Clinical Methods: systematic assessment and bedside interpretation
Scope
This paper tests systematic history taking, physical examination, interpretation of common bedside investigations (ECG, chest radiograph, arterial blood gas, urinalysis) and clinical reasoning.
Core rules
- Sequence: history, then general examination, then systemic examination, then investigations - each step should be hypothesis-driven.
- SOCRATES for pain: site, onset, character, radiation, associations, timing, exacerbating and relieving factors, severity.
- Acid–base in four steps: pH, then the primary disorder, then compensation using Winter's formula (expected PaCO2 = 1.5 × HCO3 + 8, plus or minus 2), then the anion gap (Na − [Cl + HCO3], normal 8 to 12).
Worked example
Na 140, Cl 104, HCO3 10, pH 7.22, PaCO2 24. Step 1: acidaemia. Step 2: the low bicarbonate means metabolic acidosis. Step 3: expected PaCO2 = 1.5 × 10 + 8 = 23, plus or minus 2, so the measured 24 represents appropriate respiratory compensation. Step 4: anion gap = 140 − (104 + 10) = 26, a high-anion-gap acidosis suggesting lactate, ketones, urea or toxins. Diagnosis: high-anion-gap metabolic acidosis with appropriate compensation.
Traps that cost marks
- Accepting a normal pH as excluding an acid–base disorder; mixed disorders can normalise pH.
- Confusing oxygen saturation with PaO2.
- Presenting findings without interpretation - the examiner wants the diagnosis and the reasoning behind it.
- Reporting a sign without its qualifying features, for example a murmur without timing, site and radiation.