Abstract P26

Abstract

PurPose: Venous Congestion is the top cause for free flap failure. Postoperative diagnosis of a congested flap still relies on clinical observation as the gold standard. We hypothesized that in a rat lower limb venous congestion model, Indocyanine Green (ICG) Angiography can detect venous congestion and differentiate between a congested and non-congested limb more reliably than clinical observation. Methods:A severe venous congestion model was created by bilateral amputation of the lower extremities of male Sprague Dawley rats at the level of the proximal femur leaving only the femoral vessels and femur intact. The femoral vein was occluded at the inguinal ligament while the contralateral limb served as sham control. Complete venous occlusion was achieved by suture ligature (n=11) whereas partial occlusion was achieved by surrounding the vein with a synthetic microtube to achieve 75% (n=6), 85% (n=11) and 92% (n=11) occlusions respectively. Analysis was performed at 10mins post occlusion and consisted of observation (blinded plastic surgeon), temperature, tissue oximetry (VIOPtix Inc.), ICG Angiography and measurement of TNFα and HMGB1 (by qPCR). results:Clinical assessment identified all congested limbs in the 100%, 92% and 85% groups as being congested but only 1/7 animals in the 75% occlusion group was diagnosed with congestion. However, the decision to operate on a congested limb, a corollary for the severity of occlusion, was made in 11/11 (100% group) 10/11 (92% group), 9/11 (85% group) and 0/7 (75% group). Temperature and tissue oximetry showed no significant difference between limbs in any group. By comparison, ICG Angiography was able to detect statistically significant differences in limb perfusion within the first 2 minutes of ICG injection (12mins from occlusion) in all animals in the 100%, 92% and 85% groups (paired t-test p=0.001, p=0.040 and p=0.030 respectively). ICG Angiogrpahy did not show a significant difference in limb perfusion in the 75% occlusion group. TNFα and HMGB-1 showed up-regulation as occlusion increased and the latter demonstrated >3-fold increase in the 100% occlusion group compared to the 75% occlusion group (1.49±0.48 vs. 0.44±0.22). ConClusion:We demonstrate that LAICGA is able to detect venous congestion in a rat lower extremity model reliably at occlusion rates greater than 75%. However, clinical judgment is less reliable in determining the severity of congestion. Our model serves as a basis to further study varying venous occlusion levels and their long term effects