in OSAHS are part of the cycle of events that involves both arousal from sleep and oxyhemoglobin desaturation. Sympathetic nervous system activation results as patients with untreated OSA undergo cyclic episodes of hypoxia and reoxygenation. This process leads to elevation of proinflammatory cytokines and may also induce oxidative stress of vascular endothelium, thus inducing an even more heightened state of systemic inflammation in obese patients with OSA. Levels of many different inflammatory mediators, including IL-6, high-sensitivity C-reactive protein (hs-CRP), leptin, TNF-α, IL-1, reactive oxygen species, and adhesion molecules, such as intracellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), are increased in patients with OSAHS. Thus obesity, the metabolic syndrome, and OSAHS are interrelated diseases that significantly alter a patient’s inflammatory disease profile and increase multiple health risks, particularly those of cardiovascular and airway origin. Importantly, surgical intervention to cause weight loss has been shown not only to improve obesity-related respiratory disease, but it also can lead to significant and sustained increases in plasma adiponectin levels while decreasing both IL-6 and hs-CRP levels as well as improve NK cell function and increase IL-12, IL-18, and interleukin-γ plasma levels.

Behavioral Interventions and Modification

Behavioral interventions and behavioral modification are essential for obese patients to change their learned habits related to eating and physical activity in order to produce weight loss and long-term weight reduction. This applies both for nonsurgical and surgical approaches to weight loss. The key features of typical behavioral programs include self-monitoring, goal setting, nutrition and exercise education, stimulus control, problem solving, cognitive restructuring, and relapse prevention. Patients often benefit from referral to multidisciplinary weight loss programs that incorporate diet, physical activity, and behavioral interventions to achieve their weight loss goals because these combined interventions provide the best weight loss and weight maintenance results without pharmacologic or surgical intervention. However, it is essential to identify and treat patients with eating disorders or major psychiatric disorders who require specialized psychiatric and psychological treatment to achieve meaningful weight loss.

Pharmacotherapy for Weight Loss

Recommendations for pharmacotherapy as a treatment of obesity, first and foremost, stress lifestyle and behavioral modifications as the initial approaches to initiate weight loss. Patients who do not reach their established reasonable weight loss goals by a combination of diet and exercise may be directed to pharmacotherapy to increase weight loss. There are weight loss drugs that have been approved by the Food and Drug Administration (FDA) and are currently prescribed for long-term use. These are typically used adjunctively with diet and exercise for patients having a BMI of 30 or greater (≥27 for patients with obesity-related risk factors or comorbid diseases). In current practice, there are only two categories of weight loss drugs: appetite suppressants and lipase inhibitors. Three drugs are currently available for the specific indication of weight loss: phentermine, lorcaserin, and orlistat. Phentermine, an adrenergic reuptake inhibitor, augments adrenergic signaling within the central nervous system and peripheral tissues. Phentermine decreases appetite and food intake and increases resting metabolic rate to promote weight loss. Its side effects include tachycardia and hypertension. Lorcaserin is a selective 5-HT _2C receptor agonist that reduces food intake through the activation of pro-opiomelanocortin. Due to its selectiveness for the 5-HT _2C receptor, lorcaserin has a better safety profile than the previous serotonin agonists for weight loss that have since been removed from the U.S. market due to increased risk of stroke and acute coronary syndrome. Lorcaserin should not be used in patients on selective serotonin reuptake inhibitors (SSRIs) or monoamine oxidase inhibitors (MAOIs) due to the risk of serotonin syndrome, which can be life threatening. Orlistat, a lipase inhibitor, reversibly binds to lipase and prevents both absorption and digestion of certain dietary fats. Because orlistat also interferes with the absorption of fat-soluble vitamins, patients using this drug need to supplement fat-soluble vitamins A, D, E, and K. It has significant gastrointestinal side effects including diarrhea, steatorrhea, flatulence, fecal incontinence, and oily rectal discharge.

