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Brain tissue oxygen pressure, carbon dioxide pressure, and pH during hypothermic circulatory arrest
W E Hoffman1, F T Charbel, G Edelman
1Anesthesiology Department, University of Illinois at Chicago 60612, USA.
Background:
This study evaluated brain tissue oxygen pressure (PO2), carbon dioxide pressure (PCO2), and pH in a patient during hypothermic circulatory arrest.
Methods:
A combined PO2, PCO2, and pH sensor was placed in cortex tissue. Brain temperature was then decreased to 17 degrees C followed by circulatory arrest for 44 minutes during an endarterectomy of the M1 segment of the middle cerebral artery.
Results:
Brain tissue PO2 increased during brain cooling from 10 mmHg-30 mmHg and decreased to zero following exsanguination. During circulatory arrest, tissue PCO2 increased to >200 mmHg and pH decreased to 6.0. Tissue PCO2 and pH recovered during circulatory rewarming but the increase in PO2 was delayed. Tissue parameters continued to improve during 2 days of postsurgical monitoring and were correlated with neurologic recovery.
Conclusions:
These results show that brain tissue PO2, PCO2, and pH measures indicate the severity of ischemia during hypothermic cardiac arrest and recovery in the postoperative period.