What is a typical ABG pattern in methanol poisoning?

• A. High anion gap metabolic acidosis (often with severe acidemia)
• B. Respiratory alkalosis
• C. Normal ABG
• D. Metabolic alkalosis

Answer: (A)

Methanol poisoning leads to accumulation of formic acid, a strong organic acid, which drives a high anion gap metabolic acidosis. In arterial blood gas terms, you’ll see a low pH with a reduced bicarbonate and an elevated anion gap, often with a strong ventilatory response that lowers the CO2 (compensated by hyperventilation). This creates a severely acidemic state, which is the hallmark pattern for methanol toxicity.

Other patterns don’t fit: respiratory alkalosis would show low CO2 with a high pH and no metabolic acidosis; normal ABG means no disturbance; metabolic alkalosis would raise bicarbonate and pH.