Treatment of Hypernatremia
Hypernatremia should be treated with free water administration, with the rate of correction based on the acuity of onset and careful monitoring to prevent neurological complications. The approach varies depending on whether the hypernatremia is acute or chronic and the patient's volume status.
Initial Assessment
- Determine if hypernatremia is acute (<48 hours) or chronic (>48 hours)
- Assess volume status (hypovolemic, euvolemic, or hypervolemic)
- Calculate water deficit
- Identify and address underlying cause
Treatment Algorithm
Step 1: Determine Rate of Correction
- Acute hypernatremia (developed within 48 hours): Can be corrected more rapidly at 1 mmol/L/hour
- Chronic hypernatremia: Correct slowly at 0.5 mmol/L/hour, not exceeding 8-10 mmol/L in 24 hours to prevent cerebral edema 1, 2
Step 2: Choose Appropriate Fluid Based on Volume Status
For Hypovolemic Hypernatremia:
- First: Restore intravascular volume with isotonic fluids (0.9% NaCl)
- Then: Administer hypotonic fluids (5% dextrose in water or 0.45% NaCl) to correct free water deficit 1, 3
For Euvolemic Hypernatremia:
- Administer hypotonic fluids (5% dextrose in water) 1
- Consider treating underlying diabetes insipidus if present
For Hypervolemic Hypernatremia:
- Loop diuretics to promote sodium excretion
- Hypotonic fluids (5% dextrose in water) 1
Step 3: Calculate Water Deficit
Water deficit (L) = Current total body water × [(Current Na⁺/Desired Na⁺) - 1]
- Total body water ≈ 0.5-0.6 × body weight (kg) in adults
Special Considerations
For Critically Ill Patients
- More frequent monitoring of serum sodium (every 2-4 hours initially)
- Adjust fluid administration rates based on sodium concentration changes
- Be vigilant for ongoing water losses 4
For Patients with Nephrogenic Diabetes Insipidus
- Avoid salt-containing solutions, especially 0.9% NaCl
- Use 5% dextrose in water for rehydration
- 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 5
For Patients with Severe Symptoms
- Seizures, altered mental status, or coma require more aggressive correction initially
- Target initial correction of 5 mEq/L in the first few hours, then slow down 1
- Monitor neurological status closely during correction
Monitoring During Treatment
- Serial serum sodium measurements (frequency based on severity)
- Neurological assessments
- Fluid balance (intake and output)
- Weight measurements
- Urine osmolality and electrolytes when appropriate
Pitfalls to Avoid
- Too rapid correction in chronic hypernatremia can lead to cerebral edema and neurological damage 6
- Inadequate correction can lead to persistent neurological symptoms and increased mortality
- Failure to identify and treat the underlying cause will lead to recurrence
- Using isotonic saline alone in patients with diabetes insipidus can worsen hypernatremia 5
Prevention in High-Risk Patients
- Regular monitoring of serum sodium in patients receiving diuretics
- Ensure adequate free water intake in patients with impaired thirst or access to water
- Adjust fluid therapy in patients with ongoing losses (e.g., diarrhea, fever)
- Use appropriate maintenance fluids in hospitalized patients
By following this structured approach to hypernatremia management, clinicians can effectively correct sodium abnormalities while minimizing the risk of neurological complications.