How should I manage a patient with hypernatremia?

Management of Hypernatremia

The most effective approach to managing hypernatremia is to identify the underlying cause and correct the water deficit with hypotonic fluids, while ensuring a controlled correction rate of no more than 10 mEq/L per 24 hours to avoid cerebral edema. 1

Assessment and Classification

Hypernatremia is defined as serum sodium concentration >145 mEq/L and can be classified based on severity:

• Mild: 146-150 mEq/L
• Moderate: 151-159 mEq/L
• Severe: ≥160 mEq/L

Initial Evaluation

1. Volume status assessment:

   • Hypovolemic: Signs of dehydration (dry mucous membranes, decreased skin turgor, orthostatic hypotension)
   • Euvolemic: Normal vital signs without edema
   • Hypervolemic: Edema, ascites, elevated JVP

2. Key laboratory tests:

   • Serum sodium, potassium, BUN, creatinine
   • Serum osmolality
   • Urine osmolality and sodium
   • Glucose level (to rule out hyperglycemia)

Management Algorithm

Step 1: Determine Acuity and Severity

• Acute hypernatremia (developed within 48 hours): More aggressive correction is warranted
• Chronic hypernatremia (>48 hours): Slower correction to avoid cerebral edema

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: Correct at 1-2 mEq/L/hour until Na⁺ <145 mEq/L
• Chronic hypernatremia: Correct at maximum rate of 8-10 mEq/L/24 hours 1

Step 4: Choose Appropriate Fluids

• Hypovolemic hypernatremia:

  • Initial resuscitation with isotonic fluids if hemodynamically unstable
  • Then switch to hypotonic fluids (0.45% saline or 5% dextrose in water)

• Euvolemic hypernatremia:

  • 5% dextrose in water or 0.45% saline
  • Address underlying cause (diabetes insipidus, inadequate water intake)

• Hypervolemic hypernatremia:

  • Loop diuretics plus 5% dextrose in water
  • Consider hemodialysis in severe cases with renal failure

Special Considerations

Monitoring

• Check serum sodium every 2-4 hours initially during active correction
• Monitor neurological status for signs of cerebral edema
• Track fluid balance (intake/output) and daily weights

Complications to Watch For

• Cerebral edema: Can occur with overly rapid correction of chronic hypernatremia
  • Signs: Headache, altered mental status, seizures, coma
  • Management: Slow or temporarily halt correction, consider hypertonic saline if severe symptoms develop

Specific Scenarios

Diabetes Insipidus

• Central DI: Consider desmopressin (DDAVP)
• Nephrogenic DI:
  • Treat underlying cause
  • Consider thiazide diuretics, amiloride, or indomethacin
  • Low-solute diet and adequate water intake

Hypernatremia in Critical Illness

• More aggressive monitoring
• Consider continuous renal replacement therapy in hemodynamically unstable patients

Prevention of Recurrence

• Ensure adequate free water intake
• Address underlying causes
• Educate patients/caregivers about importance of fluid intake
• Adjust medications that may contribute to hypernatremia

Pitfalls to Avoid

• Correcting chronic hypernatremia too rapidly
• Failing to account for ongoing fluid losses
• Not addressing the underlying cause
• Using inappropriate fluids (e.g., normal saline can worsen hypernatremia)
• Inadequate monitoring during correction

By following this structured approach to hypernatremia management, you can effectively correct sodium abnormalities while minimizing the risk of complications such as cerebral edema.