What is the treatment for hypernatremia?

Hypernatremia Treatment

For hypernatremia, replace free water deficit with hypotonic fluids (0.45% NaCl or D5W), correcting at a maximum rate of 10-15 mmol/L per 24 hours for chronic cases to prevent cerebral edema, while addressing the underlying cause. 1

Initial Assessment

Before initiating treatment, determine three critical factors:

• Duration: Acute (<48 hours) vs. chronic (>48 hours) hypernatremia, as this dictates correction speed 2, 3
• Volume status: Hypovolemic (dehydration, renal losses), euvolemic (diabetes insipidus), or hypervolemic (excessive sodium intake) 3
• Severity: Mild (145-149 mmol/L), moderate (150-159 mmol/L), or severe (≥160 mmol/L) 3

Assess neurological symptoms (confusion, altered mental status, seizures), vital signs, volume status, and measure urine osmolality to differentiate causes 1, 3

Fluid Selection Strategy

The choice of fluid is critical and depends on the clinical scenario:

• D5W (5% dextrose in water): Preferred for most cases as it delivers no renal osmotic load and allows controlled plasma osmolality reduction 1
• 0.45% NaCl (half-normal saline): Contains 77 mEq/L sodium; appropriate for moderate hypernatremia with some volume depletion 1
• 0.18% NaCl (quarter-normal saline): Contains ~31 mEq/L sodium; provides more aggressive free water replacement for severe cases 1

Never use isotonic saline (0.9% NaCl) as initial therapy—this will worsen hypernatremia, especially in patients with nephrogenic diabetes insipidus or renal concentrating defects. 1

Correction Rate Guidelines

The single most critical safety principle is avoiding overly rapid correction:

Chronic Hypernatremia (>48 hours)

• Maximum correction rate: 10-15 mmol/L per 24 hours 1, 2
• Never exceed 0.4 mmol/L per hour 3
• Slower correction is essential because brain cells synthesize intracellular osmolytes over 48 hours to adapt to hyperosmolar conditions 1
• Rapid correction causes cerebral edema, seizures, and permanent neurological injury 1, 2

Acute Hypernatremia (<48 hours)

• Can be corrected more rapidly, up to 1 mmol/L per hour if severely symptomatic 1
• For severe cases with altered mental status, combine IV hypotonic fluids with free water via nasogastric tube 1

Treatment Based on Volume Status

Hypovolemic Hypernatremia

• Administer hypotonic fluids to replace free water deficit 1
• Avoid isotonic saline as initial therapy 1
• Replace ongoing losses (diarrhea, vomiting, burns) with appropriate fluid composition 1

Euvolemic Hypernatremia (Diabetes Insipidus)

• Central diabetes insipidus: Desmopressin (Minirin) is the primary treatment 2
• Nephrogenic diabetes insipidus: Requires ongoing hypotonic fluid administration to match excessive free water losses 1
• Low salt diet (<6 g/day) and protein restriction (<1 g/kg/day) may be beneficial 1

Hypervolemic Hypernatremia

• In cirrhosis: Discontinue IV fluids and implement free water restriction; focus on negative water balance rather than aggressive fluid administration 1
• In heart failure: Sodium and fluid restriction, limiting intake to ~2 L/day for most hospitalized patients 1
• For persistent severe hypernatremia with cognitive symptoms, vasopressin antagonists (tolvaptan, conivaptan) may be considered short-term 1

Special Clinical Scenarios

Nephrogenic Diabetes Insipidus

• Requires continuous hypotonic fluid administration to match excessive free water losses 1
• Isotonic fluids will cause or worsen hypernatremia in these patients 1

Severe Burns or Voluminous Diarrhea

• Hypotonic fluids required to match ongoing free water losses 1
• Match fluid composition to losses while providing adequate free water 1

Heart Failure with Hypernatremia

• Fluid restriction (1.5-2 L/day) may be needed after initial correction 1
• Careful monitoring of serum sodium and fluid balance essential 1

Monitoring Requirements

• Regular monitoring: Serum sodium, potassium, chloride, bicarbonate levels 1
• Assess: Renal function and urine osmolality 1
• Track: Body weight, fluid balance, neurological status 1
• Close laboratory controls are essential during correction 2

Critical Pitfalls to Avoid

• Never correct chronic hypernatremia faster than 10-15 mmol/L per 24 hours—this causes cerebral edema and neurological injury 1, 2
• Never use isotonic saline in patients with renal concentrating defects—this exacerbates hypernatremia 1
• Avoid rapid correction when starting renal replacement therapy in patients with chronic hypernatremia 2
• Do not use prolonged induced hypernatremia to control intracranial pressure in traumatic brain injury—it requires an intact blood-brain barrier and may worsen cerebral contusions 1