The renal response to acute asphyxia in spontaneously breathing newborn lambs.

The effects of acute asphyxia on neonatal renal function were examined in spontaneously breathing newborn lambs. 25 min of asphyxia were induced by addition of a respiratory dead space to reduce PaO2 to 41 +/- 3 mm Hg, pH to 7.03 +/- 0.05 and increase PaCO2 to 68 +/- 5 mm Hg (mean +/- S.E.M.). Glomerular filtration rates did not change significantly during or after asphyxia. Immediately following asphyxia significant (P less than 0.05) increases over the baseline were found in urinary flow rates, fractional sodium excretion, absolute sodium excretion and osmolar clearances. These changes were in part secondary to significant (P less than 0.05) increases in plasma glucose concentrations associated with increases (P less than 0.05) in circulating arterial catecholamine concentrations. The percentage of tubular reabsorption of glucose decreased significantly (P less than 0.05) and urinary glucose excretion increased significantly. Renal blood flow was unchanged. Therefore, asphyxia induced significant hyperglycemia which contributed to the concomitant natriuresis and osmotic diuresis in these newborn lambs.