How is hypernatremia (elevated sodium levels) managed?

Management of Hypernatremia

Hypernatremia treatment should focus on correcting water deficits, addressing ongoing water losses, and treating underlying causes while carefully monitoring the rate of sodium correction to prevent neurological complications.

Assessment and Classification

Proper management of hypernatremia begins with accurate diagnosis and classification:

• Definition: Hypernatremia is defined as serum sodium level >145 mEq/L

• Classification by volume status:

  • Hypovolemic hypernatremia: Water and sodium loss with greater water than sodium loss
  • Euvolemic hypernatremia: Pure water loss
  • Hypervolemic hypernatremia: Sodium gain exceeds water gain

• Diagnostic steps:

  1. Exclude pseudohypernatremia
  2. Confirm glucose-corrected sodium concentrations
  3. Determine extracellular volume status
  4. Measure urine sodium levels
  5. Measure urine volume and osmolality
  6. Check ongoing urinary electrolyte free water clearance
  7. Assess other electrolyte disorders 1

Treatment Approach

Step 1: Distinguish Between Acute and Chronic Hypernatremia

• Acute hypernatremia (developed <48 hours): Correct more rapidly
• Chronic hypernatremia (developed >48 hours): Correct more slowly to prevent cerebral edema 1, 2

Step 2: Calculate Water Deficit

Water deficit can be calculated using the formula:

• Water deficit = Total body water × [(measured serum Na⁺/140) - 1]
• Total body water = Weight (kg) × correction factor
  • 0.6 for children and non-elderly men
  • 0.5 for non-elderly women and elderly men
  • 0.45 for elderly women 1

Step 3: Determine Rate of Correction

• For acute hypernatremia: Decrease serum sodium by 1-2 mEq/L/hour
• For chronic hypernatremia: Decrease serum sodium by no more than 8-10 mEq/L/day 1, 3

Step 4: Select Appropriate Replacement Solution

• Hypotonic fluids are the mainstay of treatment:
  • 5% Dextrose in water (D5W): Free water without electrolytes
  • 0.45% Saline: Hypotonic solution with some sodium
  • 0.9% Saline: May be used initially for hypovolemic patients 4, 3

Step 5: Monitor and Adjust Treatment

• Check serum sodium every 2-4 hours initially
• Adjust fluid rate based on sodium correction rate
• Monitor for signs of cerebral edema during correction 3

Special Considerations

Diabetes Insipidus Management

For hypernatremia due to diabetes insipidus:

• Central diabetes insipidus: Consider desmopressin (DDAVP)
• Nephrogenic diabetes insipidus: Consider thiazide diuretics, NSAIDs, or amiloride 1

Critically Ill Patients

• Hypernatremia in ICU patients is associated with increased mortality
• Careful monitoring of sodium and water balance is essential
• Avoid iatrogenic causes (excessive sodium administration, inadequate free water) 3

Complications of Treatment

• Too rapid correction: Can lead to cerebral edema, seizures, permanent neurological damage
• Inadequate correction: Can result in continued neurological symptoms, dehydration, and increased mortality 2

Prevention Strategies

• Ensure adequate free water intake in high-risk patients
• Monitor sodium levels in patients receiving hypertonic solutions
• Adjust fluid therapy in patients with impaired thirst mechanisms or access to water 4

Remember that hypernatremia management requires careful attention to the rate of correction, with different approaches for acute versus chronic cases, while addressing the underlying cause.