Salvage of free flaps after secondary venous ischemia by local delivery of heparin.

Recent studies have demonstrated that heparin may protect against reperfusion injury through a direct effect on the microvascular endothelium that is independent of its effect on systemic coagulation. The purpose of this study was to determine whether local delivery of low-dose heparin has a role in the salvage of musculocutaneous flaps after secondary venous ischemia and revascularization. Cutaneous maximus musculocutaneous flaps were transplanted to the contralateral groin in adult Sprague-Dawley rats. All flaps were subjected to 2 hours of primary arteriovenous ischemia followed by 20 hours of reperfusion. The flaps were then subjected to a 6-hour secondary venous ischemic insult followed by anastomotic revision and reperfusion. Animals in group I received no adjunctive treatment. Those in group II were treated with low-dose heparin (5-6 U per kilogram per hour) infused systemically via the inferior epigastric vein. Those in group III received the same dose of heparin infused locally into the flap via the inferior epigastric artery. The dose of heparin used in groups II and III was insufficient to prolong the activated partial thromboplastin time above normal values. At 7 days, mean flap necrosis was 60.8% in group I and 62.1 in group II. Local heparin delivery (group III) resulted in complete survival of all flaps. Histological examination after 48 hours of reperfusion demonstrated improved microvascular patency and reduced neutrophilic infiltration in the flaps of group III animals. Thus, local infusion of low-dose heparin resulted in significantly improved flap salvage through a mechanism independent of its effect on systemic coagulation.