The effect of time of vascular island skin flap elevation on tolerance to warm ischemia.

The effect of time of vascular island skin flap elevation on tolerance to a subsequent 12-hour period of warm ischemia was studied. Sixty rats were separated into five equal groups; the rat epigastric island flap was used as the model. In group 1 flaps were elevated and immediately subjected to 12 hours of complete ischemia by application of microvascular clamps to both artery and vein of the pedicle. In group 2 the flap was elevated, and after 12 hours of recovery ischemia was induced for 12 hours. Groups 3 to 5 were similar to group 2 except that the time interval between initial elevation and subsequent ischemia varied: 24 hours for group 3; 72 hours for group 4; 144 hours for group 5. Necrosis was evaluated on postoperative day 7. Those flaps elevated 24 hours before ischemic insult (group 3) had significantly better survival than all other groups (p less than 0.025 at least). There were no significant differences between the other groups. Flap elevation 24 hours before a complete ischemic episode significantly increased tolerance to ischemia. Elevating a flap earlier or later than 24 hours did not have any significant benefit.