How do you treat hypernatremia?

Treatment of Hypernatremia

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, and avoid isotonic saline as initial therapy, especially in patients with nephrogenic diabetes insipidus. 1

Initial Assessment and Volume Status Determination

Evaluate the patient's clinical status including neurological symptoms (confusion, coma), vital signs, volume status, and body weight to determine fluid deficits 1. Measure blood electrolyte concentrations, acid-base status, hematocrit, and blood urea nitrogen to assess hydration status 1. Check urine osmolality to differentiate between causes—concentrated urine suggests extrarenal losses, while dilute urine suggests diabetes insipidus 2.

Hypernatremia can be classified by volume status:

• Hypovolemic hypernatremia: Results from renal or extrarenal water losses exceeding sodium losses 2
• Euvolemic hypernatremia: Typically indicates diabetes insipidus (central or nephrogenic) 2
• Hypervolemic hypernatremia: Caused by excessive sodium intake or primary hyperaldosteronism 2, 3

Correction Rate Guidelines

The correction rate is critically dependent on chronicity:

• Chronic hypernatremia (>48 hours): Reduce sodium by no more than 10-15 mmol/L per 24 hours (approximately 0.4 mmol/L/hour) to avoid cerebral edema 1, 4, 2
• Acute hypernatremia (<24-48 hours): Can be corrected more rapidly, up to 1 mmol/L/hour if severely symptomatic 1, 4

Correcting chronic hypernatremia too rapidly can lead to cerebral edema, seizures, and permanent neurological injury because brain cells synthesize intracellular osmolytes over 48 hours to adapt to hyperosmolar conditions 1. Rapid correction causes water to shift into brain cells faster than osmolytes can be eliminated 1.

Fluid Replacement Strategy by Volume Status

Hypovolemic Hypernatremia

• Administer hypotonic fluids (0.45% NaCl, 0.18% NaCl, or D5W) to replace free water deficit 1, 5
• Avoid isotonic saline as initial therapy, particularly in nephrogenic diabetes insipidus, as this will worsen hypernatremia 1
• For patients with severe burns or voluminous diarrhea, match fluid composition to ongoing losses while providing adequate free water 1

Euvolemic Hypernatremia (Diabetes Insipidus)

• Central diabetes insipidus: Administer desmopressin (Minirin) along with hypotonic fluid replacement 4
• Nephrogenic diabetes insipidus: Requires ongoing hypotonic fluid administration to match excessive free water losses; isotonic fluids will cause or worsen hypernatremia 1
• Consider a low salt diet (<6 g/day) and protein restriction (<1 g/kg/day) 1

Hypervolemic Hypernatremia

• Focus on achieving negative water balance rather than aggressive fluid administration 1
• Induce negative Na+ and K+ balance in excess of negative water balance using IV D5W and furosemide 3
• For cirrhosis patients, discontinue intravenous fluid therapy and implement free water restriction 1

Special Population Considerations

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
• For persistent severe hypernatremia with cognitive symptoms, vasopressin antagonists (tolvaptan, conivaptan) may be considered for short-term use 1

Cirrhosis Patients

• Evaluate for hypovolemic vs. hypervolemic state 1
• Provide fluid resuscitation with hypotonic solutions for hypovolemic hypernatremia 1
• Focus on attaining negative water balance for hypervolemic hypernatremia 1

Severe Hypernatremia with Altered Mental Status

• Combine IV hypotonic fluids with free water via nasogastric tube 1
• Target correction rate of 10-15 mmol/L per 24 hours 1
• After initial correction, fluid restriction (1.5-2 L/day) may be needed with careful monitoring 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
• Close laboratory controls are important to prevent overly rapid correction 4
• Monitor for signs of cerebral edema if correction is too rapid 1

Common Pitfalls to Avoid

• Never use isotonic saline in patients with renal concentrating defects, as this exacerbates hypernatremia 1
• Avoid correcting chronic hypernatremia faster than 10-15 mmol/L per 24 hours to prevent cerebral edema and seizures 1
• The use of prolonged induced hypernatremia to control intracranial pressure in traumatic brain injury is not recommended, as it requires an intact blood-brain barrier and may worsen cerebral contusions 1
• Be aware that hypernatremia is associated with hyperchloremia, which may impair renal function 1

Alternative Treatment Options

For acute hypernatremia (<24 hours), hemodialysis is an effective option to rapidly normalize serum sodium levels 4. However, when starting renal replacement therapy in patients with chronic hypernatremia, avoid a rapid drop in sodium concentration 4.