Evaluating the safety and efficacy of BMI-based preoperative administration of low-molecular-weight heparin in morbidly obese patients undergoing Roux-en-Y gastric bypass surgery

Background: One of the most concerning and potentially fatal complications of gastric bypass surgery is pulmonary embolism (PE) with published rates exceeding 1%. Although this procedure has been proven effective in reducing the morbidity and mortality of obesity and associated health care costs, it is elective and risk must be minimized. No dosing guidelines exist for pharmacologic prophylaxis in obese patients who are already at increased risk for these events. Although the current ASMBS and Chest guidelines recommend preoperative pharmacologic prophylaxis against thromboembolic events, no standard dosing protocols exist for the obese population. We propose a protocol including immediate pre followed by twice daily postoperative BMI-based dosing of low-molecular-weight heparin (LMWH), along pneumatic compression devices, and early ambulation. Methods: We retrospectively reviewed the charts of 170 patients who underwent Roux-en-Y gastric bypass surgery between March 2004 and December 2007. The incidence of deep venous thrombosis (DVT) and PE and bleeding complications associated with a BMI-based preoperative dosing protocol of LMWH was determined. Results: All patients received LMWH preoperatively within 1 h of the incision, with doses varying between 30 and 60 mg given subcutaneously. Eleven patients received 30 mg, 145 patients received 40 mg, 9 patients received 50 mg, and 5 patients received 60 mg. None of the patients suffered from clinically significant DVT or PE during the hospital stay or in follow up (>2 years). Five patients (2.9%) were treated with discontinuation of lovenox and blood transfusion for postoperative bleeding. One of those patients returned to the operating room for exploration. Conclusions: We propose that immediate BMI-based preoperative dosing of LMWH along with postoperative prophylaxis is both safe and effective and should be standard for all patients undergoing Roux-en-Y gastric bypass surgery.