The number of venous anastomoses advisable for a free flap continues to be controversial. Intrinsic transit time (ITT) is the time it takes dye during indocyanine green (ICG) microangiography to travel from the arterial to the venous anastomosis. ITT provides information on blood flow velocity and can predict postoperative circulatory complications. This study investigated the effect of the number of venous anastomoses on ITT.Methods
The study enrolled 126 patients who had undergone microsurgical reconstruction and intraoperative ICG microangiography. Selection was limited to free gracilis and anterolateral thigh flaps as flaps with a single venous system. The retrospective assessment included reconstruction characteristics of the flaps, clinical outcome, ITT, and the number of venous anastomoses.Results
The two groups were homogenous in terms of reconstruction characteristics. The single-venous anastomosis group (n = 75) had a reduced ITT (23.6 ± 11.7 vs. 43.8 ± 23.7 seconds; p < 0.001) compared with the double-anastomosis group (n = 51). A shorter ITT resulted in a significant reduction in the risk of reexploration for anastomotic thrombosis (OR 0.96; p = 0.024). Despite this, a higher reexploration rate tended to occur in the single-venous anastomosis group (9.3 vs. 7.8%; p = 1.0).Conclusion
The results highlight the effect of shortening the ITT (thromboprotective blood flow acceleration) by using only one venous anastomosis. However, if the ITT is already at a low enough level with two veins, restriction to one vein does not appear to result in a reduced reexploration rate. For these flaps, the advantages of double-venous anastomosis prevail in terms of a backup drainage.