Effects of acidosis on the activity of creatine phosphokinase and its isoenzymes in the serum of newborn infants.

The total creatine phosphokinase (CPK) activity and the levels of activity of its MM, MB and BB isoenzymes were measured in sera obtained within four hours after birth from 32 newborn infants. The total CPK level and activity of its MM, MB, and BB isoenzymes increased significantly with increasing acidosis. In addition, statistically significant correlations were found between the total CPK level in infants' sera and their one-minute Apgar scores. The infants' birth weight, gestational age, and mode of delivery did not correlate significantly with the serum total CPK activity. Infants who died within ten days after birth from causes related to asphyxia had significantly higher total CPK activity levels in their sera in comparison with the survivors. The data suggest that perinatal asphyxia with acidosis may result in the leakage of CPK and its isoenzymes from the damaged cells into the circulation and that a marked elevation of their values may indicate a poor prognosis for survival.