THE SKIN BLEEDING-TIME TEST AS A PREDICTOR OF BRAIN BLEEDING-TIME IN A RAT MODEL

Previous studies have indicated that the skin bleeding time test does not accurately reflect visceral bleeding time (BT). The present study examines the predictive value of the skin bleeding time for brain blee ding tendency. Sixteen Sprague-Dawley rats were divided into equal gro ups. The first group (control) underwent standardized skin and brain b leeding time tests under general anesthesia. Mean skin BT was found to be 168.8 sec with a standard deviation of +/- 20.8 sec. Mean brain BT was found to be 172.5 sec with a standard deviation of +/- 19.6 sec. The second group was given 23.2 mg/kg of aspirin per day for five days prior to skin and brain bt testing. Mean skin BT in this group was 31 5 seconds with a standard deviation of +/- 72.3 sec which proved to be significantly different from the control skin BT (P = 0.0005). Brain BT in the aspirin treated group was 155.6 sec was a standard deviation of +/- 22.6 sec. Brain BT in both control and aspirin treated groups was not significantly different (P = 0.13). All animals were euthanize d 30 minutes after brain BT and their brains harvested. One animal in the control group showed evidence of a small subcortical hemorrhage up on brain sectioning. Sectioned brains in the aspirin-treated group sho wed no evidence of subcortical hematoma. The results indicate that ski n BT is prolonged by aspirin administration, but brain bleeding time i s unaffected. Brain hemostasis is likely more dependent on intrinsic p rocoagulant than platelet function. The skin BT test may therefore be of little utility as a preoperative screening test for neurosurgical p atients.