The Standardized Normal Ivy Bleeding Time and Its Prolongation by Aspirin

A standardized, reproducible Ivy bleeding time technic has been describedwhich permits one to obtain accurate bleeding time data in man. Thetechnic was used to standardize an aspirin tolerance test in which 60 normal males had a control bleeding time; were given, on a double blind basis,either placebo or 1 Gm. of aspirin, and had a second bleeding time 2 hourslater. The control values were: mean, 5 min.; mean ± 2 st. dev., 2 min.,30 sec. to 10 min. The values after placebo were: mean, 5 min., 30 sec.;mean ± 2 st. dev., 2 min., 30 sec. to 11 min. The values after aspirin were:mean, 9 min., 30 sec.; mean ± 2 st. dev., 4 min. to 21 min. The differencebetween the mean bleeding time after placebo and after aspirin was highlysignificant (p < 0.001). The distribution of the bleeding times after aspirinsuggested that normal subjects do not respond to aspirin as a single population. The degree of prolongation of the bleeding time and the large size ofthe drops of blood observed in some subjects suggested to us that smallamounts of aspirin may exert a significant effect upon hemostasis in normalindividuals.

Submitted on January 10, 1969 Accepted on April 23, 1969