The Effect of Combined Respiratory and Nonrespiratory Alkalosis on Energy Metabolites and Acid‐Base Parameters in the Rat Brain

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Abstract
In order to study the cerebral effects of a combined respiratory and nonrespiratory alkalosis, rats under nitrous oxide anesthesia were hyperventilated for 45 min. During the last 13 min, the animals were either injected with 5.5 mEq/kg of NaCl, or with an equimolar amount of NaHCO3. Both groups had arterial CO2 tensions close to 16 mm Hg, but the injection of sodium bicarbonate increased the arterial pH further from 7.58 to 7.80. In both hyperventilated groups, there were marked increases in the tissue lactate concentrations, and in the calculated lactatelpyruvate and NADH/NAD+ ratios. In the group injected with sodium bicarbonate there was a small further increase in the intracellular lactate concentration, but no significant changes in the extracellular lactate, pyruvate, or bicarbonate concentrations, or in the CSF pH. In none of the hyperventilated groups there were changes in the tissue contents of phosphocreatine, ATP, ADP or AMP indicative of clearcut tissue hypoxia.