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Neonatal reference values for ionized calcium, phosphate and magnesium. Selection of reference population by
Insights
This study established reference values for ionized calcium in healthy newborns. Ionized calcium levels were found to be lowest on day 1 and increased significantly by day 5 post partum.
Area of Science:
- Neonatal physiology
- Pediatric biochemistry
Background:
- Accurate reference ranges for ionized calcium are crucial for neonatal care.
- Previous studies may not have exclusively focused on healthy, breastfed infants meeting strict optimality criteria.
Purpose of the Study:
- To establish reliable reference values for ionized calcium in full-term, healthy, breastfed newborns.
- To document the typical changes in ionized calcium concentrations during the first five days of life.
- To highlight the limitations in calculating ionized calcium from total calcium.
Main Methods:
- Investigated 31 full-term newborns meeting stringent optimality criteria.
- Collected capillary blood samples via heel puncture on postnatal days 1, 3, and 5.
- Measured ionized calcium using a semi-automatic electrode system (ICA 1).
Main Results:
- Established reference ranges for ionized calcium: Day 1 (1.05-1.37 mmol/l), Day 3 (1.10-1.42 mmol/l), Day 5 (1.20-1.48 mmol/l).
- Mean ionized calcium concentration was significantly lower on day 1 compared to days 3 and 5.
- Provided reference values for total calcium, magnesium, and phosphate.
Conclusions:
- Ionized calcium levels in healthy newborns increase progressively after birth.
- Direct measurement of ionized calcium is necessary; it cannot be reliably calculated from total calcium.
- These reference values are essential for the clinical assessment of calcium homeostasis in neonates.
Abstract:
Thirty-one full-term newborn babies were investigated in order to establish reference values for ionized calcium. Only children fulfilling certain optimality criteria (with best possible maternal and infant conditions and uncomplicated pregnancy and delivery) were included. All infants were breast fed. Capillary blood for analysis of ionized calcium was collected by heel puncture on day 1 (6-36 h post partum, p.p.), day 3 (60-84 h p.p.) and day 5 (108-132 h p.p.). Ionized calcium was measured with a semi-automatic electrode system ICA 1 (Radiometer A/S, Copenhagen, Denmark). The reference ranges (mean +/- 2 SD) for days 1, 3 and 5 were 1.05-1.37, 1.10-1.42 and 1.20-1.48 mmol/l, respectively. The mean ionized calcium concentration on day 1 was significantly lower than on days 3 and 5. Reference values are also given for total calcium, magnesium and phosphate. We emphasize that it is impossible to calculate ionized calcium from total calcium or vice versa.
