This Article Full Text Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Nollert, G. Articles by Reichart, B. Search for Related Content PubMed Articles by Nollert, G. Articles by Reichart, B.

(Circulation. 1995;92:327-333.)
© 1995 American Heart Association, Inc.

Articles

Determinants of Cerebral Oxygenation During Cardiac Surgery

Georg Nollert, MD; Patrick Möhnle, MD; Peter Tassani-Prell, MD; Bruno Reichart, MD

From the Department of Cardiac Surgery and Institute for Anesthesiology (P.T.-P.), Klinikum Großhadern, University of Munich, Munich, Germany.

Correspondence to Georg Nollert, MD, Department of Cardiac Surgery, Institute for Anesthesiology, Klinikum Großhadern, University of Munich, Marchioninistr 15, 81366 Munich, Germany.

Background Neuropsychological deficits after cardiac surgery are attributed to the side effects of cardiopulmonary bypass (CPB). To protect the brain from ischemic damage, the influences of temperature, blood pressure, blood gases, acid-base status, and hemodilution on cerebral oxygenation have to be elucidated and quantified.

Methods Forty-one consecutive patients were investigated during cardiac surgery while on CPB. Operative management included moderate hypothermia of 26°C and the alpha-stat pH management. With near-infrared spectrophotometry, changes in oxygenated hemoglobin (HbO₂, representing oxygen delivery) and oxidized cytochrome a,a3 (CtO₂, cellular oxygenation) in brain tissue were obtained noninvasively. In addition, venous saturation of the brain was measured via a catheter in the jugular bulb (S_BJO₂). The influence of operative management parameters on cerebral oxygenation was calculated by univariate and multiple regression analyses.

Results Before and after CPB there was no significant multivariate determinant of cerebral oxygenation. During CPB, HbO₂ depended solely on PCO₂ (P<.01; r=.89). CtO₂ was determined by pH (P<.01), esophageal temperature (P<.01), PCO₂ (P<.01), and Hb (P<.01). These parameters explained nearly all changes of the cytochrome measurements during CPB (r=.99). Arterial PCO₂ (P<.01) and pH (P<.01) influenced brain venous oxygen saturation (S_BJO₂; r=.98).

Conclusions Cerebral oxygenation is autoregulated during cardiac surgery before and after CPB. During CPB, Hb, temperature, pH, and PCO₂ determine at least 85% of all changes in cerebral oxygenation. The main causes of impaired cerebral oxygenation are the decrease in Hb with hemodilution, vasoconstriction due to hypocapnia, and the leftward shift of the Hb binding curve in alkalosis and hypothermia.

Key Words: cardiopulmonary bypass • extracorporeal circulation • oxygen • surgery • near infrared spectrophotometry

This article has been cited by other articles:

				A. Rozanski, J. A. Blumenthal, and J. Kaplan Impact of Psychological Factors on the Pathogenesis of Cardiovascular Disease and Implications for Therapy Circulation, April 27, 1999; 99(16): 2192 - 2217. [Abstract] [Full Text] [PDF]

				J. Lynch, N. Krause, G. A. Kaplan, R. Salonen, and J. T. Salonen Workplace Demands, Economic Reward, and Progression of Carotid Atherosclerosis Circulation, July 1, 1997; 96(1): 302 - 307. [Abstract] [Full Text]