Hypernatraemia
Serum sodium concentration >145mmol/L occurring due to a deficit of free water relative to sodium levels.
Epidemiology and Risk Factors
Pathophysiology
Aetiology
| Water Loss | Salt Gain |
|---|---|
Renal:
Extra-renal:
|
|
Diabetes insipidus is covered in detail under Diabetes Insipidus.
Clinical Features
Significant neurological features typically emerge when Na+ > 155mmol/L.
- Polydipsia
- Confusion
- Obtundation → Coma
- Seizures
- Hyperthermia
Assessment
History
Exam
Investigations
Bedside:
Laboratory:
Imaging:
Other:
Diagnostic Approach and DDx
Management
- Correct free water deficit
Avoid rapid correction to minimise cerebral osmotic shifts.
Resuscitation:
Specific therapy:
Free water deficit can be crudely estimated as: \(Free \ Water \ Deficit = 0.6 \times Weight \times (1 - {Na_{ideal} \over Na_{serum}})\)
Where:
- Free water deficit is in litres
- Weight is in kg
- Serum sodium is in mmol/L
- Pharmacological
- Procedural
- Physical
Supportive care:
Disposition:
Preventative:
Marginal and Ineffective Therapies
Anaesthetic Considerations
Complications
- D
- Subarachnoid haemorrhage
Due to cerebral osmotic effects, causing excessive ↓ cerebral volume causing vascular injury.
- Subarachnoid haemorrhage
Prognosis
Key Studies
References
- Adrogué HJ, Madias NE. Hypernatremia. N Engl J Med. 2000;342(20):1493-1499. doi:10.1056/NEJM200005183422006