FCPS Part-1 cheat sheet

Action potential: resting membrane potential ≈ −70 mV; threshold ≈ −55 mV; depolarization is driven by Na⁺ influx, repolarization by K⁺ efflux, and the Na⁺/K⁺-ATPase (3 Na⁺ out, 2 K⁺ in) restores gradients.

Cardiac output = heart rate × stroke volume; stroke volume rises with preload (Frank–Starling) and contractility, and falls with rising afterload.

Oxygen delivery = cardiac output × arterial O₂ content, where O₂ content ≈ (1.34 × Hb × SaO₂) + (0.003 × PaO₂); hemoglobin-bound O₂ dominates.

Autosomal recessive disease appears in 25% of offspring of two carriers; autosomal dominant in 50% from one affected heterozygote; X-linked recessive affects mostly males, with 50% of sons of carrier mothers affected.

Hardy–Weinberg equilibrium: p + q = 1 and p² + 2pq + q² = 1; carrier frequency for a recessive allele = 2pq, approximately 2q when q is small.

Renal handling: glucose reabsorption saturates at transport maximum (≈375 mg/min, splay around 180–200 mg/dL plasma); inulin clearance equals GFR; PAH clearance estimates renal plasma flow.

Acid–base: Henderson–Hasselbalch pH = 6.1 + log([HCO₃⁻]/0.03 × PaCO₂); respiratory compensation is fast, renal HCO₃⁻ adjustment takes 2–4 days.

Pharmacokinetics: half-life t½ = 0.693 × Vd / CL; steady state is reached in about 4–5 half-lives; loading dose = Vd × target concentration / bioavailability.

Acute coronary syndrome: ST-elevation myocardial infarction needs immediate reperfusion (primary PCI within 90–120 min of first contact); aspirin plus a P2Y12 inhibitor and anticoagulation are standard adjuncts.

Acute asthma severity: unable to speak in sentences, silent chest, SpO₂ < 92%, peak flow < 33% predicted, or rising PaCO₂ indicate life-threatening attack requiring oxygen, nebulized bronchodilators, systemic steroids, and urgent senior review.

Stroke: non-contrast CT excludes hemorrhage before thrombolysis; intravenous alteplase is licensed within 4.5 hours of symptom onset, and thrombectomy for large-vessel occlusion up to 6 hours (selected cases longer).

Diabetic ketoacidosis: treat with isotonic saline, fixed-rate intravenous insulin (≈0.1 unit/kg/h), potassium replacement once K⁺ < 5.5 mmol/L and urine output confirmed; continue insulin until ketones clear, not merely until glucose normalizes.

Meningitis: suspected bacterial meningitis in an adult gets immediate empiric ceftriaxone plus vancomycin (plus ampicillin if Listeria risk); dexamethasone before or with the first antibiotic dose reduces hearing loss in pneumococcal disease.

Sepsis: sepsis is infection plus organ dysfunction (SOFA rise ≥ 2); septic shock is persistent hypotension needing vasopressors despite fluids with lactate > 2 mmol/L; give broad-spectrum antibiotics within 1 hour.

Upper GI bleeding: pre-endoscopic intravenous proton pump inhibitor and endoscopy within 24 hours; variceal bleeding adds a vasoactive drug and prophylactic antibiotics; Glasgow–Blatchford score guides need for admission.

Hyponatremia: correct chronic hyponatremia by ≤ 8–10 mmol/L in 24 hours to avoid osmotic demyelination; symptomatic or seizing patients receive hypertonic 3% saline with frequent sodium checks.