Diabetes , hypertension , hyperlipidemia , congestive heart failure , as well as obesity itself are risk factors for perioperative cardiac morbidity often present in candidates for bariatric surgery. Despite multiple risk factors for coronary vascular disease (CVD) , cardiac events are infrequent in modern bariatric surgery. In an evaluation of risk factors for perioperative events following 25,469 bariatric procedures in the Michigan Bariatric Surgery Collaborative (MBSC) database , only 22 patients suffered a myocardial infarction or cardiac arrest (0.1 %) [1]. Major cardiac events remain a major cause of perioperative mortality. Among 6114 patients with available 30-day follow-up in the Longitudinal Assessment of Bariatric Surgery (LABS) , cardiac events were the second most common cause of perioperative mortality, accounting for 28 % of deaths (0.08 % of the total cohort) [2].

An appropriate, evidence-based preoperative cardiac evaluation can reduce the incidence of major adverse cardiac events. The 2014 ACC/AHA guideline on perioperative cardiovascular evaluation recommend starting with a clinical risk assessment and evaluation of functional status [3]. Patients with moderate or better functional capacity (climbing a flight of stairs or walking on level ground at 4 mph) may usually proceed to surgery without stress testing. Stress testing is indicated in patients with poor or unknown functional capacity. Surgery should be delayed 14 days after balloon angioplasty , 30 days after implantation of bare metal stents, and 365 days after drug-eluting stent implantation. The risk/benefit of discontinuation of antiplatelet agents should be discussed with the treating cardiologist. Beta-blockers should be continued in patients who have been on them chronically, but should not be started on the day of surgery in beta-blocker-naïve patients. The ACC/AHA guideline should be reviewed for more detailed perioperative treatment recommendations in patients at higher risk for perioperative cardiac events .

The published incidence of deep venous thrombosis (DVT) and pulmonary embolism (PE) in bariatric surgery ranges from 0 to 6 %. With the implementation of venous thromboembolism (VTE) prophylaxis pathways in the vast majority of metabolic and bariatric surgery programs, the incidence of VTE in most large series is less than 1 % [4]. VTE was the third leading cause of perioperative mortality in LABS, accounting for 17 % of the deaths following bariatric surgery [2]. The MBSC identified risk factors for VTE following bariatric surgery including prior VTE (OR 4.15), male gender (OR 2.08), operative time over 3 h (OR 1.86), increasing age, increasing BMI, and procedure type (BPD/DS > open RYGB > laparoscopic RYGB > sleeve gastrectomy > LAGB) [5]. Additional risk factors may include immobility, venous stasis disease, and use of hormone therapy.

There is no class I evidence to guide the choice of VTE prophylaxis, although guidelines from the ASMBS [4], American College of Chest Physicians [6], and the MBSC recommend combination therapy with mechanical and chemoprophylaxis. A review of the MBSC database demonstrated superiority of low-molecular-weight heparin (LMWH) over unfractionated heparin for VTE prophylaxis [7]. Extended, post-discharge prophylaxis with LMWH should be considered in the highest risk patients including those with a prior history of VTE, those with venous insufficiency, and those with a BMI ≥60.

CT angiography of the chest is the diagnostic study of choice in the postoperative patient with suspected pulmonary embolism. As the symptom complex of tachycardia and shortness of breath are also present in anastomotic leakage, combining the CTA with an abdominal CT adds little time, and may help in determining the etiology of the patient’s symptoms. Compression ultrasonography is the preferred test for suspected DVT. LMWH or fondaparinux is preferred in the initial treatment of VTE. The latest guideline update from the ACCP [8] recommends factor Xa or direct thrombin inhibitors over warfarin for the extended treatment of VTE. The standard duration of anticoagulation is 3 months.

Rhabdomyolysis is a syndrome caused by injury to skeletal muscle which results in the release of potentially toxic intracellular contents into the bloodstream, including creatinine kinase (CK) , myoglobin, potassium, and phosphate. Myalgias , generalized muscle weakness, and dark urine are presenting symptoms. A CK level 5 times the reference range suggests rhabdomyolysis, though levels 100 times the reference range may occur. The precipitation of myoglobin in the glomeruli may lead to acute kidney injury. Rhabdomyolysis has been reported following bariatric surgery in numerous case series and reviews. A systemic review identified 145 patients with rhabdomyolysis following bariatric surgery with 14 % developing acute renal failure. Male sex, higher BMI, and longer operative times were risk factors [9]. A multicenter prospective study or rhabdomyolysis in bariatric surgery identified rhabdomyolysis in 62 of 480 patients (12.9 %), defining rhabdomyolysis as a postoperative CK >1000 U/L [10]. Duration of surgery was the only independent risk factor, with an operative time greater than 230 min as the best cutoff predictor. Although the incidence of clinically relevant rhabdomyolysis is much lower, the diagnosis must be considered in patients with dark or decreased urine output, particularly following longer procedures in high-BMI patients.

Preventative measures include padding of all pressure points, changes in patient position, and minimizing operative time. Following the diagnosis of rhabdomyolysis, aggressive hydration titrated to maintain a urine output of 200 mL/h should be continued until myoglobinuria is no longer present. Alkalization of the urine by the administration of intravenous sodium bicarbonate, as well as diuretic therapy with mannitol or furosemide, has been recommended to prevent acute kidney injury. Serum CK measurements should be obtained every 6–12 h. Patients should be monitored for the development of disseminated intravascular coagulation (DIC). Electrolyte disturbances , particularly hyperkalemia , should be corrected.