Supraclavicular Block

The spinal block of the arm.

Blockade provides excellent analgesia to the arm, though may miss much of the shoulder. Phrenic nerve may still be anaesthetised via proximal spread.

Indications

  • Analgesia for arm and hand surgery
    In particular:
    • Mid-distal humerus fracture
    • Major elbow surgery
    • Major forearm/wrist surgery
      Axillary block also effective if surgery is in the ulnar nerve distribution.

Contraindications

Absolute:

  • Contralateral recurrent laryngeal or phrenic nerve injury
  • Contralateral pneumonectomy/pneumothorax

Relative:

  • Reduced respiratory reserve

Anatomy

The upper limb is supplied by the brachial plexus:

  • Formed by the anterior primary rami of C5 to T1
    • Variably C4 to T2
  • Divided into roots, trunks, devisions, cords, and branches
    Blocking the plexus at different levels will give a different distribution of sensory block.
  • Runs between the clavicle and third rib
  • Runs with the axillary artery into the upper limb, where it forms the major terminal branches

Sections of Brachial Plexus

The brachial plexus has five key sections:

  • Five roots
    The nerve roots that give rise to the plexus. May be imaged as they emerge from the vertebral foramen.
  • Three trunks
    Roots merge together to form three trunks:
    • May be imaged at the interscalene level
      Deep to SCM, between anterior and middle scalene. Key landmarks:
      • Lateral border of SCM
      • Scalenus anterior
      • Interscalene groove
    • Superior trunk
      From C5 & C6.
    • Middle trunk
      From C7.
    • Inferior trunk
      From C8 and T1.
  • Six divisions
    Three anterior and three posterior, which then re-merge to form the cords.
    • Lie posterior and cephalad to the subclavian artery
    • May be imaged at the supraclavicular level.
  • Three cords
    Imaged wrapping around the axillary artery at the infraclavicular level, and include:
    • Lateral cord
    • Posterior cord
    • Medial cord
  • Branches
    • Divided into major and minor terminal branches
    • Major terminal branches may be imaged in the axilla

Major Terminal Branches

The major terminal branches include:

  • Radial nerve
    • Sensation to the dorsum of the hand, generally the lateral 2.5 digits.
    • Motor: Extension of elbow and fingers
  • Median nerve
    • Sensation to the palm, and the palmar surface and dorsum of the distal phalanges of the lateral 3.5 digits
    • Motor: Flexion of fingers
  • Ulnar nerve
    • Sensation to the medial 1.5 fingers, the ulnar border of the hand (including the dorsum), and sometimes the ulnar part of the forearm
    • Motor: Flexion of 4th and 5th digits and opposition of 1st digit
    • Most effectively blocked with a targeted axillary block
  • Musculocutaneous nerve
    • Sensation to the lateral aspect of the forearm
    • Motor: Flexion and supination of forearm
  • Axillary nerve
    • Sensation over the “regimental patch” of the shoulder

Minor Terminal Branches

From the roots:

  • Dorsal scapular nerve
  • Long thoracic nerve
  • Branch to phrenic nerve

From the trunks:

  • Nerve to subclavius
  • Suprascapular nerve

From the cords:

  • Lateral pectoral nerve
  • Subscapular nerve
  • Thoracodorsal nerve
  • Median pectoral nerve
  • Intercostal brachial nerve
  • Medial brachial cutaneous nerve
  • Medial antebrachial cutaneous nerve Supplies upper medial part of the forearm, and can be covered with a subcutaneous bleb just distal to the axillary hairline.

Equipment

  • 50-100mm 22-24G needle
  • Local anaesthetic
    20-30ml of:
    • 1-2% lignocaine
    • 0.75-1% ropivacaine
      0.2-0.5% ropivacaine sufficient for post-operative analgesia. Higher concentrations required for surgical anaesthesia.
    • 1% lignocaine with 0.5% ropivacaine
  • High to intermediate frequency linear transducer

Technique

  • Position semirecumbent
    • Head rotated to contralateral side
  • Place probe parasagitally in supraclavicular fossa
  • Identify brachial plexus
    In the “corner pocket”:
    • Superoanterior to SCA
      Pleura and 1st rib should be identifiable deep to SCA.
    • Between scalenus anterior and scalenus medius
    • Deep to omohyoid
  • Note presence of dorsal scapular artery superficial to brachial plexus Use colour doppler over planned needle trajectory to minimise risk of vascular injury.
  • Can use IP or OOP technique
    Ensure needle tip is placed superficial to the 1st rib.

Complications

Specific complications include:

  • PTHx/HTx
  • Phrenic nerve block
  • Horners Syndrome
  • SCA injury

References