Preoperative Evaluation in Bariatric Surgery

Introduction

Obesity is a worldwide increasing concern, and is believed to be the second most preventable cause of mortality in the United States (US). ¹ The prevalence of obesity has risen rapidly over the past several decades in the United States, and according to the latest figures for 2011 to 2014 from the Centers for Disease Control and Prevention, 36% of U.S. adults and 17% of youth are obese. ²

Obese individuals are at increased risk for many health problems, including cancer, heart disease, stroke, type 2 diabetes mellitus, hypertension, and gastroesophageal reflux disease (GERD) among others. ³ In addition to the devastating health comorbidities associated with obesity, this condition has important economic consequences. The percent of the United States' national medical expenditures devoted to treating obesity-related illness in adults rose from 6.13% in 2001 to 7.91% in 2015, an increase of 29%. ⁴ Medical management of obesity includes pharmacotherapy targeting obesity and medications treating associated comorbidities. ⁵ However, since nonsurgical treatment for weight loss in the morbidly obese patients is rarely successful in the long term, bariatric surgery has gained in acceptance and popularity in the last years. ⁶

An adequate preoperative workup is critical for the success of bariatric surgery. This review will focus on the preoperative studies and counseling that are needed for patients planning to undergo bariatric surgery.

Patient Education

An integral component of the preoperative evaluation involves a comprehensive patient education about surgical outcomes and the postoperative behavioral regimen required. A multidisciplinary assessment by a team of endocrinologists, dieticians, psychologists, and the surgeon, preoperatively to evaluate and educate the patient, helps in appropriate patient selection to ensure that the patient is physically and psychologically fit to undergo weight loss surgery (WLS). Candidate selection criteria for bariatric surgery include body mass index, presence, and effect of comorbidities to patient's overall health, and a history of prior weight loss attempts. Personalized assessment of the risk and benefits of the procedure, along with the assessment of the individual's ability to comply with postoperative care is vital to the preoperative assessment and education of the patient.

Many patients seeking WLS hold unrealistic expectations, without a complete understanding of the procedures and the subsequent long-term implications.^7–9 Patient understanding of long-term consequences of WLS, such as postoperative lifestyle modification, psychosocial implications, need for long-term follow-up, and consistent implementation of recommended postoperative regimens, facilitates a more informed decision making.

The preoperative education is pivotal in managing expectations and dispelling any misconceptions that patients may have. It is crucial to evaluate each patient, in terms of existing comorbid conditions to establish individual patient goals and expectations. For instance, while WLS has significant benefits of sustained weight loss and improvements in metabolic comorbidities,^10–13 it is important to be cognizant of the effect of existing comorbidities on perioperative morbidity.

Overall, a thorough discussion of the potential postoperative morbidity and patient expectations of postsurgical weight loss, including the potential for weight regain, is strongly recommended.

Medical Evaluation and Clearance

A comprehensive medical evaluation entails meticulous history taking, a thorough physical examination, including a review of the cardiovascular, pulmonary, and gastrointestinal systems, as well as a metabolic and nutritional status assessment.

A complete medical history should include weight history, past diet history, social history, complete psychological history (including history of eating disorders and substance abuse), physical activity, medication review, and psychosocial factors that may affect weight loss. ¹⁴ The clinical examination should include an assessment of anthropometrics, biochemical laboratory values (including electrolytes, vitamins, iron, folate, and calcium levels), and a complete metabolic panel. All efforts should be made to achieve optimal glycemic control perioperatively to minimize the risk of postoperative complications. ¹⁵

Obesity is a well-established risk factor for cardiovascular comorbidities including coronary artery disease, arrhythmias, left-ventricular hypertrophy, and heart failure. ¹⁶ While the American Heart Association Assessment classifies intraabdominal surgery as an intermediate risk procedure, optimization of these comorbidities is essential to prevent poor surgical outcomes in bariatric surgery patients.^17–19 Cardiac evaluation includes a 12-lead electrocardiogram, followed by assessment of cardiac function with stress testing. The traditional stress testing methods (e.g., treadmill exercise, scintigraphic imaging) may not be feasible in morbidly obese patients given the weight limitations of the testing equipment and the difficulty to accurately interpret the images owing to the patient's body habitus.^20,21 Pharmacological stress echocardiography, with or without ultrasound contrast agents, is an effective alternative for this patient population that can provide an accurate assessment of cardiac function.^22,23

