Efficacy and Safety of Weight-Adjusted Extended Duration Tinzaparin for Prevention of Post-Operative Venous Thromboembolism after Bariatric Surgery

Background: Patients having bariatric surgery are at moderate-to-high risk for post-operative venous thromboembolism (VTE), with pulmonary embolism representing the most common cause of post-operative death. The optimal dosing and duration of anticoagulant prophylaxis is uncertain.

Aim: To evaluate the efficacy and safety of extended-duration, weight-adjusted tinzaparin for post-operative thromboprophylaxis after bariatric surgery.

Methods: Retrospective cohort of 793 bariatric surgery patients who received routine post-operative weight-adjusted tinzaparin, 4,500-14,000 IU daily (75 IU/kg, rounded to the nearest pre-filled syringe) for 7 days after hospital discharge. The primary efficacy and safety outcomes were the frequency of VTE and major bleeding, respectively, within 30 days of surgery in patients receiving at least 1 dose of tinzaparin.

Results: 793 patients who underwent bariatric surgery from 2009 to 2012 were reviewed. There were 44 (5.5%) patients excluded from analyses: need for therapeutic-dose anticoagulation (n=16); no post-operative tinzaparin (n=27); surgery aborted (n=1). There were 646 and 645 patients included in the 30-day efficacy and safety analyses, respectively (mean age, 44.6 years [SD 9.7], median body mass index, 47.1 kg/m² [range: 19.4-81.0]). An additional 106 patients had outcome data only during hospital admission. VTE occurred in 1/645 patients (0.3%; pulmonary embolism) after hospital discharge and in 1/752 patients (0.1%; superior mesenteric vein thrombosis) in hospital. Major bleeding occurred in 12/645 patients (1.9%). Trough anti-Xa levels measured 7-10 days post-operatively were undetectable in 143/190 (75.3%) patients. In the other 47 patients the median trough anti-Xa level was 0.12 IU (range: 0.10-0.41).

Conclusions: Weight-adjusted, extended-duration tinzaparin appears effective and safe for post-operative thromboprophylaxis after bariatric surgery. There was no drug accumulation with large doses of tinzaparin.