Flow recovery and vasoconstriction following microvascular anastomosis

A variety of factors may limit blood flow recovery in free flaps. In this study one of these factors, vasoconstriction, and its consequences was investigated. Blood flow recovery at the skin level following microvascular anastomosis was evaluated in the rat orthotopic groin free flap model using a laser Doppler velocimeter. In a study of 41 rats, measurements of external vessel diameter were made using a standard machinist's drum micrometer. After each flap was raised and the anastomoses performed, the field was flooded with either saline, 2% lidocaine, or 0.75% bupivacaine (Marcaine). The vascular clamps were released and measurements of flow were recorded as a percentage of the control value. In the saline-control group, it was found that flow gradually recovered to 91% of the preoperative value in an average time of 5.7 minutes. Six of 12 vessels in this group were found to have measurable spasm of the pedicle. In the lidocaine-treated group, flow recovered to 93% of the preoperative value in an average of 5.0 minutes. Two of 15 vessels had measurable spasm. In the Marcaine-treated group, flow recovered to 94% of the preoperative value in an average of 5.1 minutes. Three of 14 vessels showed measurable spasm. The final level of flow recovery showed no statistical difference in any of these groups whether or not spasm was present. We therefore conclude that, in this model, alteration in the diameter of the vascular pedicle as a consequence of performing a microvascular anastomosis affects only the time it takes to achieve ultimate recovery of flow but does not affect its final level.