Oxygen in tissues during deep hypothermia

¹ Department of Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York

An oxygen electrode and a thermistor were placed in the brain stem, leg muscle, or abdomen of a rat cooled to 17–15 C. When the rat was thereafter kept at 16° the electrode usually showed a steady current. At 13–11° the apparent Po₂ of tissue in most instances diminished during 2–3 hr unless artificial breathing was given. Forced breathing of air or oxygen ordinarily raised the Po₂; of nitrogen usually, but not always, lowered the Po₂. When the apparent Po₂ was not thus raised or lowered, the flow of blood to the one tissue being examined, but not necessarily to all tissues, was evidently inadequate. The heart could be stopped reversibly by further cooling to 9–5°; brain Po₂ diminished only gradually at that low temperature. Survival was assured by a Po₂ that was high and steady, but often occurred also after a diminishing or zero Po₂. In the hypothermic rat, either pulmonary ventilation or systemic blood flow or an unidentified factor could limit the rat's survival.

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				R. K. ANDJUS, Z. DZAKULA, J. L. MARKLEY, and S. MACURA Brain Energetics and Tolerance to Anoxia in Deep Hypothermia Ann. N.Y. Acad. Sci., June 1, 2005; 1048(1): 10 - 35. [Abstract] [Full Text] [PDF]