From the Guidelines
Normal venous lactate levels typically range from 0.5 to 2.2 mmol/L (or 4.5 to 19.8 mg/dL) in healthy adults at rest. This range may vary slightly depending on the specific laboratory reference values used by different institutions. Lactate is produced during anaerobic metabolism when tissues don't receive enough oxygen, causing cells to generate energy without oxygen. The liver normally clears lactate efficiently from the bloodstream, maintaining these low levels. Elevated lactate levels (above 2.2 mmol/L) may indicate tissue hypoxia, poor perfusion, or impaired lactate clearance, which can occur in conditions like shock, sepsis, cardiac arrest, severe trauma, or liver dysfunction.
Key Points to Consider
- Lactate levels are often used in clinical settings to assess tissue perfusion and as a marker of illness severity, with levels above 4 mmol/L generally considered significantly abnormal and potentially indicating serious underlying pathology requiring urgent medical attention 1.
- The use of lactate levels as a diagnostic parameter and prognostic marker of haemorrhagic shock has been established since the 1960s, with studies showing that changes in lactate concentrations provide an early and objective evaluation of a patient’s response to therapy 1.
- Some studies have shown that the initial lactate levels were higher in non-survivors after major trauma, and that the prolonged time for normalisation of lactate levels of more than 24 hours was associated with the development of post-traumatic organ failure 1.
Clinical Implications
- Elevated lactate levels should be taken seriously and prompt further investigation and management, as they may indicate underlying tissue hypoxia or impaired perfusion 1.
- Lactate levels should be interpreted in the context of the patient's clinical presentation and other laboratory results, such as base deficit and vital signs 1.
- The use of lactate levels in conjunction with other clinical parameters, such as vital signs and base deficit, can increase the sensitivity for identifying major injury and predicting mortality in trauma patients 1.
From the Research
Normal Lactate Levels in Venous Blood
- The normal lactate range in venous blood is less than 2.3 mmol/L, as stated in the study by 2.
- Another study by 3 found that peripheral venous lactate (PVL) levels can be used to predict arterial lactate levels, with a cut-off value of 2 mmol/L having 100% sensitivity for predicting arterial hyperlactatemia.
- However, it's important to note that peripheral venous lactate levels tend to be higher than arterial lactate levels, with mean differences ranging from 0.18 mmol/L to 1.06 mmol/L, as found in the systematic review by 4.
Comparison of Arterial and Venous Lactate Levels
- The study by 5 found a strong correlation between arterial and peripheral venous lactate levels, with a correlation coefficient of 0.68 at baseline and 0.95 at the 6-hour time point.
- However, the study by 4 found that the agreement between arterial and peripheral venous lactate levels is poor in hyperlactatemia, making peripheral venous lactate an unreliable parameter to use interchangeably in the ED.
- The study by 6 found that baseline arterial lactate was higher in septic and cardiogenic shock patients than in healthy volunteers, with mean values of 3.2 +/- 2.6 mmol/L and 2.8 +/- 0.4 mmol/L, respectively, compared to 0.9 +/- 0.20 mmol/L in healthy volunteers.
Clinical Implications
- The study by 2 found that lactate concentrations within the "normal" range can be a useful prognostic indicator in septic shock, and that patients with lactate levels less than or equal to 1.4 mmol/L may benefit from vasopressin infusion.
- The study by 5 found that combining lactate levels and its clearance is a reliable predictor of mortality in sepsis, with an arterial lactate level > 3.2 mmol/L and clearance of < 20% being considered the cutoff for mortality risk.