Mechanical mitral valve on warfarin for retinal detachment surgery71-year-old man, 78 kg, for urgent vitreoretinal surgery for retinal detachment

The patient

The examiner asks

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1. Consider

   What are your concerns?

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   • A 71-year-old with a mechanical mitral valve on warfarin, for urgent retinal surgery under block. Patient
   • At 71 with heart failure, can he lie flat and still for the whole case? I also screen cognition.
   • A mechanical mitral valve is high thrombotic risk; stopping warfarin would need bridging. Disease
   • Retinal surgery can proceed with his INR in range, so warfarin continues.
   • A sub-Tenon block suits an anticoagulated eye better than a sharp-needle block. Surgery
   • No endocarditis prophylaxis; this isn't a dental procedure. Disease

2. Prepare

   Take me through his risk assessment and preparation.

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   • Urgency: his sight is at stake, so hours to days; I assess but don't delay. Stem trigger
   • Active cardiac conditions? He has none: compensated failure, rate-controlled AF. Disease
   • Risk score: heart failure is his only RCRI item, so RCRI 1.
   • Functional capacity: two flights of stairs, so over 4 METs.
   • Decision: RCRI 1, so proceed without further cardiac testing.
   • Any change to warfarin or bridging is agreed with his cardiologist and surgeon.
   • Monitoring, airway kit and resuscitation drugs at the block, with atropine drawn up. Crisis

3. Plan

   What is your anaesthetic plan?

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   • Sub-Tenon block with light sedation, oxygen and capnography. Disease
   • Bisoprolol continues to keep his rate controlled.
   • If gas goes into the eye, no nitrous oxide now, and a warning bracelet for weeks after. Surgery
   • Nitrous oxide would expand the bubble and can occlude his central retinal artery.
   • Warfarin continues tonight; he positions his head exactly as the surgeon directs. After surgery

4. Crisis

   Three minutes after the block he becomes unresponsive and stops breathing; BP 92/50, HR 64. What do you do?

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   • Brainstem anaesthesia: local anaesthetic tracking along the optic nerve sheath. Crisis
   • Call for help; bag-mask ventilation with 100% oxygen.
   • Intubate if mask ventilation is poor; stop the sedation.
   • Support his pressure with phenylephrine 50–100 mcg.
   • Seizures would point to intra-arterial injection: midazolam 1–5 mg IV.
   • Care is supportive; he should recover fully within hours.
   • Surgery postponed or continued under GA with the surgeon; monitored until fully recovered. After surgery

5. Crisis

   Later, under GA, during globe traction his HR falls to 34 and BP to 72/40. What do you do?

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   • Bradycardia algorithm: HR 34 with hypotension during traction, the oculocardiac reflex. Crisis
   • Reversible cause first: surgeon stops the traction; I check oxygenation, CO2 and depth.
   • Still slow and hypotensive: atropine 1 mg IV now, and again every 3–5 minutes up to 3 mg in total.
   • Glycopyrrolate 0.1–0.2 mg IV is the alternative for a milder reflex.
   • Not responding to atropine: adrenaline 2–10 mcg/min, or transcutaneous pacing.
   • Should his pulse go: start CPR; adrenaline 1 mg every 3–5 minutes.
   • Traction resumes gently, with atropine ready. After surgery