One versus two venous anastomoses in microvascular free flap surgery

BACKGROUND:: The authors' goal was to determine whether one or two venous anastomoses results in superior blood flow through microvascular free flaps. METHODS:: During flap harvest, blood velocity was measured in each of two venae comitantes using Doppler ultrasonography. Next, one of the two veins was occluded with a microvascular clamp and blood velocity was measured in the open vein. The clamp was then removed and placed on the other vein, and blood velocity was measured in the first vein. The pedicle was divided and microvascular anastomosis of either one or two veins was performed. Venous blood velocity was then compared between flaps with one versus two venous anastomoses. RESULTS:: Eighty-one free flaps were performed. Before pedicle division, the peak venous blood velocity in each of the two venae comitantes averaged 6.3 ± 4.8 cm/second. When one of the veins was occluded, the peak venous blood velocity increased to 19.5 ± 17.3 cm/second (p < 0.00001). One venous anastomosis was performed in 69 flaps and two venous anastomoses were performed in 12 flaps. The mean blood velocity in flaps in which one venous anastomosis was performed was greater than the mean blood velocity in either vein when two venous anastomoses were performed (13.1 ± 7.3 cm/second versus 7.5 ± 4.3 cm/second, respectively; p = 0.001). CONCLUSIONS:: When one vena comitans is occluded, blood velocity in the second vena comitans increases significantly. Venous blood velocity is significantly greater after a single venous anastomosis than in either of two veins when two venous anastomoses are performed. These results argue against routinely performing two venous anastomoses.