A 34-year-old man arrives at the emergency room with new-onset confusion and lethargy. Laboratory studies are obtained, including an arterial blood gas. The graph below depicts the changes in his blood gas parameters. Point A represents the patient's physiologic baseline, and point B represents his state upon arrival at the emergency department. Which of the following is the most likely diagnosis?

Question

A 34-year-old man arrives at the emergency room with new-onset confusion and lethargy. Laboratory studies are obtained, including an arterial blood gas. The graph below depicts the changes in his blood gas parameters. Point A represents the patient's physiologic baseline, and point B represents his state upon arrival at the emergency department.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

Eductional Objective: Point B on the graph above indicates that this patient has a lower pH than his baseline physiologic state, indicating acidosis. The next step is to figure out whether the acidosis is caused by a metabolic or respiratory problem. Acidosis can occur as a result of either a decrease in serum bicarbonate (metabolic) or an increase in PaCO₂ (respiratory). This patient has low serum bicarbonate, indicating that metabolic acidosis is the primary problem. The lower PaCO₂ represents respiratory compensation (via hyperventilation to expel CO₂) to aid in pH normalization.

A 34-Year-Old Man Arrives at the Emergency Room with New-Onset