MONITORING OF THE CEREBRAL OXYGENATION WI TH NEAR-INFRARED SPECTROSCOPY IN COMPARISON TO JUGULAR BULB OXYGEN-SATURATION DURING CAROTID ENDARTERECTOMY

Objective: Monitoring the central nervous system during carotid endart erectomy plays an important role in detection of cerebral ischemia. Wi th optical spectroscopy in the near-infrared light range it is now pos sible to measure regional cerebral oxygen saturation (rSO(2)) noninvas ively. Numerous studies emphasize the importance of cerebral oxygen ba lance rather than absolute values of cerebral blood flow or metabolic rate. In this study data from oxygen saturation measured in the jugula r bulb (SJO(2)) were compared to rSO(2). Methods: 10 patients undergoi ng elective carotid endarterectomy were enrolled after written informe d consent and approval by the local ethics committee. rSO(2) data were measured by cerebral spectroscopy (INVOS(R) 3100, Somanetics, Michiga n/USA). To avoid lesions of the internal carotid artery, a 4-F oxymetr y catheter (OPTICATH(R), Abbot GmbH, Wiesbaden) was placed in the jugu lar bulb by retrograde approach after preparation by the surgeon. Anae sthesia and mechanical ventilation were standardised. Results: After c ross-clamping of the internal carotid artery rSO(2) significantly decr eased (60.5+ 3.5%) compared to baseline (66.0 +/- 1.4%). After declamp ing rSO(2) increased significantly (63.0 +/- 4.2%) and was close to ba seline at the end of operation (65.0 +/- 2.8%). The SJO(2) time course showed good correlation compared to rSO(2) data (r = 0.85). After cro ss-clamping SJO(2) decreased significantly (51.5 +/- 6.3%) in comparis on to baseline (59.5 +/- 4.9%). Declamping increased SJO(2) to 59.5 +/ - 6.3 %. No changes in latencies or amplitudes of SEP were observed th roughout the operation. Conclusions: Noninvasive cerebral optical spec troscopy is a useful tool to determine the brain tissue oxygenation. T he positive correlation to jugular bulb oxygen saturation is somewhat unexpected as rSO(2) evaluates regional while SJO(2) measures global o xygen content. However our results suggests that both methods are able to detect episodes of cerebral ischemia during carotid endarterectomy . The interpretation of the changes of cerebral oxygen saturation with respect to neurological outcome warrants further studies.