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DA > Regional Anaesthesia > Flashcards

Regional Anaesthesia Flashcards

1
Q

Classify Regional Anaesthesia

A
  1. Topical application
  2. Local infiltration
  3. Intravenous regional anaesthesia (Bier’s Block)
  4. Peripheral nerve blocks
    - Plexus
    - Peripheral
  5. Neuraxial Anaesthesia
    - Spinal
    - Epidural
    - Caudal
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2
Q

Can spinal anaesthesia be performed in an emergency department?

A

No. Requires a fully equipped theatre with a functioning anaesthetic machine in case the need arises to convert to a general anaesthetic

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3
Q

What are the indications for regional anaesthesia

A
  1. Surgical anaesthesia alone
  2. Supplementary and in conjunction with GA
  3. Post-operative analgaesia
  4. Acute and chronic pain management
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4
Q

What are the contraindications to regional anaesthesia

A
  1. Uncooperative (deaf/blind/adolescent/mental/obtunded)
  2. Coagulopathy (Plt < 75 | INR > 1.5
  3. Site of infection: Infection/Trauma/Burns
  4. Allergy LA
  5. Inadequate resuscitation/monitoring facilities
  6. Patient refusal (despite adequate explanation)
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5
Q

What are the advantages of regional anaesthesia

A
  1. Pre-emptive analgaesia (prevents ‘wind-up response’)
  2. Postoperative analgaesia
  3. Fewer physiological derangements (ANS stability)
  4. Rapid postoperative recovery
  5. Reduced complications GA (PONV, Aspiration, CICO, MH)
  6. Decreased VTE in orthopedic surgery of lower limbs
  7. Reduction of surgical stress response (best when continued for 24 to 48 hours after surgery: Epidural catheters/ indwelling catheter for plexus blocks)
    - elimination of painful afferent signal
    - Blockade of SNS efferents
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6
Q

What are the disadvantages of regional anaesthesia

A
  1. Patient may prefer GA (requires co-operation)
  2. Skill required
  3. All blocks have a small but finite failure rate (also consent for GA)
  4. Time factor: some blocks take 30 minutes
  5. Risk of systemic toxicity
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7
Q

What are the three types of topical LA

A
  1. Aerosolised (2 - 4 % lignocaine in a Macintosh sprayer) to anaesthetise the larynx / vocal cords
  2. Cream: Ametop / EMLA
  3. Direct application (eye drops)
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8
Q

Give examples of when topical LAs can be used

A
  1. Laryngoscopy / Bronchoscopy (aerosolized)
  2. Minor eye surgery (drops)
  3. Paediatric / needle phobic venepunture (ametop / EMLA)
  4. Skin graft donor sites
  5. Cytoscopy
  6. I&D of quinsy abscess
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9
Q

What is intravenous regional anaethesia (Bier’s block) commonly used for

A
  1. Carpal tunnel release
  2. Reduction of Colles fracture
  3. Hand Surgery
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10
Q

Why is the Bier’s block useful

A

Can provide intense anaesthesia for short surgical procedures (<45 - 60) with quick recovery

–> Brachial Plexus blocks will last as long last 12 hours

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11
Q

Describe the Bier’s block technique

A
  1. Monitoring /Resuscitation equipment available
  2. 2 x 20 ml syringes with 0.5% lidocaine (Bup C/I)
  3. Double cuff tourniquet ideal
  4. IV cannula (22G) as distal as possible on the dorsum of the hand.
  5. Site a second IV cannula on the contralateral arm
  6. Elevate arm and exsanguinate with compression (Smirch) bandage
  7. Inflate both tourniquets to 100mmHg above SBP
  8. Remove compression bandage
  9. Slowly inject 40 ml 0.5% lidocaine into the vein
  10. Remove cannula
  11. Anaesthesia established after 5 - 10 mins
  12. Anaesthesia persists for as long as the tourniquet is inflated - max time is 2 hours
  13. When tourniquet pain starts - deflate the distal tourniquet then re-inflate the distal tourniquet. Now deflate the proximal tourniquet.
  14. Tourniquet must be left on for at least 30 minutes (even if surgical procedure is 15 mins) to allow lignocaine to become ‘fixed’ within the arm and to avoid a rapid bolus of lidocaine into the systemic circulation.
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12
Q

What is a ‘differential block’ and why does it occur?

A

DIFFERENTIAL BLOCK

SNS block 2 dermatomes higher than:
- judged by temperature sensitivity

SENSORY block 2 dermatomes higher than:
- judged by pain/pressure/light touch

MOTOR block

This occurs for two reasons:

  1. The different classes of nerve fibres (diameter and myelination) have different sensitivity to LA
  2. The concentration of LA decreases with increasing distance from the injection site
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13
Q

Describe the layers that the spinal needle punctures

A
  1. Skin and SC tissue
  2. Supraspinous and interspinous ligaments
  3. Ligamentum flavum
  4. Epidural space
  5. Dura mater
  6. Subarachnoid space
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14
Q

What are the absolute contraindications to neuraxial blockade

A
  1. Coagulopathy
  2. Local infection at injection site
  3. Shock/Severe hypovolaemia (intolerant of SNSectomy)
  4. Active intracranial disease ± RICP
  5. Fixed CO states (Severe AS/MS/HOCM)
  6. Allergy LA
  7. Patient refusal
  8. Patient unable to give consent
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15
Q

What are the relative contraindications to neuraxial blockade

A
  1. Sepsis/SIRS
  2. Uncooperative patient (deaf/blind)
  3. Pre-existing neurological deficits (demyelinating/peripheral neuropathies)
  4. Severe spinal deformity
  5. Prior back surgery
  6. Complicated surgery: prolonged/major blood loss/respiratory restriction
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16
Q

