Lactate and Pyruvate Levels in Brain and Skeletal Muscle During Hyperthermia in Dogs

Tissue hypoxia, as shown by an increase of the arterial concentration of lactate and of the lactate–pyruvate (L/P) ratio, has been observed during hyperthermia in free-breathing animals with high arterial . The effect of raising body temperature to 41.9 °C for 2 h on lactate and pyruvate concentrations in arterial, muscle venous, and sagittal sinus blood and cerebrospinal fluid was studied in anesthetized dogs. The animals were paralyzed with gallamine, and arterial pH and maintained at normal levels by artificial ventilation with 50% O2. A slight increase in lactate and pyruvate took place in the arterial blood and parallel changes were observed both in the muscle venous and sagittal sinus blood. The L/P ratio did not change. Lactate and pyruvate increased markedly in the CSF, without a change in the L/P ratio. Therefore hyperthermia, in the absence of respiratory alkalosis, does not appear to induce tissue hypoxia associated with an increase in L/P ratio. The lack of correlation between lactate and pyru...