Treatment of Euvolemic Hypernatremia
The primary treatment for euvolemic hypernatremia is administration of hypotonic fluids, preferably oral water if the patient can tolerate it, or intravenous 5% dextrose in water (D5W) if they cannot. 1
Understanding Euvolemic Hypernatremia
Euvolemic hypernatremia is characterized by elevated serum sodium concentration (>145 mEq/L) without changes in total body sodium content. It typically results from pure water loss without sodium loss, leading to:
- Normal extracellular fluid volume
- Increased serum sodium concentration
- Absence of clinical signs of volume depletion or excess
Common causes include:
- Impaired thirst mechanism
- Lack of access to water
- Diabetes insipidus (central or nephrogenic)
- Insensible losses (fever, burns, hyperpnea)
Treatment Approach
Step 1: Calculate Water Deficit
Calculate the free water deficit using the formula:
- Water deficit = Total body water × [(Current Na⁺/140) - 1]
- Total body water is approximately 60% of body weight in men and 50% in women
Step 2: Administer Hypotonic Fluids
- First-line therapy: Oral water if the patient can tolerate it
- Alternative: Intravenous 5% dextrose in water (D5W)
- For severe cases: Consider 0.45% saline if some sodium replacement is also needed
Step 3: Control Rate of Correction
- Target correction rate: 4-6 mEq/L in 24 hours, not exceeding 8 mEq/L/day 2
- Monitor serum sodium levels every 4-6 hours during active correction
- Adjust fluid administration rate based on sodium concentration changes
Step 4: Address Underlying Cause
- For central diabetes insipidus: Desmopressin (DDAVP)
- For nephrogenic diabetes insipidus: Thiazide diuretics, NSAIDs, or amiloride
- For impaired thirst mechanism: Scheduled fluid intake
Special Considerations
- Avoid overly rapid correction which can cause cerebral edema
- In patients with impaired consciousness, careful monitoring of fluid balance is essential
- For patients with diabetes insipidus, specific treatment of the underlying disorder is necessary alongside free water replacement
Monitoring During Treatment
- Serum sodium levels every 4-6 hours initially
- Fluid intake and output
- Neurological status for signs of cerebral edema (headache, nausea, vomiting, altered mental status)
- Weight changes
- Urine output and osmolality
Pitfalls to Avoid
- Administering isotonic fluids (0.9% saline) which will not correct hypernatremia
- Correcting sodium too rapidly, which can lead to cerebral edema
- Failing to identify and treat the underlying cause
- Inadequate monitoring of serum sodium during correction
- Overlooking concurrent electrolyte abnormalities
For patients with severe symptoms (altered mental status, seizures), more aggressive initial correction may be warranted, but still with careful monitoring to avoid complications from overly rapid correction.