Treatment of Hypernatremia
The treatment of hypernatremia requires addressing the underlying water deficit with hypotonic fluids, with a correction rate not exceeding 10-15 mmol/L per 24 hours to prevent cerebral edema. 1, 2
Assessment and Diagnosis
Before initiating treatment, proper assessment is essential:
- Confirm true hypernatremia (Na >145 mmol/L) and exclude pseudohypernatremia
- Determine extracellular volume status (hypovolemic, euvolemic, or hypervolemic)
- Assess for symptoms (altered mental status, seizures, neurological deficits)
- Evaluate urine osmolality and sodium to determine the cause
- Check for ongoing water losses (gastrointestinal, renal, insensible)
Treatment Algorithm
1. Acute vs. Chronic Hypernatremia
- Acute hypernatremia (<48 hours): Can be corrected more rapidly
- Chronic hypernatremia (>48 hours): Requires slower correction to prevent cerebral edema
2. Treatment Based on Volume Status
Hypovolemic Hypernatremia
- First step: Volume resuscitation with isotonic fluids (0.9% NaCl) to restore hemodynamic stability
- Second step: Switch to hypotonic fluids (5% dextrose or 0.45% NaCl) to correct free water deficit
- Calculate water deficit: 0.6 × body weight (kg) × [(measured Na/140) - 1]
Euvolemic Hypernatremia
- Primary treatment: Free water replacement with 5% dextrose solution
- For diabetes insipidus: Address underlying cause and consider desmopressin if central DI
Hypervolemic Hypernatremia
- Primary treatment: Diuretics to remove excess sodium
- Free water administration to correct hypernatremia
- Low salt diet (≤6 g/day) 1
3. Rate of Correction
- Maximum correction rate: 10-15 mmol/L per 24 hours 1
- For symptomatic patients: Initial rapid correction followed by slower rate
- Monitor serum sodium: Every 2-4 hours during active correction
4. Choice of Replacement Fluid
- Avoid salt-containing solutions like 0.9% NaCl for maintenance, especially in nephrogenic diabetes insipidus 1
- Preferred fluid: 5% dextrose in water (delivers no renal osmotic load)
- Calculate initial fluid rate based on physiological demand:
- Children: First 10 kg: 100 ml/kg/24h; 10-20 kg: 50 ml/kg/24h; remaining: 20 ml/kg/24h
- Adults: 25-30 ml/kg/24h 1
Special Considerations
- Critically ill patients require more frequent monitoring of serum electrolytes and adjustment of fluid therapy 3
- Diabetes insipidus: May require specific treatments (desmopressin for central DI, thiazides for nephrogenic DI)
- Iatrogenic hypernatremia: Common in VLBW infants due to incorrect replacement of transepidermal water loss 1
Monitoring During Treatment
- Serum sodium levels (every 2-4 hours initially)
- Fluid balance (intake and output)
- Neurological status for signs of cerebral edema
- Other electrolytes (potassium, chloride, bicarbonate)
- Renal function
Pitfalls to Avoid
- Overly rapid correction can lead to cerebral edema, seizures, and neurological injury
- Using isotonic saline for maintenance can worsen hypernatremia, especially in patients with diabetes insipidus
- Underestimating ongoing losses can lead to inadequate replacement
- Failure to identify and treat the underlying cause can lead to recurrence
By following this structured approach to hypernatremia management, clinicians can effectively correct sodium imbalances while minimizing the risk of complications from treatment.