Relation of Hypoxemia and/or Hypocapnia to Lactic Acid Content of Brain and Cardiovascular Response

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

The lactic acid concentration of brain was measured 3 hours after death in dogs which had been subject to hypocapnia, hypoxemia with hypocapnia, and hypoxemia without hypocapnia for 15 minutes. There was no elevation of brain lactic acid above the control level in those dogs subjected to hypocapnia or hypoxemia alone, however, when hypocapnia and hypoxemia were combined there was a significant increase. Cardiovascular and blood chemical analyses support the conclusion that variations in cerebral blood flow, availability of oxygen at the tissue level and interference with oxidative metabolism are important determining factors in brain lactic acid build-up. The results agree with those obtained in altitude-exposed animals, for they likewise show an elevation of brain lactic acid.