Management of Hypernatremia
Initial Assessment and Correction Rate
For chronic hypernatremia (>48 hours duration), correct sodium at a rate of 10-15 mmol/L per 24 hours to prevent cerebral edema and neurological injury. 1
Acute hypernatremia (<24-48 hours) can be corrected more rapidly—up to 1 mmol/L/hour if the patient is severely symptomatic—because brain cells have not yet synthesized intracellular osmolytes to adapt to hyperosmolar conditions. 1 However, slower correction of chronic hypernatremia is critical because brain cells synthesize these osmolytes over 48 hours, and rapid correction causes water to shift into brain cells, resulting in cerebral edema, seizures, and permanent neurological injury. 1
Treatment Based on Volume Status
Hypovolemic Hypernatremia
Administer hypotonic fluids to replace the free water deficit. 1 Avoid isotonic saline as initial therapy, especially in patients with nephrogenic diabetes insipidus, as this will worsen hypernatremia. 1
- Primary fluid choices: 0.45% NaCl (half-normal saline with 77 mEq/L sodium), 0.18% NaCl (quarter-normal saline with 31 mEq/L sodium), or D5W (5% dextrose in water) 2
- For patients with severe burns or voluminous diarrhea, hypotonic fluids are required to match ongoing free water losses 1
- Isotonic saline should never be used in patients with renal concentrating defects, as this exacerbates hypernatremia 1
Hypervolemic Hypernatremia (Cirrhosis)
Focus on attaining negative water balance rather than aggressive fluid administration. 1
- Discontinue intravenous fluid therapy and implement free water restriction 1
- Close monitoring of serum sodium and fluid status is essential 1
- Evaluate for the underlying cause and provide appropriate management for the hypervolemic state 1
Euvolemic Hypernatremia
Implement dietary modifications and address underlying causes. 1
- Low salt diet (<6 g/day) and protein restriction (<1 g/kg/day) may be beneficial 1
- For nephrogenic diabetes insipidus, ongoing hypotonic fluid administration is required to match excessive free water losses 1
Special Clinical Scenarios
Heart Failure with Hypernatremia
Implement sodium and fluid restriction, limiting fluid intake to around 2 L/day for most hospitalized patients. 1
- Consider stricter fluid restriction for diuretic-resistant or significantly hypernatremic patients 1
- For persistent severe hypernatremia with cognitive symptoms, vasopressin antagonists (tolvaptan, conivaptan) may be considered for short-term use 1
- After initial correction, fluid restriction (1.5-2 L/day) may be needed with careful monitoring of serum sodium and fluid balance 1
Severe Hypernatremia with Altered Mental Status
Combine IV hypotonic fluids with free water via nasogastric tube, targeting correction of 10-15 mmol/L per 24 hours. 1
Monitoring Requirements
Regular monitoring of serum sodium, potassium, chloride, and bicarbonate levels is essential during treatment. 1
- Assess renal function and urine osmolality 1
- Monitor for hyperchloremia, which may impair renal function 1
- Track fluid balance and adjust replacement accordingly 1
Critical Pitfalls to Avoid
Never correct chronic hypernatremia faster than 10-15 mmol/L per 24 hours (approximately 0.4 mmol/L/hour). 1, 3 Overly rapid correction leads to cerebral edema, seizures, and permanent neurological injury. 1
- Do not use prolonged induced hypernatremia to control intracranial pressure in traumatic brain injury, as it requires an intact blood-brain barrier and may worsen cerebral contusions 1
- Be aware of "rebound" ICP elevation during correction as brain cells synthesize intracellular osmolytes 1
- Avoid isotonic fluids in patients with nephrogenic diabetes insipidus or other renal concentrating defects 1