Treatment of Hypernatremia
The treatment of hypernatremia requires careful correction of the free water deficit using hypotonic fluids, with a maximum correction rate of 8-10 mmol/L per day for chronic hypernatremia (>48 hours) to prevent neurological complications. 1, 2
Diagnosis and Classification
Before initiating treatment, it's essential to:
- Confirm hypernatremia (serum sodium >145 mEq/L)
- Determine volume status (hypovolemic, euvolemic, or hypervolemic)
- Assess chronicity (acute <48 hours vs. chronic >48 hours)
- Identify underlying cause
Treatment Algorithm
Step 1: Assess Volume Status
- Hypovolemic hypernatremia (most common): Dehydration, excessive water loss
- Euvolemic hypernatremia: Diabetes insipidus, impaired thirst mechanism
- Hypervolemic hypernatremia: Rare, excessive sodium intake or administration
Step 2: Calculate Water Deficit
Water deficit (L) = 0.6 × body weight (kg) × [(current Na⁺/140) - 1]
Step 3: Determine Rate of Correction
- Acute hypernatremia (<24-48 hours): Can correct more rapidly
- Chronic hypernatremia (>48 hours): Maximum correction rate of 8-10 mmol/L/day 2
Step 4: Choose Appropriate Fluid
- Hypovolemic: Initial isotonic saline to restore hemodynamic stability, then hypotonic fluids (0.45% saline or 5% dextrose in water)
- Euvolemic: 5% dextrose in water or other hypotonic fluids
- Hypervolemic: Diuretics plus hypotonic fluids 1, 3
Special Considerations
Diabetes Insipidus
For patients with central diabetes insipidus, desmopressin (DDAVP) administration is indicated alongside fluid replacement 2
Continuous Renal Replacement Therapy
For patients requiring renal replacement therapy, dialysate/replacement fluid sodium concentration can be adjusted in a step-wise manner to achieve safe correction 4
Monitoring
- Check serum sodium levels every 2-4 hours initially
- Adjust fluid rate based on sodium measurements
- Monitor for signs of cerebral edema (headache, altered mental status, seizures)
Pitfalls and Caveats
- Too rapid correction can lead to cerebral edema, especially in chronic hypernatremia
- Inadequate correction may result in continued neurological symptoms
- Failure to identify and treat underlying cause will lead to recurrence
- Hemodialysis should be considered for acute severe hypernatremia but must be carefully monitored to prevent overly rapid correction 2
Specific Patient Populations
- Elderly patients: Often have impaired thirst mechanism and are at higher risk
- Critically ill: May require more frequent monitoring and adjustment
- Patients with heart or kidney failure: Require careful volume management
Remember that hypernatremia is less common than hyponatremia but carries significant morbidity and mortality if not properly managed 1.