Effectiveness and Safety of Twice Daily Versus Thrice Daily Subcutaneous Unfractionated Heparin for Venous Thromboembolism Prophylaxis at a Tertiary Medical Center.

The direct comparison of twice daily (BID) and thrice daily (TID) dosing of subcutaneous low dose unfractionated heparin (LDUH) for venous thromboembolism (VTE) prophylaxis in a mixed inpatient population is not well-studied. This study evaluated the effectiveness and safety of BID compared to TID dosing of LDUH for prevention of VTE. Retrospective, single-center analysis of patients who received LDUH for VTE prophylaxis between July and September 2015. Outcomes were identified by ICD-9 codes. A matched cohort was created using propensity scores and multivariate analysis was conducted to identify independent risk factors for VTE. The primary outcome was incidence of symptomatic VTE. In the full cohort, VTE occurred in 0.71% of patients who received LDUH BID compared to 0.77% of patients who received LDUH TID (p = 0.85). There was no difference in major (p = 0.85) and minor (p = 0.52) bleeding between the BID and TID groups. For the matched cohort, VTE occurred in 1.4% of BID patients and 2.1% of TID patients (p = 0.32). Major bleed occurred in 0.36% of BID patients and 0.52% of TID patients (p = 0.7), while a minor bleed was seen in 3.4% of BID patients and 2.1% of TID patients (p = 0.13). Personal history of VTE (p = 0.002) and weight (p = 0.035) were independently associated with increased risk of VTE. This study did not demonstrate a difference in effectiveness or safety between BID and TID dosing of LDUH for VTE prevention.