Ultrasound- Guided Interscalene Brachial Plexus Block

 

Nerves Blocked:         Nerve Roots C5,C6,C7

 

Location:                     Interscalene groove (between anterior and middle scalene muscles)

 

Difficulty:                     Green/ Blue

 

Indications:                 Shoulder and proximal humerus surgery

 

Patient Position:         Supine, head to face opposite side

Needle:                        50mm short beveled regional block needle

 

Probe:                         High frequency linear

 

Tiger Territory:             Vertebral artery (often in close proximity to C7 nerve root)

Carotid artery & internal jugular vein

Phrenic nerve (on surface anterior scalene muscle)

 

Think Twice if:             Contralateral pneumothorax/ phrenic nerve palsy/ pneumonectomy

Severe respiratory disease eg.COPD

Interscalene block already in opposite side

 

Image Optimisation:   Screen depth 1-2cm

Identify brachial plexus behind the subclavian artery & trace proximally

Or identify the structures as the probe is slid laterally from midline.

Slight caudad intent of probe may help

Key:     C5, C6, C7 nerve roots

TP- transverse process, MSm- Middle scalene muscle, ASm- Anterior scalene muscle, SCMm-Sternocleidomastoid muscle, VA-Vertebral artery, DSn- Dorsal scapular nerve

 

Needling:                     In-plane (IP) or out-of-plane (OOP)

                                    IP

Ø  Better visibility of needle/nerve interface.

OOP

Ø  More comfortable (shorter needle path)

Ø  Avoid risk of damage to dorsal scapular or long thoracic nerves (in middle scalene muscle)

Ø  Ideal for perineural catheter placement.

Deposit local anaesthetic to surround C5 & C6 nerve roots

 

Complications/SEs:    Phrenic nerve block, hence caution in respiratory disease

Horner’s syndrome (stellate ganglion block)

Recurrent laryngeal nerve block

Vertebral artery puncture/injection

Spinal/ epidural injection

 

Pearls:                                    Plexus at this level appears as a string of hypoechoic circles (“traffic lights”)

Superficial block- usually nerve roots 1-2cm from skin

C6 root often divides into two structures (“double bubble” appearance)

Use colour doppler to identify vascular structures, especially the vertebral artery

Nerve roots can be traced back to their intervertebral foramen to aid identification

Vertebral transverse processes (TP) have characteristic appearances

Ø  C5 TP bifid with large posterior tubercle

Ø  C6 TP bifid with large anterior tubercle (Chassaignac’s)

Ø  C7 TP has no anterior tubercle.

Use lower volumes to reduce the incidence of unwanted side effects (e.g phrenic nerve block)

Open surgery may need additional superficial cervical plexus block or surgical infiltration