1 What is the Neonatal TPN Calculator?
The Neonatal TPN Calculator builds a total parenteral nutrition prescription for an infant unable to tolerate full enteral feeds, supporting two order types: a single-bag Stock Solution (dextrose, electrolytes, and amino acids together) or Multi-Line TPN (Line 1: electrolytes + amino acids; Line 2: lipid + multivitamin + heparin; Line 3: calcium + dextrose). It calculates each component's volume from per-kg/day doses, mixes dextrose stock strengths to hit a target glucose infusion rate (GIR), and checks the resulting prescription's nutritional adequacy.
3 Formula & method
Component doses follow ESPGHAN proposed ranges shown in the app: Sodium 2–5 mEq/kg/day (as 3% NaCl, 0.5 mEq/mL); Potassium 1–3 mEq/kg/day (as KH₂PO₄ 4 mEq/mL or KCl 2 mEq/mL); Aminoven 10% 1.5–3.5 g/kg/day (0.1 g/mL); Lipid SMOF 20% 1–3 g/kg/day, max 4 (0.2 g/mL); GIR starting at 4–8, advancing to 8–10, max around 12 mg/kg/min. Dextrose requirement is calculated as GIR × weight(kg) × 1.44 g/day, and the app auto-picks a bracketing pair of dextrose stock strengths (0/5/10/25/50%) to mix to the required concentration. A safety banner flags the result: up to 12.5% dextrose is 'safe for peripheral infusion,' 12.5–20% is 'caution — prefer central line if prolonged,' and above 20% is 'central line strongly recommended.' The app hard-blocks combining KH₂PO₄ with calcium in a single stock bag (calcium-phosphate precipitation risk), requiring KCl instead or a switch to multi-line TPN. For multi-line orders it also computes the NPC:N ratio and calories per gram of amino acid, interpreted per ESPGHAN 2022: NPC:N below 70:1 signals high protein intake (seen in severe catabolism); 70–100:1 is described as 'IDEAL for preterm infants... optimal for protein anabolism and growth'; 100–150:1 is acceptable; above 150:1 signals low protein intake and catabolism risk. Calories per gram amino acid: under 30 kcal/g is insufficient; 30–40 kcal/g is the recommended range; above 40 kcal/g is adequate.
4 Frequently asked questions
What's the difference between Stock Solution and Multi-Line TPN in this calculator?
Stock Solution is a single bag combining dextrose, electrolytes, and amino acids. Multi-Line TPN splits components across three lines: Line 1 electrolytes + amino acids, Line 2 lipid + multivitamin + heparin, Line 3 calcium + dextrose.
Why does the calculator block KH₂PO₄ with calcium?
In a single stock bag they precipitate as calcium phosphate. The app requires switching the potassium source to KCl, setting calcium to zero, or moving to Multi-Line TPN, which keeps phosphate and calcium in separate lines.
How is the dextrose concentration determined?
From the target GIR: dextrose (g/day) = GIR × weight (kg) × 1.44. The app then auto-selects two dextrose stock strengths to mix to that concentration.
What GIR range does the app suggest starting with?
The ESPGHAN proposed range shown in the app is to start at 4–8 mg/kg/min, advancing up to 8–10 (max around 12) mg/kg/min.
What does an NPC:N ratio of 70–100:1 mean?
The app labels this range 'IDEAL for preterm infants,' citing ESPGHAN 2022, as optimal for protein anabolism and growth.