The effects of acute total asphyxia and metabolic acidosis on cerebrospinal fluid bicarbonate regulation in newborn puppies.

Abstract

We evaluated CSF [HCO3-] regulation in lightly anesthetized newborn puppies following: (1) acute total asphyxia; (2) metabolic acidosis; and (3) metabolic acidosis induced after acute asphyxia. Five and one-half min of total asphyxia resulted in a 4.4 mM/liter decrease in mean CSF [HCO3-]. During 65 min of recovery with mechanical ventilation mean CSF [HCO3-] increased 1.7 mM/liter. Mean plasma [HCO3-] decreased 7 mM/liter and recovered 4.5 mM/liter in the same period. We produced a stable metabolic acidosic for 4 hr using a peritoneal dialysis technique with PaCO2 maintained at the normal value. With acidosis in nonasphyxiated control puppies, CSF [HCO3-] decreased steadily. At 4 hr, the ratio, delta CSF [HCO3-]/delta plasma [HCO3-], was 0.43, a value close to that observed in adults of many species with metabolic acid-base disturbances, 0.41. With acidosis in asphyxiated puppies allowed 1 hr of recovery, the time course and mean values of plasma and CSF [HCO3-] were indistinguishable from those of the nonasphyxiated acidotic controls. Newborn puppies appear to regulate CSF [HCO3-] in response to acute asphyxia or metabolic acidosis, and acute asphyxia does not impair the puppy's ability to regulate CSF [HCO3-] in metabolic acidosis.