Improved survival in free skin flap transfers in rats.

We have demonstrated previously that oxygen-derived free radicals are important mediators of tissue injury in experimental island skin flaps that have been subjected to prolonged ischemia (vascular occlusion) followed by reperfusion. In this study the role of oxygen free radicals in ischemia/reperfusion injury has been investigated in free flap transfers. Groin skin flaps were harvested, stored at room temperature for 21 to 24 hours, and transplanted to the contralateral groin. These free flap transfers normally exhibit a high incidence of complete necrosis. Treatment before the onset of reperfusion with a single dose of superoxide dismutase (SOD), a scavenger of superoxide radicals, increased the survival rate of these skin flaps from 38% in the control group to 76% (p less than 0.025). Tissue levels of SOD were measured before ischemia, after ischemia but before reperfusion, and 30 minutes after reperfusion: untreated flap tissues, which were destined to undergo necrosis, exhibited a significant decrease in SOD activity after reperfusion, whereas SOD-treated flap tissues, destined to survive, demonstrated increased enzyme activity. High levels of tissue SOD activity thus appeared to be associated with improved flap survival. The results have significant clinical implications with regard to organ preservation and transplantation.