The list of comorbid conditions that contribute to surgical risk is large and offers multiple opportunities for preoperative treatment and optimization. Bariatric surgery programs should acquire familiarity with current medical guidelines for optimal management of comorbid conditions as appropriate diagnosis and management will improve outcomes. It is no longer sufficient to rely fully on outside busy specialists to assess and manage the investigation of comorbid conditions. Specialists who are accountable to the bariatric program should collaborate closely with the bariatric team throughout the preoperative process.

Each comorbid condition that has been identified as a risk factor is listed in Table 13.1, together with management strategies to be considered in order to reduce risk.

Cardiopulmonary conditions which add to risk including obese cardiomyopathy, ischemic heart disease, congestive heart failure, obesity hypoventilation, pulmonary hypertension, obstructive sleep apnea, and chronic obstructive lung disease are extremely important as they offer many opportunities for treatment and optimization before intervention [4–10]. Many of these conditions may be undiagnosed or inadequately investigated prior to the evaluation for bariatric surgery. Proper management requires that the bariatric program team members have familiarity with the diagnosis and management of these conditions. Close and ongoing collaboration with specialists will be necessary to optimize many comorbid conditions.

Functional assessment is an important part of the assessment of severity and prognosis of many conditions and also can be used as an index of response to treatment. A simple test for functional assessment, which can easily be incorporated into the bariatric surgery evaluation process, is the 6-min walk test [11]. Optimization of the more serious cardiopulmonary conditions like obesity hypoventilation, congestive heart failure, and pulmonary hypertension will likely delay surgery or mandate decisions regarding lower risk interventions. All of the cardiopulmonary conditions will improve with preoperative weight loss (to be discussed later in this chapter).

Thromboembolism is a modifiable risk factor for mortality and adverse events. All patients with extreme obesity are at increased risk for venous thromboembolism [12], and thromboembolism is a leading cause of postoperative fatality after bariatric surgery. The multiple factors that contribute to the increased thromboembolism risk in obesity are discussed in Chap. 7. With current frequent use of thromboembolism prophylaxis, overall thromboembolism rates are <0.5 %, but are higher in cohorts with added risk factors which include male gender, prior venous thromboembolism, superobesity, older age, functional impairment, use of hormone therapy, obesity hypoventilation syndrome, pulmonary hypertension, venous stasis disease, and longer operative time [12]. Bariatric surgery candidates with additional risk factors may benefit from more detailed hematologic assessment as thrombophilia is more common in extreme obesity [13]. Recommendations for prophylaxis for bariatric surgery patients are outlined in Table 13.1 [14]. The reader is also referred to the current American Society for Metabolic and Bariatric Surgery (ASMBS) position statement on thromboembolism prophylaxis for current best practice recommendations [12].

A small subset of bariatric surgery candidates with cardiopulmonary diseases or histories of thromboembolism require therapeutic anticoagulation. These patients are at significant risk for perioperative bleeding complications and will require special attention during the preparation for surgery. Specific challenges include the indications for bridging anticoagulation, the timing of transition from prophylaxis to therapeutic anticoagulation after bariatric surgery in the context of a short hospital stay, and the transition to oral anticoagulation. Traditionally, bariatric surgery programs have delegated this management issue to the physician prescribing the anticoagulation. An example of problems with this approach occurs in the gastric bypass patients who require chronic warfarin and must be restarted on warfarin after successful surgery. Gastric bypass patients usually require a lower dose of warfarin in the first 30 days after surgery, and the lack of awareness of this has resulted in a high incidence of readmissions for bleeding related to overdosing with warfarin [15]. The cause of this is unknown, but may involve a negative vitamin K balance during the initial weeks after gastric bypass. The bariatric surgery team should manage these patients with the transition to warfarin closely monitored with weekly or bi-weekly coagulation studies. The reader is referred to current practice guidelines regarding anticoagulation management during invasive procedures [16].

