Post-Mortem Diagnosis of Hypoxia by Means of Brain Lactic Acid Concentration

Simulated altitude exposure elevates the postmortem brain lactic acid concentration up to 98 mg/100 gm above controls depending on species used, duration, and intensity of exposure. The sharp difference in post-mortem brain lactic acid concentration between altitude exposed animals and controls remains demonstrable for the longest postmortem intervals studied (20 hr. in the dog, 30 hr. in the rabbit, and 6 hr. in the rat). Upon recovery from altitude exposure the brain lactic acid and/or precursors return toward pre-exposure levels in accordance with first order reaction kinetics during the first few minutes. The velocity constant is .32 and the half-life is 2.2 minutes. Elevated post-mortem brain lactic acid concentration is a constant finding in animals which were hypoxic at the time of death and appears to be a suitable criterion for establishing ante-mortem altitude exposure or other physiologically similar oxygen deficiency situations.