Regional - Interscalene block





Indication

  • Shoulder surgery - Upper trunk consistently blocked

Inferior trunk not blocked 50% of the time → not good enough for forearm surgery

Contraindication

  • COPD
  • Thoracic trauma
  • Head trauma
    • Horner's syndrome will interfere with neurological assessment



Brachial plexus block - Interscalene approach using USS

Positioning

  • Supine
  • Neck turn slightly away (from the side to be blocked)

USS placement and anatomy

USS probe is placed in the transverse plane on the neck, 3 to 4 cm superior to clavicle

Roughly at the level of the cricoid cartilage

  1. Identify the internal jugular vein and carotid artery
  2. Move more lateral/posterior to identify:
    • Anterior scalene muscle (ASM)
    • Middle scalene muscle (MSM)
    • Brachial plexus should be between ASM and MSM
      • Should be able to see three ventral nerve roots
      • C5, C6, C7 ventral nerve roots (from superficial to deep)
      • Typically visualised at a depth of 1 to 3cm

⦿ NB:

  • There is substantial variation in the anatomy
  • Brachial plexus is found between ASM and MSM in 60% of people
    • Cadaver study
    • Most common variation is direct penetration of ASM by C5 or C6 (34%)
  • High-frequency transducer is preferred since the nerve is superficial

Needle insertion and placement

Needle is inserted using an in-plane (IP) approach

  • Can be:

    • Anterior approach (through ASM)
      • i.e. Needle insertion point is medial to the USS probe
    • Posterior approach (through MSM)
      • i.e. Needle insertion point is lateral to the USS probe

  • Needle tip should be placed between C5 and C6 nerve roots

    • Typically at a depth of 1 to 3 cm (usually less than 2cm)

  • Additonal bolus can be given:

    • Above (superficial to) C5
    • Above the prevertebral fascia (for blocking superficial ?sympathetic chain, i.e. cutaneous sensation)

➤ Nerve stimulator:

  • Twitching of the deltoid and/or biceps brachii
  • Aim for response at 0.3 to 0.5 mA
  • Motor response may not always occur

LA

Use 1% lignocaine, 0.5% bupivacaine, or 0.75% ropivacaine

LA volume = 15 to 25 mL in total

⦿ NB:

Dr Sardesai uses:

  • Posterior IP approach
  • 30mL of 0.25% levobupivacaine