FRCA Notes

Infraclavicular Brachial Plexus Block

Resources

  • The infraclavicular BPB aims to anaesthetise the cords of the brachial plexus; the lateral, posterior and medial cords
  • It is described as a more technically challenging block than other BPB, but confers some benefits which may make it advantageous in select patients

Boundaries of the infraclavicular fossa

  • Anteriorly: pectoralis minor and major
  • Posteriorly: subscalpularis
  • Medially: the ribs and intercostal muscles
  • Laterally: the humerus
  • Superiorly: clavicle and coracoid process

The brachial plexus at the infraclavicular fossa

  • The plexus divides from trunks into divisions after passing over the outer border of the first rib; this is the site of supraclavicular brachial plexus block
  • As the three divisions pass inferolaterally they each divide into an anterior and posterior branch behind the clavicle
  • These branches fuse to form the three cords, which are named in relation to their position with respect to the axillary artery: posterior, medial and lateral
    • The precise location of the cords relative to the artery is, however, highly variable which can make identification using ultrasound challenging
    • The cords also lie deeper relative to the skin surface
  • The three cords are amenable to blockade within the infraclavicular fossa

Distribution & benefits

  • Anaesthetises the cords of the brachial plexus, which typically makes it unsuitable for shoulder surgery as it will miss C5/6 dermatomes
  • Good coverage for procedures at or below the elbow joint i.e. elbow, forearm and hand surgery

  • Benefits from a lack of the need for patient upper arm mobility to perform the block, which may be beneficial in those with acute limb trauma or shoulder joint arthropathy
  • More reliable coverage of the ulnar nerve than interscalene or supraclavicular approaches
  • Reduced rate of phrenic nerve palsy, pneumothorax, and Horner’s syndrome compared to more proximal BPB
  • Better at negating tourniquet pain than axillary BPB although may still require supplementary intercostobrachial nerve block
  • Better blockade of musculocutaneous nerve than axillary block

  • Variations on the block exist, including:
    • Vertical infraclavicular block, which is said to have a 95% success rate
    • Pericoracoid infraclavicular block, which is said to have a 91% success rate
    • Parasagittal infraclavicular block, which is said to have an 85-91% success rate with a higher rate of vascular puncture, but lower rate of pneumothorax or phrenic nerve palsy

Contraindications

General Specific
Patient refusal Dislocation or fracture of the clavicle
Local anaesthetic allergy Chest wall deformities
Localised infection A short neck or thick pectoral region
(if a retroclavicular approach is used)
Lack of appropriate resources
Coaguloapthy
Pre-existing nerve injuries


Standard regional anaesthetic set-up

  • Patient consent obtained
  • Ensure appropriate equipment available
  • Ensure adequate staffing i.e. trained assistant
  • Access to resuscitation equipment including intralipid
  • IV access obtained
  • Monitoring in situ
  • Correct LA dosing calculated
  • Stop Before You Block moment

Positioning/equipment/ergonomics

  • Ultrasound (linear probe or small, high-frequency curvilinear probe (the latter may provide a broader view of the relevant structures)) ± peripheral nerve stimulator ± pressure monitoring
    • Ultrasound associated with shorter block performance time, improved sensory and motor block and reduced need for supplementation
    • Reduces incidence of complications such as pneumothorax and LAST
  • 80 - 100mm echogenic short-bevel needle

  • Supine, head turned contralaterally
  • Operator sat on ipsilateral side to block with ultrasound opposite them
  • Abducting the patient's arm 90° may improve visualisation and reduce depth to the plexus

  • If a nerve stimulator is used:
    • Wrist/finger extension (radial nerve) or flexion (median nerve) are the best predictors of subsequent a successful block
    • Stimulation at below 0.2mA may indicate intra-neural placement, whereas stimulation 0.5-1mA is unlikely to result in successful block

Local anaesthetic

  • Minimum effective LA volume described as 35ml in 90% of patients
  • One article described 30ml 0.375% levobupivacaine of being the authors' LA of choice
  • Most sources suggest 20-30ml required

Performance (parasagittal approach)

  • Transducer placed parasagittally
  • The key anatomical landmark is the axillary artery, which along with the plexus lies deeper here (~4-5cm) than at other sites of BPB
  • The angle of approach may therefore be quite steep, and require a 'heel-in' manouevre to help identify the needle

  • Needle inserted immediately below the clavicle, medial to the coracoid process
  • Advanced towards the hyperechoic, round cords (lateral, posterior and medial) which surround the axillary artery
    • The lateral cord tends to lie superior (cranially) to the artery
    • Medial cord lies inferiorly (caudally), often between the axillary artery and vein
    • Posterior cord is said to lie posteriorly, but often lies below the lateral cord
    • NB acoustic enhancement posterior to the axillary artery may lead to a misinterpretation of the position of the posterior cord

  • Advance needle postero-laterally to the axillary artery (8 o'clock position) and inject LA to achieve spread around the artery
  • ± further advancement inferior to the artery (6 o'clock position); this was shown to provide a 96% success rate
  • Needle repositioning is required in up to 75% of patients in order to successfully block the plexus
  • Placement of LA in a 'horseshoe' shape below the artery, between 3 o'clock and 11 o'clock positions, is ideal

  • The plexus is deeper here than at other sites making the angle of approach steep, which can make needle and needle tip visualisation more challenging
  • May still cause phrenic nerve palsy (3%) despite being a more distal block if large volumes of local anaesthetic are used, although highly unlikely with ultrasound and lateral para-sagittal approach
  • Pneumothorax (0.7%)
  • Risk of vascular puncture (2-33%) e.g. axillary vein or arterial puncture
    • Cephalic vein and other small vessels often lie between insertion site and the plexus
    • Difficult to apply pressure if vascular injury does occur

Generic


  • The infraclavicular fossa is an ideal location for placement of a catheter as:
    • The musculature of the chest wall aids stabilisation and securing of the catheter
    • The depth of the BPB at this site helps reduce catheter dislodgement
    • It may be more tolerable for the patient
  • The catheter tip should lie posteriorly to the artery, which will help facilitate LA placement in the correct position to catch all three cords
  • Regimens include 5ml/hr 0.125% levobupivacaine ± patient-controlled 5-8ml boluses every hour