Does Lactated Ringer's (LR) increase serum lactate levels?

Does Lactated Ringer's Increase Serum Lactate?

Lactated Ringer's solution causes a modest, clinically insignificant increase in serum lactate levels (approximately 0.9-1.0 mmol/L) that does not interfere with clinical interpretation of lactate as a marker of tissue hypoperfusion or shock. 1

Evidence from Clinical Studies

Magnitude of Lactate Increase

• A randomized controlled trial in healthy volunteers receiving 30 mL/kg of LR demonstrated a mean serum lactate increase of 0.93 mmol/L (95% CI 0.42-1.44 mmol/L), which remained well below the pathological threshold of 2 mmol/L. 1

• Importantly, normal saline also caused a small lactate increase of 0.37 mmol/L in the same study, and there was no statistically significant difference between LR and NS groups (p = 0.2). 1

• An earlier prospective, randomized, double-blind study found no clinically or statistically significant differences in lactate values between subjects receiving LR versus normal saline when 1 L was infused over 1 hour, with lactate values never exceeding 2 mmol/L. 2

Clinical Context in Hemorrhagic Shock

• In a swine model of uncontrolled hemorrhagic shock, LR resuscitation resulted in higher serum lactate levels (4.7 ± 2.2 mmol/L) compared to NS (1.7 ± 1.7 mmol/L, p < 0.01), but this elevation was not associated with acidosis—the LR group actually had better pH (7.45 ± 0.06) than the NS group (7.28 ± 0.12). 3

• This paradoxical finding demonstrates that lactate elevation from LR represents substrate delivery rather than tissue hypoperfusion, as the LR group showed superior outcomes with less fluid requirement and better coagulation parameters. 3

Metabolic Fate of Infused Lactate

• Both L-lactate and racemic lactate (the form in standard LR) are metabolized at nearly identical rates, with both effectively increasing buffering capacity without causing metabolic acidosis. 4

• The lactate in LR is rapidly metabolized by the liver to bicarbonate, providing an alkalinizing effect rather than contributing to acidosis. 4

Clinical Interpretation Algorithm

When evaluating elevated lactate in patients receiving LR:

1. If lactate is <4 mmol/L and pH is normal or alkalotic: The elevation is likely from LR infusion and does not indicate tissue hypoperfusion. 1, 3

2. If lactate is >4 mmol/L with metabolic acidosis: This represents true tissue hypoperfusion regardless of LR administration, as the lactate from LR should not cause acidosis. 3

3. If lactate is rising despite adequate resuscitation: Do not attribute this to LR administration—investigate for ongoing shock, inadequate source control, or other causes of elevated lactate (liver failure, medications, seizures). 5

Critical Pitfalls to Avoid

• Do not disregard elevated lactate concentrations in patients receiving rapid LR infusion—clinically significant lactate elevation indicates tissue hypoperfusion, not the infused lactate. 2

• Avoid drawing lactate samples from the same IV line used for LR infusion, as inadequate catheter clearance can falsely elevate lactate measurements. 2

• Remember that lactate-guided resuscitation improves mortality in septic shock (RR 0.67; 95% CI 0.53-0.84), so trending lactate remains valuable even when using LR. 5

Contraindications for LR Use

• Severe traumatic brain injury or head trauma: LR is hypotonic (273-277 mOsm/L vs plasma 275-295 mOsm/L) and can worsen cerebral edema—use 0.9% saline instead. 6

• Rhabdomyolysis or crush syndrome: The potassium content (4 mmol/L) poses additional risk in these conditions. 6