Hypernatremia Management
Initial Assessment and Correction Rate
For chronic hypernatremia (>48 hours duration), correct sodium at a rate of 10-15 mmol/L per 24 hours to prevent cerebral edema and neurological injury. 1
Acute hypernatremia (<48 hours) can be corrected more rapidly—up to 1 mmol/L/hour if the patient is severely symptomatic—but chronic cases require slower correction because brain cells synthesize intracellular osmolytes over 48 hours to adapt to hyperosmolar conditions. 1 Rapid correction in chronic cases causes cerebral edema, seizures, and permanent neurological injury. 1
Fluid Selection Strategy
Primary Hypotonic Fluids
Administer hypotonic fluids such as 0.45% NaCl (half-normal saline), 0.18% NaCl (quarter-normal saline), or D5W (5% dextrose in water) to replace free water deficit. 1
- 0.45% NaCl contains 77 mEq/L sodium with osmolarity ~154 mOsm/L, appropriate for moderate hypernatremia correction 1
- 0.18% NaCl contains ~31 mEq/L sodium, providing more aggressive free water replacement for severe cases 1
- D5W delivers no renal osmotic load and allows controlled decrease in plasma osmolality 2
Critical Contraindication
Never use isotonic saline (0.9% NaCl) as initial therapy, especially in patients with nephrogenic diabetes insipidus or renal concentrating defects, as this will worsen hypernatremia. 1 Isotonic saline delivers excessive osmotic load—requiring 3 liters of urine to excrete the osmotic load from just 1 liter of fluid—which risks worsening hypernatremia. 2
Volume Status-Based Approach
Hypovolemic Hypernatremia
Replace free water deficit with hypotonic fluids and avoid isotonic saline. 1 In patients with severe burns or voluminous diarrhea, match fluid composition to ongoing losses while providing adequate free water. 1
Hypervolemic Hypernatremia
Focus on attaining 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, 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
Special Clinical Scenarios
Nephrogenic Diabetes Insipidus
Provide ongoing hypotonic fluid administration to match excessive free water losses. 1 These patients require continuous hypotonic fluids because isotonic saline will cause or worsen hypernatremia. 1
Heart Failure with Persistent Severe Hypernatremia
Consider vasopressin antagonists (tolvaptan, conivaptan) for short-term use in patients with cognitive symptoms despite fluid restriction. 1 For severe hypernatremia with altered mental status, combine IV hypotonic fluids with free water via nasogastric tube, targeting correction of 10-15 mmol/L per 24 hours. 1
Traumatic Brain Injury
Avoid prolonged induced hypernatremia to control intracranial pressure. 1 This approach requires an intact blood-brain barrier to be effective and may worsen cerebral contusions. 1 There is risk of "rebound" ICP elevation during correction as brain cells synthesize intracellular osmolytes. 1
Monitoring and Safety
Monitor serum sodium, potassium, chloride, and bicarbonate levels regularly during treatment. 1 Assess renal function and urine osmolality, as hypernatremia is associated with hyperchloremia, which may impair renal function. 1
Track daily weight and fluid balance meticulously to monitor effectiveness and adjust treatment accordingly. 2
Common Pitfalls to Avoid
- Never correct chronic hypernatremia faster than 10-15 mmol/L per 24 hours—this causes cerebral edema and seizures 1
- Never use isotonic saline in patients with renal concentrating defects—this exacerbates hypernatremia 1
- Never ignore ongoing free water losses—match replacement to losses in burns, diarrhea, or diabetes insipidus 1
- Never use hypertonic saline in hypervolemic hypernatremia without life-threatening symptoms—this worsens edema and ascites 2