Impact of arterial cross-clamping during vascular surgery on arterial stiffness measured by the augmentation index and fractal dimension of arterial pressure

Arterial cross-clamping is a common strategy used in vascular surgery and its duration is an independent predictor of surgical outcomes. The impact of arterial cross-clamping on the viscoelastic properties of the arterial system and its underlying mechanisms still remain unclear. The aim of this study was to evaluate the effect of arterial cross-clamping on arterial stiffness. A cross-sectional, observational, before-after study was designed to enroll adult patients undergoing vascular surgery. The Augmentation Index normalized to 75 beats-per-minute (AIx@75) and Fractal Dimension (FD) –indirect indicators of arterial stiffness– were calculated from radial arterial pressure tracings during surgery. The arterial pressure tracings from 8 patients were analyzed. Overall data included 4 aortic and 11 iliofemoral interventions. In both aortic and iliofemoral interventions, after arterial clamping, median AIx@75 rose and FD dropped significantly; the opposite occurred after arterial unclamping. Spearman’s correlation suggests a strong significant negative correlation between median AIx@75 and FD during each hemodynamic state for aortic interventions. Our results are consistent at many levels: a) opposite events (i.e., clamping and unclamping) produce changes in different directions, b) two different indicators (i.e., AIx@75 and FD) suggest the same underlying phenomenon, and c) similar results are observed at different vascular locations (i.e., aortic and iliofemoral). Overall, our data consistently suggests an increase in arterial stiffness during clamping and a reduction during unclamping. Despite the large distance from the aortic or iliofemoral intervention sites, radial artery pressuremonitoring is still able to detect consistently these vascular events.