Internal Medicine: Stabilization, Pattern Recognition, and Next Best Step
Internal medicine: prioritize stabilization and pattern recognition
Start with ABCs and a focused problem representation: acutely ill vs chronic, stable vs unstable, and whether the finding is a complication of treatment. High-yield concepts include ACS, heart failure, COPD/asthma exacerbation, sepsis, diabetes emergencies, CKD and electrolytes, thyroid disease, GI bleeding, and anticoagulation. For chest pain, time-sensitive decisions hinge on ECG and troponin; for dyspnea, separate cardiac from pulmonary causes using history, exam, BNP, and imaging. In sepsis, cultures and antibiotics follow rapid resuscitation. Electrolyte questions often test the next step rather than the diagnosis: severe hyponatremia with seizures needs hypertonic saline, while asymptomatic chronic hyponatremia is corrected slowly.
Traps
Do not anchor on one abnormal lab; check whether it fits the clinical picture. Distinguish anion-gap from non-gap metabolic acidosis, and calculate the delta-delta when multiple disorders coexist. Watch for drug-induced problems, such as ACE-inhibitor angioedema or NSAID-associated AKI. In heart failure, do not treat hypertension reflexively if the patient is hypoperfused.
Worked rule
For a metabolic acidosis, calculate anion gap = Na − (Cl + HCO3). If the gap is elevated, check the delta ratio: (measured AG − normal AG)/(normal HCO3 − measured HCO3). A ratio near 1 suggests pure high-gap acidosis; <1 suggests coexisting normal-gap acidosis; >2 suggests coexisting metabolic alkalosis. This prevents missing a mixed disorder.