Anticoagulation before colonoscopy: reading the procedural guidance
Mrs Joan Whitfield, 74, is booked for an elective colonoscopy at 09:00 on 14 May for iron-deficiency anaemia. The endoscopist has documented that a polypectomy is 'likely'. She has atrial fibrillation and takes apixaban 5 mg twice daily (08:00 and 20:00); her eGFR was 58 mL/min/1.73 m² three months ago. She also takes aspirin 75 mg once daily after a TIA two years ago. She lives alone, has had two recent falls, and bruises easily. The endoscopy unit protocol states: (1) for apixaban, omit 48 hours before low-risk procedures and 72 hours before high-risk procedures; (2) polypectomy is high risk; (3) do not bridge with LMWH unless there is a mechanical heart valve or recent VTE; (4) continue aspirin for secondary prevention unless the bleeding risk is judged high; (5) confirm eGFR within three months. The pre-assessment nurse asks you to confirm the medication plan.
1. Calculate the last dose of apixaban and justify your timing. Show your reasoning.
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Polypectomy is high risk, so the protocol requires omitting apixaban for 72 hours before the procedure. The colonoscopy is at 09:00 on 14 May. Counting back 72 hours gives 09:00 on 11 May. Because Mrs Whitfield takes apixaban at 08:00 and 20:00, the last dose should be the morning dose on 11 May; the evening dose on 11 May would be only about 61 hours before the procedure and would not satisfy the protocol. A dose at 20:00 on 10 May would also be more than 72 hours before, so either the evening dose on 10 May or the morning dose on 11 May is acceptable - but the evening dose on 11 May must be omitted. I would write the exact date and time in the instructions and check her understanding, because 'stop 72 hours before' is easy to misapply with twice-daily dosing.
2. Should aspirin be continued? Explain the competing risks and what you would do.
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I would not stop aspirin automatically. The protocol says continue aspirin for secondary prevention unless bleeding risk is judged high. She had a TIA two years ago, so stopping aspirin raises thrombotic risk; however, she has had recent falls and bruises easily, and polypectomy carries bleeding risk. The decision needs to be shared with the endoscopist. If the bleeding risk is judged high, a short pre-procedure pause might be considered, but that must be balanced against her cerebrovascular risk and documented. I would explain the trade-off to her, check whether she has had any recent GI bleeding or falls causing head injury, and record the endoscopist's decision. The key is not to apply a blanket rule in either direction.
3. What additional checks would you make before signing off the plan?
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Before signing off, I would confirm: (1) a current eGFR within three months - the result is three months old, so it is at the limit and may need repeating; (2) the exact procedure time and whether polypectomy is still anticipated; (3) the last apixaban dose and whether she has missed any doses; (4) whether aspirin is to continue, with the endoscopist's agreement; (5) her falls history, bruising, Hb and any bleeding; (6) transport home and whether she lives alone; (7) her understanding and consent, including the risk of bleeding and thromboembolism. I would also check for interacting drugs such as NSAIDs or SSRIs, and confirm that no LMWH bridging is planned because she has neither a mechanical valve nor recent VTE.