Experimental prevention of free flap thrombosis. II: Normovolemic hemodilution for thrombosis prevention.

A microvascular free flap failure model consisting of raising an epigastric groin flap on the femoral pedicle, while cutting the femoral artery, twisting it around the femoral vein and resuturing it, has been previously described. As it was being evaluated, normovolemic hemodilution as a means to prevent thrombosis was simultaneously assessed using an additional experimental group. Twenty percent of the blood mass of each rat was taken and replaced with a hydroxyethyl starch solution immediately before surgery. Only 14 out of 20 anastomoses presented with thrombosis (13 venous and one mixed), as opposed to 19 out of 20 animals operated on without hemodilution (P< 0.05). Normovolemic hemodilution appears to be an effective method of reducing microvascular free flap failure.