Venous endothelial changes after experimental cooling of free flaps.

The free epigastric rabbit flap was used to observe morphological alterations in the microvasculature following prolonged hypothermic ischemic intervals. Free flaps were raised, cooled 1-6 days, and reanastomosed. The epigastric artery, vein, and dermal vessels were examined by electron microscopy. Efforts to keep flap tissues in the cold less than or equal to 5 days were successful (85% of flaps survived following reanastomosis N = 15). Flap failures were accompanied by extensive disruption to the endothelial cells of the epigastric vein. The findings support the efficacy of a cooling period less than or equal to 5 days for free flaps. The morphological alterations in the venous endothelium of the flap also suggest a plausible explanation for flap failures which occur in spite of patent anastomotic sites.