When should a lactate (lactic acid) level be ordered?

From the Guidelines

Lactic acid tests should be ordered in scenarios where there is a suspicion of tissue hypoperfusion, such as sepsis, shock, or severe hypoxemia, as elevated lactate levels are associated with worse outcomes and can guide resuscitation efforts. The following are reasons when a lactic acid test should be ordered:

• Suspected sepsis or severe infection, as elevated lactate levels can indicate tissue hypoperfusion and are part of sepsis diagnostic criteria 1
• Assessing shock of any etiology (cardiogenic, hypovolemic, or distributive) to evaluate tissue perfusion and guide resuscitation efforts
• Patients with symptoms of severe hypoxemia, significant trauma, seizures, or severe exertion may require lactate measurement to assess oxygen debt
• Certain medications like metformin, antiretrovirals, and propofol can cause lactic acidosis as a side effect, necessitating monitoring 1
• Patients with liver disease may need lactate testing since the liver normally clears lactate, and impaired function can lead to accumulation
• Diabetic ketoacidosis, carbon monoxide poisoning, and certain inherited metabolic disorders also warrant lactate measurement
• Serial lactate measurements are particularly useful in critically ill patients to monitor treatment response, as decreasing levels generally indicate improving tissue perfusion 1
• Lactate-guided resuscitation has been shown to reduce mortality in patients with septic shock, with a significant reduction in mortality seen in lactate-guided resuscitation compared to resuscitation without lactate monitoring 1 Guiding resuscitation to normalize lactate in patients with elevated lactate levels as a marker of tissue hypoperfusion is a weak recommendation, but with low quality of evidence, it is still considered beneficial in improving patient outcomes 1.

From the Research

Reasons to Order Lactic Acid

• Lactic acidosis is a common condition in critically ill patients, and elevated lactate levels are associated with significant morbidity and mortality 2, 3, 4
• Measurement of serum lactate is important for diagnosis, monitoring, and prognostication in acute and intensive care settings 2, 3, 4
• Lactic acidosis can be caused by various factors, including:
  • Tissue hypoxia and anaerobic glycolysis 2, 5, 4
  • Increased production of lactate due to underlying conditions such as sepsis, shock, or cancer 2, 5, 6
  • Decreased removal of lactate due to liver or kidney dysfunction 6
• Type B lactic acidosis should be considered in patients with persistently elevated lactate without evidence of inadequate oxygen delivery 5
• Lactate measurement can help identify patients with lactic acidosis who may require specific treatment, such as addressing the underlying cause of the acidosis 2, 3, 4

Clinical Implications

• Elevated lactate levels are associated with poor outcomes, including increased mortality 2, 3, 4
• Serial lactate measurements can help monitor the effectiveness of treatment and guide clinical decision-making 2, 3, 4
• Lactate measurement can help differentiate between different types of lactic acidosis, such as type A (due to tissue hypoxia) and type B (due to other causes) 5, 6