Can Lactated Ringer's (LR) solution increase serum sodium levels?

Lactated Ringer's Solution Can Increase Serum Sodium in Hypovolemic Hyponatremia

Yes, Lactated Ringer's (LR) solution can increase serum sodium levels, particularly in patients with hypovolemic hyponatremia. While LR is slightly hypotonic compared to plasma, its sodium content (130 mEq/L) is sufficient to raise serum sodium in specific clinical scenarios.

Sodium Content and Tonicity of LR

• LR contains 130 mEq/L of sodium, making it slightly hypotonic with an osmolarity of 273 mOsm/L compared to plasma (approximately 308 mOsm/L) 1
• Despite being slightly hypotonic, LR is recommended as a preferred crystalloid for fluid resuscitation in hypovolemic hyponatremia 1

Clinical Scenarios Where LR Raises Sodium

Hypovolemic Hyponatremia

• For hypovolemic hyponatremia, treatment guidelines specifically recommend LR as a preferred crystalloid solution for fluid resuscitation 1
• In this setting, LR effectively increases serum sodium by correcting the volume deficit that triggered water retention and dilutional hyponatremia 1

Specialized LR Formulations

• Hypertonic lactated Ringer's solution (HLS) with sodium concentration of 213 mEq/L has been shown to prevent hyponatremia and hypoosmolarity in patients undergoing transurethral resection of the prostate 2

Comparison to Other Solutions

• Normal saline (0.9% NaCl) contains 154 mEq/L of sodium and has an osmolarity of 308 mOsm/L, making it isotonic 1
• In healthy volunteers, LR caused a small, transient decrease in serum osmolality (4±3 mOsm/kg) that returned to baseline within an hour, while normal saline did not affect osmolality 3
• However, in patients with hypovolemic states, the volume expansion effect of LR can outweigh its slightly hypotonic nature, resulting in a net increase in serum sodium 1

Special Considerations

Patients with Liver Disease

• In patients with cirrhosis and hyponatremia, LR is specifically recommended for treating hypovolemic hyponatremia 1
• The American Association for the Study of Liver Diseases recommends LR as the preferred crystalloid for fluid resuscitation in hypovolemic hyponatremia in cirrhotic patients 1

Patients with Head Injury

• LR should be avoided in patients with severe head trauma due to its slightly hypotonic nature 1
• In children with severe head injury, hypertonic saline was superior to LR, with fewer interventions needed to control intracranial pressure 4

Lactate Content Considerations

• The lactate in LR does not significantly raise serum lactate levels compared to normal saline 5
• A randomized controlled trial in healthy volunteers showed that after a 30 mL/kg bolus of LR, serum lactate increased by only 0.93 mmol/L, which was not statistically different from the increase seen with normal saline 5

Clinical Decision Algorithm

1. For hypovolemic hyponatremia: LR is appropriate and can help raise serum sodium 1
2. For euvolemic or hypervolemic hyponatremia: LR is not recommended; fluid restriction and other targeted therapies are preferred 1
3. For patients with head trauma: Avoid LR; use isotonic or hypertonic solutions instead 1, 4
4. For patients requiring large volume resuscitation: Monitor serum sodium closely, as the effect of LR on sodium levels may vary based on the patient's volume status 3

In conclusion, while LR is slightly hypotonic, it can effectively increase serum sodium levels in patients with hypovolemic hyponatremia by correcting the underlying volume deficit that triggered water retention mechanisms.