Pain and regional anaesthesia02 / 13
CRPS: removing ankle metalwork from the affected limb29-year-old man, 78 kg, for elective removal of right ankle metalwork
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Know this first
- Budapest criteria: symptoms in 3 of 4 categories and signs in 2 or more, with no better diagnosis.
- Categories: sensory, vasomotor, sudomotor/oedema, motor/trophic.
- Type I has no nerve injury; type II follows injury to a defined nerve.
- Peri-operative CRPS care: regional catheter, subanaesthetic ketamine, alpha-2 agonists, short tourniquet time.
The patient
29-year-old man, 78 kg, for elective removal of right ankle metalwork, 14 months after the fracture.
CRPS of the right foot, stable for 6 months: allodynia, a cool mottled foot and swelling persist.
Drugs: pregabalin 150 mg twice daily, amitriptyline 25 mg at night.
Vitals: BP 124/76, HR 72, SpO2 99% on air, RR 12; resting pain 3/10.
The examiner asks
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Consider
What are your considerations?
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- A 29-year-old with right-foot CRPS, for elective metalwork removal on that same limb. Patient
- Elective surgery on a CRPS limb should wait for control; his has been stable 6 months. Surgery
- His amitriptyline continues on the day of surgery, and so does his pregabalin. Disease
Prepare
Is this really CRPS, and how do you prepare him?
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- Budapest criteria: symptoms in 3 of 4 categories and signs in at least 2. Disease
- He has allodynia, colour and temperature change, and swelling: sensory, vasomotor and oedema signs. Patient
- No other diagnosis may explain it, so I exclude infection, DVT and nerve entrapment in his leg. Disease
- No named nerve was injured, so this is type I; type II follows a defined nerve injury.
- The pain team and his physiotherapist plan his rehabilitation before and after surgery. After surgery
Plan
How do you anaesthetise him?
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- A regional technique with a catheter, infusing local anaesthetic to cover his ankle after surgery. Disease
- Subanaesthetic ketamine, roughly 0.25 mg/kg IV as a bolus, then 0.05–0.35 mg/kg/h.
- Clonidine or dexmedetomidine, and IV magnesium, are reasonable additions for him.
- I ask the surgeon for the shortest tourniquet time and the smallest approach. Surgery
Crisis
In recovery his pain is 9/10 despite 10 mg of morphine in increments. He is drowsy but rousable. RR 10, SpO2 94% on 2 L, BP 150/90, HR 104. What do you do?
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- No more morphine now: he's drowsy with RR 10, so another bolus is unsafe. Crisis
- If his block has worn off I bolus the catheter; if it's misplaced I re-site it.
- A ketamine bolus, roughly 0.25 mg/kg IV, then an infusion, treats pain without more opioid.
- Paracetamol 1 g IV, regularly every 6 hours.
- Monitoring of RR, depth of breathing, SpO2 and conscious level; naloxone 40 mcg if RR keeps falling.
- Pain team review daily; early physiotherapy, then mirror and motor imagery therapy. After surgery
Fatal mistakes
- Dismissing his pain as exaggerated.
- Stacking morphine in a drowsy patient without monitoring.
- Repeated blocks with no rehabilitation plan.
- A long tourniquet time and an open approach when a smaller one would do.
Checked against: Faust · Stoelting 8e · Barash 9e
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