Given that obesity is a risk factor for airway disease secondary to mechanical restriction, routine preoperative pulmonary function tests help assess the pulmonary reserve and identify those at risk for postoperative pulmonary complications, such as atelectasis, laryngospasm, and the need for reintubation.^24,25 While a large proportion of patients undergoing WLS often have associated obstructive sleep apnea (OSA), some may receive the diagnosis during the preoperative workup for the surgery. ²⁶ The patients at risk for OSA, as identified by any of the screening tools (e.g., Epworth Sleepiness Score, the Berlin Questionnaire or the STOP-BANG questionnaire) are further evaluated using an overnight polysomnography test. Additionally, some patients may present with daytime hypercapnia; a pulmonary derangement termed obesity hypoventilation syndrome (OHS). Most patients diagnosed with OSA and/or OHS benefit from continuous positive airway pressure or bilevel positive pressure preoperatively.^27–29 While routine spirometry testing in all patients undergoing WLS is debatable, some have suggested a benefit of preoperative spirometry in those at a high risk for pulmonary complications.^30,31

Venous thromboembolism (VTE) remains an important cause of postoperative morbidity in patients undergoing WLS. While the optimal approach for VTE prophylaxis in these patients is not clear, most receive some form of prophylaxis, including lower extremity compression, pharmacologic prophylaxis, or both. The standard antithrombotic regimen minimizes the risk of VTE, ³² with a growing body of evidence suggesting superiority of standard (i.e., nonadjusted) low-molecular-weight heparin over unfractionated heparin.^33,34 Evidence for the benefit of routine venous duplex scan is lacking, and is not currently recommended.^35–37

A comprehensive assessment and stratification of the risk of adverse events can inform clinical decision making, and help identifying ideal candidates for bariatric surgery and those that may require closer postsurgical monitoring.

Psychological Evaluation and Clearance

Psychosocial factors have a significant impact on the long-term outcomes of bariatric surgery including adherence to recommended postoperative lifestyle regimen, emotional adjustment, and weight loss outcomes. Thus, a comprehensive evaluation by bariatric behavioral clinicians is recommended, to identify risk factors that may affect optimal surgical outcomes and weight loss goals. The preoperative psychological evaluation also helps establish a trusting working relationship between the behavioral clinician and the patient. ³⁸ The psychological evaluation includes a thorough clinical interview for assessment of:

Weight history

The psychological evaluation is critical to determine the quality and extent of social support available to the patient. Evidence suggests that the presence of self-reported support from family, friends, and/or community is associated with a higher likelihood of successful outcomes. ³⁹ Patients with a greater perceived affective response and emotional involvement are associated with long-term health behaviors that promote weight maintenance. ⁴⁰ Thus, the psychological evaluation serves to identify coexisting risk factors that may affect postoperative weight loss outcomes, and recommend interventions before or after surgery to optimize surgical outcomes.

Nutritional Evaluation

The nutrition professional is a key component of the multidisciplinary bariatric care, and should be in charge of the nutritional assessment, preoperative weight loss efforts, and diet education regarding postoperative eating behaviors. ⁴¹ Adequate preoperative nutrition counseling by a registered dietician facilitates better tolerance to postoperative lifestyle modification, including changes in diet patterns, thereby minimizing the risk of nutritional deficiencies.

All patients should undergo a rigorous nutritional evaluation, including micronutrient measurements, before any bariatric surgical procedure. In comparison with purely restrictive procedures, more extensive perioperative nutritional evaluations are required for malabsorptive procedures. ⁴²

Preoperative Gastrointestinal Imaging

Preoperative Weight Loss

Preoperative weight loss should not be considered in isolation when clearance for bariatric surgery is being evaluated. ⁶¹ For instance, Alami et al. ⁶² conducted a randomized trial comparing a group of patients with a preoperative 10% weight loss requirement and a group that had no weight loss requirements. The percentage of excess weight loss at 6 months for the weight loss group and nonweight loss group was 53.9% and 50.9% (P = NS). ⁶² However, preoperative weight loss should be strongly encouraged as it facilitates the operation by reducing the abdominal fat and the liver volume, which improves the access to the upper stomach during laparoscopic surgery and shortens the operative time.^63–65

Conclusions

An adequate preoperative workup is critical for the success of bariatric surgery. A comprehensive discussion of patient expectations of postsurgical weight loss, including the potential for weight regain, is strongly recommended. In addition, a complete assessment and stratification of patients' comorbidities (especially cardiovascular and respiratory) can inform clinical decision making, and help identifying ideal candidates for bariatric surgery and those that may require closer postsurgical monitoring. Abdominal ultrasound and EGD are recommended during the preoperative workup. Preoperative weight loss should be strongly encouraged.