Plasma Antioxidant Consumption Associated With Ischemia/Reperfusion During Carotid Endarterectomy

Abstract

Background and Purpose Thirteen patients undergoing carotid endarterectomy were studied to correlate changes in jugular bulb venous oxygen saturation (S j o 2 ) with indices of free radical production during cerebral ischemia/reperfusion. Levels of oxidant species were also monitored in arterial samples to determine any change across the cerebral circulation. Methods Blood was sampled from a venous catheter inserted in the ipsilateral jugular bulb and from an arterial catheter. Co-oximetry measurements were made to determine jugular bulb venous oxygenation saturation. To monitor changes in oxidant stress, a colorimetric assay was used to determine plasma antioxidant potential, and electron paramagnetic resonance spectroscopy was used to quantify free radical–spin trap adducts formed in a blood sample treated with the spin trap α-tert-butyl phenyl nitrone (PBN). Results S j o 2 decreased significantly from 68±11% to 61±10% ( P <.05) during clamping of the internal carotid artery and returned to baseline (65±11%) when the carotid clamp was removed. Jugular venous plasma antioxidant potential decreased significantly from 32.76±5.42% inhibition to 28.02±6.77% inhibition ( P <.05). There was no concomitant change in arterial plasma antioxidant potential values, indicating a decrease in antioxidant capacity across the cerebral circulation. However, analysis of spin trap–free radical adducts did not provide conclusive evidence for free radical production. Conclusions These results provide supportive evidence for oxidant production during cerebral ischemia/reperfusion in a clinical setting.