Bariatric Surgery Preoperative Assessment

Function

Body mass index (BMI) is a widely used screening tool to assess weight status. Obesity in adults is typically defined as a BMI ≥30. It is further categorized into different classes based on increasing intervals of BMI: class 1 obesity ranges from 30 to 34.9, class 2 obesity ranges from 35 to 39.9, and class 3 obesity, or severe or severe obesity, is defined as a BMI ≥40.[8] Obesity in children is defined as a sex-specific BMI ≥95th percentile and severe obesity >120th percentile.[2] 

Obesity is a multifactorial disease process; genetics and environment play a role in the development of obesity.[9][8] Medications, diet, thyroid function, mood disorders, lifestyle, genetics, and socioeconomic status or ethnicity can influence obesity.[8] Weight gain results from an excess of consumed calories compared to energy expended. For some individuals, creating a negative energy balance is sufficient for weight loss and maintaining a healthy BMI. Other individuals have minimal results with decreasing calories consumed and increasing physical activity.

The body invokes compensatory measures when placed in a negative expenditure state, either by increasing the drive for food or altering the utilization of resources.[10] Weight loss surgery can be considered a viable therapeutic option when dietary and lifestyle modifications alone are insufficient to manage obesity or in cases where patients have metabolic disorders.[8]  

Weight loss procedures have traditionally been classified as either malabsorptive or restrictive procedures. However, this mindset is evolving along with the understanding of the physiologic mechanisms of weight loss and how weight loss procedures influence these mechanisms.[11] According to a global survey conducted in 2014, sleeve gastrectomy emerged as the most frequently performed weight loss surgery procedure, followed by the Roux-en-Y gastric bypass and the adjustable gastric band.[12] In 2018, over 250,000 weight loss procedures were recorded in the United States.[13] 

All surgical interventions for obesity or metabolic conditions require an in-depth preoperative assessment. The goals of the assessment are to identify appropriate candidacy for the procedure; identify, assess, and offer interventions for comorbidities that increase intraoperative morbidity and mortality; obtain informed consent; and ensure the patient understands the procedure and its risks. A thorough preoperative assessment improves outcomes in patients undergoing weight loss surgery.[14]

Issues of Concern

Patients may qualify for weight loss surgery if they have failed nonsurgical weight management and present with a BMI >40. Patients may also qualify if nonsurgical management has failed and the BMI is >35 in the presence of an obesity-related comorbidity such as type 2 diabetes, hypertension, osteoarthritis, coronary artery disease, or major depression.[14] Weight loss surgery may also be indicated for patients with a BMI <35 in the setting of significant metabolic dysfunction, such as diabetes that remains uncontrolled despite optimal medical therapy.[15][16]

Patient Age

Consideration of the age of the patient is essential. Weight loss surgery in patients under 18 years of age is controversial. However, the risk of developing obesity-related comorbidity increases the longer an individual is obese; children with obesity are therefore at increased risk of obesity-related complications.[17] 

Older guidelines recommended postponing weight loss surgery in adolescence, ages 10 through 19, until prospective patients have achieved a Tanner stage 4 maturity level or 95% of linear growth determined by bone age.[18] The American Society for Metabolic and Bariatric Surgery Pediatric Committee recommends focusing on comorbidity severity and early weight loss surgery to decrease and possibly reverse the effects of obesity-related comorbidities.[19] 

The Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS), a prospective, multi-institutional study, indicates that metabolic surgery is safe, effective, and does not impact future growth or development.[18] This study's overall complication rate for weight loss surgery in adolescents was approximately 14%.[20] Data collected from the National Surgical Quality Improvement Data reveal that the most common early complications of weight loss surgery in adolescents are urinary tract infections and surgical sites. Long-term complications in adolescents undergoing weight loss surgery include gastroesophageal reflux disease, incisional hernia, treatment failure requiring a second procedure, and nutritional deficiencies.[20] When considering weight loss surgery in adolescents with obesity, the ability to consent, the family environment, patient compliance with therapy, the risk of complications, and overall future health must be considered. 

