American Board of Internal Medicine (ABIM) Certification Practice Exam

For suspected ethylene glycol or methanol ingestion, intravenous sodium bicarbonate therapy is advised when the blood pH is below what value?

1. 7.10

2. 7.20

3. 7.30

4. 7.40

The correct answer is: 7.30

Intravenous sodium bicarbonate therapy is indicated in cases of suspected ethylene glycol or methanol ingestion when the blood pH falls below a certain threshold. When the pH drops below 7.30, it indicates a significant metabolic acidosis typically associated with these toxic alcohol ingestions. Administering sodium bicarbonate helps to raise the blood pH by buffering excess acids in the body, which can be crucial for stabilizing the patient and preventing further metabolic complications. In the context of ethylene glycol and methanol poisoning, metabolic acidosis occurs due to the accumulation of organic acids from the metabolism of these substances. The decision to initiate sodium bicarbonate therapy at a pH of less than 7.30 leaves an appropriate margin for intervention to manage acidemia effectively. This threshold is generally supported by clinical guidelines that emphasize the importance of addressing severe acidosis in toxicological emergencies.