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Updates on Brachial Plexus Block with or without Sonar guidance

E S S A Y

Submitted for Fulfillment of MSC Degree of Anaesthesiology

By

Marwan Mohamed Ahmed Foued

M.B.,B.Ch. (Cairo University)

Supervisors

Prof. Dr. Tarek Ahmed Mostafa Radwan

Professor of Anaesthesiology& Intensive CareFaculty of Medicine

Cairo University

Prof. Dr. Mohammad Yosry Mohammad Ahmad

Professor of Anaesthesiology& Intensive CareFaculty of Medicine

Cairo University

Dr. Ahmed Abd El-Aziz Arif

Assistant Professor of Anaesthesiology & Intensive CareFaculty of Medicine

Cairo University

Faculty of MedicineCairo University

2012

Key word

Brachial Plexus-Sonar guidance-CN XI-Brachial Plexus Block Approaches.

Abstract

Conventional brachial plexus block techniques are performed

without visual guidance and are highly dependent on surface anatomical

landmarks for localization of neural structures. It is, therefore, not

surprising that a reported failure rate of up to 20% occurs because of

incorrect needle and/or local anesthetic placement. Multiple trial and

error attempts at needle placement lead to operator frustration,

unwarranted patient pain and time delay in the operating room. Imaging

technology such as MRI and CT scan can successfully localize neural

structures. However, ultrasound is likely the most practical imaging tool

for assisting nerve blocks as it is portable, moderately priced and non-

invasive without radiation risk.

Acknowledgement

First thanks are all to "Allah" for blessing me this work until it reached its end, as a little part of his generom help thought life.

I would like to express my sincere appreciation and deep gratitude to Prof Dr. Tarek Ahmed Mostafa RadwanProfessor of anesthesiology and intensive care, Faculty of Medicine, Cairo University for his moral support, continuous encouragement, really it’s a great honor to work under his guidance and supervision.

It gives me a great pleasure to express my deepest gratitude to Prof Dr. Mohammad Yosry Mohammad Ahmad Professor of anesthesiology and intensive care, Faculty of Medicine, Cairo University for his kind advice, valuable supervision and his great efforts through this work.

I cannot forget to express my deepest thanks to Dr. Ahmed Abd El-Aziz Arif Assistant Professor of anesthesiology and intensive care, Faculty of Medicine, Cairo University for hiscontinuous encouragement, sincere help and endless cooperation.

Marwan Mohamed Ahmed Fouad

List of Contents

Pages

List of Abbreviations

List of Tables

List of Figures

I

II

III

Introduction …………………………………………………. 1

Review of Literature

Chapter (1)

Anatomy of Brachial Plexus …………………………………… 3

Chapter (2)

Basic Principles and Physics of Ultrasound …………………… 9

Chapter (3)

Patient Management …………………………………………… 15

Chapter (4)

Brachial Plexus Block Approaches …………………………...... 23

Chapter (5)

Approaches of Ultrasound Guided Brachial Plexus Block ……... 44

Summary ……………………………………………………… 60

References ……………………………………………………. 62

Arabic Summary …………………………………………….

I

List of Abbreviations

µg Microgram

AA Axillary Artery

ASM Anterior Scalene Muscle

AV Axillary Vein

c Speed of time

CA Carotid Artery

CN XI Cranial Nerve XI

D Depth

dB Decibel

DIC Disseminated Intravascular Coagulopathy

ƒ Frequency

FR First Rib

HZ Hertz

IJV Internal Jugular Vein

IP In Plane

IV Intravenous

mA milliAmpere

MHz Mega Hertz

MSM Middle Scalene Muscle

N Nerve

OOP Out Of Plane

OR Operating Room

PABA Para-Amino Benzoic Acid

PACU Post Anaesthesia Care Unit

PMiM Pectoralis Minor Muscle

PMM Pectoralis Major Muscle

SA Subclavian Artery

SCM Sternocleidomastoid Muscle

T Time

TP Transverse Process

λ Wavelength

II

List of Tables

Tables Pages

١ Interpreting Responses to Nerve Stimulation

(Interscalene block).

27

2 Complications of Interscalene block and How to Avoid

Them.

28

3 Interpreting responses to nerve stimulation

(Infraclavicular block).

37

4 Complications of Infraclavicular block and How to

Avoid Them.

38

5 Interpreting responses to nerve stimulation (Axillary

block).

42

6 Complications of Axillary block and how to avoid

them.

43

III

List of Figures

Figures Pages

١ Brachial plexus from roots to terminal divisions 4

2 Surface anatomy landmarks for Interscalene block. 23

3 Patient position and needle insertion for Interscalene

block.

24

4 The goal for Interscalene block. 26

5 Surface anatomy and landmarks for supraclavicular

block.