Alternative Pharmacologic Options

Allison and colleagues reviewed the literature on dietary and herbal medications for weight loss. These agents are marketed as “food supplements,” thereby escaping the purview of the FDA. Even though these supplements cannot legally claim to treat a disease, they can claim to reduce the risk of a disease. According to the review, claims for weight loss have been made for multiple products such as chitosan, chromium picolinate, conjugated linoleic acid, ephedra alkaloids (ma huang), and Garcinia cambogia . Most of the reports involving these compounds are from poor quality studies without any randomization, control groups, or blinding, thereby placing in question both efficacy and safety of these compounds. The only studies involving herbals that have consistently demonstrated weight loss involve combinations of ephedrine and caffeine. Pharmacologically, this is expected because ephedrine, an adrenergic agonist, is known to be an appetite suppressant and a thermogenic agent. For this reason, ma huang , a natural source of the ephedra alkaloid, is added to most, if not all, dietary supplements marketed for weight loss. The success of ephedrine as a weight loss agent in combination with caffeine and or aspirin is well established. Unfortunately, multiple cases of cardiac and neurological issues, including hypertension, stroke, seizure, and even death have been reported, possibly related to the inconsistent doses in the preparations and the lack of medical supervision in people consuming these products for weight loss. Consequently, the National Institutes of Health has banned these products from any recommended weight loss regimen.

Implanted Electrical Stimulators

Implantable gastric stimulators are subcutaneously placed devices that resemble cardiac pacemakers and stimulate along the lesser curvature of the stomach. These gastric stimulators have been tried since the early 2000s and have been found to cause modest weight loss with few side effects. Numerous clinical trials conducted in the United States and Europe have shown some promising results. Most studies demonstrated weight loss during the first 12 months; however only a few studies had a follow-up period of longer than 1 year. One study documented a 25% excess weight loss, improved response to oral glucose tolerance test, decreases in arterial blood pressure, and an improvement in symptoms of gastroesophageal reflux disease (GERD), along with an increased parasympathetic drive. No serious side effects were noted in the first 65 patients reported on in this study or in the 20 patients followed in another. Ghrelin levels may play a role in the success of these devices.

Operative Procedures

Surgery for obesity is one of the fastest growing surgeries performed worldwide. The operative group can be divided into gastric restrictive procedures and procedures that combine gastric restriction with induction of nutrient malabsorption. These procedures can be performed using an open, laparoscopic, or robot-assisted approach. In general, minimally invasive (laparoscopic, robotic) approaches are preferred over an open procedure as they have a lower complication rate, hospital stay, and morbidity. The rate of open bariatric procedures has continued to decrease steadily to the extent that nearly 90% of surgical bariatric cases are now performed laparoscopically.

Restrictive Procedures

The surgical goal of restrictive operative procedures is to reduce and limit the patient’s food intake capacity. This is most commonly achieved by reducing the stomach’s reservoir capacity. The vertical band gastroplasty was a widely practiced restrictive procedure in the previous three decades, but it was replaced by the minimally invasive laparoscopic gastric band procedure (LGB), which was very popular. However, in recent years, the percentage of bariatric procedures represented by LGB surgery performed has also decreased from 35% in 2011 to approximately 3% in 2016. This decline in LGB operations is probably secondary to only modest amount of weight loss and high rates of band revisions and adjustments required. Recently, the sleeve gastrectomy (SG) has become the most commonly performed surgery for obesity. As illustrated in Fig. 58.2 , in SG surgery, a tubular stomach is created around a 32 to 40 French bougie by removing the greater curvature of the stomach. The SG has been shown to be safe and effective, with a mean excess weight loss of approximately 65%. The weight loss noted after a SG is not only due to the restrictive stomach, but also due to the decrease in hormonal level of ghrelin that regulates appetite and food intake.

Sleeve gastrectomy: a tubular stomach is created as the fundus and greater curvature of the stomach are removed around a 32F to 40F bougie.

Malabsorptive Procedures

The surgical goal of malabsorptive procedures is to cause weight loss both by gastric restriction and nutrient malabsorption. Historically, early surgical procedures involved creation of a long jejunoileal bypass. Patients achieved significant weight reduction but this was commonly accompanied by an unacceptable incidence of serious vitamin and protein malabsorption, osteoporosis, and hepatic failure.

