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Fluids & Electrolytes

Sodium Deficit (Hyponatraemia)

Estimates the sodium deficit needed to raise serum sodium to a target in a hyponatraemic child.

Written for clinicians. If you're a parent or patient, don't act on these numbers — talk to your child's doctor.

Scope: Uses TBW = 0.6 × weight. A guide to total deficit only — it does not set the infusion rate, which must respect the daily correction limit.

Inputs

FieldUnitNotes
Weight kg 0.5–150
Measured sodium mEq/L 100–135
Target sodium mEq/L Commonly 135 (or 125 as an initial safe target)
Total body water fraction Young infants run a higher TBW

FAQ

What is the Sodium Deficit (Hyponatraemia)?

Estimates the sodium deficit needed to raise serum sodium to a target in a hyponatraemic child.

What inputs does the Sodium Deficit (Hyponatraemia) need?

Weight (kg), Measured sodium (mEq/L), Target sodium (mEq/L), Total body water fraction.

Are there any limitations?

Uses TBW = 0.6 × weight. A guide to total deficit only — it does not set the infusion rate, which must respect the daily correction limit.

Related guides

Sodium Deficit in Pediatric Hyponatremia: The 8 mEq/L per 24h Ceiling and 3% Saline for Seizures

Estimating the sodium deficit to reach a target Na in a hyponatremic child — the TBW formula, why correction must stay ≤8 mEq/L/24h to avoid osmotic demyelination, and 3% saline 2 mL/kg for acute seizures.

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