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Persistent Lactic Acidosis Sepsis Differential — FRCA Final MCQ

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HardIntensive Care MedicinePersistent Lactic Acidosis Sepsis DifferentialFRCA Final

A 55-year-old man (ASA III) in ICU with septic shock has persistent lactic acidosis (lactate 7.5 mmol/L) despite adequate MAP, cardiac output, and ScvO2. All standard sepsis management has been optimised. What should be considered as a cause of persistent lactic acidosis in this context?

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Correct answer: C — Persistent lactic acidosis always indicates ongoing tissue hypoxia only

Persistent lactic acidosis in sepsis despite apparently adequate oxygen delivery has multiple potential causes beyond simple tissue hypoxia: (1) Type B lactic acidosis: thiamine (vitamin B1) deficiency impairs pyruvate dehydrogenase, preventing pyruvate from entering the TCA cycle (common in malnourished/alcoholic ICU patients – give thiamine 200-300 mg IV), (2) impaired hepatic lactate clearance (liver receives 60% of lactate for gluconeogenesis), (3) mesenteric ischaemia (occult abdominal pathology), (4) adrenaline-driven aerobic glycolysis, (5) beta-2 agonist use.

Reference: SSC – 2021 – Sepsis guidelines; RCOA – 2023 – ICM acid-base physiology