Increased survival of island skin flaps by systemic heparin in rats

The effects of systemic heparin on the survival of island skin flaps have been evaluated. Island flaps measuring 3 x 6 cm were created in the abdomen/groin of rats based on an inferior epigastric neurovascular pedicle. The venous drainage from the flap was occluded for various lengths of time ranging from 5 to 10 hours in the control rats and from 8 to 15 hours in the heparin-treated group of rats. The rats in the treated group received 1 ml of heparin solution (300-400 U/kg) through the contralateral saphenous vein immediately prior to the onset venous occlusion and an equivalent dose every 4 hours during venous occlusion. The group of control rats received 1 ml of saline solution. Flap survival was evaluated daily for 7 days. The flaps of control rats demonstrated a gradual decline of the survival rate after 6 hours of venous occlusion and no survival after 10 hours of venous occlusion. The flaps of heparin-treated rats exhibited complete survival until 12 hours of venous occlusion and no survival after 13 hours of venous occlusion. Thus, systemic heparin prolonged tissue tolerance to venous occlusion from 10 to 13 hours. The flaps of control rats demonstrated a significant accumulation of inosine plus hypoxanthine to 260% of normal after 8 hours of venous occlusion. The flaps of heparin-treated rats exhibited little alteration of inosine plus hypoxanthine, and contained a greater concentration of glucose and lactate than the flaps of control rats after 8 hours of venous occlusion. The results demonstrate that systemic heparin can increase tissue tolerance to venous occlusion and improve significantly the flap survival following subsequent reperfusion.