Effects of altitude and of anesthesia on brain electrolytes and lactic acid

¹ Department of Physiology-Biophysics, School of Aviation Medicine, USAF, Randolph Air Force Base, Texas

The concentration of lactic acid, sodium, potassium and calcium was measured in four structures of the brain 3 hours after death in anesthetized and unanesthetized dogs which had been subjected to simulated altitude and ground level control protocols for 15 minutes. The effect of the simulated altitude was elevation of a) the sodium concentration in the corona radiata but not in the cerebral cortex or caudate nucleus, b) the calcium concentration in the cortex, corona radiata and caudate nucleus and c) the lactic acid concentration in all the tissues. No potassium changes were noted. The effect of the anesthesia was very slight and only indirectly detectable. The sampling problem was studied and caudate nucleus and cortex recommended as sampling sites for the detection of hypoxia by lactic acid elevation if a whole hemisphere cannot be used. It is pointed out that accuracy in diagnosing ante mortem hypoxia depends upon discrete anatomical sampling since lactic acid is not evenly distributed within the brain. A chemical approach to give compensation for the uneven distribution of lactic acid is presented.