Treatment for Hypernatremia
The primary treatment for hypernatremia is restoration of plasma tonicity through administration of hypotonic fluids, with the correction rate determined by whether the hypernatremia is acute (<24-48 hours) or chronic (>48 hours). 1
Classification and Correction Rate Guidelines
For chronic hypernatremia (>48 hours duration), correction must be slow—no more than 10-15 mmol/L per 24 hours or 0.4 mmol/L per hour—to prevent cerebral edema, seizures, and neurological injury. 1, 2, 3 This cautious approach is critical because rapid correction can cause devastating neurological complications including osmotic demyelination syndrome. 2
For acute hypernatremia (<24-48 hours), rapid correction is both safe and improves prognosis by preventing cellular dehydration effects, without significant risk of neurological complications. 1, 3
Diagnostic Approach to Guide Treatment
Before initiating treatment, determine the underlying etiology through systematic assessment:
- Assess volume status clinically to classify hypernatremia as hypervolemic, euvolemic, or hypovolemic, as this guides fluid selection 3, 4
- Measure urine osmolality and urine sodium to differentiate renal from extrarenal losses 3, 4
- Check for diabetes insipidus (central vs. nephrogenic) in euvolemic hypernatremia by measuring urine volume and osmolality 3, 4
Treatment Based on Etiology
Hypovolemic Hypernatremia (Most Common)
Replace both water and sodium deficits with hypotonic solutions such as 0.45% NaCl (half-normal saline) or 0.18% NaCl, depending on severity. 5 The choice depends on the magnitude of hypernatremia and ongoing losses. 5
Euvolemic Hypernatremia (Diabetes Insipidus)
For central diabetes insipidus, administer desmopressin (Minirin) in addition to free water replacement. 2 For nephrogenic diabetes insipidus (often medication-induced by lithium or caused by hypokalemia), address the underlying cause while providing ongoing hypotonic fluid replacement. 3
Hypervolemic Hypernatremia
Acute hypervolemic hypernatremia from excessive sodium intake (hypertonic NaCl or NaHCO3 solutions) requires hemodialysis for rapid normalization of serum sodium. 2, 3 Chronic hypervolemic hypernatremia may indicate primary hyperaldosteronism requiring specific endocrine management. 3
Fluid Selection and Administration
The preferred replacement fluid is 5% dextrose in water (D5W) for pure water deficit, or 0.45% NaCl when some sodium replacement is also needed. 5 Avoid isotonic saline (0.9% NaCl) in patients with renal concentrating defects, as this will worsen hypernatremia. 5
Calculate initial fluid administration rates based on physiological maintenance requirements: 25-30 mL/kg/24 hours for adults. 5
Special Populations
Neonates and Preterm Infants
Neonates, particularly those <34 weeks gestation with very low birth weight, require careful attention to etiology through assessment of intravascular volume and hydration status. 1 Corrections more rapid than 48-72 hours increase the risk of pontine myelinolysis in this population. 5
Therapeutic measures should be based on etiology, with symptomatic hypovolemia requiring volume replacement and a slow correction rate of 10-15 mmol/L per 24 hours, along with daily monitoring of weight and serum electrolytes. 1
Neurosurgical Patients
Between 10-30% of tube-fed patients develop hypernatremia, which may represent transient diabetes insipidus in neurosurgical patients requiring specific management. 6
Monitoring Requirements
Close laboratory monitoring is essential during correction, with frequent sodium checks to ensure the correction rate does not exceed safe limits. 2 For chronic hypernatremia, check serum sodium every 4-6 hours initially, then adjust frequency based on response. 1
Monitor daily weights and assess for signs of overcorrection or undercorrection, both of which are associated with poor prognosis. 1
Critical Pitfalls to Avoid
Never correct chronic hypernatremia faster than 10-15 mmol/L per 24 hours—too rapid correction can induce cerebral edema, seizures, and permanent neurological injury. 1, 2 This is the single most important safety consideration.
When initiating renal replacement therapy in patients with chronic hypernatremia, avoid rapid drops in sodium concentration by using appropriate dialysate sodium concentrations. 2
Do not use isotonic fluids in patients with nephrogenic diabetes insipidus or other renal concentrating defects, as this delivers excessive osmotic load and worsens hypernatremia. 5