Inter scalene block

Inter scalene block

Brief history:

First brachial plexus block was performed by William Steward Halsted in 1889 → by exposing the brachial plexus and using cocaine for blockade.

Inter-scalene block was first described by Winnie in 1970.

It often spares the lower branches of the plexus the C8 and T1 fibres innervating ulnar border of the forearm.

Table of Contents

CLINICAL IMPLICATION –

Low inter-scalene block below C6 just superior to clavicle was devised to provide sufficient anaesthesia and analgesia for procedures on the lower part of upper arm.

Relevant anatomy:

After leaving the inter-vertebral foramina, the nerves course antero- laterally and inferiorly to lie between the anterior and middle scalene muscles and fuse literally to enclose the brachial plexus in a fascial sheath.

Anatomical factors helpful in successful blockade:

The fascial peri-vascular sheath – extends from the origin the scalene muscles to the middle of upper arm.
The vertical arrangement of cervical nerve roots which form the trunks of brachial plexus

Indications:

Anaesthesia and analgesia for open and shoulder surgery.(eg: acromioplasties, total shoulder replacement, debridement of labral and rotator cuff tears)
Mobilisation (eg: frozen shoulder)
Closed reduction of the shoulder dislocation
Anaesthesia for upper arm surgery

PATIENT POSITIONING AND ANATOMICAL LANDMARKS

Patient is made to lie down and raise his head against closed glottis

This helps to make sternocleidomastoid muscle prominent.

3 anatomical landmarks are most significant

Posterior border of sternocleidomastoid
External jugular vein
Scalene groove

Equipments
Standard regional anaesthesia tray
Sterile towels for draping
Sterile gauze pieces
2 of 10/20 mL syringes containing local anaesthetic
Sterile gloves
Marking pen
Surface electrodes
3 mL syringe and 25 G needle for skin infiltration with local anaesthetic
Peripheral nerve stimulator with stimuplex needle
usg machine

Techniques of inter-scalene block

Landmark guided
PNS guided
USG guided

Landmark guided Inter-scalene block

Skin overlying the area is prepared by antiseptic solution
At the level of cricothyroid notch (C6 ) at the inter-scalene groove, a 25 gauge,1^1/2 inch needle is inserted with a slight caudad and inferior trajectory
If inter-scalene groove is not identified , the needle is inserted slightly behind posterior border of sternocleidomastoid.

PARASTHESIA will occur at 1/4 to 1 inch depth when needle is advanced quite slowly in perpendicular direction to reach inter-scalene groove and it’s tip impinges the brachial plexus.

Gentle aspiration and if aspiration is negative , local anaesthetic is injected slowly with close monitoring of the patient.

Nerve stimulation technique

Same as landmark technique using 22G 35 -50 mm insulated needle directed medial, caudal and posterior in the direction of C6 transverse process near posterior border of sternocleidomastoid corresponding to cricothyroid.

Caudal tilt is important as it avoids-

Either entering neural foramen
Injection into the dural nerve root sheath

Thus preventing spinal cord injury and high spinal .

Nerve localisation–

Apply an initial current of 0.8mA – 1mA and the current is aimed for a threshold of 0.4 mA before injecting after motor response.

Avoid diaphragm /trapezius stitches with cervical plexus stimulation.

Response should be from→pectoralis muscle, deltoid muscle, triceps muscle, biceps muscle or any twitch of the muscle of the hand or the fore-arm.

After negative aspiration gradually 20 to 30 mL of local anaesthetic is injected in small increments

(Picture 3)

USG guided technique

Advantages

Distribution of local anaesthetic is visualised for adequate spread around the plexus
Allows multiple injections around the brachial plexus thus eliminating the possibility of failed block
Helps to reduce the volume of anaesthetics
Avoids the risk of major vessel or nerve puncture
Repetition of block is also possible

A linear USG probe is placed over previously identified location ( same as the one used in landmark guided and PNS techniques) in the transverse plane and a sonogram is obtained.

At inter-scalene level structures observed are:

Superficially — pre-vertebral fascia, superficial cervical plexus and sternocleidomastoid muscle are observed
Medially — carotid artery, anterior scalene muscle
Laterally — middle scalene muscle
Transducer is moved in superior – inferior direction until 2/more brachial plexus trunks are seen in the space between scalenes.
In plane approach preferred.

Sonoanatomy

Roots of brachial plexus appear as hypoechoeic round or oval multifascicular structures with hyperechoeic perineurium

Colour Doppler used to identify carotid artery,internal jugular vein and vertebral artery

Probe is moved slightly superior and inferiorly so as to get the appearance of traffic spotlight sign of brachial plexus

Probe settings

Depth 3cm, frequency 8-14 Hz, linear transducer

Patient position

Supine with head turned away from side to be blocked

Transducer position

Transverse orientation on the neck over the pulse of carotid artery 4 cm above clavicle

Slide the transducer laterally and slightly up and down to visualise traffic signal sign .

In plane approach used to inject local anaesthetic

Tips –

Higher resistance to injection >15psi pressure indicates intra fascicular injection and requiring repositioning of needle.
Gentle pressure with transducer prevents collapse of vein and their subsequent puncture

Complications

Vascular puncture
Hematoma
Infection
Local anaesthetic systemic toxicity
Nerve injury
Total spinal anaesthesia
Horne syndrome
Diaphragm paralysis
Epidural injection
Pneumothorax

Contra – indications

Contralateral phrenic and recurrent laryngeal nerve paresis
Chronic obstructive pulmonary disease (relative contraindication)

General tips

General neurological examination to identify pre-existing neurological deficits is necessary before brachial plexus block so that such effects are not later attributed to the block
Supplementation for C8 fibers may be needed by peripherally blocking ulnar nerve in surgeries where C8 distribution is involved which may get spared with inter scalene block

References

Millers anaesthesia 8th edition

Textbook of anaesthesia Barash 7th edition

Hadzics regional anaesthesia 5th edition

Waldmann’s interventional pain management 5th edition

Nysora website