Cervical Plexus Block

Blockade of the sensory nerves of C2-4 running between SCM and prevertebral fascia, in order to provide anaesthesia to the neck.

Three cervical plexus blocks are described, based on site of injection of local anaesthetic:

• Superficial plexus block
  Anaesthetic superficial to the deep cervical fascia.
  • Equivalent to deep blockade
  • Notably no phrenic nerve blockade
• Intermediate plexus block
  Anaesthetic between the deep cervical fascia and the prevertebral fascia.
• Deep plexus block
  Anaesthetic deep to the prevertebral fascia.
  • ↑ risk of complications, particularly phrenic nerve blockade

Indications

Include:

• Superficial neck surgery
• Carotid endarterectomy
• IJ central line insertion

Contraindications

Anatomy

The cervical plexus is:

• Only occasionally visible on ultrasound.
• Deep to deep cervical fascia
  Facial fascial layer deep to SCM.
• Anterior to the prevertebral fascia
  Fascia overlying the middle and anterior scalene muscles.
• The nerve roots that supply four terminal sensory nerves of the head and neck:
  • Greater auricular
  • Lesser occipital
  • Transverse cervical
  • Supraclavicular

Equipment

• 22G 4cm needle
• Local anaesthetic
  10-20ml of dilute solution (purely sensory nerves; do not require high concentrations):
  • 0.25-0.5% ropivacaine
  • 0.25% bupivacaine
  • 1% lignocaine

Technique

Position:

• Supine
• Head turned away from side

Probe:

• Place at midpoint of SCM
• Identify SCM on ultrasound and position the posterior edge of SCM in the middle of the screen
• Identify the brachial plexus between ASM and MSM
• Attempt to identify the cervical plexus overlying the prevertebral fascia superficial to the brachial plexus

Needle:

• If plexus identified:
  • Place needle IP through skin, platysma, and fascia adjacent to plexus
  • Confirm injection site with 1-2ml LA
  • Deposit remainder of LA around plexus
• If plexus not identified:
  • Place needle IP through skin as above
  • Split later between deep cervical and prevertebral fascia with 5ml of LA
  • Withdraw and fan cranially ~45° and split fascial layers
  • Withdraw and rotate needle caudally 45° and split facial layers again
    Goal is to achieve a large pool of LA between the fascial layers, and ensure adequate coverage.

Complications

Include:

• General
  • LAST
  • Haematoma
  • Infection
• Specific
  • Phrenic nerve block
    With deep cervical plexus block.
  • Spinal anaesthesia
    Travel of LA along dural sleeve of plexus nerves; particularly with high volumes and high injection pressures.

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References