Adults over 60 years of age also warrant careful preoperative assessment. Although obesity profoundly affects life expectancy and overall quality of life, older adults are more likely to have multiple comorbidities or disabilities that increase the risk of adverse events of weight loss surgery and negatively impact postoperative recovery. These complications and adverse events may worsen the quality of life rather than improve it.[21] Older adults considering weight loss surgery must be extensively counseled regarding its risks and benefits within the context of reasonable life expectancy. To facilitate these discussions, functional status can be measured and used as a predictive tool for postoperative morbidity and mortality; a lower baseline functional status indicates increased postoperative complications.[22][23][24] However, overall life expectancy continues to increase, and obesity is present in the older population; age should not be used as an absolute contraindication to weight loss surgery.  

Contraindications to Weight Loss Surgery

Contraindications for weight loss surgery include the risk of intraoperative complications and the dangers of poor patient compliance with therapeutic regimens in the postoperative period. The American Society of Anesthesiologists (ASA) physical status classification system evaluates perioperative comorbidities to assess operative risk, stratifying patients into 6 classes. Patients meeting Classes IV or V criteria have a high risk of intraoperative mortality; weight loss surgery would not be recommended.[25] 

Patients who cannot understand the operation or its future implications are not candidates for weight loss surgery. Patients with poorly controlled mental illness, eating disorders, alcohol use disorder, or any disease process that impairs their ability to understand the importance of lifestyle modification as an adjunct to weight loss surgery will likely benefit from a referral for formal psychological evaluation and treatment in the preoperative period.[26] The benefits of such a referral and treatment are particularly well documented in patients with eating disorders.[27]  All patients considering weight loss surgery must be screened for alcohol use disorder (AUD) and substance use during the preoperative assessment. The Longitudinal Assessment of Bariatric Surgery-2 (LABS-2) prospective observational study evaluated AUD and illicit substance use after weight loss surgery and found that one-fifth of participants reported AUD symptoms and increased substance use.[28] 

Finally, a lack of postoperative support can preclude a patient from weight loss surgery. Many patients require postoperative care in a rehabilitative facility, some of which cannot accept patients over a certain weight. Additionally, social support is needed to follow guidelines, attend postoperative visits, and maintain a healthy lifestyle following the procedure.[27]

Preoperative Assessment

Patients that meet the criteria for weight loss surgery must undergo an extensive preoperative assessment process. This process is best undertaken with a multidisciplinary team of experts, including the bariatric surgeon, a registered dietitian, a behavioral medicine professional, nurse educators, and possibly subspecialty providers such as cardiologists, pulmonologists, endocrinologists, and anesthesiologists. This preoperative assessment process evaluates and manages all aspects of the procedure and requires multiple appointments, educational sessions, planning, additional laboratory and diagnostic testing, and medical interventions as dictated by the clinical situation.[16]

A comprehensive medical history must be obtained, and a thorough physical examination must be performed. The patient must undergo a complete metabolic assessment to identify and assess comorbidities.[29] The failure of an implemented medically supervised diet plan must be documented.[16] A comprehensive understanding of the patient and their history facilitates the identification of factors impacting their obesity and allows for the planning necessary to ensure postoperative weight loss.

Metabolic assessment includes a complete blood count, complete metabolic panel, fasting blood glucose, hemoglobin A1c, lipid panel, urinalysis, and coagulation studies. The patient's overall nutritional status must be objectively evaluated with serum vitamin B12, folic acid, vitamin D, and iron studies. Serum albumin and prealbumin are important indicators of overall nutritional status.[30] The risk of malabsorption unique to the planned procedure dictates the significance of preoperative nutritional deficiencies.[16]

