Trial OSCE exam: 'jen and deb 2' by Deborah Maher

You are taking part in a trial exam created by Deborah Maher. There are 9 OSCEs in this exam (90 minutes).
 

You have 3 minutes reading time. This OSCE will run for a maximum of 7 minutes.

Scenario:

A normally healthy 47yo lady has been found to have a distal radius fracture after a fall. It is an isolated injury and requires reduction. You have decided to perform this under regional IV anaesthesia.

Your junior registrar has never done a Bier's block before and is keen to learn.

Instructions for the candidate

You are to explain to your registrar the steps of a Bier's block to allow them to set up the equipment. Then proceed to gain informed consent from the patient.

Domains being examined

  • Medical Expertise
  • Communication
  • Scholarship and Teaching
 
The candidate has 3 minutes reading time. This OSCE is expected to run for a maximum of 7 minutes.

For the actor

Registrar: You have minimal knowledge of how to do a Bier's block, but are a quick learner.

Prompt for specifics eg "What pressure does the cuff go to?"

Questions to ask: "Why do you choose that local anaesthetic agent?" "What are the risks?" "How long does it take to work?" "Do we need to have anything else prepared?" "How long does it stay inflated for?"

Patient: You are a fit and well with no medical history, medications or allergies. You have never had an anaesthetic before. You had a simple mechanical fall. Your wrist is very painful. you have no other injuries.

For the examiner

Ideally have the cuff available to demonstrate on.

Domains Assessment Objectives

Medical Expertise
Knowledge of regional IV anaesthesia technique

Communication
Clear articulation of process and needs to registrar.
Clear description and explanation to patient of process and expectations, informed consent

Scholarship and Teaching
Good teaching methods to registrar.

Other Assessment Notes

1. Consent
- Indications and Contraindications
- Absolute: allergy to agent, uncontrolled hypertension
- Relative: Raynaud's, Buerger's, crushed/hypoxic injury, procedure > 90 minutes, uncooperative patient, sickle cell, prior LA use to exceed maximal dose
- Complications
lignocaine allergy
lignocaine toxicity (dizziness, tinnitus, headache, perioral numbness, cardiac, seizures)
- Mainly due to overdose or improper tourniquet deflation
thrombophlebitis
extravasation of LA into tissue
Agent specific
- prilocaine - methaemoglobinaemia
- bupivicaine - cardiac toxicity

2. Process
informed consent
optional sedation / analgesia
LA:
*Prilocaine 2.5mg/kg
- max dose 5-6mg/kg
- low toxicity
- high tissue binding
*Lignocaine (no adrenaline)
- dilute 1% to 0.5% in n/saline
- dose: 1.5 - 3mg/kg
- if using thigh cuff for proximal lower limb, dilute LA to 0.25% for greater volume
*No bupivicaine! (cardiac toxicity)

cotton padding under double cuff
IV access as close to pathologic site as possible (eg dorsum of hand)
at least 10cm distal to cuff
Rescue IV access on other limb
Exsanguinate the limb by elevating and optional distal->proximal firm bandage, brachial artery compression
Keep limb elevated and inflate cuff to 100mmHg above SBP (~250mmHg in arm)
- Child: 50mmHg above SBP
- Elderly/obese may be difficult to achieve
- Leg: 2x SBP
Lower limb, remove wrapping bandage
Inject anaesthetic into tourniqueted arm
Blotchy erythema may appear as blood displaced superficially
Progression of anaesthesia:
- Parasthaesia / warmth from fingertips to proximal
- Progressive anaesthesia in 10-20 minutes
- May retain some touch / proprioception / motor until full onset
Can top up low dose lignocaine further 0.5mg/kg to max 3mg/kg or prilocain additional 0.5mg/kg (after ~5 mins)
Remove infusion needle and do procedure
Deflate cuff
- If > 30 mins, just deflate (safer to cycle still)
- If < 30 mins cycle deflate - deflate 5 seconds, inflate 1-2 mins x 3 times
-- if any symptoms of toxicity, re-inflate cuff and wait a little longer (first symptom = perioral tingling)
Resolution of anaesthesia within 10 minutes (often parasthaesia first)
Observe for 45-60 minutes