Circulatory changes after prolonged ischemia in the epigastric flap

The circulation system seems to have early encounters with pathophysiologic processes during ischemia and reperfusion, such as overproduction of oxygen radicals, nitric oxide depletion, and leukocyte plugging. The aim of this study was to determine the superficial perfusion and vessel distribution of the epigastric flap with a laser Doppler Imaging (LDI) system during ischemia/reperfusion, and to observe the clinical outcomes 7 days after reperfusion in a separate set of animals. An epigastric flap from male Sprague-Dawley rats (320 to 380 g) was used to assess perfusion in sham animals (n=6) or in 12 hr-ischemia animals (12 hr of ischemia and 3 hr of reperfusion, n = 10) with the LDI system. In a separate experiment, flap size, flap failure index, and histologic sections of the flap from sham animals (n=6) and 12-hr ischemia animals (n=6) were evaluated 7 days after reperfusion. Evaluation of the vessel distribution demonstrated a diffuse picture of flap perfusion after clamp release. Moreover, in the distal portion of the flap, circulation stopped immediately, resulting in a significantly decreased perfusion in the 12-hr ischemia animals during reperfusion, when compared with pre-surgical values (100 percent) or sham animals (77 +/- 26.5 vs. 108 +/- 9.6 percent PU). On day 7, the flaps of animals after ischemia and reperfusion showed significant shrinkage, an increase in flap failure index, as well as necrosis, edema, and leukocyte infiltration. Based on the findings, the authors propose that, after prolonged ischemia, the circulation becomes diffuse, and "no-reflow" occurs in the distal portions of the myocutaneous flap during reperfusion. Perfused areas, assessed with the LDI early during reperfusion, might still become necrotic after several days. In the authors' flap model, edema formation and leukocyte infiltration seem to be related more to ischemia reperfusion damage than to thrombus formation.