Objective qualitative and quantitative assessment of blood flow with near-infrared angiography in microvascular anastomoses in the rat model.

Intraoperative near-infrared indocyanine-green (ICG) angiography enables the visualization of microvascular perfusion and may help in the early detection of complications. The purpose of the present study was to examine whether the effect of microvascular stenoses can be quantitatively assessed by analysis of ICG-angiography in a microvascular model. Graded stenoses and total vessel occlusion of the carotid, aorta, and femoral arteries were created in 25 Wistar rats. Stenoses were graded to reduce arterial flow by 25%, 50%, 75%, and 100% of baseline flow as measured by transit-time flowmeter analyzing the emission signal of the ICG detected and investigated by the mathematical software tool (FLOW 800). ICG angiography was performed to assess vessel perfusion and flow curves were analyzed and correlated with the stenosis rate. A total of 576 investigations were performed. The area under the curve (P < 0.001), first and second maximum (P < 0.001), and the maximum slope to the first maximum (P < 0.001) were found to be of high prognostic value in evaluating the different flow patterns. Differences were displayed in comparisons by the maximum intensity of the ICG-concentrations. The maximum slope to the second maximum was found to be predictive in selected vessel types, and specific changes of the flow curve were found to indicate compromised vascular flow. The FLOW 800 tool applied for ICG angiography has shown to be a quick and reliable method for assessing blood flow in vessels in this study. The dynamic assessment of the ICG signal allows reliable identification of microanastomotic complications with the described parameters.