THE EFFECT OF PROLONGED CLAMPING AND VASCULAR STASIS ON THE PATENCY OF ARTERIAL AND VENOUS MICROANASTOMOSES

During free tissue transfer, an artery and one or two veins must be su tured, Either the artery or the vein can be repaired first, but the op timal order of vascular repair has not been established. Maintaining a clamp on a vessel is associated with vessel injury, and releasing the clamp may cause bleeding and vascular stasis. The purpose of this stu dy was to determine if the order of vessel repair and the length of va scular clamping affects surgical outcome. Free flaps were created on S prague-Dawley rats (400-450 g) as follows: Bilateral abdominal skin fl aps (3 x 3 cm) based on the superficial inferior epigastric vessels we re elevated. The femoral artery and vein were tied and divided distal to the branching of the inferior epigastric vessels. Proximal to the b ranching, the artery and vein were divided. The animals were then rand omized into four groups as follows: In group I (N = 16), the artery wa s repaired and then the clamps were released to revascularize the flap . Venous stasis occurred as the vein was being repaired because of the venous clamp. In group II (N = 15), the artery was repaired, but the clamp was maintained to prevent blood from coming in contact with the fresh arterial anastomosis and to prevent venous stasis. The vein was; hen repaired. In group ill (N = 15), the vein was repaired first but t he venous clamp was not released until the artery was repaired. In gro up IV (N = 15), the vein was repaired first and the clamps were releas ed, allowing venous blood to contact ?he fresh anastomosis while the a rtery was being repaired, After final clamp removal, all anastomoses w ere assessed immediately for evidence of thrombosis. Five days postope ratively the skin flap was evaluated for evidence of necrosis and the anastomosis was inspected for evidence of late thrombosis. The anastom oses were resected for histopathological evaluation. Flap success was compared between groups using chi-squared analysis, Eleven of 16 flaps failed (69%) in group I, and 3 of 15 flaps failed (20%) in each of gr oups II, III, and IV. Statistical significance was reached in comparin g group I with the other three groups (p < 0.01), All failures in grou p I were caused by immediate venous thrombosis. The other failures wer e secondary to arterial thrombosis, Histopathological analysis failed to demonstrate any differences between the groups. According to these results, arterial repair followed by clamp release prior to the comple tion of the venous repair results in a low success rate, probably seco ndary to venous stasis within the draining vein while the venous anast omosis is being completed. if the arterial repair is performed first, then it is recommended that the arterial clamp be maintained until the venous repair is completed, if the vein is repaired first, then it ca n be clamped or unclamped with similar results.