Effect of Subcutaneous Unfractionated Heparin Prophylaxis on Activated Partial Thromboplastin Time: A Retrospective Evaluation

Study Objective: Characterize the incidence of elevated aPTT results in patients treated with prophylactic, subcutaneous unfractionated heparin (UFH). Design: Retrospective, cohort analysis. Setting: Single-center, university hospital. Measurements: Evaluation of 257 patients with activated partial thromboplastin time (aPTT) testing both prior to and following subcutaneous (SC) unfractionated heparin (UFH) therapy. Main Results: Evaluated patients received UFH 5000 units every 8 hours. Baseline aPTT values were within the normal range (mean +/- SD, 32.0 +/- 8.5 seconds). After initiation of UFH, aPTT values increased (mean SD, 37.6 +/- 15.2 seconds). After 24 hours of SC UFH, mean aPTT values (mean SD, 38.6 +/- 15.5) exceeded the normal laboratory range (23.3-35.7 seconds). An elevated aPTT result after UFH was associated with baseline aPTT, length of therapy, and weight-based UFH dose. A significant association was not identified between aPTT elevation and age, race, sex, history of liver disease, type of admission, or transfusion of blood products. Conclusions: Treatment with UFH resulted in a small, but significant, increase in aPTT. (C) 2016 Elsevier Inc. All rights reserved.