[The causes of necrosis of arteriovenous flap and its modification]

Arteriovenous flaps have been developed for more than ten years, however the cause of necrosis of the flap remains obscure. We observed the changes in the microcirculation of the flap, and it was revealed that most of capillaries were occluded in the early arterialized stage, and the capillary patency was only 10%-20%. The latter was increased to 80%-90% three days later. All these changes were due to the damage of endothelial cells by arterial blood, because of high pressure and oxygen tension, resulting if cell swelling, fissuring, exfoliation and finally thrombosis. As a consequence, the effective microcirculation volume became decreased. As venous endothelial cells required time to adapt arterial blood, and expansion of skin could increase tissue capillaries in number, the arteriovenous flap was modified by skin expansion before arterialization. This method improved the survival rate remarkably.