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Hypertonic Electrolyte Solution — ICP/Hyponatraemia Management Pregnancy: Use with caution — maternal hypernatraemia affects fetal fluid balance; use only in life-threatening situations

Sodium Chloride 3% (Hypertonic Saline)

Brand names: NaCl 3%, HyperSal

Adult dose

Dose: Hyponatraemia (symptomatic): 150 mL of 3% over 20 min; repeat ×2 if persistent seizures. Raised ICP: 100–250 mL 3% bolus titrated to ICP/serum Na. Cerebral oedema: 250 mL boluses, target Na 145–155 mmol/L
Route: IV (central line preferred; can use large peripheral vein short-term)
Frequency: Bolus as needed or titrated infusion
Max: Rate of Na correction: max 10 mmol/L/24h (risk of osmotic demyelination syndrome); in acute symptomatic hyponatraemia: 1–2 mmol/L/hour until symptoms resolve
3% NaCl contains 513 mmol Na/L (vs. 154 mmol/L in 0.9%). Used for: symptomatic hyponatraemia (seizures, coma), raised intracranial pressure (TBI, liver failure), brain herniation. Avoid in hypernatraemia.

Paediatric dose

Dose: 2–4 mL/kg
Route: IV
Frequency: Bolus over 15–30 min
Max: 250 mL
Symptomatic hyponatraemia in children: 2–4 mL/kg of 3% NaCl over 15–30 min under specialist guidance. Raised ICP: 3–5 mL/kg bolus.

Dose adjustments

Renal

Monitor sodium carefully — renal failure impairs Na excretion; risk of rapid overcorrection.

Hepatic

Caution in liver disease — ascites and fluid overload risk.

Paediatric weight-based calculator

Symptomatic hyponatraemia in children: 2–4 mL/kg of 3% NaCl over 15–30 min under specialist guidance. Raised ICP: 3–5 mL/kg bolus.

Clinical pearls

  • Osmotic demyelination syndrome (ODS): develops 2–6 days after overcorrection of chronic hyponatraemia — quadriplegia, dysarthria, encephalopathy. Strict rate limit: maximum 10 mmol/L per 24 hours (8 mmol/L in high-risk patients: alcoholism, malnutrition, liver disease)
  • For raised ICP: hypertonic saline increasingly preferred over mannitol — less rebound, no diuresis-related hypovolaemia, longer duration of effect
  • In acute symptomatic hyponatraemia (<48h duration): rapid correction IS appropriate — neurological risk from oedema outweighs ODS risk; correct 1–2 mmol/L/hour until symptoms resolve, then slow to 10 mmol/L/24h

Contraindications

  • Hypernatraemia (Na >145 mmol/L)
  • Hyperchloraemia
  • Pulmonary oedema (relative — use with caution)

Side effects

  • Osmotic demyelination syndrome (ODS/central pontine myelinolysis) — if Na corrected too rapidly
  • Hypernatraemia
  • Hyperchloraemic acidosis
  • Fluid overload
  • Phlebitis (peripheral administration)

Interactions

  • Loop diuretics (combined use for ICP management — furosemide reduces cerebral oedema without raising Na)
  • Steroids (additive sodium retention in some contexts)

Monitoring

  • Serum sodium every 2–4 hours during active treatment
  • Serum osmolality
  • Neurological status
  • ICP monitoring (if invasive ICP bolt in situ)
  • Fluid balance and urine output

Reference: BNFc; BNF 90; EASL Guidelines on Hyponatraemia; NICE NG158 (Head Injury); Neurocritical Care Society Guidelines 2023; BNFc. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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