Cerebral oximetry for the detection of cerebral ischemia during temporary carotid artery occlusion

The near-infrared spectroscopy cerebral oximeter was assessed as a monitoring device for detecting and/or predicting cerebral ischemia during carotid endarterectomy (CEA) and the balloon occlusion test in 24 patients, 12 males and 12 females aged 28 to 77 years (mean 59.9 years). Tolerance testing of complete internal carotid artery (ICA) occlusion by balloon inflation for 20 minutes was performed in nine patients (cerebral aneurysm 6, neck tumor 3) and CEA was performed in 15 patients. The probe of the cerebral oximeter was placed on the forehead of the affected side and regional cerebral oxygen saturation (rSO2) was monitored continuously during all procedures. Stump pressure was measured just after ICA occlusion. Collateral circulation detected by digital subtraction angiography was classified into three groups: good, moderate, or poor. Stump pressure was 41-90 mmHg (mean 61.3 mmHg) in the good collateral circulation group, 40-43 mmHg (41.5 mmHg) in the moderate group, and 14-30 mmHg (23.8 mmHg) in the poor group. Change in rSO2 after ICA occlusion was +3.5(-)-4.2% (mean -1.6%) in the good collateral circulation group, -1.2(-)-6.6% (-3.2%) in the moderate group, and -2.4(-)-10.2% (-6.6%) in the poor group. Changes in rSO2 were significantly different between the good and poor collateral circulation groups (p < 0.01). A greater than 5% fall in rSO2 was observed in 0 of 15 patients in the good collateral circulation group, one of five in the moderate group, and three of four in the poor group. The cerebral oximeter is a useful, real-time, non-invasive method to measure brain oxygenation during CEA, skull base surgery, or other procedures which need to evaluate brain ischemia. A fall of greater than 10% from the rSO2 baseline value is dangerous, but less than 5% is safe.