What is the treatment for hypernatremia?

Treatment of Hypernatremia

The treatment of hypernatremia should focus on restoring plasma tonicity by addressing the underlying cause and correcting the water deficit, with correction rates not exceeding 0.4 mmol/L/hour for chronic hypernatremia to prevent neurological complications. 1

Classification of Hypernatremia

Hypernatremia occurs when plasma sodium concentration exceeds 145 mmol/L and can be classified based on:

1. Duration:

   • Acute (developed within 48 hours)
   • Chronic (developed over days)

2. Severity:

   • Mild
   • Moderate
   • Threatening

3. Volume status:

   • Hypervolemic: Excess sodium relative to water
   • Hypovolemic: Loss of water exceeds sodium loss
   • Euvolemic: Pure water deficit

Diagnostic Approach

Before initiating treatment, proper diagnosis is essential:

• Exclude pseudohypernatremia
• Confirm glucose-corrected sodium concentrations
• Determine extracellular volume status
• Measure urine sodium levels and osmolality
• Assess urine volume and free water clearance
• Check for other electrolyte disorders 2

Treatment Algorithm

Step 1: Identify and Address the Underlying Cause

• Hypervolemic hypernatremia:

  • Acute: Often due to hypertonic NaCl or NaHCO₃ solutions
  • Chronic: May be due to primary hyperaldosteronism 1

• Euvolemic hypernatremia:

  • Often due to diabetes insipidus (central or nephrogenic)
  • Central: May be triggered by traumatic, vascular, or infectious events
  • Nephrogenic: May be due to medications (e.g., lithium) or hypokalemia 1

• Hypovolemic hypernatremia:

  • Due to renal or extrarenal water losses 1

Step 2: Determine Acuity and Set Correction Rate

• Acute hypernatremia (< 48 hours):

  • Rapid correction improves prognosis by preventing cellular dehydration 1

• Chronic hypernatremia (> 48 hours):

  • Slow correction rate (no more than 0.4 mmol/L/hour) is recommended 1
  • Avoid correcting by more than 10 mmol/L/day to prevent neurological complications

Step 3: Calculate Water Deficit and Replacement

Calculate the water deficit using the formula:

• Water deficit = Total body water × [(measured Na⁺/desired Na⁺) - 1]
• Total body water ≈ 0.6 × body weight (kg) for men, 0.5 × body weight for women

Step 4: Select Appropriate Replacement Fluid

• Hypervolemic hypernatremia:

  • Loop diuretics to promote sodium excretion
  • Hypotonic fluids (0.45% saline or 5% dextrose) 2

• Euvolemic hypernatremia:

  • Hypotonic fluids (0.45% saline or 5% dextrose)
  • For diabetes insipidus: DDAVP (central DI) or treat underlying cause (nephrogenic DI) 2

• Hypovolemic hypernatremia:

  • Initial volume resuscitation with isotonic fluids if hemodynamically unstable
  • Then switch to hypotonic fluids for sodium correction 3, 2

Step 5: Monitor and Adjust Treatment

• Check serum sodium levels every 2-4 hours initially
• Adjust fluid rate based on correction rate
• Monitor for signs of cerebral edema if correction is too rapid
• Consider additional therapy for specific causes like diabetes insipidus 2

Special Considerations

• Diabetes insipidus:

  • Central DI: DDAVP (desmopressin)
  • Nephrogenic DI: Treat underlying cause, thiazide diuretics, amiloride, or NSAIDs 2

• Elderly patients:

  • More susceptible to hypernatremia due to impaired thirst mechanism
  • May require closer monitoring during correction 3

• Critical illness:

  • May have multiple contributing factors
  • Requires more frequent monitoring and adjustment of therapy

Pitfalls to Avoid

• Overly rapid correction in chronic hypernatremia can lead to cerebral edema
• Inadequate assessment of volume status can lead to inappropriate fluid selection
• Failure to address ongoing losses during treatment
• Neglecting to treat the underlying cause while focusing only on sodium correction

By following this structured approach, hypernatremia can be effectively managed while minimizing the risk of neurological complications.