BRAIN AND CEREBROSPINAL FLUID LACTATE CONCENTRATION IN RESPIRATORY ACIDOSIS AND ALKALOSIS

Brain CO2 buffering capacity and Csf bicarbonate concentration increase in respiratory acidosis and decrease in respiratory alkalosis. To study the mechanism responsible for these adjustments, lactate and pyruvate concentrations were measured at intervals in brain, cisternal Csf and arterial blood of dogs during 6 hr of hyper- and hypocapnia. PCO2, pH, bicarbonate concentration and PO2 were also measured in all Csf and arterial blood samples. During respiratory acidosis lactate concentration in brain and Csf fell at 30 min, returning to normal values by 6 hr. During respiratory alkalosis brain lactate rose significantly in the first 30 min, fell slightly by 2 hr, but rose to its highest value by 6 hr. Cisternal Csf lactate rose continuously. The mild and transient fall in brain and Csf lactate during respiratory acidosis does not account for the upward shift in brain CO2 buffering capacity and simultaneous increase in Csf bicarbonate content. During respiratory alkalosis, the rise in lactate explains partially the downward shift in brain buffering capacity and may account for one-third of the bicarbonate fall in the Csf. © 1969.