Cerebral metabolism in newborn dogs during reversible asphyxia

Acute, systemic asphyxia was induced in paralyzed, lightly anesthetized 1‐ to 2‐day‐old dogs by respiratory arrest. Measurements of arterial blood pressure, acid‐base balance, and concentrations of pyruvate, lactate, and glucose in blood were correlated with electroencephalographic activity and with concentrations of high‐energy phosphates and glycolytic substrates in the cerebral cortex. Most animals tolerated 15 minutes, but not 20 minutes, of asphyxia with apparently normal behavioral recovery. Asphyxia was always accompanied by bradycardia, systemic hypotension, and a progressive decline in arterial pH; the concentration of blood lactate and the lactate/pyruvate ratio rose. Blood glucose levels were unaffected, at least during the first 10 minutes. Concentrations of glucose and phosphocreatine in cerebral cortex declined rapidly during asphyxia to low levels, but levels of adenosine triphosphate remained within normal limits for up to 5 minutes despite the fact that electrical activity in brain ceased within 2 minutes. The intravenous injection of carbon black into animals asphyxiated for 21/2, 5, 10, or 15 minutes revealed substantial reductions in blood flow to brain during asphyxia; however, relative to the cerebral cortex, brainstem structures received a preferential blood supply.