How to correct hypernatremia?

Management of Hypernatremia

Immediate Treatment Approach

For hypernatremia, administer hypotonic fluids to replace the free water deficit, with a target correction rate of 10-15 mmol/L per 24 hours for chronic cases, while avoiding isotonic saline as initial therapy. 1

The cornerstone of hypernatremia management is restoring plasma tonicity through careful free water replacement, with the rate of correction critically dependent on whether the condition developed acutely or chronically 2, 3.

Assessment and Classification

Before initiating treatment, determine three key factors:

• Acuity: Acute hypernatremia (<48 hours) can be corrected more rapidly, up to 1 mmol/L/hour if severely symptomatic, whereas chronic hypernatremia requires slower correction at no more than 0.4 mmol/L/hour 2, 1
• Volume status: Classify as hypovolemic, euvolemic, or hypervolemic through clinical examination, vital signs, and assessment of body weight 3, 2
• Severity: Measure serum sodium, electrolytes, acid-base status, hematocrit, and blood urea nitrogen to assess hydration status and guide fluid replacement 1

Fluid Replacement Strategy

For Hypovolemic Hypernatremia

Administer hypotonic fluids (0.45% NaCl, 0.18% NaCl, or D5W) to replace free water deficit. 1

• Never use isotonic saline as initial therapy, especially in patients with nephrogenic diabetes insipidus, as this will worsen hypernatremia 1
• In patients with severe burns or voluminous diarrhea, hypotonic fluids are required to match ongoing free water losses 1
• For severe hypernatremia with altered mental status, combine IV hypotonic fluids with free water via nasogastric tube 1

For Euvolemic Hypernatremia (Diabetes Insipidus)

• Provide hypotonic fluid replacement to match excessive free water losses 1
• Consider low salt diet (<6 g/day) and protein restriction (<1 g/kg/day) 1
• Ongoing hypotonic fluid administration is required to match excessive free water losses in nephrogenic diabetes insipidus 1

For Hypervolemic Hypernatremia

• In cirrhotic patients, discontinue intravenous fluid therapy and implement free water restriction 1
• Focus on achieving negative water balance rather than aggressive fluid administration 1
• In heart failure patients, implement sodium and fluid restriction, limiting fluid intake to around 2 L/day 1

Correction Rate Guidelines

The rate of correction is the most critical safety consideration to prevent cerebral edema:

• Chronic hypernatremia: Correct at 10-15 mmol/L per 24 hours (no more than 0.4 mmol/L/hour) 1, 2
• Acute hypernatremia: Can be corrected more rapidly, up to 1 mmol/L/hour if severely symptomatic 1

Why Slow Correction Matters

Brain cells synthesize intracellular osmolytes over 48 hours to adapt to hyperosmolar conditions 1. Rapid correction of chronic hypernatremia causes these osmolytes to draw water into brain cells, leading to cerebral edema, seizures, and permanent neurological injury 1, 4.

Monitoring During Treatment

• Check serum sodium, potassium, chloride, and bicarbonate levels frequently during active correction 1
• Assess renal function and urine osmolality regularly 1
• Monitor for signs of cerebral edema: altered mental status, seizures, or neurological deterioration 4
• Track fluid balance and daily weights 1

Special Populations

Heart Failure Patients

• Limit fluid intake to 1.5-2 L/day after initial correction 1
• For persistent severe hypernatremia with cognitive symptoms, consider vasopressin antagonists (tolvaptan, conivaptan) for short-term use 1
• Implement sodium restriction alongside fluid management 1

Cirrhotic Patients

• Evaluate for hypovolemic versus hypervolemic state before treatment 1
• For hypovolemic hypernatremia: provide fluid resuscitation with hypotonic solutions 1
• For hypervolemic hypernatremia: focus on negative water balance, not aggressive fluid administration 1

Critically Ill Patients

• Hypernatremia occurs in up to 27% of ICU patients and is an independent risk factor for increased mortality 5, 6
• Intensivists must carefully manage sodium and water balance, as impaired consciousness prevents thirst-driven regulation 5
• Consider diuretics to promote renal sodium excretion when appropriate 5

Common Pitfalls to Avoid

• Never use isotonic saline in patients with renal concentrating defects - this will worsen hypernatremia 1
• Never correct chronic hypernatremia too rapidly - this causes cerebral edema, seizures, and neurological injury 1, 4
• Never ignore hypernatremia in ICU patients - allowing persistence of any degree of hypernatremia is associated with increased mortality and length of stay 6
• Never use prolonged induced hypernatremia to control intracranial pressure in traumatic brain injury - this requires an intact blood-brain barrier and may worsen cerebral contusions 1

Underlying Causes Requiring Specific Treatment

• Neurogenic diabetes insipidus: May require desmopressin in addition to fluid replacement 2
• Nephrogenic diabetes insipidus: Address underlying causes (discontinue lithium, correct hypokalemia) 2
• Primary hyperaldosteronism: Requires specific endocrine management 2
• Excessive sodium intake: Discontinue hypertonic NaCl or NaHCO3 solutions 2