Sodium d-fructose-1,6-diphosphate vs. sodium monohydrogen phosphate in total parenteral nutrition: A comparative in vitro assessment of calcium/phosphate compatibility

Background: The supply of high amounts of calcium (Ca) and phosphorus (P) d uring total parenteral nutrition (TPN) is matter of concern because of the risk associated with calcium phosphate precipitation. The in vitro Ca-P com patibility in ready-for-use TPN solutions after the addition of different c oncentrations of inorganic phosphate or d-fructose-1,6-diphosphate (FDP) an d calcium chloride was evaluated. Methods: Four series of experiments for e ach Ca + P couple were carried out by varying amino acid concentrations (2% or 4%), temperature (25 degrees C or 37 degrees C), and pH. The extent of precipitation was estimated by visual inspection and particle count. The ar eas of maximal compatibility (ie, areas showing the complete absence of pre cipitates) were drawn from the precipitation curves. Results: The precipita tion extent was considerably higher in conditions mimicking body environmen t for both Ca + P couples. The compatibility area at 37 degrees C and 2% am ino acid for CaCl2 + Na2HPO4 admixtures was included within 2.50 mmol/L CaC l2 and 2.22 mmol/L Na2HPO4, whereas that for CaCl2 + FDP was within 33.3 mm ol/L CaCl2 and 10.0 mmol/L FDP (20 mEq/L of P). Unlike inorganic calcium ph osphate, FDP dicalcium salt precipitation was kinetically delayed and was o nly minimally enhanced by decreasing amino acid concentration. Conclusions: Our data indicated that the use of FDP as the P source in parenteral nutri tion solutions was effective in avoiding the life-threatening calcium phosp hate precipitation. Thus, the addition of FDP to TPN admixtures represents a safe choice, allowing the simultaneous administration of high amounts of Ca and P in restricted fluid volumes, even at low amino acid concentrations .