Effect of sequence, timing of vascular anastomosis, and clamp removal on survival of microsurgical flaps.

The effects of the timing and order of clamp removal in microsurgical transplants were studied in rat groin skin flap and rat latissimus dorsi muscle flap models. Forty rats were divided into four groups. In Group 1, the arterial pedicle of the skin flap was anastomosed first, and the clamp was released after the anastomosis was completed. The venous pedicle was then repaired after inflow was restored. In Group 2, the venous pedicle of the skin flap was anastomosed first. The venous clamp was not released until completion of the arterial anastomosis. In Group 3, the arterial pedicle was anastomosed first in the muscle flap. The venous anastomosis was then performed after the arterial clamp was released. In Group 4, the venous pedicle was anastomosed first, and both clamps were released simultaneously. The blood perfusion of the skin flaps was examined after both clamps were released in Groups 1 and 2. The flap survival status was examined 5 days postoperatively for skin flaps and at 3 days for muscle flaps. Skin flaps in an additional six rats were harvested for histology. The results showed that the flap blood flow for Group 1 was statistically significantly higher than for Group 2 flaps in the first 20 min after reperfusion. There was no significant difference of flow between these two groups during the 30 to 90 min after reperfusion. The difference in survival rates for the four groups was not significant. Histology revealed extensive congestion in the flaps from Group 1 after completion anastomoses, but the congestion was significantly decreased at 3 hr following reperfusion. In conclusion, a brief venous stasis during anastomosis, after establishment of arterial inflow, is not detrimental to flap survival. The sequence of anastomosis will not affect outcome for either the cutaneous flap or the muscle flap models. Early flap perfusion was increased when the arterial anastomosis was performed first.