Effect of clamp versus anastomotic-induced ischemia on critical ischemic time and survival of rat epigastric fasciocutaneous flap

Background. There are many models used to explore ischemic-related phenomen a. The rat epigastric fasciocutaneous flap model is the one most commonly u sed. Critical ischemic time is the maximum ischemic insult that tissue can undergo and still remain viable. Experimentally, ischemia is induced either by clamping the vascular pedicle or by dividing the pedicle then performin g microvascular arterial and venous anastomosis. We sought to determine wha t effect the different methods of inducing ischemia have on the critical pr imary ischemic time and, thus, flap survival. Methods. A right 3 cm x 6 cm groin flap based on the inferior epigastric Ve ssels was raised in each rat. Ischemic times of 4, 6, 8, or 10 hours were i nduced either by placing temporary occlusion clamps on each vessel of the v ascular pedicle (island pedicle group) br by ligation and division of the p edicle with subsequent microvascular anastomosis (free flap group). Surviva l was assessed at 7 days. Results. The primary ischemic time at which one half of free flaps are pred icted to die was calculated to be 7.60 hours, compared with 6.09 hours for the island pedicle flaps (p <.05). Conclusions. Fasciocutaneous flaps undergoing ligation and anastomosis are more resistant to ischemia than are those undergoing clamping of the pedicl e. Possible etiologic factors responsible for this experimental finding are discussed. (C) 1999 John Wiley & Sons, Inc.