Diabetes has historically been associated with a perioperative infection risk. More recently, hyperglycemia in the perioperative period has been associated with immune dysfunction [17] and is a proven risk factor for perioperative infections in general and vascular surgery [18]. A recent study has demonstrated an association between perioperative hyperglycemia and adverse outcomes in a veteran population undergoing colectomy for cancer [19]. Many bariatric surgery candidates with type II diabetes have poor glucose control, and perioperative hyperglycemia is common with bariatric surgery. Perioperative management strategies focusing on tighter glucose control utilizing insulin infusion have been shown to improve outcomes [20] and are now considered an emerging perioperative quality indicator. Although the impact of hyperglycemia on bariatric surgical morbidity has not been formally studied, most agree that tighter glucose control is an opportunity for risk reduction [21]. The reader is also referred to the discussion of perioperative glycemic control in Chap. 14.

Hypoalbuminemia has recently been identified as a risk factor in bariatric surgery [22], and other studies have identified hypoalbuminemia as an important prognostic indicator in major surgery [23, 24]. Hypoalbuminemia is common among patients with acute and chronic medical conditions. It can be caused by many conditions including the nephrotic syndrome, hepatic cirrhosis, heart failure, and malnutrition. In addition, it is often caused by an acute or a chronic inflammatory response. This condition may be present in 1–12 % of bariatric surgery candidates (Chap. 6, Table 6.​1) [25, 26]. If hypoalbuminemia is identified in bariatric surgery candidates, the etiology must be determined. If related to protein malnutrition, this should be corrected prior to surgery [27]. An evaluation for cirrhosis [28], another significant bariatric surgery risk factor [29, 30], is also indicated.

Impaired functional status has been identified recently in several studies as a risk factor for adverse outcomes following bariatric surgery (Chap. 12, Table 12.​1). Functional impairment and reduced levels of physical activity are common among candidates for bariatric surgery. Accelerometer data and patient diaries from the Longitudinal Assessment of Bariatric Surgery Study (LABS) indicate that more than half of the candidates for bariatric surgery have very limited levels of physical activity (Fig. 13.1) and that the extent of physical activity is inversely related to BMI [31]. The same investigators later demonstrated that walking limitations are very common in candidates for bariatric surgery. Of 2,458 candidates asked to perform a long corridor walk test, 28 % were ineligible because of limiting comorbidity or they declined to participate, and only 65 % were able to complete the walk test [32]. Most of the focus on physical activity in bariatric surgery thus far has been during the postoperative period where the improvements are well documented [33, 34]. However, the identification of functional impairment as a surgical risk factor as well as the observations that preoperative attention to physical activity leads to an increase in preoperative physical activity [35], to increased physical activity readiness [35], and to an increase in postoperative physical activity [36] are shifting the focus to the preoperative preparation phase.

The health benefits of physical activity include improved flexibility, strength, and balance; improved bone health; improved cardiovascular health; improved diabetic control; improved psychological well-being; improved cognitive function; enhanced sleep quality; and improved longevity [31, 37]. Most bariatric surgery candidates are unable to take advantage of these health benefits. The recent evidence of increased surgical risk associated with functional impairment and the finding that poor aerobic fitness among bariatric surgery candidates is associated with in increased risk of adverse events [38] have stimulated interest in the enhancement of physical activity in the preoperative period before bariatric surgery. Although there is little evidence thus far supporting an outcome advantage with increased preoperative physical activity, there is evidence that intensive physical activity programs together with diet can improve comorbid conditions and induce significant weight loss in severely obese patients [39].

The term “prehabilitation” is the process of enhancing functional capacity in order to allow an individual to better withstand a physiologically stressful event such as surgery. Studies in prehabilitation have thus far come from Canada perhaps because of the longer waiting period for elective surgery. The lengthy preoperative preparation process, which is the rule for bariatric surgery, will easily accommodate prehabilitation strategies. Studies in prehabilitation are available in other surgical specialties and have documented some important physiologic improvements prior to surgery. In a study of 112 patients prior to major colorectal surgery, structured exercise regimens were tested for a mean of 52 days before surgery. A significant fraction of the patients tested demonstrated improvements in maximal oxygen consumption and performance in the 6-min walk test as a result of the prehabilitation program [40]. In this study, 33 % improved physical function, 38 % did not change significantly, and 29 % deteriorated (mostly because of lack of adherence to the regimen). Patients who deteriorated were at greater risk for a life-threatening complication. Those who improved had a more rapid functional recovery after surgery [41]. A simple walking and breathing program seemed to be successful with good patient participation in this study.