Patients with a history of gastroesophageal reflux disease (GERD) or findings consistent with gastrointestinal pathophysiology should be evaluated by a gastroenterologist in the preoperative period. Preoperative esophagogastroduodenoscopy (EGD) is frequently recommended for these patients to evaluate the presence of a hiatal hernia, Helicobacter pylori disease, Barrett esophagus, or pathologic lesions of the upper gastrointestinal tract.[31] The EGD may reveal a finding that affects the choice of weight loss procedure or dictates additional follow-up visits in the postoperative period.[31][32] The Bariatric Outcomes Longitudinal Database, a prospective registry of bariatric surgeries performed at centers of excellence, evaluated the evaluation or improvement of GERD symptoms after different weight loss procedures and found that the Roux-en-Y gastric bypass was more successful in decreasing GERD symptoms.[33] The presence of Barret esophagus, a precursor lesion of esophageal adenocarcinoma caused by poorly managed GERD, is a relative contraindication to sleeve gastrectomy; sleeve gastrectomy can worsen GERD and allow for the progression of Barret esophagus.[34]

Patients pursuing weight loss surgery should be evaluated for underlying endocrinopathies in the preoperative period. Unmanaged endocrinopathies such as type 2 diabetes, thyroid disease, and polycystic ovarian syndrome can negatively affect outcomes after weight loss surgery. Assessment of serum hemoglobin A1c, thyroid stimulating hormone, and androgen levels is recommended.[35] In particular, type 2 diabetes, a common comorbidity in patients with obesity, needs to be well controlled before proceeding with weight loss surgery to decrease perioperative risks such as poor wound healing.[36] An endocrinologist should manage diabetes that is longstanding or has proven refractory to medical therapy. To reduce intraoperative and postoperative risk, patients with diabetes mellitus should demonstrate a hemoglobin A1c of 6.5% to 7%, a fasting blood glucose <110 mg/dL, and a 2-hour postprandial glucose <140 mg/dL.[16][37]

Candidates for weight loss surgery should meet with a registered dietitian for a clinical nutrition evaluation in the preoperative period. The success of weight loss surgery hinges on modifying dietary habits; patients require a nutritional plan and access to an expert for assistance with questions or concerns.[29]

Preoperative psychosocial and behavioral assessment is strongly recommended for patients considering weight loss surgery. Patients with obesity frequently have underlying mood, eating, and behavioral disorders that, if left unidentified and unmanaged, negatively affect postoperative outcomes and overall weight loss.[38] Psychosocial assessment can also identify deficiencies and provide strategies for improving interpersonal relationships, support systems, and lifestyle behaviors to achieve and sustain weight loss after surgery.[39][29] 

Patients with obesity pursuing weight loss surgery should be informed of excess skin and tissue possibilities after weight loss. Body changes after extreme weight loss can challenge mental and emotional health and quality of life. Consultation with a plastic surgeon to discuss medical and surgical strategies to improve overall body image following extreme weight loss can mitigate these challenges.[40]

Patients with obesity are at significantly increased anesthesia-related risks. Patients considering weight loss surgery for severe obesity frequently present with known or undiagnosed respiratory conditions such as obstructive sleep apnea or hypoventilation syndrome of obesity.[41][42] Consultation with a pulmonologist is recommended in these cases. Patients with obstructive sleep apnea require CPAP therapy in the preoperative period for perioperative risk reduction.[43]  The recommended therapy for hypoventilation syndrome of obesity is preoperative weight loss. Preoperative weight loss also reduces the weight on the chest and abdominal walls, improving intraoperative ventilation, easing surgical access to the peritoneal cavity, and decreasing anesthesia-related risks. Despite this risk reduction, patients undergoing weight loss surgery frequently require postoperative admission to the intensive care unit and should be counseled as such.[41]

Preoperative weight loss should be discussed with all patients considering weight loss surgery, even absent obesity-related pulmonary conditions. The benefits of preoperative weight loss include improved respiratory function and reduced liver size; both contribute to a technically easier and better-tolerated surgery.[44][45]

Obesity is a risk factor for venous thromboembolic disease, and all patients considering weight loss surgery require a risk assessment for this disease process. In addition to obtaining a comprehensive medical history, risk calculators such as the Caprini, Aberdeen, Geneva, or IMPROVE scores can be used in different settings to quantify risk.[46][47][46] Patients at increased risk for venous thromboembolic disease can be anticoagulated in the perioperative period. Postoperative use of sequential compression devices is strongly advised. Inferior vena cava filters are not routinely recommended unless otherwise indicated; the risks often outweigh the benefits.[47][48][27]

