Na+ > 145 mmol/L usually means water loss plus inability to drink. Restore volume first if shocked, then replace the free-water deficit plus ongoing losses, lowering Na+ by about 10 mmol/L/day in chronic cases.
At the bedside
Timed steps- 1
Volume
FirstShock or hypovolaemia: isotonic crystalloid boluses first.
- 2
Classify
CauseRenal water loss (osmotic diuresis from glucose/urea/mannitol, diabetes insipidus), GI/insensible losses, or sodium gain (hypertonic saline, bicarbonate). Urine osmolality < 300 with polyuria suggests DI.
- 3
Free water
ReplaceEnteral water via NG tube is best; IV 5% dextrose or 0.45% saline. Use the free-water deficit or Adrogué-Madias formula and add ongoing losses.
- 4
Chronic (> 48 h)
RateLower Na+ by ≤ 10-12 mmol/L per 24 h to avoid cerebral oedema; acute (hours, e.g. salt ingestion) can be corrected faster.
- 5
Central
DIDesmopressin 1-2 mcg IV/SC (or 10 mcg intranasal) and replace losses; common after neurosurgery, TBI, brain death.
Calculators for this topic
Hypernatraemia
Step 1 of ~4
Decision: Hypovolaemic shock?
Based on Adrogué HJ, Madias NE. Educational use; follow local protocol.
Evidence
- Adrogué & Madias 2000: classic review; formula for change in Na+ per litre of infusate.
Controversies
- Observational data in adults suggest faster correction (> 0.5 mmol/L/h) is not clearly harmful, but the 10-12 mmol/day limit remains standard practice.
🇮🇳 India notes
- Elderly patients with poor water access and fever in summer, heat illness, and post-neurosurgical DI are common scenarios.
References
Test yourself
Module quiz · score 70% to complete the module
Educational reference for trained clinicians. Check doses against your hospital protocol and the patient in front of you.