Secondary critical ischemia time of experimental skin flaps.

Secondary ischemia time represents the interval between a postoperative vascular thrombosis of a free flap and its successful revascularization. Using an island-flap model in pigs, the skin was found to tolerate an average secondary ischemia time of 7.2 hours. The safe secondary critical ischemia time (10 percent probability of necrosis) is 4.7 hours. This compares with the primary ischemia times of 13.1 hours (average) and 7.0 hours (10 percent necrosis). The discrepancies between these observed values are discussed.