ISCHEMIC PRECONDITIONING OF MUSCULOCUTANEOUS FLAPS - EFFECTS OF ISCHEMIA CYCLE LENGTH AND NUMBER OF CYCLES

Previous work in our laboratory has indicated that ischemic preconditi oning improves musculocutaneous flap survival 2.5 rimes that of the co ntrol flap area when the flaps are subsequently subjected to 4 hours o f global ischemia. The preconditioning protocol used in this study was arbitrarily designed to be 10 minutes of pedicle clamping followed by 10 minutes of reperfusion. This sequence was repeated for three cycle s with a total preconditioning time of 1 hour, There are no published works comparing different preconditioning protocols in musculocutaneou s flaps. The goal of this study was to determine if the ischemic cycle time and the number of cycles influenced the effectiveness of ischemi c preconditioning. Fifty-one male: Sprague-Dawley rats were divided in to one control and six treatment groups of 6 to 10 animals in each gro up, A transverse rectus abdominis musculocutaneous flap based on the i nferior epigastric vessels was elevated in each animal, Flaps were pre conditioned by pedicle clamping and reperfusion for either 5 or 10 min utes per cycle. This was repeated for one, tyro, or three cycles. Cont rols were simply perfused for 30 minutes. Each flap was then subjected to 4 hours of global ischemia. Flap surface survival area was calcula ted on the fifth postoperative day by computerized video planimetry, D ifferences in survival areas between control and preconditioned flaps were compared using analysis of Variance and t-tests. There was an ove rall statistical significance in the comparison of flap survival of pr econditioned flaps with that of controls. A single 5-minute cycle impr oved flap survival 2.5 times the mean control area. Two and three 5-mi nute cycles resulted In a reduction of ''the preconditioning effect, w ith flap survival no different than controls. Ten-minute preconditioni ng cycles increased flap survival 1.5 to 3 times the mean control area . Flap survival was improved by increasing the number of 10-minute cyc les. Cycle time and number of cycles have definite effects on the surv ival areas of preconditioned musculocutaneous flaps. Ischemic precondi tioning with 10-minute cycles is superior to 5 minute cycles, Three cy cles of 10-minute preconditioning is statistically superior to one or two cycles. Future studies are planned to study four or more cycles an d longer cycle times.