What is the treatment for hypernatremia?

Treatment of Hypernatremia

Immediate Treatment Approach

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 (>48 hours duration), while acute hypernatremia (<24 hours) can be corrected more rapidly at up to 1 mmol/L/hour if severely symptomatic. 1, 2, 3

The cornerstone of hypernatremia management is replacing the water deficit while avoiding overly rapid correction that can cause cerebral edema, seizures, and permanent neurological injury 1, 2, 3.

Diagnostic Assessment

Before initiating treatment, rapidly assess the following 4:

• Volume status: Determine if the patient is hypovolemic (dehydration, renal/extrarenal losses), euvolemic (diabetes insipidus), or hypervolemic (excessive sodium intake, primary hyperaldosteronism) 3, 4
• Chronicity: Distinguish acute (<24-48 hours) from chronic hypernatremia, as this determines correction rate 2, 3
• Urine osmolality and sodium: Helps differentiate between diabetes insipidus and other causes 3, 4
• Neurological symptoms: Confusion, altered mental status, seizures, or coma indicate severe hypernatremia requiring urgent intervention 5, 2

Fluid Replacement Strategy

Hypovolemic Hypernatremia

• Administer hypotonic fluids (0.45% NaCl or 0.18% NaCl) to replace free water deficit 1, 5
• Never use isotonic saline as initial therapy, especially in patients with nephrogenic diabetes insipidus, as this will worsen hypernatremia 1
• For severe cases with altered mental status, combine IV hypotonic fluids with free water via nasogastric tube 1

Euvolemic Hypernatremia (Diabetes Insipidus)

• Replace free water deficit with hypotonic solutions 1, 3
• Consider desmopressin (Minirin) for central diabetes insipidus 2
• Implement low salt diet (<6 g/day) and protein restriction (<1 g/kg/day) for long-term management 1

Hypervolemic Hypernatremia

• Focus on negative water balance rather than aggressive fluid administration 1
• In cirrhotic patients, discontinue intravenous fluid therapy and implement free water restriction 1
• Consider diuretics to promote renal sodium excretion 6

Correction Rate Guidelines

Chronic Hypernatremia (>48 hours)

The maximum correction rate is 10-15 mmol/L per 24 hours (approximately 0.4 mmol/L/hour) to prevent cerebral edema. 1, 2, 3

• Brain cells synthesize intracellular osmolytes over 48 hours to adapt to hyperosmolar conditions 1
• Rapid correction causes water to shift into brain cells, resulting in cerebral edema, seizures, and permanent neurological injury 1, 2
• Close laboratory monitoring every 2-4 hours during active correction is essential 2

Acute Hypernatremia (<24 hours)

• Can be corrected more rapidly, up to 1 mmol/L/hour if severely symptomatic 1
• Rapid correction improves prognosis by preventing effects of cellular dehydration 3
• Hemodialysis is an effective option for rapidly normalizing sodium levels in acute cases 2

Special Population Considerations

Heart Failure Patients

• Implement sodium and fluid restriction, limiting fluid intake to 1.5-2 L/day 1
• After initial correction, maintain fluid restriction with careful monitoring of serum sodium and fluid balance 1
• For persistent severe hypernatremia with cognitive symptoms, consider vasopressin antagonists (tolvaptan, conivaptan) for short-term use 1

Cirrhotic Patients

• Evaluate for hypovolemic vs. hypervolemic state 1
• For hypovolemic hypernatremia: provide fluid resuscitation with hypotonic solutions 1
• For hypervolemic hypernatremia: focus on attaining negative water balance, discontinue IV fluids, implement free water restriction 1

Patients with Renal Concentrating Defects

• Require ongoing hypotonic fluid administration to match excessive free water losses 1
• Never use isotonic saline, as this will exacerbate hypernatremia 1
• In nephrogenic diabetes insipidus, hypotonic fluids are essential to replace free water deficit 1

Monitoring During Treatment

• Check serum sodium every 2-4 hours during active correction 2, 4
• Monitor serum potassium, chloride, bicarbonate, and renal function regularly 1
• Assess urine osmolality and volume 1, 4
• Track neurological status for signs of cerebral edema (worsening confusion, seizures) 5, 2
• Calculate and monitor fluid balance meticulously 4

Critical Pitfalls to Avoid

• Never correct chronic hypernatremia faster than 10-15 mmol/L per 24 hours - this causes cerebral edema and permanent neurological injury 1, 2
• Never use isotonic saline in patients with diabetes insipidus or renal concentrating defects - this worsens hypernatremia 1
• Never delay treatment while pursuing a complete diagnostic workup in symptomatic patients 5
• When starting renal replacement therapy in chronic hypernatremia, avoid rapid sodium drops by adjusting dialysate composition 2
• In traumatic brain injury, prolonged induced hypernatremia to control intracranial pressure is not recommended, as it may worsen cerebral contusions 1