RECIPIENT BED VASCULARITY AND THE SURVIVAL OF ISCHEMIC FLAPS

The purpose of this study was to identify the length of the ischaemic period required to induce the 'no-reflow' phenomenon in a rat epigastr ic flap on an avascular recipient site. The vascularity of the recipie nt bed may affect flap survival in the early postischaemic stage after flap transfer. Initially, we designed epigastric flaps in 300-350 g S prague-Dawley rats and separated the rats into four groups of 5 rats e ach (total 20 rats). In groups 1, 2, 3, the flaps were made ischaemic for 1 hour, 6 hours and 10 hours, respectively, by temporarily clippin g the epigastric artery and vein. In group 4, the epigastric artery an d vein were divided to create permanent ischaemia. In groups 1, 2 and 3, ischaemia was ended by removing the clips. After the ischaemic flap s were reperfused, their viability was studied by measuring the flap s urvival rate at postoperative day 7. Flap survival was studied by dire ct observations, laser Doppler flowmeter measurement of flap blood flo w, histopathology, and carbon particle perfusion of the flap vasculatu re. Ischaemic flaps of groups 1 and 2 recovered almost completely afte r reperfusion due to the short period of ischaema.In a second series o f experiments, in order to evaluate the contribution to flap survival of the recipient vascularised bed, another four groups of epigastric f laps (of 5 animals each, using the same time periods as above) were ra ised and a piece of Biobrane was interposed between the flap and the r ecipient bed before the flap wound was closed, to eliminate all nutrie nt supply from the recipient bed. The results showed that the combined effect of the reperfused flap vasculature plus the metabolic contribu tion of the recipient bed significantly (P < 0.01) increased the exten t of flap survival of the 6- and 10-hour ischaemic flaps as well as th e divided pedicle flaps, which were never reperfused. An absolute 'no- reflow' rat model flap for further flap salvage studies was also devel oped.