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Acute respiratory acidosis — FRCA Primary MCQ

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HardPhysiologyAcute respiratory acidosisFRCA Primary

In recovery, an opioid-treated patient has pH 7.25, PaCO2 9.0 kPa and bicarbonate 26 mmol/L. There is no known chronic lung disease. Which interpretation is best?

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Correct answer: B — Acute respiratory acidosis

The raised PaCO2 with low pH indicates respiratory acidosis, and the near-normal bicarbonate suggests it is acute rather than chronically compensated. Chronic respiratory acidosis would have a more elevated bicarbonate due to renal retention. Metabolic disorders would be led by a primary bicarbonate change. Opioid-induced hypoventilation is a common peri-operative cause.

Reference: Ganong Review of Medical Physiology; West Respiratory Physiology