The effect of postoperative aspirin on random pattern flaps in rats.

Our laboratory has been studying the effect of aspirin, given alone or in combination with other medications, on random pattern skin flaps. We have consistently found that preoperative aspirin in high doses (200 mg/kg) increases flap survival, apparently as a result of its ability to modify the inflammatory reaction and/or direct vasodilatation, and not as a consequence of antiaggregation of platelets. In an effort to further elucidate how this effect is modulated, we designed this experiment in which we gave aspirin after the operative procedure to simulate an acute clinical surgical problem such as a failing or ischemic flap. Our results failed to show any difference between the rats that received postoperative aspirin and the untreated control group. It would appear that aspirin given postoperatively is not able to counteract the noxious elements that affect flap survival. This work indicates an important relationship between the timing of administration and the beneficial effects of aspirin. By investigating fully the mechanism whereby aspirin is able to improve flap survival, we hope to isolate this mechanism so an alternative pharmacological agent, safer than aspirin, can be found for clinical use.