Internal Medicine (including allied specialties)
What is tested
Medicine is the largest FMGE domain. Expect acute coronary syndrome and heart failure, asthma versus COPD, arterial blood gases, diabetes and thyroid disease, acute kidney injury, stroke and meningitis.
Core rules
- STEMI: reperfusion within 12 hours of symptom onset; primary PCI preferred, thrombolysis if PCI cannot be achieved within 120 minutes.
- Ischemic stroke: intravenous thrombolysis within 4.5 hours of onset after imaging excludes hemorrhage.
- Diabetes: fasting plasma glucose ≥126 mg/dL, 2-hour value ≥200 mg/dL on OGTT, or HbA1c ≥6.5%.
- AKI: fractional excretion of sodium <1% with urine sodium <20 mEq/L favors prerenal disease; >2% favors intrinsic renal injury.
- ABG in four steps: pH, then PaCO₂, then HCO₃⁻, then compensation. A raised anion gap metabolic acidosis suggests ketoacidosis, lactate, uremia or toxin.
Worked example
A 22-year-old with type 1 diabetes has glucose 480 mg/dL, pH 7.12, PaCO₂ 20 mmHg, HCO₃⁻ 8 mEq/L and ketonuria. Reasoning: the pH is acidemic, so the primary disorder is metabolic acidosis; the low PaCO₂ is respiratory compensation (expected PaCO₂ ≈ 1.5 × 8 + 8 = 20, so compensation is appropriate). Serum potassium may be normal or high despite total-body depletion, so potassium is replaced once it falls below 5.2 mEq/L during insulin infusion.
Traps
Giving bicarbonate routinely in DKA; withholding insulin until potassium is 'normal'; and mislabeling a compensatory respiratory alkalosis as a second primary disorder.