Internal Medicine
Internal Medicine is the integrating domain of the CPSP IMM paper: it tests whether you can move from a common adult presentation to a prioritized differential, a safe immediate plan, and evidence-based definitive management. Questions often cross subspecialty boundaries, so think in systems rather than labels.
Core rules
- Resuscitate first: ABCDE, oxygen target 94–98% (88–92% in COPD), IV access, and early senior help.
- Sepsis: measure lactate, take cultures before antibiotics only if this causes no delay, give broad-spectrum antibiotics within 1 hour in septic shock, and 30 mL/kg crystalloid for hypotension or lactate ≥4 mmol/L.
- Acid–base: calculate anion gap (Na − [Cl + HCO3]); if raised, check delta gap/delta ratio. Winter formula: expected pCO2 = 1.5 × HCO3 + 8 ± 2.
- Hyponatremia: assess volume status, urine osmolality and urine sodium before treatment. Symptomatic or severe: 3% saline; correct by ≤8–10 mmol/L in 24 hours.
- VTE: use a validated score plus age-adjusted D-dimer; direct oral anticoagulants are first-line for most uncomplicated cases.
- Transfusion: restrictive threshold Hb <7 g/dL (<8 g/dL in ACS or active bleeding).
Worked example
A 68-year-old man is confused, BP 88/50, HR 118, glucose 14 mmol/L, Na 128 mmol/L, lactate 3.2 mmol/L. Do not anchor on hyperglycemia. This is possible sepsis: obtain cultures, give antibiotics and 30 mL/kg crystalloid, reassess perfusion, check urine output and renal function. The hyponatremia is likely hyperglycemic translocation; correct sodium only after glucose falls, and avoid rapid hypertonic saline unless seizures occur. Look for a source (chest, urine, skin) and review medications.
Traps
- Treating the glucose and missing shock.
- Correcting sodium before glucose or exceeding 10 mmol/L/day.
- Using the wrong anion gap formula or ignoring a mixed disorder.
- Delaying antibiotics for investigations in unstable patients.
- Transfusing to a normal hemoglobin instead of a restrictive threshold.