One hundred twenty-nine patients undergoing total hip replacement were treated with aspirin at a level of either 300 mg four times a day (1.2 g/day) or 900 mg four times a day (3.6 g/day). Baseline bleeding times before aspirin treatment averaged 4.18±1.44 minutes. Two hours after 300 mg and 900 mg of aspirin, the bleeding times were 5.83±1.88 and 5.72±1.57 minutes, respectively. After three to five days of aspirin therapy at 1.2 g/day and 3.6 g/day, the bleeding times were 6.27±2.27 and 6.43±2.11 minutes, respectively. The bleeding times for all the aspirin-treated groups were longer than baseline times. No paradoxical shortening of the bleeding time was noted at the 3.6-g/day dose. Perioperative blood loss for those receiving aspirin was not increased in six of eight subsets by operation and anesthesia when compared with historical control subjects. Neither a bleeding time greater than ten minutes nor a prolongation of the bleeding time by aspirin of more than four minutes over baseline bleeding times was associated with increased perioperative blood loss.
Amrein PC, Ellman L, Harris WH. Aspirin-Induced Prolongation of Bleeding Time and Perioperative Blood Loss. JAMA. 1981;245(18):1825-1828. doi:10.1001/jama.1981.03310430017013