Age-related reference values for ionized calcium in the first week of life in premature and full-term neonates

Reference values for ionized calcium were measured in anaerobic samples of capillary blood from 22 healthy premature neonates, gestational age 33-36 weeks, birth weight 1660-2480 g. Reference values (mean +/- 2SE) for premature neonates aged 5-12, 13-19, 25-48, 51-72, 77-99, 108-140, 150-185 h were: 1.21 +/- 0.16, 1.17 +/- 0.12, 1.21 +/- 0.16, 1.28 +/- 0.18, 1.34 +/- 0.14, 1.38 +/- 0.13, 1.40 +/- 0.16 mmol/l, respectively. Ionized calcium in 59 full-term neonates with mild pathological hyperbilirubinaemia (no phototherapy needed) and 28 neonates born by section (no neonatal complications) showed no statistical difference (unpaired t-test) in age-related values compared with matching healthy neonates with no clinical remarks. Data for full-term neonates were pooled and age-related reference values (mean +/- 2SE) for ionized calcium in capillary whole blood for 168 full-term neonates, gestational age 38-41 weeks, birth weight 2550-4700 g, aged 1-12, 13-24, 25-48, 49-72, 73-99, 99-120, 121-144, 146-168, 178-264 h were: 1.24 +/- 0.11, 1.19 +/- 0.12, 1.21 +/- 0.13, 1.22 +/- 0.14, 1.29 +/- 0.17, 1.35 +/- 0.12, 1.37 +/- 0.12, 1.38 +/- 0.16, 1.40 +/- 0.10 mmol/l, respectively.