In a small study of operable lung cancer patients prior to thoracotomy, a structured exercise regimen was prescribed with the goal to increase physical fitness. The exercise program was individually tailored to each patient’s fitness level and supervised by specialists. Outcome assessments included the 6-min walk test and measurement of maximum oxygen consumption (VO_2peak). The investigators demonstrated that a short-term preoperative exercise program did improve aerobic fitness and walking capacity (Fig. 13.2a, b). No information regarding the impact on surgical outcome is provided [42].

These pilot studies in prehabilitation indicate that improvement in physical function is possible in preoperative patients. Similar feasibility studies are needed in bariatric surgery candidates, especially those with functional impairment. Functional impairment among candidates for bariatric surgery has multiple causes including cardiopulmonary comorbid disease, musculoskeletal degenerative disease, and mental health conditions such as severe depression. In these patients, prehabilitation can be enhanced by concomitant weight loss programs, which will favorably affect nearly all comorbid conditions. In older adults, the combination of exercise and weight loss has a greater positive effect on physical function than either intervention alone [43].

The implementation of prehabilitation programs will be a challenge for bariatric programs because of the physical impairments common to extreme obesity and the reluctance of bariatric surgery candidates to participate because of fear of embarrassment and failure. Additional expertise in exercise therapy will be necessary to provide counseling and assessment of each patient’s physical capacity in order to individualize physical activity programs [44]. Such individualized effort will have the advantage of enhancing patient confidence in the program, which should enhance patient accountability and compliance. Progress can be monitored by sequential functional assessments such as the 6-min or long corridor walk tests. The establishment of milestones and documentation of attainment will provide additional motivation and sense of involvement for patients. Hopefully, the official designation of obesity as a disease will allow for expanded resources available for multidisciplinary obesity centers and development of prehabilitation programs for impaired patients.

Tobacco smoking is a well-known cause of preventable deaths worldwide and also known to surgeons as a risk factor for surgical morbidity. Several studies have confirmed that smoking is a risk factor for adverse events after bariatric surgery (Chap. 12, Table 12.​1) [45–47]. In a survival analysis of 18,972 postoperative bariatric surgery patients studied between 1986 and 2001 (mean postoperative follow-up of 8.3 years), there were 654 mortalities (3.45 %). The risk for death of smokers in this cohort was twice that of nonsmokers (hazard ratio 2.05; 95 % confidence interval 1.67, 2.52; p < .0001) [48]. Another VA study of bariatric surgery using the NSQIP methodology found that the extent of smoking correlated with the odds ratios of failure to wean from mechanical ventilation within 48 h of the procedure [45]. Smoking also influences adverse events after bariatric surgery as a contributor to the risk of thromboembolism [49, 50] and marginal ulcer [51].

Mechanisms for the physiological impact of smoking on surgical complications include alterations in respiratory epithelium with impaired mucociliary clearance, an increase in closing volume predisposing to atelectasis, and a decline in expiratory airflow rates. Bariatric surgery candidates frequently have significant abnormalities in pulmonary function related to the extent of obesity, and this may heighten the clinical impact of smoking on pulmonary reserve. The majority of the morbidity related to smoking after surgery, however, involves wound complications including wound infection, flap necrosis, and wound dehiscence. Many of the important components of wound healing are adversely affected by smoking. The effects of smoking on each phase of wound healing are summarized in Table 13.2 [52].

Cessation of smoking does reverse the adverse effects of smoking on wound perfusion and on inflammatory cell function. The effects on the proliferative phase remain impaired [52].

Although this has not as yet been studied in bariatric surgery, there is substantial evidence that smoking cessation can be achieved in preparation for surgery and can reduce surgical morbidity. A systematic review of 11 randomized controlled trials in 1,194 patients found that preoperative smoking cessation programs involving regular (weekly) individual counseling and nicotine replacement therapy carried out over 1–2 months prior to surgery do result in both short- and longer term smoking cessation. The review found that those smoking cessation programs that were of lesser intensity were not significant in their impact on smoking cessation. In addition, a meta-analysis of the pooled results found that interventions for smoking cessation are able to significantly reduce surgical morbidity (pooled risk ratio 0.45; 95 % confidence interval 0.41–0.78; p < 0.001) [53]. The optimum duration of smoking cessation prior to surgery is 8 weeks or more [54], and there is some evidence that cessation for less than 4 weeks prior to surgery may be of no benefit and actually increase the risk of pulmonary complications [55

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