The benefit of perfusion washout in both experimental and clinical skin flaps has long been debated. By perfusing ischemic rat pedicled flaps with UW solution, a recently developed, high-molecular-weight, organ-preservation medium, a 170 percent increase in the critical ischemia time of treated versus untreated control flaps was demonstrated. Sixty rats were used in this study. A 3- x 6-cm unilateral abdominal skin flap based on the superficial inferior epigastric artery and vein was raised. The flaps were divided into three groups: Group 1 (control--no perfusion washout (n = 15); Group 2 (LR)--perfusion washout with lactated Ringer's solution (n = 15); Group 3 (UW)--perfusion washout with UW solution (n = 30). Flaps were subjected to varying periods of ischemia, ranging between 8 and 30 hr. The primary ischemia time at which 50 percent of the flaps survived clinically was 10 hr for Group 1, 15 hr for Group 2, and 27 hr for Group 3. The differences between the survival rates for flaps in Groups 1, 2, and 3 were statistically significant (p less than .0005). By bathing the vascular and parenchymal cells in an impermeant preservation solution, it was hypothesized that cellular swelling would be inhibited, thereby significantly improving a skin flap's tolerance to warm ischemia. Furthermore, after reviewing the pertinent literature, it is evident that the primary critical ischemia time of 27 hr is the highest reported to date for the normothermic experimental rat pedicled flap. Clinical application of these findings, as well as the need for further studies, are discussed.

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A myriad of investigations have been published on the pharmacologic manipulation of flaps to enhance tolerance to ischemia. We recently reported a threefold increase in ischemic tolerance of the rat abdominal skin flap pedicle after 6 hours of primary ischemia and 12 hours of reperfusion. Flaps underwent normothermic perfusion washout with lactated Ringer's or U.W. solution, a newly developed organ preservation medium. Perfusion washouts were performed at one of three different points in the protocol: (1) onset of primary ischemia; (2) onset of secondary ischemia; or (3) 2 hours after onset of secondary ischemia. The last group was used to simulate the clinical situation in which flaps are discovered and salvage procedures instituted at a delayed time interval. This is the longest normothermic ischemic interval reported. We undertook the present study to determine the utility of the U.W solution in prolonging the tolerance of the flap to a second ischemic insult after a period of reperfusion. Seventy-five unilateral rat abdominal skin flaps were raised. Secondary ischemia was produced by placing a microvascular clamp across the inferior epigastric pedicle. Flap survival was assessed at 1 week postoperatively. While none of the nonperfused flaps survived 8 hours of secondary ischemia, at least 50% of the U.W. perfused flaps survived an average of 14 hours of secondary ischemia. Lactated Ringer's perfusion washout only modestly increased the ischemic tolerance. Perfusion washout in the secondary ischemic phase improved the ischemic tolerance to a significantly greater degree than in the primary ischemic interval. (OTOLARYNGOL HEAD NECK SURG 1993;108:149-55.)

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