The effect of total hip/knee replacement surgery and prophylactic dabigatran on thrombin generation and coagulation parameters

Introduction: Total hip/knee replacement surgery (THR/TKR respectively) is associated with an increased risk of venous thromboembolism. Dabigatran is recommended as a thromboprophylactic agent post orthopaedic surgery. The aim of this study was to assess the post-operative (Day-1 and Day-2) effect of prophylactic Dabigatran on: the thrombin generation (TG) assay; prothrombin fragment 1.2 (F1.2); thrombin-antithrombin complexes (TAT); D-dimer (D-D); and other coagulation parameters. Methods and samples: Nineteen patients (12 THR, 7 TKR) who received 110 mg dabigatran 4 hours post-operatively, then 220 mg the following day, were recruited. Blood was collected: pre-operatively (Pre-); peri-operatively (Peri-); 19 hours after 110 mg dabigatran (Day-1); and 17 hours after 220 mg dabigatran (Day-2). The TG assay was measured using the Calibrated Automated Thrombogram and a low concentration of tissue factor. Other coagulation parameters measured included activated partial thromboplastin time (APTT), thrombin-time (TT), ecarin-clotting time (ECT) and Hemoclot tests. Results: From Pre- to Peri-, ETP/peak-thrombin, F1.2, TAT and D-D increased significantly. From Peri-to Day-1 and Day-2: TAT reduced progressively; D-D increased; F1.2 did not change significantly; lag-time and time-to-peak prolonged; ETP/Peak-thrombin increased spuriously, due to Dabigatran interfering with the alpha-2 macroglobulin: thrombin complex in the TG assay. APTT, TT, ECT and Hemoclot increased progressively post-operatively; good correlations were seen between these tests. Conclusion: The effect of dabigatran on the TG assay, showed a spurious increase in ETP and Peak-thrombin due to its interference with the TG assay. Dabigatran reduced TAT, but not F1.2, suggesting that thrombin was still being generated after surgery, but was blocked by Dabigatran. (C) 2011 Elsevier Ltd. All rights reserved.