Low-dose preoperative aspirin therapy, postoperative blood loss, and transfusion requirements.

The effects of three low-dose regimens of preoperative aspirin therapy on postoperative blood loss, transfusion requirements, and length of hospital stay were recorded in a prospective cohort study of 202 patients undergoing elective coronary artery bypass grafting. One hundred one patients had been prescribed daily aspirin by the referring cardiologist (44 at 75 mg, 28 at 150 mg, and 29 at 300 mg); the remaining 101 patients who had not been prescribed aspirin acted as a control group. A median postoperative blood loss of 870 mL in the control group was increased by 280 mL in the 75-mg aspirin group (p less than 0.001), by 490 mL in the 150-mg aspirin group (p less than 0.001), and by 230 mL in the 300-mg aspirin group (p = 0.03). The median requirement for blood transfusion of 2 U red blood cell concentrates in the control group was increased by 2 U in the 75-mg aspirin group (p less than 0.001), 2 U in the 150-mg aspirin group (p less than 0.001), and 1 U in the 300-mg aspirin group (p = 0.05). Hemostatic "packs" (fresh frozen plasma, platelets, and cryoprecipitate) were required in 20 patients in the aspirin groups as compared with 5 in the control group (p less than 0.01 by chi 2 test). The mean postoperative hospital stay was 8 days for all groups. Regular daily low-dose aspirin therapy produces significant increases in postoperative blood loss, resulting in a substantial increase in blood transfusion and hemostatic pack requirements, but does not prolong postoperative hospital stay.