Background and Purpose--Ischemia-reperfusion is an established paradigm for the induction of neuro-oxidative stress. The present report highlights the limitations associated with the measurement of free radical exchange across the human brain after carotid endarterectomy if reperfusion hemodynamics are not taken into account.

Summary of Report--Only 2 human studies have reported local changes in the arterio-jugular bulb venous concentration difference (a-v_diff) of free radicals during carotid endarterectomy. The authors reported either no change or only a very minor trans-cerebral release during the course of reperfusion, which was unexpected. However, consistent with other surgical models of ischemia-reperfusion, reperfusion would have been expected to increase plasma volume consistent with reflow-hemodilution. This would artifactually dilute the local concentration of free radicals, attenuate the a-v_diff and thus underestimate the "true" magnitude of cerebral free radical release.

Conclusion--After correction for reflow-hemodilution, the cerebral generation of free radicals after carotid endarterectomy is likely to be significantly more pronounced than previously documented in humans.