Cerebral oximetry monitoring during carotid endarterectomy: effect of carotid clamping and shunting.

Cerebral oximetry is a simple method of measuring regional cerebral oxygen saturation (rSO(2)). One promising application is its use during carotid endarterectomy (CEA) to help minimize the risk of perioperative stroke. The authors used the INVOS-4100 cerebral oximeter at several steps during CEA to measure the effect of carotid clamping and shunting on rSO(2). The authors prospectively evaluated 42 consecutive CEAs in 40 patients. All had CEA under general anesthesia with the routine use of a Javid shunt. The INVOS-4100 oximeter was used to measure rSO(2) before clamping (t1), after clamping but before shunting (t2), 5 minutes after shunt insertion (t3), and after patch closure with reestablished flow (t4). The Wilcoxon signed-rank and rank-sum tests were used for analysis. Clamping of the internal carotid artery (t1 vs t2) resulted in a drop of ipsilateral rSO(2) by -12.3% (p < 0.001). Shunt insertion (t2 vs t3) increased rSO(2) by 10.9% (p < 0.001). Contralateral rSO(2) for the same time periods was insignificant. Patients with preoperative neurologic symptoms had a greater decrease in rSO(2) after clamping (-18.4%) compared with a decrease of -10.4% in asymptomatic patients (p = 0.037). Cerebral oximetry monitoring is simple and inexpensive. The study showed statistically significant changes in rSO(2) as a result of clamping and shunting of the carotid artery. Symptomatic patients had a greater drop in rSO(2).