Switching from Normal Saline to D5W for Hypernatremia (Sodium 153)
Yes, you should immediately switch from normal saline to D5W at 75 mL/hr for this patient with hypernatremia (sodium 153 mEq/L), as normal saline will worsen the hypernatremia and D5W provides the free water needed for correction. 1
Why Normal Saline is Contraindicated
- Normal saline (0.9% NaCl) has a tonicity of
300 mOsm/kg H₂O, which is approximately 3-fold higher than typical urine osmolality in patients with concentrating defects (100 mOsm/kg H₂O) 1 - This means approximately 3 liters of urine are needed to excrete the renal osmotic load provided by 1 liter of isotonic fluid, risking serious worsening of hypernatremia 1
- Salt-containing solutions, especially NaCl 0.9% solutions, should be avoided because of their large renal osmotic load 1
D5W as the Appropriate Treatment
- D5W (5% dextrose in water) is recommended as the primary fluid for free water replacement in patients with hypernatremia because it delivers no renal osmotic load 1, 2
- Application of D5W at maintenance rate will result in a slow decrease in plasma osmolality, which is the desired effect 1
- The initial rate of fluid administration should be based on physiological demand: routine maintenance rate is 25-30 mL/kg/24h in adults 1
Correction Rate Guidelines
- The rate of sodium reduction should be 10-15 mmol/L per 24 hours to avoid complications 2
- Correction rates faster than 48-72 hours for severe hypernatremia have been associated with increased risk of pontine myelinolysis 2
- Too rapid correction of hypernatremia can lead to cerebral edema 3
Monitoring Plan
- Recheck serum sodium every 4-6 hours initially to ensure correction does not exceed 10-15 mmol/L per 24 hours 2
- Monitor for neurological symptoms during correction 4
- Calculate the water deficit to guide total fluid replacement needs over 48-72 hours 3
Critical Safety Considerations
- Continuing normal saline in a patient with sodium 153 mEq/L will exacerbate hypernatremia, particularly if the patient has any degree of renal concentrating defect 1
- Extreme hypernatremia can cause fatal arrhythmias including QT prolongation and ventricular tachycardia 4
- The proposed rate of 75 mL/hr appears reasonable for gradual correction, but should be adjusted based on the patient's weight and calculated water deficit 1