Today, gastric bypass (GBP), which is illustrated in Fig. 58.3 , and biliary pancreatic diversion (BPD) are the two most commonly performed malabsorptive operations, and both have achieved success in safety and efficacy. GBP is more commonly performed than BPD, and it is considered the safer of the two malabsorption procedures. GBP surgery involves the creation of a small gastric pouch by stapling or banding the stomach. This results in an element of gastric restriction. GBP also involves the creation of a Roux-en-Y anastomosis, in which the small gastric pouch is directly connected to the middle portion of the jejunum. The OrVil device, shown along with nontapered and tapered bougies in Fig. 58.4 , may be used by the surgeon to assist with creation of the anastomosis. The orogastric portion of the OrVil device is passed through the oropharynx and then pulled through by the surgeon via a gastrostomy, until the anvil portion of the OrVil device reaches the stomach. It is then attached to a stapler to create the anastomosis. The path for food through the gastrointestinal tract subsequently bypasses the gastric remnant and the upper portion of the duodenum. This procedure can be performed with a laparotomy incision or by using laparoscopic techniques. Although this is considered to be a safe operation, the associated perioperative mortality is higher than that of restrictive procedures. Additionally, there are some important long-term complications such as vitamin B ₁₂ deficiency, anemia, incisional hernia, cholelithiasis, and staple line failure that occur with significant frequency. Often a cholecystectomy is performed concurrently to prevent future cholelithiasis. BPD is also a form of Roux-en-Y GBP reconstructive alimentary anatomy in which the bypassed intestinal segment includes the portion of duodenum at the point of entry of biliary and pancreatic secretions. This allows the bypassed intestine to be exposed to bile and pancreatic juice. The antrum is removed to avoid peptic ulceration, and food intake is only affected to a limited degree. The essential element of this operation is division of the small intestine about midlength, with the distal end of the alimentary limb being anastomosed to a generous gastric remnant. The more proximal biliopancreatic limb is anastomosed to the alimentary limb about 50 cm from the ileocecal valve. Following either the GBP or BPD form of operation, patients require life-long follow-up and may need micronutrient replacement long term.

Roux-en-Y gastric bypass: part of the stomach is detached from the rest, creating a small pouch. The pouch is connected to a lower part of the small intestine by a piece of small intestine, resembling a Y. As a result, parts of the stomach and small intestine are bypassed. However, digestive juices (bile acids and pancreatic enzymes) can still mix with the food, enabling the body to absorb vitamins and minerals and reducing the risk of nutritional deficiencies.

32F tapered bougie (top) , 40F nontapered bougie (middle) , and OrVil device (bottom) commonly used during bariatric surgery.

Minimally Invasive Procedures

There have recently been a few devices approved in the United States for weight loss. One such device is the intragastric balloon that acts in a restrictive manner. The intragastric balloon is placed in the patient’s stomach endoscopically and is filled with saline to provide a sensation of fullness and satiety. The device can be kept in the patient’s stomach for a maximum of 6 months and has been shown to decrease weight by an average of 6.8%. Most common complications of the intragastric balloon are related to gastrointestinal symptoms such as nausea, vomiting, halitosis, GERD, and abdominal discomfort; however serious complications such as balloon rupture, migration, and intestinal obstruction are possible.

Another device that has been approved for use in the United States is an endoscopically placed percutaneous gastrostomy tube to facilitate stomach emptying. The device can be used for draining ingested foods and in preliminary studies has been shown to decrease total body weight (TBW) by approximately 12%. The most common side effects were abdominal discomfort and peristomal irritation; however serious complications such as abdominal pain requiring hospitalization and peritonitis were noted infrequently.

Health Benefits of Bariatric Surgery

The two most significant outcome measures of bariatric surgical success are weight loss and resolution of comorbidities. Major effects of bariatric operations have been nicely summarized in extensive meta-analyses as well as in a major literature review. Patients undergoing bariatric surgery with either SG or GBP have lost 52% to 68% of their excess weight. This magnitude of weight loss is far greater than what is commonly achievable by nonsurgical methods, and it is considerably closer to patients’ desired and expected weight loss. Long-term maintenance of weight loss of this magnitude can also be maintained for well over a decade.

Improvement in obesity-related and metabolic syndrome-related comorbidities have also been evaluated. One clinical study demonstrated that at 1 year, type 2 diabetes remission rate with bariatric surgery was approximately 40% compared to 12% with medical treatment. Another study showed remission rate at 2 years of approximately 85% compared to 0% with medical treatment. This benefit seems to persist long-term as well, as at 6 years 62% of surgical patients experienced remission in their type 2 diabetes. Resolution of diabetes following surgery is inversely related to the preoperative duration of the disease and occurs more in those patients having diabetes controlled using oral hypoglycemic agents. This clearly distinguishes surgical treatment of obesity as an important endocrinologic intervention, especially since the modest improvement in diabetes management that is produced by nonsurgical weight loss is accompanied by relapsing disease by nearly 100% of patients within 5 years.

