Effect of D5 Normal Saline on Sodium Levels
D5 normal saline (5% dextrose in 0.9% sodium chloride) will increase serum sodium levels because it delivers 154 mmol/L of sodium while the dextrose component is rapidly metabolized, leaving behind the sodium load.
Mechanism of Sodium Effect
The key to understanding D5 normal saline's effect lies in its composition and metabolism:
- Normal saline contains 154 mmol/L of sodium, which is delivered regardless of the dextrose component 1
- The dextrose (5%) is rapidly metabolized after infusion, effectively leaving behind isotonic saline 2
- This results in a net positive sodium load to the patient, particularly when used in large volumes 1
Clinical Evidence for Hypernatremia Risk
Using normal saline as a diluent or maintenance fluid significantly increases the risk of hypernatremia:
- In ICU patients, normal saline used to dilute drugs and keep catheters open was identified as a major and preventable source of ICU-acquired hypernatremia (serum Na+ >150 mmol/L) 1
- When the default diluent was changed from D5W to saline in critically ill patients, the incidence of hypernatremia increased from 14.6% to 27.3% (adjusted OR 2.43,95% CI 1.54-3.82) 2
- Hyperchloremia also increased significantly from 20.4% to 36.9% (adjusted OR 2.09,95% CI 1.31-3.34) when saline was used instead of D5W 2
Comparison with Alternative Fluids
The sodium-raising effect becomes clearer when comparing different solutions:
- D5W alone does not increase sodium because it contains no sodium chloride 2
- Half-normal saline (0.45% NaCl) in DKA management resulted in decreased corrected serum sodium compared to normal saline 3
- Normal saline consistently produces higher serum sodium levels than lower-sodium alternatives 3
Clinical Implications and Monitoring
Key considerations when using D5 normal saline:
- Drug diluents can account for up to 21.4% of total infusion volume in ICU patients, making this a substantial sodium source 2
- Monitor serum sodium closely, especially in patients receiving multiple infusions or those at risk for fluid/electrolyte imbalances 1
- The hyperchloremic effect can lead to non-anion gap metabolic acidosis, potentially prolonging insulin infusion duration and ICU length of stay 3
Common Pitfalls to Avoid
- Do not assume the dextrose component "dilutes" the sodium effect - the dextrose is metabolized, leaving the full sodium load 2
- Avoid using normal saline-based solutions when trying to prevent hypernatremia - consider D5W or lower sodium alternatives for drug dilution 1
- In patients with existing hypernatremia or at risk for sodium overload, dissolving drugs in D5W may partially prevent potentially harmful sodium loading 1