Comparison between various conditioning methods and delay methods of prevention to ischemia/reperfusion injury in rat inferior epigastric skin flaps

Reperfusion injury by the abrupt restoration of circulation after the prolonged ischemia still remains as a not-exactly solved problem in the reconstructive surgery. In our study, the effects of ischemic preconditioning, discretely and jointly usage of ischemic postconditioning, and the usage of three different delay methods in ischemia reperfusion injury in rat skin flaps were assessed and compared. Epigastric skin flaps in sizes of 6x3 cm in 70 Wistar rats were used. Ischemic preconditioning was performed before four-hour-ischemic period by 2 cycles of 15 minutes of repeated ischemia/reperfusion periods. Ischemic postconditioning was performed as a cycle of 30 seconds of full reperfusion, followed by 30 seconds of complete occlusion. It was repeated six times after four-hour-ischemic period and prior to the unlimited reperfusion. Ischemic preconditioning+ischemic postconditioning were performed in order to combine these two methods. Delay methods were applied in three different types. Skin borders of the flap were incised in delay-1 method, contralateral pedicle was divided in delay-2 method, these two methods were performed together in delay-3 method. Secondary operation was required one week later in all delay groups. Flaps were harvested and only one pedicle were kept in second surgery. Four-hour-ischemia protocol was applied prior to placement of the flap. The animals were allocated randomly into 7 groups, each group containing 10 animals. Control group; following the flap harvesting, pedicle was clamped with microvascular clamp for four hours. After that period of complete ischemia, clamp was removed in order to allow the circulation, and flap was replaced and sutured. Ischemic preconditioning group; ischemia was performed prior to four-hour-ischemic period. Ischemic postconditioning was performed in the ischemic postconditioning group, after the four-hour-ischemic period,. Ischemic preconditioning+ischemic postconditioning group; prior to four-hour-ischemic period preconditioning was performed and after that period of four hours, ischemic postconditioning was performed. Circulation was allowed after final ischemia. Flap was replaced and sutured. One week after the surgery, surviving flap area was measured and recorded in all conditioning groups with sacrifying the rats. In delay-1 group, which had been planned, flap skin was cut without harvesting the base of. Delay-2 group, left epigastric vessels were tied and divided via 1 cm skin incision. Delay-3 group, both skin incision and dividing of left superficial epigastric vessels were applied in this group. One week after the first surgery, flaps were harvested, without dividing the pedicle, and four-hour-ischemia was performed in all delay groups. Following the ischemia, flap reperfusion was achieved. One week after the second surgery, surviving flap area was measured and recorded as a percentage to the whole flap area with sacrifying the rats. Total 10 rats (control group 1; rat died, delay-1 group 3; 1 rat died, 2 rats autocannibalised, delay-2 group 2; 1 rat died, 1 rat autocannibalised, delay-3 group 1; rat autocannibalised, ischemic preconditioninggroup 2; rats autocannibalised, ischemic preconditioning+ischemic postconditioning group 2; rats autocannibalised) were excluded from this study. In conclusion, ischemic preconditioning has more protective effects than two of delay methods on ischemia-reperfusion injury in the rat inferior epigastric skin flap model. When ischemic postconditioning is added to ischemic preconditioning, protective effect of ischemic preconditioning on ischemia/reperfusion injury is increased further than all the delay methods