Surgical effects on hypertension and hyperlipidemia are similarly impressive. A study of almost 1900 patients demonstrated that at a 6.5 year follow-up, 32% of surgically treated patients had remission of their hypertension versus 12.5% in medically managed patients. A significant decrease in triglyceride levels, approximately 30% to 40% postbariatric surgery versus 8% from medical therapy; and increase in HDL cholesterol levels, 30% postsurgery versus 7% from medical therapy, have also been noted at 5 years. Resolution of OSAHS seems to be independent of the specific bariatric surgical procedure employed, with resolution occurring overall in 85.7% of patients. Postsurgical improvement in other comorbidities has also been demonstrated, with improvement in fatty infiltration of the liver, GERD symptoms, in respiratory function and asthmatic symptoms, reversal of the cardiomyopathy of obesity, and improvements in joint pain and mobility all having been reported. The reduction in obesity-related comorbidities has been shown to endure with 5-year follow-up. Although bariatric surgery has been shown to provide greater weight loss when compared with nonsurgical lifestyle interventions, comorbidities do resolve and risk factors do improve similarly with successful conservative treatments.

Preoperative Evaluation

The preoperative assessment for anesthesia should include consideration of hypertension, diabetes, heart failure, and obesity hypoventilation syndrome. Results of the sleep study that the patient underwent are important. An AHI score greater than 30, implying severe sleep apnea, is a warning sign and a predictor for rapid and severe desaturation at induction. CPAP levels greater than 10 imply a patient with the potential for difficult mask ventilation.

Another useful piece of information in the preoperative evaluation is gleaned by examining the history of prior surgeries, their anesthetic challenges (i.e., ease or difficulty in securing the airway, intravenous access), need for intensive care unit admission, surgical outcomes, and the weight of the patient at that time. This information may either help ease some concerns or allow for better preparation for the upcoming anesthetic care. Recommended preoperative laboratory evaluations include fasting blood glucose, lipid profile, and serum chemistries (evaluating renal and hepatic function), complete blood count, ferritin, vitamin B ₁₂ , thyrotropin, and 25-hydroxyvitamin D.

If appropriately evaluated, ideally prepared, and optimally managed perioperatively, even patients with well-known coronary artery disease (CAD) have comparable morbidity and mortality as those without CAD. The effect of OSA on perioperative risk remains controversial, but most patients are screened for OSA using overnight oximetry or polysomnography, or both, if appropriate. If identified with OSA and recommended for CPAP, then patients are encouraged to initiate therapy at home and it should be continued throughout the perioperative period.

Liver function abnormalities are common in this patient population, especially nonalcoholic fatty liver disease, with the extent of disease a determining factor for perioperative risk and postoperative outcomes. Cirrhotic liver disease with portal hypertension may be considered a contraindication to bariatric surgery. Gastrointestinal symptoms of dyspepsia may indicate the presence of Helicobacter pylori , which requires treatment by standard medical regimen.

The factors that may be considered contraindications for bariatric surgery include unstable CAD, uncontrolled severe OSA, uncontrolled psychiatric disorder, intellectual disability (IQ <60), inability to understand the surgery, perceived inability to adhere to postoperative restrictions, continued drug abuse, and malignancy with a poor 5-year survival prognosis. In most situations preoperative management of the medical morbidities can help optimize risk and convert high-risk patients to ones of acceptable risk.

