Serum creatine kinase and creatine kinase-MB isoenzyme activities in perinatally asphyxiated newborns

Serum creatine kinase (CK) and creatine kinase-MB isoenzyme (CK-MB) activities were studied prospectively in serial blood samples obtained from 23 perinatally asphyxiated negroid newborns and 12 healthy controls during the first 100 h of life. The asphyxiated infants had significantly elevated mean CK and absolute CK-MB but no fractional CK-MB activities. Peak mean CK and CK-MB values (U.l-1) were 789·17 (±220), P<0·01 and 16·36 (± 3·0) P<0·001 respectively at the 6-8 h post-partum period. The healthy controls, on the other hand, showed a steady decline in the activities of these enzymes from birth. The vaginally and operatively delivered asphyxiated infants showed significantly higher CK and CK-MB activities than their respective non-asphyxiated controls, but no increase in fractional CK-MB was recorded in any of the groups. The elevation in absolute and fractional CK-MB 42·0 U.l-1 (5·1%)in respect of the infants with TTI (transient tricuspid incompetence) was significant (P<0·05) when compared with the controls with features of TTN (transient tachypnoea of the newborn) in the 6-8 h post-partum period. One of the infants with TTI at autopsy had hypoxic myocardial injury. The specificity of CK-MB, as a marker of myocardial injury in asphyxiated negroid neonates, is plausible but remains uncertain. Until the lack of rise of CK and CK-MB in healthy negroid newborns is confirmed in a larger series with further studies on MM, BB and MB isoenzymes, caution is urged in the interpretation of elevated CK and CK-MB activities in asphyxiated negroid newborns. © 1991 The European Society of Cardiology.