What is the management for hypernatremia?

Management of Hypernatremia

The primary goal of hypernatremia management is to restore plasma tonicity with correction rates not exceeding 0.4 mmol/L/hour to prevent neurological complications, while addressing the underlying cause based on volume status classification. 1

Classification and Diagnosis

Before initiating treatment, classify hypernatremia based on:

1. Duration:

   • Acute (developed over hours to <48 hours)
   • Chronic (developed over days)

2. Severity:

   • Mild
   • Moderate
   • Severe/threatening

3. Volume status:

   • Hypovolemic: Due to renal or extrarenal water losses
   • Euvolemic: Often from diabetes insipidus (central or nephrogenic)
   • Hypervolemic: From excessive sodium intake or primary hyperaldosteronism

Treatment Algorithm

Step 1: Determine Volume Status

• Hypovolemic hypernatremia:

  • Initial treatment: 0.9% NaCl to restore volume 2
  • Then switch to hypotonic solutions (0.45% NaCl or D5W) 2
  • Address underlying cause of fluid loss

• Euvolemic hypernatremia:

  • Administer 5% dextrose in water (D5W) or 0.45% NaCl 2
  • For diabetes insipidus:
    • Central: Consider desmopressin
    • Nephrogenic: Address underlying cause (discontinue lithium, correct hypokalemia)

• Hypervolemic hypernatremia:

  • Loop diuretics plus free water replacement 2
  • Treat underlying conditions (e.g., primary hyperaldosteronism)

Step 2: Calculate Water Deficit

Water deficit (L) = Total body water × [(Current Na⁺/140) - 1]

• Total body water = Weight (kg) × 0.6 (for men) or 0.5 (for women)

Step 3: Determine Correction Rate

• Acute hypernatremia: Faster correction is safer
• Chronic hypernatremia: Slow correction at rate not exceeding 0.4 mmol/L/hour (10 mmol/L/day) 1
  • Too rapid correction can cause cerebral edema and neurological damage

Step 4: Select Replacement Solution

• For moderate hypernatremia: Fluid restriction to 1,000 mL/day 2
• For severe cases: Hypotonic solutions (D5W or 0.45% NaCl)

Step 5: Monitor Response

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

Special Considerations

• Diabetes insipidus: Identify and treat the underlying cause

  • Central DI: Desmopressin
  • Nephrogenic DI: Discontinue causative medications, correct electrolyte abnormalities

• Elderly patients: More susceptible to hypernatremia due to impaired thirst mechanism

  • Ensure adequate access to water
  • More careful monitoring during correction

Common Pitfalls and Caveats

1. Avoid overly rapid correction in chronic hypernatremia, which can lead to cerebral edema
2. Don't neglect ongoing losses when calculating replacement needs
3. Regularly reassess volume status as it may change during treatment
4. Consider insensible losses in febrile or hyperventilating patients
5. Monitor for other electrolyte abnormalities that often accompany hypernatremia

The management approach should be adjusted based on the clinical response and serial sodium measurements, with particular attention to neurological status throughout the correction process.