BACKGROUND:The purpose of this study was to determine whether the focused delivery of heparin or recombinant tissue plasminogen activator (rtPA) by rinsing accords protective effects which increases the survival of free groin flaps following fatal secondary venous stasis. METHODS: Free microvascular groin flaps (n = 40) were transplanted to the necks of adult Sprague-Dawley rats 20 hours before the experiment. The study groups (each n = 10 animals) were: No adjunctive treatment (Group I), Ringer's solution (Group II), heparin solution (100 IU/kg, group III) and rtPA (2 mg/kg, group IV), respectively. The flap vein was then clamped for 35 minutes. Intravital video microscopy was applied and flap viability was assessed 14 days later. RESULTS: Mean flap necrosis was 90% in group I and II, whereas the rate of flap survival was 80% in group III and 60% in group IV, respectively. CONCLUSIONS: Even though clinical and microvascular flap perfusion parameters in both the rtPA-group and heparin group were initially similar, it has been demonstrated here in our investigations that the flaps treated with heparin showed a higher viability rate. Therefore, we can conclude that the focused delivery of heparin and rtPA resulted in a significantly improved flap salvage.