Best IV Fluid for Dehydration with Hypernatremia
Use 5% dextrose in water (D5W) as the primary IV fluid for hypernatremic dehydration, avoiding normal saline (0.9% NaCl) which will worsen hypernatremia. 1
Why D5W is the Correct Choice
Salt-containing solutions like 0.9% NaCl must be avoided because their tonicity (300 mOsm/kg) is approximately 3-fold higher than typical urine osmolality in hypernatremic states (100 mOsm/kg), meaning the kidneys require ~3 liters of urine to excrete the osmotic load from just 1 liter of isotonic fluid, risking severe worsening of hypernatremia. 1
D5W delivers no renal osmotic load, allowing for controlled correction of the water deficit without adding additional sodium burden. 1
Initial Fluid Rate Calculation
Start with maintenance rate based on physiological demand: 1
- Children: 100 ml/kg/24h for first 10 kg; 50 ml/kg/24h for 10-20 kg; 20 ml/kg/24h for remaining weight 1
- Adults: 25-30 ml/kg/24h 1
For more precise dosing, calculate the water deficit: Total body water × [(Current Na⁺/Desired Na⁺) - 1], where TBW = 0.6 × weight in kg for adult males. 2 Divide this total volume by 48-72 hours to determine hourly rate. 2, 3
Critical Correction Parameters
Correct sodium slowly to prevent cerebral edema: 2, 4, 5
- Maximum 8-10 mEq/L per day 2
- Osmolality should decrease no more than 3 mOsm/kg/hour 2, 6
- Rehydration should occur over 24-72 hours depending on severity 3
Monitor serum sodium every 4-6 hours initially and adjust D5W rate based on measurements. 2 More frequent monitoring (every 2-4 hours) may be needed in severe cases. 4
Special Considerations in Hyperglycemic Patients
If hyperglycemia is present (DKA/HHS), calculate corrected sodium to guide additional fluid choices: Corrected Na⁺ = Measured Na⁺ + 1.6 × ([Glucose - 100]/100). 6
- If corrected sodium is normal or high: use 0.45% NaCl at 4-14 ml/kg/h alongside insulin 6
- If corrected sodium is low: use 0.9% NaCl initially 6
- Once glucose normalizes but true hypernatremia persists, switch to D5W 7
In severe combined hyperglycemia and hypernatremia, consider free water via nasogastric tube and desmopressin to accelerate free water replacement. 7
Common Pitfalls to Avoid
Never use 0.9% NaCl as primary fluid - this is the most critical error, as it paradoxically worsens hypernatremia by providing excessive osmotic load. 1
Avoid rapid correction - correcting too quickly causes cerebral edema, increased intracranial pressure, stupor, and seizures. 3, 5 The rate of rehydration is more important than the exact composition of fluid. 3
Do not use measured sodium for hyperglycemic patients - always calculate corrected sodium first to determine true sodium status. 6
Monitoring Requirements
- Serum sodium every 4-6 hours (every 2-4 hours if severe)
- Serum osmolality to ensure <3 mOsm/kg/h decrease
- Neurological status for signs of cerebral edema
- Hemodynamics, input/output, weight
- Potassium and other electrolytes concurrently
Patients with cardiac or renal compromise require more intensive monitoring of osmolality and mental status. 2, 4