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Hyperventilation from salicylate poisoning — SCE Acute Medicine MCQ

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HardAcute Respiratory PresentationsHyperventilation from salicylate poisoningSCE Acute Medicine

A 31-year-old woman is assessed on the acute medical unit. She has tinnitus, vomiting and tachypnoea after an overdose. ABG shows pH 7.48 with low PaCO2, bicarbonate 17 mmol/L and raised anion gap. Initial assessment includes relevant observations, bedside tests and urgent blood results. What is the most likely underlying cause/mechanism?

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Correct answer: B — Mixed respiratory alkalosis and high anion gap metabolic acidosis

Mixed respiratory alkalosis and high anion gap metabolic acidosis is the best answer because salicylates stimulate the respiratory centre and uncouple oxidative phosphorylation, producing the characteristic mixed acid-base disturbance. Acute right ventricular pressure overload is plausible, but it is less appropriate for the physiology or timing described in this stem. The other distractors either fit a neighbouring presentation, delay definitive treatment, or miss the key immediate risk. Clinical pearl: A near-normal pH in salicylate poisoning can conceal severe toxicity.

Reference: Toxbase; BNF