EFFECTS OF TISSUE EXPANSION ON SECONDARY ISCHEMIC TOLERANCE IN EXPERIMENTAL FREE FLAPS

The effects of tissue expansion on free flap tolerance and metabolic r esponse to secondary ischemia were evaluated. A total of 178 male syng eneic Lewis rats were used: 28 in perfusion study and 75 donor and 75 recipient animals in flap survival study. Animals were organized in th ree experimental groups: control, sham operation, and expansion group. Sham group animals had the expander implanted but not insufflated. Af ter 4 weeks of tissue expansion, 3 x 5-cm epigastric free flaps were t ransplanted to recipient animals. Twenty-four hours later, secondary i schemia was produced by 3-hour venous occlusion. Flap survival, perfus ion, and enzyme activities were determined. Preexpanded skin flaps had an increase in perfusion of approximately 700% as measured by fluores cein levels compared with control flaps (p < 0.001) and demonstrated a better success rate (76%) compared with those of the control (40%) (p < 0.05) and sham (28%) groups (p < 0.05). Glutathione peroxidase, glu tathione reductase, and glucose 6-phosphate dehydrogenase of the anti- oxidant-defense systems significantly increased in skin in both the sh am and the expansion groups, In response to secondary ischemia, the co ntrol and sham groups exhibited a decrease in enzyme activities of the glutathione redox cycle, whereas the expansion group showed no signif icant changes from the elevated baseline activities. Tissue expansion improved flap tolerance to secondary ischemia by increasing flap circu lation and probably by augmenting tissue metabolic response to oxidati ve stress.