What are the treatment guidelines for hypernatremia?

Treatment Guidelines for Hypernatremia

Definition and Severity Classification

Hypernatremia is defined as serum sodium >145 mmol/L and requires prompt recognition and careful correction to prevent neurological complications. 1, 2

Severity classification:

• Mild: 145-150 mmol/L 2
• Moderate: 150-160 mmol/L 2
• Severe/Threatening: >160 mmol/L 2

Duration classification:

• Acute: <24-48 hours 1, 2
• Chronic: >48 hours 1, 2

Diagnostic Approach

Determine the volume status (hypovolemic, euvolemic, or hypervolemic) and measure urine osmolality and sodium to identify the underlying cause. 2, 3, 4

Key Diagnostic Steps:

1. Exclude pseudohypernatremia and confirm glucose-corrected sodium concentrations 4
2. Assess extracellular volume status through physical examination (skin turgor, mucous membranes, blood pressure, jugular venous pressure) 2, 3
3. Measure urine sodium concentration and urine osmolality 2, 4
4. Calculate urine volume and ongoing electrolyte-free water clearance 4
5. Consider arginine vasopressin/copeptin levels if diabetes insipidus is suspected 4

Classification by Pathogenesis:

• Hypervolemic hypernatremia: Excessive sodium intake (hypertonic saline, sodium bicarbonate) or primary hyperaldosteronism 2
• Euvolemic hypernatremia: Diabetes insipidus (central or nephrogenic) 2, 3
• Hypovolemic hypernatremia: Renal losses (osmotic diuresis, loop diuretics) or extrarenal losses (gastrointestinal, skin, respiratory) 2, 3

Treatment Principles

Correction Rate Guidelines

For chronic hypernatremia (>48 hours), the correction rate must not exceed 10-15 mmol/L per 24 hours or 0.4 mmol/L per hour to prevent cerebral edema and seizures. 5, 1, 2

• Acute hypernatremia (<24 hours): Rapid correction improves prognosis and prevents cellular dehydration 2
• Chronic hypernatremia: Slow correction at maximum 0.4 mmol/L/hour or 8-10 mmol/L/day 1, 2

Treatment Based on Volume Status

Hypovolemic Hypernatremia:

Replace volume deficits with isotonic saline initially, then switch to hypotonic fluids once hemodynamically stable. 3, 6

• First restore intravascular volume with 0.9% normal saline 3
• Once hemodynamically stable, switch to hypotonic solutions (0.45% saline or D5W) to correct free water deficit 3, 6

Euvolemic Hypernatremia (Diabetes Insipidus):

Administer hypotonic fluids and desmopressin (DDAVP/Minirin) for central diabetes insipidus. 1, 3

• Central diabetes insipidus: Desmopressin 1-4 mcg IV/SC or 10-20 mcg intranasally 1
• Nephrogenic diabetes insipidus: Address underlying cause (discontinue lithium, correct hypokalemia), provide free water replacement 2, 3

Hypervolemic Hypernatremia:

Use loop diuretics to promote sodium excretion combined with hypotonic fluid replacement. 3, 6

• Administer furosemide or other loop diuretics 3, 6
• Replace urinary losses with hypotonic fluids (D5W or 0.45% saline) 3, 6

Calculating Water Deficit

Water deficit (L) = 0.5 × body weight (kg) × [(current Na/140) - 1] 3, 4

• Replace calculated deficit plus ongoing losses (insensible losses ~500-1000 mL/day) 4
• Adjust for gender: use 0.5 for men, 0.45 for women 3

Fluid Selection

Choose hypotonic solutions (D5W or 0.45% saline) for free water replacement after initial volume resuscitation. 3, 6

• D5W (5% dextrose in water): Provides pure free water 3, 6
• 0.45% saline: Provides both free water and some sodium 3, 6
• Oral water: Preferred route if patient can tolerate 3, 4

Monitoring During Treatment

Monitor serum sodium every 2-4 hours initially, then every 4-6 hours once stable correction is achieved. 1, 6

• Check for signs of overcorrection: confusion, seizures, altered mental status 1
• Adjust infusion rate based on serial sodium measurements 6, 4
• Monitor urine output and ongoing losses 4

Special Considerations

Acute Severe Hypernatremia:

For life-threatening acute hypernatremia, hemodialysis provides rapid correction when conventional therapy is insufficient. 1

• Consider hemodialysis for acute hypernatremia (<24 hours) with severe symptoms 1
• Use caution when initiating renal replacement therapy in chronic hypernatremia to avoid rapid sodium drops 1

Critically Ill Patients:

Hypernatremia is an independent risk factor for mortality in ICU patients and requires meticulous attention to fluid balance. 6

• Many ICU patients cannot regulate water intake due to altered consciousness 6
• Physicians must carefully manage sodium and water balance 6
• Provide adequate free water through enteral or parenteral routes 6

Common Pitfalls to Avoid

• Overly rapid correction of chronic hypernatremia leading to cerebral edema, seizures, and neurological injury 5, 1
• Inadequate monitoring of sodium levels during active correction 1, 6
• Failing to replace ongoing losses (insensible, urinary, gastrointestinal) in addition to calculated deficit 4
• Using isotonic saline alone in hypernatremia without transitioning to hypotonic fluids 3
• Not addressing the underlying cause (discontinuing causative medications, treating diabetes insipidus) 2, 3