Sodium Phosphate Pediatric Dose — Electrolyte Replacement
Sodium phosphate is an inorganic phosphate salt used intravenously to correct hypophosphatemia in pediatric patients. It replenishes serum phosphate, which is essential for cellular energy metabolism, bone mineralization, and respiratory muscle function. It is commonly indicated in critically ill children, those receiving parenteral nutrition, or patients with refeeding syndrome.
Pediatric Dosing
The recommended IV dose for phosphate replacement in pediatric patients is 0.2–0.4 mmol/kg per dose, infused over 4–8 hours. The maximum single dose is 15 mmol, regardless of weight.
- Mild-to-moderate hypophosphatemia: 0.2 mmol/kg IV over 4–8 hours
- Moderate-to-severe hypophosphatemia: 0.4 mmol/kg IV over 4–8 hours
- Maximum dose: 15 mmol per dose
Worked example: For a 20 kg child with moderate hypophosphatemia: 20 × 0.4 mmol/kg = 8 mmol administered IV over 4–8 hours. For a 50 kg adolescent: 50 × 0.4 = 20 mmol, capped at the maximum of 15 mmol. Consult institutional protocol for repeat dosing intervals and reassessment thresholds.
Indications and Clinical Context
Intravenous sodium phosphate is indicated for the treatment of hypophosphatemia in pediatric patients who cannot tolerate or absorb oral supplementation. Clinical scenarios include critically ill patients in the PICU, children receiving prolonged parenteral nutrition, post-operative patients with poor oral intake, and those at risk for refeeding syndrome. Hypophosphatemia can impair cardiac contractility, diaphragmatic function, red blood cell oxygen delivery, and neurological status, making timely correction important in symptomatic or severe cases.
The IV route is preferred when serum phosphate is critically low (<1.0 mg/dL), when the patient is symptomatic, or when enteral access is unavailable. Dose selection within the 0.2–0.4 mmol/kg range is typically guided by the severity of hypophosphatemia and the patient’s clinical status.
Administration and Monitoring
Sodium phosphate must be administered by slow IV infusion over 4–8 hours; rapid infusion can precipitate hypocalcemia, hypotension, and cardiac arrhythmias. It should be diluted in a compatible IV fluid (typically 0.9% sodium chloride or dextrose-containing solution) prior to administration. Do not administer as an IV bolus. Sodium phosphate is incompatible with calcium-containing solutions and may precipitate if mixed inappropriately.
- Monitor serum phosphate, calcium, potassium, and magnesium before and after infusion
- Assess renal function prior to dosing; use with caution in patients with renal impairment due to risk of hyperphosphatemia
- Watch for signs of hypocalcemia (tetany, paresthesias, prolonged QT) during and after infusion
- Repeat dosing should be guided by repeat serum levels; consult institutional protocol for frequency of reassessment
Disclaimer: This article is an educational reference summarizing standard pediatric dosing values. It is not a substitute for clinical judgment. Always verify doses against institutional protocols, the current edition of authoritative references (e.g., Lexicomp, Harriet Lane Handbook, PALS guidelines), the patient’s accurate weight, and any patient-specific factors (renal/hepatic function, allergies, comedications) before administration.