Heparin Dosing and Postoperative Blood Loss in Patients Taking Aspirin

Abstract

A large number of patients scheduled to undergo elective coronary artery bypass grafting continue to take aspirin along with other antianginal medication up to the day of surgery. Patients taking aspirin preoperatively are known to bleed more in the postoperative period than those not taking aspirin. This study was undertaken to determine whether the method of heparin administration (protocol-based bolus dose versus an individualized dose) affected postoperative blood loss or requirements of blood and blood products in patients taking aspirin preoperatively. In this prospective study, 300 consecutive patients taking aspirin prior to coronary artery bypass graft surgery were randomly assigned to receive heparin either as a protocol-based bolus of 400 IU·kg⁻¹ (group A) or according to a dose-response curve to obtain an activated coagulation time of 500 seconds on cardiopulmonarybypass (group B). Group B required significantly less heparin (mean 275 IU·kg⁻¹)and less protamine than group A. Postoperative blood loss, requirement of blood and blood products, and time spent on hemostasis in group B was significantly less at 24 hours than group A. We concluded that individualized dosing of heparin using a dose-response curve is preferable to a protocol-based bolus heparin dose in patients taking preoperative aspirin.