BRAIN-TISSUE OXYGEN-PRESSURE, CARBON-DIOXIDE PRESSURE, AND PH DURING HYPOTHERMIC CIRCULATORY ARREST

BACKGROUND This study evaluated brain tissue oxygen pressure (PO2), ca rbon dioxide pressure (PCO2), and pH in a patient during hypothermic c irculatory arrest. METHODS A combined PO2, PCO2, and pH sensor was pla ced in cortex tissue. Brain temperature was then decreased to 17 degre es C followed by circulatory arrest for 44 minutes during an endartere ctomy of the M1 segment of the middle cerebral artery. RESULTS Brain t issue PO2 increased during brain cooling from 10 mmHg-30 mmHg and decr eased to zero following exsanguination. During circulatory arrest, tis sue PCO2 increased to >200 mmHg and pH decreased to 6.0. Tissue PCO2 a nd pH recovered during circulatory rewarming but the increase in PO2 w as delayed. Tissue parameters continued to improve during 2 days of po stsurgical monitoring and were correlated with neurologic recovery. CO NCLUSIONS These results show that brain tissue PO2, PCO2, and pH measu res indicate the severity of ischemia during hypothermic cardiac arres t and recovery in the postoperative period.