REGIONAL ISCHEMIA DURING CEREBRAL BYPASS-SURGERY

BACKGROUND We evaluated brain tissue oxygen pressure (PO2), carbon dio xide pressure (PCO2), and pH during regional ischemia produced by temp orary brain artery occlusion. METHODS This 45-year-old woman with cere bral occlusive disease was scheduled for right superficial temporal ar tery (STA) to middle cerebral artery (MCA) bypass. Two Paratrend 7 sen sors measuring PO2, PCO2, and pH were inserted into the cortex in the distribution of the MCA at a distance of 1 cm from each other. Jugular bulb oxygen saturation was measured by oximetry. Local perfusion was measured with a flow probe on the MCA and using a laser Doppler. Tissu e responses were recorded during: (1) 100% oxygen ventilation, (2) hyp ercapnia, and (3) an 18 minute occlusion of the right MCA. RESULTS Und er baseline conditions, tissue PO2, PCO2, and pH suggested that ischem ia was present in tissue measured by both sensors. Tissue PO2 rose 40% -50% in both regions during 100% oxygen ventilation. During hypercapni a, blood flow increased in the MCA, but local perfusion did not increa se in region 2. During temporary occlusion of the MCA, ischemic change s in PO2, PCO2, and pH were seen in region 2 but not in region 1. Loca l perfusion decreased 80% in region 2, where ischemic changes were see n. CONCLUSIONS These results show that changes in tissue PO2, PCO2, an d pH are consistent with local perfusion. The use of multiple tissue s ensors can detect the presence of watershed ischemia that is not demon strated by jugular bulb measurement. (C) 1997 by Elsevier Science Inc.