Microcirculatory response to surgical trauma in composite-tissue transfer

A rat cremaster muscle-flap model for direct in vivo microcirculatory studies was combined with a rat hind-limb amputation/replantation model, to evaluate changes related to transfer trauma. Forty-eight inbred Sprague-Dawley rats were studied in two experimental groups. In a control group, the cremaster muscle was dissected as an island tube flap, transposed into the hind limb, and anchored at ankle level. No amputation was performed. In a second composite-limb-cremaster-graft group, the limb, with the inserted cremaster muscle flap, was amputated at mid-thigh level, and transferred to a recipient animal. In both groups, at follow-up periods of 1, 24, 48, and 72 hr, the cremaster flap was withdrawn from the limb and prepared for microcirculatory studies. The following parameters were measured: vessel diameters, RBC velocities, capillary density, and leukocytes in the postcapillary venules. Arteriolar and venular diameters, as well as RBC velocity values, were comparable in both groups. However, the composite isografts presented 50 percent more leukocytes sticking to the lumen of the postcapillary venules (p < 0.05) immediately following transfer. In addition, a significant decrease (12 percent) in the number of perfused capillaries was observed in the composite grafts throughout 72 hr. In this study on composite tissue transfer, trauma alone compromised the microcirculatory integrity of the tissue and proved to act as an independent factor. This should be considered during allotransplantations, where the addition of a rejection factor can further compromise graft survival.