What is the management of hypernatremia?

Management of Hypernatremia

The management of hypernatremia requires identifying the underlying cause, determining whether it is acute or chronic, and correcting the free water deficit at an appropriate rate to avoid neurological complications, with a recommended reduction rate of 10-15 mmol/L/24h. 1

Diagnosis and Assessment

Before initiating treatment, a thorough assessment should include:

• Determination of chronicity (acute: <48 hours vs. chronic: >48 hours)
• Evaluation of volume status (hypovolemic, euvolemic, or hypervolemic)
• Assessment of clinical symptoms and severity
• Laboratory evaluation including:
  • Serum electrolytes and osmolality
  • Urine electrolytes and osmolality
  • Acid-base status
  • Renal function tests

Treatment Algorithm

Step 1: Determine the Rate of Correction

• Chronic hypernatremia (>48 hours): Correct at a rate of 10-15 mmol/L/24h 1
• Acute hypernatremia (<24 hours): Can be corrected more rapidly, but hemodialysis may be considered for rapid normalization 2

Step 2: Calculate Free Water Deficit

Free water deficit can be calculated using the formula:

• Free water deficit = Total body water × [(Current Na⁺ / Desired Na⁺) - 1]
• Total body water is approximately 60% of body weight in men and 50% in women

Step 3: Select Appropriate Fluid Replacement

Based on volume status:

Hypovolemic Hypernatremia

• First, restore intravascular volume with isotonic fluids (0.9% saline)
• Then, administer hypotonic fluids (0.45% saline, 5% dextrose in water) to correct free water deficit

Euvolemic Hypernatremia

• Administer hypotonic fluids (0.45% saline, 5% dextrose in water)
• Consider desmopressin (DDAVP) for diabetes insipidus 2

Hypervolemic Hypernatremia

• Loop diuretics to remove excess sodium
• Hypotonic fluid replacement

Step 4: Monitor and Adjust Treatment

• Check serum sodium levels every 4-6 hours during active correction
• Adjust fluid administration rate based on sodium correction
• Monitor for neurological symptoms
• Reassess volume status regularly

Special Considerations

Diabetes Insipidus Management

• Central diabetes insipidus: Desmopressin (DDAVP)
• Nephrogenic diabetes insipidus: Treat underlying cause, thiazide diuretics, NSAIDs, amiloride

Ongoing Losses

• Account for ongoing water losses (insensible losses, gastrointestinal losses, renal losses)
• Replace these losses in addition to the calculated deficit

Pitfalls and Caveats

1. Overly rapid correction: Can lead to cerebral edema, seizures, and neurological injury 1
2. Inadequate monitoring: Failure to monitor serum sodium frequently during correction
3. Incorrect assessment of volume status: Leading to inappropriate fluid choice
4. Failure to identify and treat the underlying cause: Resulting in recurrent hypernatremia
5. Overlooking ongoing losses: Leading to inadequate replacement

Specific Situations

Critically Ill Patients

• More frequent monitoring of electrolytes
• Consider continuous renal replacement therapy for severe cases with hemodynamic instability

Pediatric Patients

• Higher total body water percentage (70-75%)
• More susceptible to rapid changes in serum sodium
• Require careful calculation of maintenance fluids and deficit correction

The management of hypernatremia requires a systematic approach with careful monitoring to avoid complications. The rate of correction should be tailored based on the chronicity of hypernatremia, with slower correction for chronic cases to prevent neurological complications.