Internal Medicine: Structured Reasoning at the Bedside
What you must know
Own a systematic approach to the major adult presentations: chest pain, breathlessness, oedema, fever, cough, weight loss, diarrhoea, jaundice, altered consciousness and raised blood pressure. For each, know the discriminating bedside findings and the confirmatory test. Be fluent with the definitions of hypertension, the classification of asthma and COPD, the diagnostic criteria for diabetic ketoacidosis, and the practical approach to anaemia and tuberculosis.
Classic traps
- DKA versus hyperosmolar hyperglycaemic state. DKA means ketosis with acidosis and glucose usually 15-30 mmol/L. HHS means glucose often above 30 mmol/L, high osmolality and minimal ketones.
- Pneumonia that does not resolve should prompt sputum testing for AFB, not another course of antibiotics.
- Heart failure versus COPD. Crackles, raised JVP, a third heart sound and a displaced apex favour a cardiac cause; a hyperinflated chest with rhonchi favours COPD.
- Total body potassium is depleted in DKA even when the serum potassium is normal or high, because insulin drives potassium into cells.
Rule of thumb
In DKA give isotonic saline, check potassium, and only then start insulin. If potassium is below 3.5 mmol/L, replace it before insulin. Add dextrose when glucose falls to about 10-15 mmol/L so the insulin infusion can continue until ketones clear. In suspected bacterial meningitis, never delay antibiotics for a lumbar puncture; treat first. Do not perform a lumbar puncture with focal neurology, papilloedema or coagulopathy unless raised intracranial pressure has been excluded.