Treatment of Hypernatremia (Elevated Sodium)
For hypernatremia, replace the free water deficit with hypotonic fluids (0.45% NaCl or D5W depending on severity), correcting sodium at a maximum rate of 10-12 mEq/L per 24 hours to prevent cerebral edema, while simultaneously addressing the underlying cause. 1
Initial Assessment
Before initiating treatment, confirm true hypernatremia by excluding pseudohypernatremia and checking glucose-corrected sodium concentrations—add 1.6 mEq/L to the measured sodium for each 100 mg/dL glucose above 100 mg/dL 1. This is critical because hyperglycemia can artificially lower measured sodium levels 2.
Assess volume status through physical examination:
- Hypovolemic signs: orthostatic hypotension, dry mucous membranes, decreased skin turgor, tachycardia 1
- Hypervolemic signs: edema, jugular venous distention 1
Fluid Selection Based on Severity
The choice of replacement fluid depends on the severity of hypernatremia and the patient's clinical condition 1:
For Moderate Hypernatremia
- 0.45% NaCl (half-normal saline): Contains 77 mEq/L sodium with osmolarity ~154 mOsm/L 1
- Provides both free water and some sodium replacement 1
For Severe Hypernatremia or Aggressive Correction
- 0.18% NaCl (quarter-normal saline): Contains ~31 mEq/L sodium, more hypotonic than half-normal saline 1
- Provides greater free water content for more aggressive replacement 1
For Central Pontine Myelinolysis or Most Severe Cases
- D5W (5% dextrose in water): Provides pure free water 1
- Reduce sodium at 10-15 mEq/L per 24 hours using D5W as primary fluid 1
Critical Safety Guidelines
Never use isotonic saline (0.9% NaCl) in hypernatremia—it will worsen the condition in patients unable to excrete free water appropriately 1. This is especially dangerous in patients with renal concentrating defects like nephrogenic diabetes insipidus 1.
The correction rate should not exceed 10-12 mEq/L per 24 hours 3. Overly rapid correction can cause cerebral edema and neurological complications 1.
Special Clinical Scenarios
Renal Concentrating Defects (Nephrogenic Diabetes Insipidus)
Patients with significant renal concentrating defects require hypotonic fluid replacement to prevent hypernatremia 1. They need ongoing hypotonic fluid administration to match their excessive free water losses 1. Do not use isotonic saline as this will exacerbate hypernatremia 1.
Voluminous Diarrhea or Severe Burns
Match fluid composition to losses while providing adequate free water 1. These patients have ongoing massive free water losses that must be continuously replaced 1.
Central Pontine Myelinolysis
Use D5W as the primary fluid and reduce sodium at 10-15 mEq/L per 24 hours 1. Correction rates faster than 48-72 hours for severe hypernatremia have been associated with increased risk of pontine myelinolysis 2.
Monitoring During Treatment
Monitor closely for signs of overcorrection, including neurological changes suggesting osmotic demyelination such as dysarthria, dysphagia, and quadriparesis 1. Adjust therapy accordingly based on serial sodium measurements 1.
Check serum sodium levels frequently during active correction—typically every 2-4 hours initially, then adjust monitoring frequency based on the rate of correction and clinical response 3.
Addressing Underlying Causes
While correcting the sodium level, simultaneously identify and treat the underlying etiology 4: