19/09/2025
■■Ddx of ⬆️ lactate
🧠 Understanding Lactate:
■Overview:
Lactate, a product of anaerobic glycolysis, serves as a crucial indicator of either Type A (oxygen delivery issues) or Type B (altered metabolism) causes. It’s predominantly cleared by the liver, and its accumulation leads to lactic acidosis.
■Lactate Levels:
•Normal Range: 0.6-1.8 mmol/L
•Hyperlactatemia: 2-5 mmol/L
•Severe Lactic Acidosis: > 5 mmol/L
•Critical Threshold: Lactate > 8 mmol/L indicates high mortality risk.
■Physiology:
Lactate is produced at approximately 20 mmols/kg/day, entering circulation and undergoing hepatic and renal metabolism (Cori cycle). All tissues can produce lactate under anaerobic conditions, with significant contributions from skin, red cells, brain, muscle, and gut.
■Lactate Metabolism:
•Primarily metabolized in the liver (60%) and kidney (30%).
•The heart can also utilize lactate for ATP production.
•Converted into glucose (50%) or CO2 and water (50%) without net acid accumulation.
■Pathophysiology:
Lactic acidosis may arise from excessive tissue lactate production or impaired hepatic clearance, often seen in conditions like sepsis and ARDS. It is crucial to differentiate between Type A (inadequate oxygen delivery) and Type B (metabolic issues).
Type A
▪︎Causes:
•Anaerobic muscular activity (e.g., sprinting, convulsions)
•Tissue hypoperfusion (e.g., shock, cardiac arrest)
•Reduced oxygen delivery/utilization (e.g., hypoxaemia, CO poisoning)
Type B
▪︎Causes:
•B1: Underlying diseases like leukemia, thiamine deficiency, or hepatic failure.
•B2: Drugs and toxins including beta-agonists, methanol, or biguanides.
•B3: Inborn errors of metabolism.
Diagnosis:
Measuring plasma lactate levels is key, followed by identifying and treating the underlying cause. D-lactate, produced by intestinal bacteria, is a noteworthy isomer not detected by standard assays.
Management:
•Address the root cause and restore adequate oxygen delivery.
•Use bicarbonate cautiously, as studies show minimal benefit in correcting lactic acidosis.
•Dialysis/haemofiltration can be a useful marker of disease progression, though not a primary treatment.
Evidence:
•Elevated lactate levels correlate with higher mortality.
•Lactate clearance is a strong prognostic marker, non-inferior to ScVO2 monitoring in guiding therapy.
Practical Tips for Sample Collection:
•Venous samples are typically equivalent to arterial ones in clinical settings.
•No need to remove the tourniquet unless venous access is prolonged.
•Store samples properly to ensure accuracy, and repeat measurements if elevated after 4 hours or sooner with a change in condition.
Understanding and managing lactate is vital for improving patient outcomes, especially in critical care settings. Let’s continue to deepen our knowledge and refine our practices to better serve our patients.
