Will D5W (Dextrose 5% in Water) lower serum sodium levels?

Will D5W Lower Serum Sodium?

Yes, D5W (Dextrose 5% in Water) will lower serum sodium levels because it is a hypotonic solution that provides free water without sodium, effectively diluting serum sodium concentration.

Mechanism of Action

D5W functions as free water once the dextrose is rapidly metabolized upon infusion 1. The solution contains no sodium (0 mEq/L) compared to normal plasma sodium of 135-145 mEq/L 2. When administered, the dextrose component is quickly oxidized to carbon dioxide and water, leaving behind hypotonic fluid that distributes across body compartments and dilutes serum sodium 1.

Clinical Evidence for Sodium Reduction

Research demonstrates that D5W effectively lowers serum sodium:

• In ICU patients with hypernatremia, parenteral D5W decreased serum sodium by an estimated mean of -2.25 mEq/L per liter of fluid administered 3
• D5W was slightly more effective than enteral free water for lowering serum sodium in critically ill patients with hypernatremia 3
• D5W administered prefilter in CRRT patients successfully prevented overcorrection of hyponatremia by providing calculated free water 4

Clinical Applications

D5W is specifically used to lower serum sodium in several contexts:

For Hypernatremia Correction

• D5W is recommended as the primary fluid for free water replacement in patients with hypernatremia 5
• It provides sodium-free water to correct elevated serum sodium levels 6

For Preventing Overcorrection in Hyponatremia

• When hyponatremia has been overcorrected too rapidly (>8 mmol/L in 24 hours), immediately switching to D5W can relower sodium levels to prevent osmotic demyelination syndrome 5
• D5W is used to deliberately slow sodium correction rates in high-risk patients 4

In Special Populations

• In nephrogenic diabetes insipidus (NDI), D5W matches the hypotonic urinary losses (very low sodium concentration) and is appropriate for fluid replacement 2
• Patients with renal concentrating defects require hypotonic fluid replacement like D5W when they develop hypernatremia 5

Important Safety Considerations

Critical warnings about D5W administration:

• Never administer D5W as a bolus due to the risk of rapid decrease in serum sodium, which can cause brain edema 2
• The rate of sodium correction should not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 2, 5
• D5W should be given via controlled infusion with frequent sodium monitoring 2

Comparison to Other Fluids

D5W is classified as a hypotonic solution with an osmolarity of approximately 252 mOsm/L (excluding dextrose, which is rapidly metabolized) 2. This contrasts with:

• Normal saline (0.9% NaCl): 154 mEq/L sodium, osmolarity 308 mOsm/L 2
• D5 0.45% NaCl: 77 mEq/L sodium, osmolarity 154 mOsm/L 2

When NOT to Use D5W

D5W is contraindicated or inappropriate in:

• Hypovolemic shock requiring acute fluid resuscitation (use isotonic fluids instead) 2
• Patients with existing hyponatremia who need sodium correction (will worsen hyponatremia) 2
• Hyperglycemic patients on insulin infusions (consider sterile water via central line instead) 6

Monitoring Requirements

When using D5W to lower serum sodium:

• Monitor serum sodium levels every 2-4 hours during active correction 5
• Track neurological status closely 2
• Maintain fluid balance records 2
• Watch for signs of too-rapid correction (dysarthria, dysphagia, oculomotor dysfunction) 5