List the complications of neuraxial blockade

A

ANS

  1. Hypotension (T1 - L2 SNS –> widespread VD)
  2. High block –> Low BP, Brady, CVs collapse, apnoea

ANATOMIC

  1. PDPH
  2. Meningitis
  3. Epidural abscess
  4. Epidural or spinal hematoma (NeuroSx within 6 hrs)
  5. Neurological sequelae (transient neuritis – paralysis)

MINOR

  1. Urinary retention (catheterise all)
  2. Backache (1/3 of GA only patients complain of post op backache and NA does not make pre-existing backache worse)
  3. Pruritis (opioids)
  4. Shivering: Rx 1. Warmth 2. Pethidine 10 - 25 mg IV
17
Q

How long until the patient should start regaining motor function in the lower limbs

A

Maximum 4 hours. If no motor function regained then Ix for severe complications

An epidural hematoma needs to be evacuated within 6 hours.

–> remove epidural and ensure tip intact (timing is NB if patient on anticoagulation

18
Q

Distinguish the extension of the subarachnoid space from the spinal cord in adults and children. Explain why this is relevant in anaesthetics

A

Subarachnoid space

  • Adults: Foramen magnum to S2
  • Kids: Foramen magnum to S3

Spinal cord

  • Adults: Foramen magnum to L1/L2
  • Kids: Foramen magnum to L3/L4

Relevance

  • Adults: Safe zone to avoid needle injury to SC during spinal anaesthesia is below L2.
  • Kids: Spinal anaesthesia is almost never routinely done in paediatric anaesthesia
19
Q

What is the name of the landmark used to identify the L3/L4 interspace for spinal anaesthesia

A

Intercrestal line - the line drawn between superior aspect of the right and left iliac crests

20
Q

Give examples of 25 G PPN and 22G sharp needle

A

25 G PPNs
Whitacre (blunt with circular hole)
Sprotte (blunt with longitudinal hole)

22 G Sharp
Quincke (sharp and bevelled)
- used for difficult spinals: thicker and sharper –> higher incidence if PDPH

21
Q

Describe the major and minor influences on the height of the block

A

Major

  1. Baricity of solution
  2. Patient posture
  3. Mass of LA injected
  4. Volume of solution injected
  5. Volume of CSF

Minor

  1. Level of injxn
  2. Height
  3. Age
  4. Weight
  5. Speed of injection
  6. Induced turbulence (barbotage)
22
Q

When is a saddle block indicated and how is it done. Comment how it differs from spinal anaesthesia

A

Short procedures in the perineum

  • Perianal abscess
  • Perineal tears post partum

Lower dose: 1.0 - 1.4 ml HYPERBARIC bupivacaine
Patient remains sitting for at least 5 minutes

Shorter duration and quicker recovery
Minimal motor block
Less risk of high spinal/significant sympathectomy

23
Q

What is contained within the dural space

A
  1. Fatty connective tissue
  2. Lymphatics
  3. Venous plexus
24
Q

What are the advantages of epidural anaesthesia over spinal anaesthesia

A
  1. Top - ups / constant infusion (catheter)

2. Graduated blocks with increments (avoids sudden changes in haemodynamics)

25
Q

What is the name of the needle used for epidural anaesthesia - describe this needle

A

Tuohy needle

  • 16G or 18G
  • blunted bevel tip (reducing risk of dural puncture)
26
Q

List the 5 steps required to ensure correct placement of the epidural catheter

A
  1. Incremental insertion of Tuohy needle with specialised low resistance syringe. Increments of 1 - 2 mm at a time with gentle bouncing of the low resistance syringe (air/saline). LOSS of RESISTANCE represents epidermal space.
  2. Catheter feeds easily
  3. Negative aspiration test (CSF/Blood)
  4. Dropping meniscus test positive
  5. Test dose lidocaine 45mg with 15 ug epinephrine –> dose not cause spinal anaesthesia
27
Q

How long can an epidural catheter stay in place postoperatively

A

3 days

28
Q

What are some common uses for thoracic epidurals

A
  1. Combined with GA for thoracic surgery

2. For analgaesia in patients with multiple rib fractures (to aid effective breathing)

29
Q

What are some common uses for lumbar epidural

A
  1. Combined with GA for abdominal surgery
  2. Labour epidural for analgaesia
  3. Caesarian section
  4. Lower extremity surgery
  5. Postoperative analgaesia
  6. Chronic pain management
30
Q

What are the indications for Caudal anaesthesia in paediatrics

A

Major abdominal surgery
Major orthopedic surgery of lower limb
Urogenital surgery

31
Q

Quantify the volume and concentration of LA required for caudal anaesthesia in paediatrics for different level of blockade

A

Lumbo-sacral —> 0.5 ml/kg of bupivacaine 0.25%

Thoraco-lumber —> 1.0 ml/kg of bupivacaine 0.25%

Mid thoracic —> 1.25 ml/kg of bupivacaine 0.25%

32
Q

What are the key difference between spinal and epidural anaesthesia

A

Spinal

  • Higher density block
  • Quick onset
  • lasts 2-3 hours
  • Obstetrics: C/S
  • 1.6 - 3.5 ml volumes used
  • Injxn site limited to L3/L4

Epidural

  • Lower density: used with GA for analgaesia
  • Slower onset
  • Can prolong duration with top up doses/infusions
  • Obstetrics: Analgaesia during vaginal delivery
  • Larger volumes / infusions used
  • Injxn sites: Lumbar/thoracic/cervical (neck)

DA (50 decks)

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