Effect of warm ischemia on neovascularization of island flaps

Poor neovascularization in free-flap transfers is considered to be a consequence of insufficient hypoxic stimulus in a transferred flap with good axial-pattern circulation and a short warm ischemia time. The purpose of the study was to investigate the effect of warm ischemia time on neovascularization of axial-pattern flaps. Oblique adipomusculocutaneous groin island flaps based on the superficial epigastric vessels were raised on the right side of 21 Wistar rats, evaluated in three groups. In Group 1 (n=7), flaps were resutured without creating ischemia; in Groups 2 (n=7) and 3 (n=7), flaps were resutured after 90-min and 180-min warm ischemic periods, respectively. At 5 days postoperatively, an intravenous fluorescein test was performed following pedicle ligation, and survival was assessed by planimetric technique 7 days after pedicle ligation. Histopathologic scoring was performed according to capillary formation, inflammation, and necrosis. The intravenous fluorescein test revealed significantly higher uptake in the group with the longest ischemic period, while the mean surviving area was greater in the groups with ischemic insult, comparing to the non-ischemic group. Similarly, histopathologic scoring showed significantly higher values in the ischemic groups. The authors demonstrated that neovascularization was enhanced after 90- and 180-min warm ischemia times. The authors concluded that short ischemia time in free flaps may be an attributable factor in late flap failures, due to pedicle obstruction.