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
.