Hypernatremia Correction with D5W
Immediate Correction Rate Calculation
For a serum sodium of 171 mEq/L in a 74.4 kg patient, the maximum safe correction rate is 10-15 mEq/L per 24 hours, which translates to approximately 0.4-0.6 mEq/L per hour. 1
Water Deficit Calculation
The free water deficit can be calculated using the formula 1:
Water deficit = 0.5 × body weight (kg) × [(current Na ÷ 140) - 1]
For this patient:
- Water deficit = 0.5 × 74.4 kg × [(171 ÷ 140) - 1]
- Water deficit = 37.2 × 0.221
- Water deficit ≈ 8.2 liters
D5W Administration Protocol
Administer D5W at a rate that replaces the water deficit over 48-72 hours to prevent cerebral edema. 2
- Initial infusion rate: 8,200 mL ÷ 48 hours = approximately 170 mL/hour
- Alternative 72-hour correction: 8,200 mL ÷ 72 hours = approximately 115 mL/hour 2
Critical Safety Parameters
The correction rate must not exceed 10-15 mEq/L per 24 hours. 1 More rapid correction risks cerebral edema and neurological deterioration. 2, 3
Monitoring Requirements
- Check serum sodium every 2-4 hours during initial correction 1
- Adjust D5W infusion rate based on sodium response
- Target reduction: 0.4 mEq/L per hour maximum 1
Special Considerations for This Patient
Volume Status Assessment
If the patient has hypervolemic hypernatremia (fluid overload with elevated sodium), furosemide must be added to D5W therapy to achieve negative sodium and potassium balance exceeding negative water balance. 4 This ensures correction of both the elevated sodium concentration and the excess total body water.
Renal Function Considerations
If renal concentrating defects are present (such as diabetes insipidus), ongoing hypotonic fluid administration will be required to match excessive free water losses, and isotonic fluids must be avoided as they will worsen hypernatremia. 1
Common Pitfalls to Avoid
- Never use isotonic saline (0.9% NaCl) in hypernatremia - it delivers excessive osmotic load requiring 3 liters of urine to excrete the osmotic load from just 1 liter of fluid, risking worsening hypernatremia 1
- Never correct faster than 48-72 hours for severe hypernatremia - correction rates faster than this are associated with increased risk of cerebral edema and pontine myelinolysis 1
- Never administer D5W without concurrent diuretic therapy in hypervolemic states - this will worsen fluid overload 4
Practical Implementation
Start D5W at 115-170 mL/hour depending on whether targeting 72-hour or 48-hour correction. 2 The slower 72-hour approach (115 mL/hour) is safer for severe hypernatremia of this magnitude (171 mEq/L). 2, 3
If using continuous renal replacement therapy (CRRT), calculate the D5W prefilter rate to prevent overcorrection while maintaining adequate effluent volume, ensuring sodium correction does not exceed 8 mEq/L per day. 5