Early Postoperative Use of Unfractionated Heparin or Enoxaparin is Associated with Increased Surgical Re-Exploration for Bleeding

Background A variety of indications (eg, prosthetic heart valves, atrial fibrillation, etc.) exist for the use of unfractionated heparin (UFH) and enoxaparin (ENOX) in the early postoperative period following open-heart surgery. However, the overall postoperative risk for hemorrhage from the use of UFH and ENOX are not known. Methods From 1998 to 2001, 2,977 consecutive open-heart or valve surgery patients were retrospectively evaluated. Postoperatively, 2,037 received no UFH or ENOX, 579 received intravenous UFH, and 361 received ENOX. Baseline characteristics were collected, patients who required surgical re-exploration for postoperative bleeding and time between surgery and re-exploration were followed-up. Results Average patient ages were 64 ± 13, 65 ± 12, and 68 ± 10 years receiving none, UFH (p< 0.01 vs none), and ENOX (p< 0.01 vs none; p< 0.01 vs UFH), respectively. Rates of surgical re-exploration were 2.7% for none, 7.8% for UFH, and 8.9% for ENOX (vs none, adjusted hazard ratio = 2.8; p< 0.001 for UFH; hazard ratio = 3.3; p< 0.001 for ENOX). Males were also at higher risk for re-exploration (hazard ratio = 1.4; p = 0.07). For those requiring re-exploration, the interval between surgery and first re-exploration was prolonged (> 4 days) among those receiving ENOX (37.5%, odds ratio = 36.7; p = 0.001) and UFH (20.0%, odds ratio = 14.7; p = 0.01) compared with none (1.8%). Prolonged times with ENOX had a greater proportion of prolonged times than UFH (odds ratio = 2.5; p = 0.09). Conclusions Early postoperative use of ENOX and UFH is associated with a significant increase in re-exploration for postoperative bleeding, often at a significantly delayed time period after the initial surgery. This delay was especially common with ENOX suggesting the need for prospective studies.