DOAC and Neuraxial Block — FRCA Final MCQ

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HardRegional AnaesthesiaDOAC and Neuraxial BlockFRCA Final

A 78-year-old woman (ASA III) with a fractured neck of femur is assessed pre-operatively. She takes dabigatran 150 mg twice daily for atrial fibrillation; her last dose was 12 hours ago. Renal function is stable with a Cockcroft–Gault creatinine clearance of 35 mL/min, and no dabigatran-specific assay (dilute thrombin time or ecarin clotting time) is available. Applying current UK Association of Anaesthetists guidance on regional anaesthesia in patients with abnormalities of coagulation, what is the recommended minimum interval from the last dabigatran dose before a spinal anaesthetic may be performed?

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Correct answer: D — 96 hours

Explanation lettering: C = shown as B · B = shown as C

D is correct. Dabigatran is predominantly renally excreted, so its effective half-life lengthens markedly as clearance falls; UK Association of Anaesthetists guidance therefore stratifies the pre-neuraxial interval by creatinine clearance — 48 hours if CrCl >80, 72 hours if 50–80 and 96 hours if 30–50 mL/min. At CrCl 35 mL/min, 96 hours is the minimum. C (72 hours) is the interval for CrCl 50–80 and is the commonest error, quoted for patients with near-normal renal function. B (48 hours) applies only to normal renal function, and A and E reflect the interval for shorter-acting agents or a single missed dose and would leave substantial residual thrombin inhibition, risking vertebral canal haematoma. Practically, hip fracture surgery should not be delayed for four days: general anaesthesia, or a dilute thrombin time/ecarin-based assay where available, guides earlier operating. Note ASRA (US) advises a more conservative 72–120 hours.

Reference: NHS Scotland Right Decisions, Preoperative Assessment Guidelines – Perioperative management of direct oral anticoagulants (dabigatran; regional anaesthesia section, citing Association of Anaesthetists, Regional anaesthesia and patients with abnormalities of coagulation, Anaesthesia 2013;68:966–72). https://www.rightdecisions.scot.nhs.uk/preoperative-assessment-guidelines/perioperative-management-of-direct-oral-anticoagulants/