"How would you determine if this patient has a pure or mixed high anion gap metabolic acidosis (HAGMA)?"
This was the question posed to me and my co-medical students by my attending (who I had met 3 minutes earlier) in front of two senior residents, two interns, and a nurse at 7:30 a.m. this March, during particularly hectic inpatient medicine morning rounds. Having taken the USMLE Step 1 exam just a few months prior, I should have been up to speed on my nephrology and answered quickly. Yet, frozen I stood. Perspiring in my embroidered medical school Patagonia jacket and feeling the windowless walls closing in on me, I realized I had just had my first introduction to a time-honored tradition of medical education: pimping.
The answer to the question would come readily to most attending internists: calculate the delta-delta, which in this case revealed a mixed rather than pure HAGMA. For me, however, the significance of the moment lay less in the calculation than in the discomfort of not knowing it. That emotional jolt drove me to study the concept with an intensity no textbook passage or Anki card had elicited (as the Yerkes-Dodson law predicts). Nephrology may never feel intuitive to me, but I am unlikely to forget the delta-delta again.
