Evaluation of blood flow in free microvascular flaps

Free flap surgery is routine today, yet little is known of its pathophysiol ogy. In this study, the authors evaluated the hemodynamics in different typ es of free microvascular flaps, by measuring intraoperative transit-time fl ow Eighty-six free transplants-21 free TRAM flaps for breast reconstruction , 18 radial forearm flaps for head and neck reconstructions, and 47 muscle flaps for head and neck, trunk and lower extremity reconstructions-were stu died. Donor artery flow was highest in the radial artery (mean: 57.5 +/- 50 (SD) ml/min) but dropped (p < 0.001) to one tenth (6.1 +/- 2 ml/min) after anastomosis. The flow was lowest (4.9 +/- 3 ml/min) in the recipient arter y of the TRAM flap but, after anastomosis, increased significantly (13.7 +/ - 5 ml/min) to the level of the flow in the donor artery The donor-artery f low in muscle flaps had a mean of 15.9 +/- 11 ml/min, and it significantly increased after anastomosing (23.9 +/- 12 ml/min). Weight-related intake of blood was highest in the radial forearm flap (18.5 +/-. 6 ml/ min/100g) an d lowest in the TRAM flap (2.5 +/- 1 ml/min/100g). The study showed that bl ood flow through a free microvascular flap does not depend on recipient art ery flow Even low-flow arteries can be used as recipients, because the flow increases according to free-flap requirements. The blood flow through a fr ee microvascular flap depends on the specific tissue components of the flap .