The ABG pH 7.51, PO2 90, PCO2 20, HCO3 24 indicates early-stage poisoning most consistent with

• A. Aspirin overdose
• B. Gabapentin toxicity
• C. Wood alcohol poisoning
• D. Iron poisoning

Answer: (A)

This ABG shows a primary respiratory alkalosis, which is classic for early salicylate (aspirin) poisoning. The high pH ( alkalemia) and the low PCO2 indicate the medullary respiratory center is being stimulated, causing hyperventilation and blowing off CO2. The bicarbonate is still normal, meaning metabolic compensation hasn’t developed yet, which fits an early stage rather than a later mixed or metabolic problem. As salicylate toxicity progresses, metabolic acidosis with an elevated anion gap often appears, but at this stage the pattern points to aspirin overdose. Other toxins typically produce different patterns: gabapentin toxicity tends toward CNS depression with hypoventilation and acidosis; wood alcohol poisoning causes metabolic acidosis with an elevated anion gap and visual symptoms; iron poisoning progresses from GI symptoms to metabolic acidosis.