Internal Medicine
Core framework
Internal medicine questions reward a disciplined approach: identify the syndrome, generate a short differential, then let the single most discriminating finding choose the answer. Master the classic presentations of ischemic heart disease, heart failure, COPD versus asthma, pneumonia, stroke localization, diabetes and its acute complications, thyroid disease, acute kidney injury versus chronic kidney disease, acid–base disorders, and the common rheumatologic and hematologic syndromes (anemia patterns, coagulopathies, vasculitis).
Concepts you must own
Acid–base interpretation: check pH, then primary disorder, then compensation, then the anion gap and delta ratio. Rhythm strip interpretation: rate, rhythm, axis, intervals, P–QRS relationship. Chest radiograph and ECG pattern recognition. Fluid and electrolyte correction rates (sodium, potassium, calcium).
Traps
- Compensation versus mixed disorder: if measured compensation is outside the expected range, call it mixed.
- Anion gap: correct for albumin; a normal gap does not exclude a raised lactate.
- Acute versus chronic: anemia, kidney disease, and hyponatremia all hinge on chronicity and volume status.
- "Most likely" versus "most appropriate next step": the latter is often a bedside test, not definitive therapy.
Worked rule of thumb
For metabolic acidosis, calculate the anion gap (Na − [Cl + HCO3]). If raised, use the delta ratio = (measured gap − 12)/(24 − HCO3). A ratio near 1 suggests pure high-gap acidosis; well below 1 suggests a coexisting normal-gap acidosis; well above 1 suggests coexisting metabolic alkalosis. Apply this before reading the answer options.