Neuroanaesthesia10 / 14
Alzheimer's dementia on donepezil for incarcerated hernia84-year-old man, 61 kg, from a care home
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Know this first
- Capacity: understand the information, appreciate it, weigh options, communicate a choice.
- Cholinesterase inhibitors cause bradycardia and prolong suxamethonium.
- Benzodiazepines, deep anaesthesia and poor analgesia raise delirium risk.
- Glycopyrrolate doesn't cross the blood–brain barrier; atropine does.
- Frailty: Clinical Frailty Scale of 4 or more.
The patient
84-year-old man, 61 kg, from a care home, with an incarcerated right inguinal hernia for urgent repair today.
Moderate Alzheimer's dementia: oriented to person only; needs help washing and dressing; Clinical Frailty Scale 6.
Drugs: donepezil, amlodipine.
Vitals: BP 146/84, HR 58, SpO2 95% on air, RR 16, temperature 37.2 °C.
The examiner asks
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Consider
What are your concerns?
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- An 84-year-old care-home resident, frail with moderate Alzheimer's, for urgent repair of an incarcerated hernia. Patient
- At 84 with dementia and CFS 6, he's frail, with a high risk of delirium.
- Donepezil slows his heart, now 58, and prolongs suxamethonium. Disease
- It's urgent, so the consent process must not delay his surgery. Surgery
Prepare
How do you obtain consent and assess him?
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- Capacity: can he understand, grasp what it means for him, weigh options, and state a choice? Patient
- His legal guardian consents, in guardianship order; failing that, his closest male relative.
- I still explain simply to him, and the decision serves his interests.
- Baseline cognition recorded, oriented to person only, so delirium can be spotted.
- His family hears that delirium and further decline are likely after surgery. After surgery
Plan
Regional or general, and how?
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- His confusion makes a block with sedation hard; GA with short-acting drugs is reasonable. Patient
- Reduced propofol, under 1.5 mg/kg, with remifentanil; no benzodiazepine.
- Rocuronium rather than suxamethonium, which donepezil prolongs. Disease
- Processed EEG to avoid excess depth; no hypotension. Patient
- Reversal planned: neostigmine adds to donepezil's slowing of his heart. Disease
- Paracetamol 1 g IV and a nerve block to spare opioids. After surgery
- Delirium care: glasses, hearing aids, family, early mobilisation, no restraints.
Crisis
He gets neostigmine with glycopyrrolate at the end; his HR falls to 32, BP 70/40, and he looks grey. What do you do?
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- Bradycardia algorithm: symptomatic bradycardia from neostigmine on top of donepezil. Crisis
- Reversible causes: give 100% oxygen, stop any vagal stimulus.
- Atropine 1 mg IV every 3–5 min, maximum 3 mg, despite its central effects.
- No response: adrenaline 2–10 mcg/min or dopamine 2–10 mcg/kg/min.
- If drugs don't work, transcutaneous pacing.
- Watch for delirium after; atropine crosses into the brain. After surgery
Fatal mistakes
- Taking consent from him when he lacks capacity.
- Neostigmine without an anticholinergic.
- A benzodiazepine for his agitation.
Checked against: Miller 10e · Saudi Guidelines for Informed Consent, First Edition 1440H (2019) · Barash 9e · Stoelting 8e
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