A suspected aspirin overdose presents with which acid-base disturbance?

A suspected aspirin overdose presents with which acid-base disturbance?

• A. Metabolic alkalosis
• B. Respiratory alkalosis only
• C. Mixed respiratory alkalosis and metabolic acidosis
• D. No disturbance

Answer: (C)

Aspirin (salicylate) poisoning causes two opposing acid-base effects at the same time. Initially it stimulates the respiratory center, leading to rapid breathing and blowing off CO2, which creates a respiratory alkalosis. At the same time, it impairs cellular energy production and promotes the formation of organic acids, producing a metabolic acidosis with an elevated anion gap. As the toxicity progresses, both processes persist, so the patient often presents with a mixed picture: low PaCO2 from hyperventilation and low bicarbonate from metabolic acidosis, frequently with a near-normal pH. That’s why the best description is a combination of respiratory alkalosis and metabolic acidosis.

Aspirin (salicylate) poisoning causes two opposing acid-base effects at the same time. Initially it stimulates the respiratory center, leading to rapid breathing and blowing off CO2, which creates a respiratory alkalosis. At the same time, it impairs cellular energy production and promotes the formation of organic acids, producing a metabolic acidosis with an elevated anion gap. As the toxicity progresses, both processes persist, so the patient often presents with a mixed picture: low PaCO2 from hyperventilation and low bicarbonate from metabolic acidosis, frequently with a near-normal pH. That’s why the best description is a combination of respiratory alkalosis and metabolic acidosis.