The anesthetic care of patients with OSA is complicated by the side effects of anesthetic drugs on an already compromised respiratory system. The commonly presented comorbidities in this patient population only accentuate the problem. The change in perioperative risk based on the anesthetic agent utilized is only deduced from anecdotal reports of different cases. There is a paucity of trials to definitively determine an optimal anesthetic regimen. Nevertheless, the American Society of Anesthesiologists and the Society for Anesthesia and Sleep Medicine have both published statements based on existing literature and consensus of expert opinion addressing the perioperative identification and management of patients who carry a formal diagnosis of OSA as well as for those who are at risk for sleep apnea but remain undiagnosed. Additional questions commonly arise and cannot yet be answered on the basis of high-grade scientific evidence: is it safe to perform procedures in patients with sleep apnea and treat them as outpatients or day surgery patients? What procedures pose sufficient risk to the patient to recommend an overnight hospital stay? Does narcotic use impact this decision? Would the increased role of nonsteroidal antiinflammatory drugs (NSAIDs) change these recommendations? Factors such as neck size and open versus laparoscopic surgery are being studied as to their impact on outcomes. Further research on these and other patient safety related questions is continuing.

Intraoperative Care

Obese patients present special intraoperative challenges for the anesthesiologist in airway management, positioning, monitoring, choice of anesthetic technique and anesthetic drugs, pain control, and fluid management. Many of these issues are equally important in their postoperative care. The most significant and best studied are airway management, including endotracheal intubation, pulmonary physiology, and techniques of maintaining adequate blood oxygenation and lung volume. Specific interventions, techniques, and approaches employed by the anesthesia care team providing anesthesia for obese patients are important determinants of outcomes.

Postoperative Management

In our practice, we prefer to have the postbariatric surgery patients stay at the same location consistently. This allows skilled nursing and ancillary care to be provided to patients on a consistent basis. These patients are kept on their CPAP or bilevel positive airway pressure machines as much as possible with monitoring of end-tidal carbon dioxide and SpO ₂ by pulse oximetry recommended. Monitoring capnometry in the postoperative period is critical for assessing a morbidly obese patient’s respiratory function since the administration of supplemental oxygen may delay the diagnosis of hypoventilation. At the Hospital of the University of Pennsylvania, patients identified as having difficult airways are distinguished with armbands, and with visible signs on their beds, their hospital charts, and on the electronic medical records for the remainder of their hospital stay. Additionally, a note by the attending anesthesiologist explaining the difficulty in intubation as well as the means utilized to secure the airway in the operating room is available in the room. In case of an unexpected emergency intubation, for whatever reason, we feel that this extra information is extremely useful to the resuscitation team.

Postoperative nausea and vomiting (PONV) is a common reason for delayed discharge from the postanesthesia care unit (PACU). Intraabdominal surgery is a known risk factor for PONV. Patients undergoing bariatric surgery have significant manipulation of their stomach, which may increase their risk of PONV. It is recommended to include a multimodal approach to PONV prophylaxis, including ondansetron, dexamethasone, and placement of a scopolamine patch when not contraindicated in order to minimize patient dissatisfaction and serious complications such as aspiration or wound and anastomotic dehiscence.

Enhanced recovery after surgery (ERAS) protocols are being used widely in surgical patients to decrease morbidity and decrease in-hospital stay. One study looking at patients undergoing an SG demonstrated a median hospital stay of 1 day in the ERAS group compared to 2 days in the control group, without any difference in postoperative complications or readmissions. The ERAS protocol included standardized preoperative patient education, shortened preoperative fasting, multimodal analgesia and antiemetic therapy, avoidance of fluid overload, early ambulation and feeding, and incentive spirometry.

Management of Complications

Bariatric surgery is considered to be very safe, but not without potential complications, which are increasingly predictable. In-hospital mortality rates for patients undergoing laparoscopic and open bariatric surgery are 0.17% and 0.79%, respectively. Mortality is associated with a need for reoperation during the same hospitalization, with intestinal leakage being a serious complication accounting for a large number of patient deaths. Risk factors also include older age, excessive obesity, poor functional status, and comorbid conditions of congestive heart failure or renal failure.

Morbidity occurring during the immediate postoperative in-hospital period typically falls into one of four categories; wound, gastrointestinal, pulmonary, and cardiovascular complications. The complication rates are significantly lower in each category for patients undergoing laparoscopic rather than open procedures. The American College of Surgeons National Surgical Quality Improvement Program database showed that patients who had an open GBP compared with a laparoscopic GBP had a morbidity rate of 7.4% versus 3.4%, return visits to the operating room rate of 4.9% versus 3.6%, and median postoperative length of stay of 3 versus 2 days, respectively. Box 58.3 provides a categorical listing of complications of bariatric surgery.

Box 58.3

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