Effect of calcium/phosphorus ratio on mineral retention in parenterally fed premature infants
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J F Pelegano1, J C Rowe, D E Carey
1Department of Pediatrics, University of Connecticut Health Center, Farmington 06032.
Insights
The optimal ratio for delivering calcium and phosphorus in total parenteral nutrition (TPN) for very low birth weight infants is 1.7:1. This ratio maximizes mineral retention and mimics fetal accretion, without adverse effects.
Area of Science:
- Neonatology
- Nutritional Science
- Pediatric Gastroenterology
Background:
- Parenteral nutrition is crucial for very low birth weight (VLBW) infants.
- Optimizing mineral delivery, specifically calcium (Ca) and phosphorus (P), is essential for growth and development.
- The ideal Ca:P ratio in total parenteral nutrition (TPN) for VLBW infants remains under investigation.
Purpose of the Study:
- To determine the optimal Ca:P ratio in TPN solutions for maximizing mineral retention in VLBW infants.
- To compare the retention of Ca and P at different TPN ratios (2:1, 1.7:1, and 1.3:1).
- To assess the impact of varying Ca:P ratios on serum mineral levels and parathyroid hormone stimulation.
Main Methods:
- Forty-one VLBW infants were randomized to receive TPN with one of three Ca:P ratios.
- Mineral retention, serum Ca, P, alkaline phosphatase, and urinary cyclic AMP were measured after 48 hours.
- Data were analyzed to compare mineral retention and biochemical markers across different TPN ratios.
Main Results:
- Calcium retention was highest with the 2:1 and 1.7:1 ratios.
- Phosphorus retention was highest with the 1.3:1 and 1.7:1 ratios.
- The 1.7:1 ratio demonstrated the highest absolute retention of both Ca and P, closely mirroring fetal accretion rates. No abnormalities were observed in serum or urine studies, and no PTH stimulation occurred.
Conclusions:
- A 1.7:1 Ca:P ratio in TPN solutions is superior for optimizing the retention of both calcium and phosphorus in VLBW infants compared to higher or lower ratios.
- This ratio supports mineral accretion similar to in utero development.
- The 1.7:1 ratio is safe and effective for TPN in VLBW infants.
Abstract:
We hypothesized that retention of parenterally delivered calcium (Ca) and phosphorus (P) is affected by the ratio of the delivered minerals and that a 1.7:1 ratio would be optimal since this is the ratio of retention of these minerals by the fetus. Forty-one very low birth weight (VLBW) infants were randomly assigned to one of three total parenteral nutrition (TPN) solutions that were different only in their Ca:P ratios: 2:1 (76 mg/kg/day Ca and 38 mg/kg/day of P), and 1.3:1 (58 mg/kg/day Ca and 45 mg/kg/day P), and 1.3:1 (58 mg/kg/day of Ca and 45 mg/kg/day of P). Serum levels of calcium, phosphorus, and alkaline phosphatase, retentions of calcium and phosphorus and urinary cyclic AMP levels were measured after 48 h on the assigned Ca to P ratio. Calcium retentions were higher with the 2:1 and 1.7:1 ratios and phosphorus retentions were higher with the 1.3:1 and 1.7:1 ratios. The 1.7:1 ratio allowed for the highest absolute retention of both minerals and was the closest to published in utero accretion of calcium and phosphorus. The serum and urine studies demonstrated no abnormalities on any of the three ratios. Cyclic AMPs were not different among groups and were not elevated compared to previous reports suggesting that none resulted in parathyroid hormone (PTH) stimulation. We conclude that the 1.7:1 ratio is better than higher or lower ratios for delivery of calcium and phosphorus in TPN solutions at the quantities studied.