Cerebral physiological and metabolic effects of hyperventilation in the neonatal dog.

To clarify the changes that occur during marked hypocarbia in the neonate, we measured brain blood flow and metabolite levels after 90 minutes of hyperventilation in neonatal dogs. Brain blood flow decreased significantly in diencephalon, brainstem, and spinal cord but not in cerebral cortex or white matter. There was no substantial change in the electroencephalogram. Lactate concentrations, both in telencephalon and in superior sagittal sinus blood, increased significantly, although there was no alteration in levels of ATP or phosphocreatine. Marked hypocarbia in the neonatal dog produces an elevated brain lactate level that may be related to changes in glycolytic rate rather than to tissue ischemia or hypoxia.