Initial D5W Dosing for Severe Hypernatremia with Hypovolemia
For a 70kg adult with severe hypernatremia and hypovolemia, begin with D5W at a maintenance rate of 1750-2100 mL over 24 hours (approximately 73-88 mL/hour), calculated as 25-30 mL/kg/24h. 1
Rationale for D5W as Primary Fluid
D5W delivers zero renal osmotic load, making it the optimal choice for hypernatremic dehydration. 1 Salt-containing solutions like 0.9% NaCl should be strictly avoided because their tonicity (300 mOsm/kg H₂O) exceeds typical urine osmolality in conditions causing hypernatremia (100 mOsm/kg H₂O) by approximately 3-fold. 1 This means roughly 3 liters of urine would be needed to excrete the osmotic load from just 1 liter of isotonic fluid, risking serious worsening of hypernatremia. 1
Initial Fluid Administration Protocol
Starting Rate Calculation
- Adults: 25-30 mL/kg/24 hours 1
- For 70kg patient: 1750-2100 mL/24h (approximately 73-88 mL/hour) 1
- Children: Use weight-based formula: first 10 kg at 100 mL/kg/24h; 10-20 kg at 50 mL/kg/24h; remaining weight at 20 mL/kg/24h 1
Critical Correction Rate Limits
Never exceed a sodium correction rate of 10 mmol/L per 24 hours (approximately 0.4 mmol/L/hour) to prevent cerebral edema. 2, 3 The induced change in serum osmolality should not exceed 3 mOsm/kg/h. 2 Too rapid correction can lead to devastating cerebral edema and neurological deterioration. 4
Special Considerations for Hypovolemia
While D5W is the primary fluid, if the patient has severe hypovolemia with hemodynamic instability, initial resuscitation may require a small volume of isotonic saline (10-20 mL/kg over 1 hour) to restore perfusion, followed immediately by transition to D5W for ongoing correction. 2 However, this should be minimized as isotonic fluids worsen hypernatremia in patients with impaired water excretion. 1
Monitoring Requirements
- Check serum sodium every 2-4 hours initially to ensure correction stays within safe limits 3
- Target correction: Aim to replace the water deficit over 48-72 hours 4
- Adjust D5W rate based on sodium response, ensuring gradual decline 1
Common Pitfalls to Avoid
Never use normal saline as the primary fluid for hypernatremia - this is the single most dangerous error, as it delivers excessive osmotic load requiring massive urine output to excrete. 1 The 3:1 ratio of urine needed to osmotic load provided makes isotonic fluids contraindicated. 1
Avoid correcting too rapidly - exceeding 10 mmol/L per 24 hours risks cerebral edema from rapid osmotic shifts. 2, 3, 4
Adjunctive Measures
If the patient has ongoing excessive water losses (such as in nephrogenic diabetes insipidus), discontinue diuretics and COX inhibitors as these worsen water loss. 1 Consider desmopressin if central diabetes insipidus is contributing. 5
For hypervolemic hypernatremia (rare), add furosemide to achieve negative sodium/potassium balance exceeding negative water balance while still administering D5W. 6