Heparin and protamine: Should we re-adjust their dosages in OPCAB?

Background: Many studies have verified that avoiding the use of cardiopulmonary bypass decreases to a great extent postoperative bleeding. However different strategies for anticoagulation and reversal are used. The goal of this study is to assess the effect of different heparin and protamine dosages in off-pump surgery, on postoperative bleeding, and their impact on the incidence of postoperative myocardial ischemic damage. Methods: Seventy-five consecutive patients undergoing off-pump coronary bypass surgery (OPCAB) were prospectively randomized in five groups: Group A received 300 IU.kg^-1 heparin with 1 mg of protamine every 100 IU of heparin, Group B received 300 IU.kg^-1 heparin with 0.5 mg of protamine every 100 IU of heparin, Group C received 150 IU.kg^-1 heparin with 1 mg of protamine every 100 IU of heparin, Group D received 150 IU.kg^-1 heparin with 0.5 mg of protamine every 100 IU of heparin and Group E received 150 IU.kg^-1 heparin with no protamine. Results: As regards the preoperative cardiac function, pre and intraoperative coagulation profile, prothrombin time, activated partial thromboplastin time and platelet count early postoperatively, there was no statistically significant difference in the five study groups. In group D total postoperative bleeding, use of blood products and pericardial effusion prevalence at discharge were significantly lower when compared to groups A, B, C, and E. Postoperatively, there was no difference in the incidence of myocardial infarction or markers of myocardial damage between the five groups. Conclusion: In OPCAB, heparin requirements are reduced yet it should be reversed with protamine, otherwise the postoperative bleeding risk might increase. Partial heparin reversal might not increase postoperative bleeding risk, but it may reduce dose-dependent protamine adverse effects, without increasing hypercoagulability-related complications.