How do you treat hypernatremia?

Treatment of Hypernatremia

For hypernatremia, administer hypotonic fluids (0.45% NaCl, 0.18% NaCl, or D5W) to replace free water deficit, with correction rates not exceeding 10-15 mmol/L per 24 hours for chronic cases to prevent cerebral edema, and never use isotonic saline as initial therapy, especially in patients with nephrogenic diabetes insipidus. 1

Initial Assessment and Volume Status Determination

• Assess volume status immediately to determine if hypernatremia is hypovolemic, euvolemic, or hypervolemic, as this dictates fluid selection 1
• Measure blood electrolyte concentrations, acid-base status, hematocrit, and blood urea nitrogen to assess hydration status 1
• Check urine osmolality to evaluate renal concentrating ability and differentiate diabetes insipidus from other causes 1
• Evaluate body weight and estimate body composition to calculate fluid deficits 1

Correction Rate Guidelines

Chronic Hypernatremia (>48 hours)

• Reduce sodium at 10-15 mmol/L per 24 hours to avoid cerebral edema, seizures, and permanent neurological injury 1
• Never exceed 0.4 mmol/L per hour for chronic cases 2
• Slower correction is critical because brain cells synthesize intracellular osmolytes over 48 hours to adapt to hyperosmolar conditions 1
• Rapid correction causes cerebral edema as water shifts into brain cells that have accumulated organic osmolytes 1

Acute Hypernatremia (<24-48 hours)

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

Fluid Selection Based on Volume Status

Hypovolemic Hypernatremia

• Administer hypotonic fluids such as 0.45% NaCl (77 mEq/L sodium, ~154 mOsm/L) for moderate hypernatremia 1
• Use 0.18% NaCl (~31 mEq/L sodium) for more aggressive free water replacement in severe cases 1
• D5W (5% dextrose in water) provides pure free water replacement 1
• Never use isotonic saline (0.9% NaCl) as it will worsen hypernatremia, particularly in nephrogenic diabetes insipidus or renal concentrating defects 1
• Match fluid composition to ongoing losses in severe burns or voluminous diarrhea while providing adequate free water 1

Euvolemic Hypernatremia

• Low salt diet (<6 g/day) and protein restriction (<1 g/kg/day) may be beneficial 1
• For diabetes insipidus, ongoing hypotonic fluid administration is required to match excessive free water losses 1
• Consider desmopressin (Minirin) for central diabetes insipidus 3

Hypervolemic Hypernatremia

• Focus on achieving negative water balance rather than aggressive fluid administration 1
• Discontinue intravenous fluid therapy and implement free water restriction 1
• May require diuretics with careful free water replacement 4

Special Clinical Scenarios

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
• After initial correction, fluid restriction (1.5-2 L/day) may be needed with careful monitoring 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
• Close monitoring of serum sodium and fluid status is essential 1

Nephrogenic Diabetes Insipidus

• Avoid isotonic saline completely as this exacerbates hypernatremia 1
• Requires ongoing hypotonic fluid administration to match excessive free water losses 1
• Isotonic fluids will cause or worsen hypernatremia in these patients 1

Traumatic Brain Injury

• Prolonged induced hypernatremia to control intracranial pressure is not recommended 1
• Risk of "rebound" ICP elevation during correction exists as brain cells synthesize intracellular osmolytes 1
• Requires intact blood-brain barrier to be effective and may worsen cerebral contusions 1

Monitoring During Treatment

• Check serum sodium, potassium, chloride, and bicarbonate levels regularly during treatment 1
• Assess renal function and urine osmolality frequently 1
• Monitor for hyperchloremia, which may impair renal function 1
• Watch for signs of cerebral edema if correction is too rapid: confusion, seizures, altered mental status 1, 5

Critical Pitfalls to Avoid

• Never correct chronic hypernatremia too rapidly - this leads to cerebral edema, seizures, and neurological injury 1
• Never use isotonic saline in patients with renal concentrating defects - this worsens hypernatremia 1
• Avoid correction rates faster than 48-72 hours for severe chronic hypernatremia due to pontine myelinolysis risk 6
• When starting renal replacement therapy in chronic hypernatremia, prevent rapid sodium drops 3
• Hypernatremia in pediatric patients carries the highest morbidity and mortality rate, primarily from CNS dysfunction 5