Patients undergoing weight loss surgery should avoid pregnancy in the immediate preoperative period and for 12 to 18 months postoperatively. Alterations in nutrient absorption caused by weight loss surgery pose harm to the patient and potential fetus should pregnancy occur during this time frame. If a patient chooses to maintain a pregnancy after weight loss surgery, medically supervised weight gain is encouraged.[16]

Smoking cessation is necessary for all patients considering weight loss surgery; smoking cessation should occur a minimum of 6 weeks before the procedure and be maintained postoperatively.[16] Cigarette smoking increases the risk of many intraoperative and postoperative events, including poor wound healing, thromboembolic and cardiovascular events, and marginal ulcer formation.[49] The preoperative assessment must include conversations regarding the consequences of tobacco use on overall health and surgical outcomes.

The preoperative assessment should also discuss the financial consideration of weight loss surgery. To obtain insurance approval, patients must have a documented medical reason for weight loss surgery. The costs associated with weight loss surgery are significant and would greatly burden a patient without approved coverage.[16][30]

Before weight loss surgery, a thorough discussion of the risks, benefits, and alternatives to the procedure must be accomplished via the informed consent process. While all surgical procedures have some inherent risk, these risks are often significantly increased in the setting of obesity and its comorbid conditions.[30]

Clinical Significance

The preoperative assessment before weight loss surgery holds significant clinical importance for several reasons. 

Weight loss surgery is not appropriate for every patient with obesity. The preoperative assessment ensures that patients are suitable candidates for the procedure, have realistic expectations, and are committed to the behavioral and lifestyle changes required to achieve and sustain weight loss.

Obesity is frequently associated with comorbid conditions, such as hypertension, obstructive sleep apnea, cardiovascular disease, and type 2 diabetes. A comprehensive preoperative assessment plays a vital role in identifying and managing various comorbidities associated with obesity before weight loss surgery. This allows the interprofessional team to tailor the procedure and perioperative care to the patient's specific needs.

Patients with obesity undergoing weight loss surgery are at increased surgical risk over baseline. The preoperative assessment helps identify preexisting conditions that may negatively impact anesthesia, surgery, and postoperative recovery. Optimization of baseline health status by addressing underlying medical conditions decreases surgical risks and improves weight loss outcomes.

The preoperative assessment offers a valuable platform for patient education and counseling. It allows interprofessional healthcare team members to discuss the potential benefits, risks, and expected outcomes of weight loss surgery with the patient and their support system. Detailed discussions regarding dietary changes, postoperative care, and long-term lifestyle modifications are crucial for ensuring patient understanding, adherence, and overall success following the procedure.

Enhancing Healthcare Team Outcomes

An interprofessional team approach can significantly improve outcomes following weight loss surgery by promoting comprehensive care, coordination, and collaboration among healthcare professionals. A team of physicians, surgeons, dietitians, mental health professionals, nurses, and other relevant healthcare professionals should participate in the preoperative assessment of patients considering weight loss surgery. The team's combined expertise ensures a holistic assessment of physical health, mental health, nutritional status, and readiness for lifestyle changes.

Collaborative decision-making within the interprofessional team allows for individualized treatment and surgical planning. The unique perspective of each team member promotes dietary plans, exercise regimens, psychological support, and postoperative care strategies uniquely designed for each patient, optimizing the chances of successful patient outcomes. During the preoperative assessment phase, the interprofessional team can coordinate preoperative testing and consultations and implement strategies to reduce surgical risks.

An interprofessional team approach improves outcomes following weight loss surgery by facilitating comprehensive patient evaluation, individualized treatment planning, enhanced perioperative management, multidisciplinary support, continuity of care, and patient education. By leveraging multiple healthcare professionals' collective expertise and collaboration, patients can receive comprehensive care and support throughout their weight loss journey, leading to improved outcomes and long-term success.