Plasma antioxidant consumption associated with ischemia/reperfusion during carotid endarterectomy

Thirteen patients undergoing carotid endarterectomy were studied to correlate changes in jugular bulb venous oxygen saturation (SjO2) 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.

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 alpha-tert-butyl phenyl nitrone (PBN).

SjO2 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.

These results provide supportive evidence for oxidant production during cerebral ischemia/reperfusion in a clinical setting.