Management of Hypernatremia
The cornerstone of hypernatremia management is administering hypotonic fluids to replace free water deficit while carefully controlling the correction rate to prevent cerebral edema—never use isotonic saline as initial therapy, especially in patients with nephrogenic diabetes insipidus or renal concentrating defects. 1
Initial Assessment and Volume Status Determination
Determine the patient's volume status through clinical examination (vital signs, skin turgor, mucous membranes, jugular venous pressure) and laboratory assessment (hematocrit, blood urea nitrogen, urine osmolality, urine sodium) to classify hypernatremia as hypovolemic, euvolemic, or hypervolemic 1, 2. This classification drives your treatment approach and fluid selection 3.
Fluid Selection Based on Volume Status
Hypovolemic Hypernatremia
- Administer hypotonic fluids such as 0.45% NaCl (half-normal saline), 0.18% NaCl (quarter-normal saline), or D5W to replace free water deficit 1
- 0.45% NaCl contains 77 mEq/L sodium with osmolarity ~154 mOsm/L, appropriate for moderate hypernatremia 1
- 0.18% NaCl contains ~31 mEq/L sodium, providing more aggressive free water replacement for severe cases 1
- In severe burns or voluminous diarrhea, match fluid composition to ongoing losses while providing adequate free water 1
Euvolemic Hypernatremia
- Consider low salt diet (<6 g/day) and protein restriction (<1 g/kg/day) 1
- For nephrogenic diabetes insipidus, provide ongoing hypotonic fluid administration to match excessive free water losses 1
- For central diabetes insipidus, desmopressin (Minirin) is the treatment of choice 4
Hypervolemic Hypernatremia
- Focus on achieving negative water balance rather than aggressive fluid administration 1
- In cirrhosis patients, discontinue intravenous fluid therapy and implement free water restriction 1
- In heart failure patients, implement sodium and fluid restriction (1.5-2 L/day) 1
Critical Correction Rate Guidelines
Chronic Hypernatremia (>48 hours)
- Limit correction to 8-10 mmol/L per 24 hours (approximately 0.4 mmol/L/hour maximum) 1, 3, 4
- Slower correction is critical 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
Acute Hypernatremia (<24-48 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
- For severe cases, hemodialysis is an effective option to rapidly normalize serum sodium 4
Monitoring Requirements
- Measure serum sodium, potassium, chloride, and bicarbonate every 2-4 hours initially 1
- Assess renal function and urine osmolality regularly 1
- Monitor body weight, intake/output, and neurological status continuously 5
- Calculate fluid and electrolyte balance to guide ongoing therapy 1
Critical Pitfalls to Avoid
Never use isotonic saline (0.9% NaCl) as initial therapy—this will worsen hypernatremia, particularly in patients with nephrogenic diabetes insipidus or renal concentrating defects 1. Isotonic saline contains 154 mEq/L sodium and provides no free water replacement 1.
Avoid correcting chronic hypernatremia too rapidly, as this leads to cerebral edema from osmotic fluid shifts into brain cells that have adapted to hyperosmolar conditions 1, 4. The target reduction rate of 10-15 mmol/L per 24 hours prevents these complications 1.
Special Clinical Scenarios
Heart Failure with Severe Hypernatremia
- For persistent severe hypernatremia with cognitive symptoms, vasopressin antagonists (tolvaptan, conivaptan) may be considered for short-term use 1
- After initial correction, maintain fluid restriction (1.5-2 L/day) with careful monitoring 1
Cirrhosis with Hypernatremia
- Evaluate for hypovolemic versus hypervolemic state 1
- Provide fluid resuscitation with hypotonic solutions for hypovolemic hypernatremia 1
- Focus on attaining negative water balance for hypervolemic hypernatremia rather than fluid administration 1