Distilled Water for Hypernatremia
Distilled water (D5W - 5% dextrose in water) is the preferred hypotonic fluid for correcting hypernatremia, particularly in patients with nephrogenic diabetes insipidus or severe hypernatremia requiring aggressive free water replacement. 1
Fluid Selection for Hypernatremia Correction
The primary hypotonic fluids recommended for hypernatremia treatment are:
- D5W (5% dextrose in water) - Contains no sodium and delivers no renal osmotic load, allowing controlled decrease in plasma osmolality 1
- 0.45% NaCl (half-normal saline) - Contains 77 mEq/L sodium with osmolarity ~154 mOsm/L, appropriate for moderate hypernatremia 1
- 0.18% NaCl (quarter-normal saline) - Contains ~31 mEq/L sodium, providing more aggressive free water replacement for severe cases 1
Why D5W is Preferred
D5W is the optimal choice because it provides pure free water replacement without adding osmotic load. 1 This is particularly critical in patients with impaired renal concentrating ability, where isotonic fluids would worsen hypernatremia by requiring excessive urine output to excrete the osmotic load. 1
Critical Contraindication
Never use isotonic saline (0.9% NaCl) as initial therapy for hypernatremia, especially in patients with nephrogenic diabetes insipidus or renal concentrating defects, as this will worsen hypernatremia. 1 Isotonic fluids deliver excessive osmotic load - requiring 3 liters of urine to excrete the osmotic load from just 1 liter of isotonic fluid. 1
Correction Rate Guidelines
The maximum correction rate should not exceed 10-15 mmol/L per 24 hours to prevent cerebral edema. 1 Acute hypernatremia can be corrected more rapidly (up to 1 mmol/L/hour) if severely symptomatic, but chronic hypernatremia requires slower correction over 48-72 hours. 1
Special Clinical Scenarios
For nephrogenic diabetes insipidus: Ongoing hypotonic fluid administration is required to match excessive free water losses, and isotonic fluids will cause or worsen hypernatremia in these patients. 1
For severe burns or voluminous diarrhea: Hypotonic fluids are required to keep up with ongoing free water losses, with fluid composition matched to losses while providing adequate free water. 1
For hospitalized patients with hypernatremia: D5W should not be administered as a bolus because of the risk of rapid decrease in serum sodium; instead, it should be given as a controlled infusion with close monitoring of clinical status, neurological condition, fluid balance, weight, and electrolytes. 2
Common Pitfall
Correcting chronic hypernatremia too rapidly can lead to cerebral edema, seizures, and neurological injury. 1 Slower correction is critical because brain cells synthesize intracellular osmolytes over 48 hours to adapt to hyperosmolar conditions, and rapid correction disrupts this adaptation. 1