Treat symptoms, not the number: severe symptoms get 3% saline boluses immediately. Then classify by osmolality, volume status and urine studies. Limit correction to 10 mmol/L in 24 h (8 if high risk of osmotic demyelination) and re-lower if overshooting.
At the bedside
Timed steps- 1
Severe symptoms?
0 minVomiting, seizures, GCS < 9, cardiorespiratory distress: 150 mL 3% saline over 20 min, check Na+, repeat up to twice until Na+ rises 5 mmol/L.
- 2
Single bolus
Moderate symptomsConfusion, nausea, headache: one 150 mL 3% bolus (or 2 mL/kg), then treat cause; target +5 mmol/L/24 h.
- 3
Rule out pseudo/translocational
CheckMeasure serum osmolality and glucose (correct Na+ for hyperglycaemia); exclude hyperlipidaemia/paraprotein, mannitol.
- 4
Urine osmolality and Na+
ClassifyUosm < 100 → water excess (primary polydipsia, beer potomania, low solute). UNa < 30 → low effective arterial volume (GI loss, heart failure, cirrhosis). UNa > 30 → SIADH, diuretics, adrenal insufficiency, hypothyroidism, cerebral salt wasting.
- 5
By cause
TreatHypovolaemia: 0.9% saline or RL. SIADH: fluid restriction < 800-1000 mL/day; oral urea 15-30 g/day or salt tablets + furosemide if refractory. Heart failure/cirrhosis: fluid restriction, treat underlying.
- 6
Every 4-6 h
MonitorLimit rise to 10 mmol/L in first 24 h and 8 mmol/L in each subsequent 24 h; in high-risk patients aim for 4-8 and do not exceed 8. Watch for aquaresis (UO > 100 mL/h).
- 7
Re-lower
OvershootStop hypertonic fluid; 5% dextrose 10 mL/kg over 1 h ± desmopressin 1-2 mcg IV/SC to bring Na+ back below the limit.
Severe symptomatic hyponatraemia
3% sodium chloride
- Dose
- 150 mL over 20 min; repeat up to 2 more times guided by Na+ (or 2 mL/kg, max 150 mL)
- Target
- Rise of 5 mmol/L in the first 1-2 h; symptoms improve
- Worked example
- 60 kg woman, Na+ 112, seizing: 150 mL 3% over 20 min → Na+ 115; repeat 150 mL → 117; stop boluses
SALSA: rapid intermittent boluses had no more overcorrection than slow continuous infusion.
High risk of osmotic demyelination: correct more slowly
| Risk factor | Note |
|---|---|
| Na+ ≤ 105 mmol/L | Highest risk |
| Alcohol use disorder | Common in Indian men with beer potomania |
| Malnutrition | Also low solute intake |
| Hypokalaemia | K+ replacement itself raises Na+ |
| Advanced liver disease | Including liver transplant candidates |
US expert panel: in high-risk patients, aim for 4-8 mmol/L per day and do not exceed 8 mmol/L in any 24 h.
Calculators for this topic
Sodium corrected for glucose
Na + 2.4 × (glucose − 100)/100 (Hillier; Katz uses 1.6).
Expected Na change per litre of infusate (Adrogue-Madias)
ΔNa = (infusate Na + K − serum Na) ÷ (TBW + 1). Estimate only; recheck Na every 2-4 h.
Calculated serum osmolality (Indian units)
2 × Na + glucose (mg/dL)/18 + urea (mg/dL)/6. Uses blood urea, as reported by most Indian labs.
References
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Hyponatraemia
Step 1 of ~4
Decision: Severe or moderate symptoms?
Based on Spasovski G, Vanholder R, Allolio B, et al. Educational use; follow local protocol.
Pathophysiology
- Brain cells adapt within 48 h by losing osmolytes; rapid correction then dehydrates them, causing osmotic demyelination 2-6 days later.
Evidence
- European guideline 2014 and US expert panel 2013 agree on 3% bolus therapy for severe symptoms and on daily limits.
- SALSA 2021: rapid intermittent bolus vs slow continuous infusion: similar overcorrection rates.
Controversies
- Tolvaptan: effective in SIADH but costly, risk of overcorrection and liver injury; avoid in liver disease.
🇮🇳 India notes
- Common Indian causes: thiazides, diarrhoeal illness, beer potomania, SIADH from TB meningitis/pneumonia, hypothyroidism and hypopituitarism (Sheehan's syndrome in women).
References
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Educational reference for trained clinicians. Check doses against your hospital protocol and the patient in front of you.