Physical compatibility of neonatal total parenteral nutrition admixtures containing organic calcium and inorganic phosphate salts in a simulated infusion at 37 degrees C.

OBJECTIVE: Within an incubator environment at 37 degrees C, we evaluated the physical compatibility of calcium (Ca) and phosphate (P) in simulated neonatal total parenteral nutrition (TPN) infusions.
DESIGN: Representative neonatal TPN formulas containing four concentrations of amino acids [AA] (1-4 g/dL) and two levels of dextrose [D] (5 and 10 g/dL) were monitored for calcium-phosphate precipitate formation over 24 hours using a laser-based particle counting technique.
SETTING: Research Laboratory.
SUBJECTS: None.
MEASUREMENTS AND MAIN RESULTS: Of the eight AA-D combinations studied, two formulas containing 1 g/dL AA with either 5 g/dL or 10 g/dL of D and high amounts of Ca and P resulted in significant increases in particle counts and visibly evident precipitation during the 24-hour infusion. Precipitation was noted only after the infusion passed through the incubator, but not in the TPN bags, demonstrating the heightened risk of calcium-phosphate incompatibility with increased temperatures.
CONCLUSIONS: Low AA concentrations and high temperatures are significant risk factors for the precipitation of the insoluble dibasic calcium phosphate that may be fatal upon intravenous infusion. When thermoregulation is required, the AA concentration of the TPN formula should not be less than 1.5 g/dL (and ideally > or =3 g/dL) when high intakes of calcium (60 mg/dL) and phosphate (46.5 mg/dL) are prescribed.