Doubling calcium and phosphate concentrations in neonatal parenteral nutrition solutions using monobasic potassium
Joyce C Wong1, Albert R McDougal, Marianne Tofan
1Department of Pharmacy, Children's and Women's Health Centre of BC, 4480 Oak Street, Vancouver, British Columbia V6H 3V4, Canada.
Insights
Premature infants can receive higher calcium and phosphate levels in TPN solutions using the monobasic regimen, preventing precipitation. This allows for increased nutrient delivery, especially when fluid intake is limited.
Area of Science:
- Nutritional Science
- Neonatal Medicine
- Biochemistry
Background:
- Premature infants require elevated calcium (Ca) and phosphorus (P) to match fetal accretion rates.
- Current phosphate salts in TPN solutions limit adequate Ca and P delivery due to precipitation.
- Optimizing TPN formulations is crucial for neonatal growth and development.
Purpose of the Study:
- To compare calcium phosphate solubility in five amino acid products using monobasic potassium phosphate versus a combination of monobasic and dibasic potassium phosphate.
- To assess if buffering capacity explains observed solubility differences in TPN solutions.
- To inform clinical practice regarding higher mineral concentrations in neonatal TPN.
Main Methods:
- TPN solutions with varying Ca:P ratios (0-45 mmol/L) were prepared using five different amino acid products.
- Precipitation was assessed macroscopically and microscopically under various time and temperature conditions.
- Buffering capacity of each amino acid product was determined via titration with sodium hydroxide.
Main Results:
- Significant variations in calcium phosphate solubility and buffer capacity were observed across different amino acid solutions.
- The monobasic regimen allowed for higher calcium and phosphate concentrations (up to 45 mmol/L) without precipitation in Primene and Vamin compared to the dibasic regimen.
- Solubility differences were primarily attributed to the final solution pH, not buffering capacity.
Conclusions:
- The monobasic regimen permits doubling current calcium and phosphate concentrations in neonatal TPN solutions, enhancing nutrient delivery.
- This finding is particularly beneficial in fluid-restricted scenarios for premature infants.
- Further investigation is needed on the impact of the resulting acid load in extremely low birth weight infants.
Background:
Premature infants require high intakes of Ca and P to mimic fetal accretion rates. With the current phosphate salt used, adequate amounts cannot be provided due to the precipitation of Ca and P in TPN solutions.
Objective:
To compare monobasic potassium phosphate (monobasic regimen) and monobasic plus dibasic potassium phosphate (dibasic regimen) on calcium phosphate solubility in 5 amino acid products, and to determine whether solubility differences observed in these products can be explained by buffering capacity.
Methods:
TPN solutions were prepared according to standard clinical practice. The following amino acid products were used at 3% concentrations: Primene, Vamin N, TrophAmine, Aminosyn-PF, and Travasol. Dextrose 10%, standard electrolytes, heparin, vitamins and trace elements were added. Calcium (as gluconate) and phosphate (as monobasic or dibasic regimen) were added in one-to-one molar ratios from 0-45 mmol/L. Solutions were inspected macroscopically and microscopically for precipitation under three conditions: immediately, 24 h after preparation at room temperature, and 3 h later in a 37 degrees C water bath. Buffering capacity was determined for each amino acid product by titrating with standardized 0.1 M NaOH.
Results:
Variations in Ca:P solubility and buffer capacity exist between amino acid solutions. With Primene and Vamin no macroscopic or microscopic precipitation was detected up to 45 mmol/L using monobasic regimen, compared to 25 mmol/L using dibasic regimen with Trophamine. Buffer capacity did not account for the solubility differences observed between the five amino acid products, which were related to the pH of the final solution.
Conclusions:
These data will allow clinicians to double the current concentrations of calcium and phosphate in neonatal TPN solutions using monobasic regimen. Although this is particularly relevant to situations when fluid intake is restricted, the effect of the acid load needs to be investigated in extremely low birth weight infants.
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