Serum ionized calcium concentrations in normal neonates
J. L. Loughead, F. Mimouni and R. C. Tsang
Department of Pediatrics, University of Cincinnati College of Medicine, OH 45267-0541.
Adult serum ionized calcium (iCa) concentrations are higher when using the
newer, highly sensitive, ion-selective electrodes compared with older
electrodes. Currently used neonatal normative ranges were established using
older electrodes and not under standardized conditions or age. Thirty term
infants, carefully screened to exclude confounding factors that could
affect serum iCa concentration, were studied at birth and 2 and 24 hours of
age for serum iCa concentrations. Mean concentrations declined from 1.45
mmol/L (5.82 mg/dL) at birth to 1.33 mmol/L (5.34 mg/dL) at 2 hours to 1.23
mmol/L (4.92 mg/dL) at 24 hours. The 95% confidence limits at 24 hours
ranged from 1.10 to 1.36 mmol/L (4.40 to 5.44 mg/dL). Using newer
ion-selective electrodes, normal neonatal ranges for iCa concentrations
during the first 24 hours of age are higher than published references.
