Does using D5 (Dextrose 5%) lactated Ringer's solution worsen hyponatremia?

D5 Lactated Ringer's Solution Can Worsen Hyponatremia

D5 lactated Ringer's solution should be avoided in patients with hyponatremia as it is hypotonic and can worsen hyponatremic states. 1

Understanding Fluid Tonicity and Hyponatremia Risk

Fluid tonicity is critical when considering the risk of hyponatremia:

• D5 lactated Ringer's solution:

  • Sodium concentration: 130 mEq/L
  • Osmolarity: 273 mOsm/L
  • Classified as a hypotonic solution when dextrose is metabolized 1
  • Contains 5% dextrose which is rapidly metabolized, leaving free water

• Isotonic solutions (for comparison):

  • Plasma sodium: 135-145 mEq/L
  • Plasma osmolarity: 308 mOsm/L
  • Examples: 0.9% NaCl (154 mEq/L sodium) or PlasmaLyte (140 mEq/L sodium) 1

Mechanism of Worsening Hyponatremia

When D5 lactated Ringer's is administered:

1. The 5% dextrose is rapidly metabolized
2. This leaves free water that dilutes serum sodium
3. The sodium content (130 mEq/L) is already below physiologic levels
4. In patients with impaired free water excretion (common in hospitalized patients), this leads to worsening hyponatremia

Clinical Evidence and Guidelines

The American Academy of Pediatrics clinical practice guideline (2018) states:

• Isotonic solutions with sodium concentrations similar to plasma (135-144 mEq/L) are recommended for maintenance IV fluids 1
• Lactated Ringer's solution (sodium 130 mEq/L) is classified as "slightly hypotonic" 1
• When combined with 5% dextrose, the solution becomes more hypotonic after dextrose metabolism

The European guideline on management of major bleeding and coagulopathy following trauma (2023) specifically recommends:

• "Hypotonic solutions such as Ringer's lactate be avoided in patients with severe head trauma" 1
• This recommendation is based on the risk of fluid shifts into damaged cerebral tissue

High-Risk Populations

Certain patients are at particularly high risk for developing hyponatremia with hypotonic fluids:

• Patients with conditions causing arginine vasopressin (AVP) excess 1, 2:

  • Pain, nausea, stress
  • Postoperative state
  • Hypovolemia
  • Pulmonary and CNS disorders (pneumonia, meningitis)
  • Medications that stimulate AVP release

• Patients with syndrome of inappropriate antidiuresis (SIAD) 2

Clinical Consequences of Hyponatremia

Hyponatremia can lead to serious complications:

• Even mild hyponatremia (131-135 mmol/L) increases risk of complications in cirrhotic patients 2
• Moderate hyponatremia (120-125 mEq/L): nausea, headache, confusion 2
• Severe hyponatremia (<120 mEq/L): seizures, coma, respiratory arrest 2
• Mortality rate of 25% in patients with sodium levels <120 mEq/L 2

Alternative Fluid Choices

For patients requiring IV fluids who are at risk for hyponatremia:

• Use truly isotonic solutions:

  • 0.9% NaCl (sodium 154 mEq/L) 1
  • PlasmaLyte (sodium 140 mEq/L) 1

• If dextrose is needed, consider:

  • D5 0.9% NaCl rather than D5 lactated Ringer's 1

Monitoring Recommendations

For patients receiving IV fluids:

• Monitor serum sodium levels every 2-4 hours initially during treatment 2
• Target correction rate for chronic hyponatremia: 4-6 mEq/L per 24-hour period, not exceeding 8 mEq/L per 24 hours 2
• Watch for signs of hyponatremia: headache, nausea, confusion, lethargy, seizures 1

Key Pitfall to Avoid

A common clinical error is assuming that lactated Ringer's solution is isotonic. While the base solution is only slightly hypotonic (130 mEq/L sodium), the addition of 5% dextrose makes it functionally hypotonic once the dextrose is metabolized, potentially worsening hyponatremia in susceptible patients.