What are the management strategies for hypernatremia?

Hypernatremia Management

Initial Assessment and Correction Rate

For chronic hypernatremia (>48 hours), correct sodium at 10-15 mmol/L per 24 hours to avoid cerebral edema, seizures, and permanent neurological injury. 1

• Acute hypernatremia (<24-48 hours) can be corrected more rapidly, up to 1 mmol/L/hour if severely symptomatic 1
• Slower correction of chronic hypernatremia is critical because brain cells synthesize intracellular osmolytes over 48 hours to adapt to hyperosmolar conditions—rapid correction causes cerebral edema 1
• Correction rates faster than 48-72 hours for severe hypernatremia increase the risk of pontine myelinolysis 2

Treatment Based on Volume Status

Hypovolemic Hypernatremia

Administer hypotonic fluids (0.45% NaCl, 0.18% NaCl, or D5W) to replace free water deficit—avoid isotonic saline as initial therapy, especially in nephrogenic diabetes insipidus. 1

• Isotonic saline will worsen hypernatremia in patients with renal concentrating defects and should never be used in these patients 1
• For severe burns or voluminous diarrhea, hypotonic fluids are required to match ongoing free water losses 1
• 0.45% NaCl (77 mEq/L sodium) is appropriate for moderate hypernatremia, while 0.18% NaCl (31 mEq/L sodium) provides more aggressive free water replacement 2

Hypervolemic Hypernatremia

Focus on attaining negative water balance rather than aggressive fluid administration, with close monitoring of serum sodium and fluid status. 1

• In cirrhosis patients with hypervolemic hypernatremia, discontinue intravenous fluid therapy and implement free water restriction 1
• The European Association for the Study of the Liver emphasizes negative water balance over fluid administration in these patients 1

Euvolemic Hypernatremia

• A low salt diet (<6 g/day) and protein restriction (<1 g/kg/day) may be beneficial 1
• Patients with nephrogenic diabetes insipidus require ongoing hypotonic fluid administration to match excessive free water losses 1

Fluid Selection and Administration

Use hypotonic solutions (0.45% NaCl, 0.18% NaCl, or D5W) for free water replacement, with the specific choice depending on severity and clinical status. 2

• D5W is recommended as the primary fluid for free water replacement 2
• For patients with severe hypernatremia and altered mental status, combine IV hypotonic fluids with free water via nasogastric tube 1
• Match fluid composition to ongoing losses while providing adequate free water 1

Special Populations

Heart Failure Patients

• 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
• After initial correction, fluid restriction (1.5-2 L/day) may be needed with careful monitoring of serum sodium and fluid balance 1
• For persistent severe hypernatremia with cognitive symptoms, vasopressin antagonists (tolvaptan, conivaptan) may be considered for short-term use 1

Traumatic Brain Injury

The use of prolonged induced hypernatremia to control intracranial pressure is not recommended—it requires an intact blood-brain barrier and may worsen cerebral contusions. 1

• Risk of "rebound" ICP elevation exists during correction as brain cells synthesize intracellular osmolytes 1
• There is a weak relationship between serum sodium and ICP 1
• Hypernatremia is associated with hyperchloremia, which may impair renal function 1

Monitoring Requirements

Regular monitoring of serum sodium, potassium, chloride, and bicarbonate levels is essential during treatment. 1

• Assess renal function and urine osmolality throughout treatment 1
• Close laboratory controls are important to avoid overly rapid correction 3
• Monitor for signs of cerebral edema if correction is too rapid: confusion, seizures, neurological deterioration 1

Common Pitfalls to Avoid

• Never use isotonic saline in patients with nephrogenic diabetes insipidus or renal concentrating defects—this exacerbates hypernatremia 1
• Correcting chronic hypernatremia too rapidly leads to cerebral edema, seizures, and neurological injury 1
• Do not exceed 8-10 mmol/L reduction per day for chronic hypernatremia (>48 hours) 3
• Hypernatremia often results from dehydration with impaired thirst mechanism or lack of water access—address underlying cause 4