How is hypernatremia treated?

Management of Hypernatremia

The treatment of hypernatremia should focus on correcting the underlying cause and carefully restoring normal serum sodium levels with hypotonic fluids, with the correction rate not exceeding 0.4 mmol/L/hour or 8-10 mmol/L/day to prevent neurological complications.

Classification and Assessment

Hypernatremia is defined as serum sodium concentration >145 mmol/L. Before initiating treatment, it's essential to classify the type of hypernatremia based on volume status:

1. Hypovolemic hypernatremia: Water and sodium losses with greater water than sodium loss

   • Causes: Excessive sweating, diarrhea, osmotic diuresis, diuretic use
   • Signs: Decreased skin turgor, dry mucous membranes, orthostatic hypotension

2. Euvolemic hypernatremia: Pure water loss with normal total body sodium

   • Causes: Diabetes insipidus (central or nephrogenic), inadequate water intake
   • Signs: Normal hemodynamics without edema or signs of dehydration

3. Hypervolemic hypernatremia: Sodium gain exceeding water gain

   • Causes: Iatrogenic (hypertonic saline or sodium bicarbonate administration)
   • Signs: Edema, hypertension

Diagnostic Workup

• Serum sodium, osmolality, and creatinine
• Urine sodium and osmolality
• Assessment of volume status (vital signs, skin turgor, mucous membranes)
• Evaluation for underlying causes (medication review, history of fluid losses)

Treatment Approach

General Principles

1. Correction rate:

   • For chronic hypernatremia (>48 hours): Maximum correction of 8-10 mmol/L/day or 0.4 mmol/L/hour 1
   • For acute hypernatremia (<48 hours): Faster correction may be appropriate but still monitored carefully

2. Fluid choice:

   • Hypotonic fluids (5% dextrose in water, 0.45% saline)
   • Avoid isotonic (0.9% NaCl) fluids as they can worsen hypernatremia 2

Treatment Based on Volume Status

1. Hypovolemic Hypernatremia

• First step: Restore intravascular volume with hypotonic fluids
• Calculation:
  • Water deficit = Total body water × [(current Na⁺/desired Na⁺) - 1]
  • Total body water ≈ 0.6 × weight in kg (for men), 0.5 × weight in kg (for women)
• Administration: Divide the calculated deficit over 48-72 hours

2. Euvolemic Hypernatremia

• Treatment: Replace free water deficit using the formula above
• Route: Oral water or 5% dextrose in water intravenously
• For diabetes insipidus:
  • Central: Desmopressin (DDAVP)
  • Nephrogenic: Treat underlying cause, consider thiazide diuretics

3. Hypervolemic Hypernatremia

• Treatment: Loop diuretics to promote sodium excretion plus free water replacement
• Severe cases: Consider hemodialysis if renal function is impaired

Special Considerations

Traumatic Brain Injury

• Controlled hypernatremia is not recommended for managing intracranial pressure in severe TBI 2
• Hypernatremia in TBI patients can worsen outcomes by increasing cerebral contusions if blood-brain barrier is disrupted

Critically Ill Patients

• Hypernatremia is an independent risk factor for increased mortality in ICU patients 3
• Careful monitoring of sodium and fluid balance is essential
• Regular monitoring of serum electrolytes (every 4-6 hours initially)

Monitoring During Treatment

• Check serum sodium every 4-6 hours during active correction
• Monitor urine output and daily weights
• Assess for neurological symptoms that might indicate cerebral edema from overly rapid correction
• Adjust fluid rate based on sodium measurements

Pitfalls to Avoid

1. Overly rapid correction: Can cause cerebral edema and neurological complications
2. Using isotonic saline: May worsen hypernatremia in patients with impaired free water excretion
3. Failure to identify and treat the underlying cause: Will lead to recurrence
4. Inadequate monitoring: Can result in under or overcorrection

By following this structured approach to hypernatremia management, clinicians can effectively restore normal sodium levels while minimizing the risk of complications associated with treatment.