From the Research
The main difference between measuring lactic acid in plasma and whole blood is that plasma measurements typically yield lower values than whole blood measurements by approximately 7-40%. This distinction is crucial because treatment decisions for conditions like lactic acidosis depend on accurate interpretation of values relative to the appropriate reference range for the specific testing method used 1.
Key Differences
- Plasma lactic acid testing requires immediate separation of blood cells from plasma through centrifugation to prevent ongoing glycolysis by red blood cells, which artificially increases lactic acid levels.
- Whole blood measurements, while more convenient as they don't require this separation step, include lactic acid from both plasma and blood cells, resulting in higher values.
- Temperature also affects these measurements differently - whole blood samples should be placed on ice to minimize continued lactate production, while plasma samples require prompt processing.
Clinical Implications
- Clinicians must be aware of these differences when interpreting results, as reference ranges differ between the two methods.
- Most modern point-of-care testing uses whole blood, while traditional laboratory testing often uses plasma.
- The severity of lactic acidosis in critically ill patients correlates with overall oxygen debt and survival, and lactate determinations may be useful as an ongoing monitor of perfusion as resuscitation proceeds 2.
- Therapy of critically ill patients with lactic acidosis is designed to maximize oxygen delivery in order to reduce tissue hypoxia by increasing cardiac index, while maintaining hemoglobin concentration 2.