Perfusion washout: increasing a microvascular free flap tolerance to ischemia.

Thirty-five Sprague-Dawley rats were divided into control (non-exsanguinated) groups of 8 and 10 hr of ischemia, and exsanguinated groups of 8, 10, 14, 16, and 18 hr of ischemia. Free flaps based on the superficial inferior epigastric artery were anastomosed to the contralateral femoral vessels after their designated ischemia period. Reperfusion was assessed by measuring fluorescein uptake in the free flaps after clamp release. In the exsanguinated groups, 100 percent (5/5) of the 8-hr, 10-hr, and 14-hr ischemia groups survived; 80 percent (4/5) of the 16-hr ischemia group free flaps survived; and none (0/5) of the 18-hr ischemia flaps survived. In the control groups, 100 percent (5/5) of the 8-hr ischemia flaps survived, while none (0/5) of the control 10-hr ischemia flaps survived. Fluorescein uptake correlated well with flap survival. By exsanguinating an experimental microvascular free flap prior to its ischemia period, it is possible to dramatically increase flap tolerance to ischemia.