skip to main content

Platelet Dysfunction Post-CPB — FRCA Final MCQ

Instant feedback + full explanation. One question, done properly.

ModerateCardiothoracic AnaesthesiaPlatelet Dysfunction Post-CPBFRCA Final

A 68-year-old man (ASA III) undergoes elective CABG ×3 on cardiopulmonary bypass. He is heparinised (ACT 520 seconds). At the end of bypass, protamine is administered at a dose ratio of 1 mg per 100 units of heparin. The ACT returns to 145 seconds (baseline 130). Five minutes later, the surgical field shows ongoing microvascular bleeding despite a normal ACT. What is the most likely cause?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: C — Platelet dysfunction from CPB

CPB causes significant platelet dysfunction through: mechanical shear stress from the bypass circuit, hypothermia-related impairment, contact activation with artificial surfaces, and haemodilution. Despite adequate heparin reversal (ACT returned to near-baseline), platelet function is impaired, causing microvascular bleeding. This is the most common cause of non-surgical bleeding after CPB. Management: platelets if count <100 or clinical coagulopathy, desmopressin (DDAVP 0.3 mcg/kg), tranexamic acid, and point-of-care testing (TEG/ROTEM) to guide targeted therapy.

Reference: RCOA – 2023 – Cardiothoracic anaesthesia; NICE – 2015 – NG24 Blood transfusion