Clearance is the removal of a substance from blood, expressed as a volume (milliliters) over time (minutes). However, changes in lactate levels are the sum of ongoing production and removal from the blood by excretion (e.g., urine, sweat) and its metabolism (e.g., uptake by cells as a direct source of energy, conversion to glucose by the liver). To talk about “lactate clearance” when actually describing a decrease in blood level is wrong and misleading. Following the review of 96 studies, Vincent et al. concluded that given recent evidence, measurements every 1–2 h would give clinically relevant data about the decrease in lactate levels.

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