D5W Infusion Rate for Hypernatremia in a 75 kg Male
For a 75 kg male patient with hypernatremia, administer D5W at an initial rate of 100-125 mL/hour (approximately 2400-3000 mL/24 hours, or 32-40 mL/kg/24 hours for adults). 1
Rationale for D5W Selection
D5W is the preferred fluid for hypernatremia because it delivers no renal osmotic load, allowing controlled decrease in plasma osmolality without worsening the hypernatremic state. 1, 2 Salt-containing solutions like normal saline (0.9% NaCl) must be avoided—their tonicity (~300 mOsm/kg H₂O) exceeds typical urine osmolality by approximately 3-fold, requiring around 3 liters of urine to excrete the osmotic load from just 1 liter of isotonic fluid, which risks serious worsening of hypernatremia. 1, 2
Initial Rate Calculation
For adults, the physiological maintenance rate is 25-30 mL/kg/24 hours. 1, 2 For a 75 kg patient:
- Minimum rate: 25 mL/kg/24h × 75 kg = 1875 mL/24h (78 mL/hour)
- Maximum rate: 30 mL/kg/24h × 75 kg = 2250 mL/24h (94 mL/hour)
Starting at the higher end of this range (100-125 mL/hour) is appropriate because D5W delivers no renal osmotic load, resulting in slow sodium decrease unless diuretics are withdrawn. 1
Critical Correction Parameters
The rate of plasma sodium correction must not exceed 8-10 mmol/L per 24 hours for chronic hypernatremia (>48 hours). 3 More specifically, the induced change in serum osmolality should not exceed 3 mOsm/kg/hour to prevent cerebral edema from overly rapid correction. 4, 2
For acute hypernatremia (<48 hours), a faster correction of 1 mmol/L/hour for the first 6-8 hours may be acceptable, but this is rarely the case in clinical practice. 3
Monitoring Requirements
- Check plasma sodium every 2-4 hours initially to ensure safe correction rate 2
- Adjust infusion rate based on sodium response—if sodium drops too rapidly (>10 mmol/L in 24h), slow the rate 3
- Monitor for signs of cerebral edema if correction is too rapid: altered mental status, seizures, or neurological deterioration 5, 6
Special Considerations for This Patient
If the patient has nephrogenic diabetes insipidus (NDI) or other renal concentrating defects causing ongoing massive free water losses, the maintenance rate may need substantial increase to match losses. 1 In NDI specifically, patients may require rates exceeding 100 mL/kg/24h due to urine volumes of 3-4 L/day or more. 1
Avoid adding electrolytes to D5W initially—the goal is pure free water replacement. 1, 2 Once sodium approaches normal range, consider transitioning to D5W with appropriate maintenance electrolytes. 1
Common Pitfalls to Avoid
- Never use normal saline or lactated Ringer's for hypernatremia correction—these will worsen the condition 1, 2
- Never correct chronic hypernatremia faster than 10 mmol/L per 24 hours—this causes cerebral edema 5, 3
- Never assume standard maintenance rates are sufficient without monitoring—individual variation requires frequent sodium checks 1, 2
The rate should be titrated based on serial sodium measurements, with the overarching principle that slow correction over 48-72 hours is safer than rapid correction. 5, 3