29

6 Surface anatomy landmarks for Infraclavicular block. 33

7 The site of needle insertion for Infraclavicular block. 35

8 The goal for Infraclavicular block. 36

9 Surface anatomy landmarks and position of the patient

for Axillary block.

39

10 The site of needle insertion for Axillary block. 40

11 The site of needle insertion for Musculocutaneous

Nerve Block.

41

12 Probe position for the interscalene brachial plexus. 44

13 Ultrasonic image of brachial plexus in interscalene

groove.

45

14 Ultrasonic scanning of interscalene groove (cephalic). 46

15 Ultrasonic scanning of interscalene groove (caudal). 47

16 Probe position for the supraclavicular brachial plexus

block.

49

17 Ultrasonic image of brachial plexus in supraclavicular

region.

50

IV

List of Figures (Cont.)

Figures Pages

18 Image of needle in contact with brachial plexus in

supraclavicular region.

51

19 Probe position for the Infraclavicular brachial plexus

block.

52

20 Ultrasonic image of brachial plexus in Infraclavicular

region.

53

21 Needle in contact with the posterior cord behind the

axillary artery.

55

22 Probe position for the Axillary brachial plexus block. 56

23 Transverse Sonogram in Axillary region. 57

24 Ultrasonographic findings of variation in nerve

location around the Axillary artery

58

- 1 -

Introduction

Introduction

Peripheral nerve blocks play an important role in modern regional

anaesthesia and pain medicine. The concept of direct visualization of

nerve structures via ultrasonography is convincing and supported by

recent publications.[1]

Advocates of use of ultrasound believe that the use of ultrasound

technology provides a superior technique by allowing visualization of the

target structure (i.e. the nerve) and other structures of interest (i.e. blood

vessels, lung, pleura,…), a real time examination of the spread of local

anaethetic as it is injected, and the ability of reposition of the needle to

both avoid injury and increase success rates.[2]

Ultrasonographic guidance for peripheral nerve blocks offers

significant advantages compared with conventional methods such as

peripheral nerve stimulation and nerve mapping. It shortens sensory onset

times, improves the quality and the duration of blocks, may avoid

complications such as intraneuronal punctures, inadvertent vessel

punctures and pneumothorax during periclavicular brachial plexus blocks,

and enables a reduction of the volume of local anaesthetic due to precise

administration of the local anaesthetic solution.[3]

Ultrasound guidance may eliminate the need for electrical

stimulation and therefore reduce pain of the block. This was confirmed by

a study of an infraclavicular block comparing ultrasound guidance and

nerve stimulator guidance in children.[4]

- 2 -

Introduction

Claimed benefits of ultrasound guided regional anaesthesia include

that it is easier to learn and perform, quicker to perform, has a faster

onset, results in higher success rates, results in more complete block,

requires lower volumes of local anaesthetic, and increases safety.[5]

Chapter (1)

- 3 -

Anatomy of Brachial Plexus


Anatomy of Brachial Plexus:

The anterior horn cells that are cell bodies for motor neurons

resides in the ventral horn of the spinal cord and send their motor outflow

through the ventral root. The ventral roots exit the spinal cord and

combine with the dorsal roots to form spinal nerves .The spinal nerves

divide into anterior and posterior rami, and there are the anterior rami that

contribute to the formation of the brachial plexus.[6]

The brachial plexus receives contributions from cervical roots C5,

C6, C7, C8 and T1 .The sympathetic supply to the head and neck arises

from the first thoracic segment and reaches the spinal nerves through the

grey ramus from the inferior cervical ganglion .Damage to the T1 root

may result in an ipsilateral Horner's syndrome [Fig. 1].[6]

In the neck, the brachial plexus lies between the scalenus anterior

and scalenus 0medius and then deep to the sternocleidomastoid muscle.It

emerges from below the sternocleidomastoid muscle and three trunks are

formed above the clavicle[( upper) C5-C6, (middle)C7, (lower)C8-T1.[6]

Behind the clavicle, the anterior and posterior divisions of the

trunks reconfigure to form three cords. The upper two anterior divisions

unite together to form the lateral cord, the anterior division of the lower

trunk runs on as the medial cord, while all three posterior divisions unite

together to form the posterior cord.[6]

Chapter (1)

- 4 -


Fig. (1): Brachial plexus from roots to terminal divisions.[6]

Roots :

The anterior rami of the spinal nerves of C5, 6, 7, 8 and T1 form

the roots of the brachial plexus; the roots emerge from the transverse

processes of the cervical vertebrae immediately posterior to the vertebral

artery, which travels in a cephalocaudal direction through the transverse

foramina. Each transverse process consists of a posterior and anterior

tubercle, which meets laterally to form a costotransverse bar.[6]

Chapter (1)

- 5 -


The transverse foramen lies medial to the cost transverse bar and

between the posterior and anterior tubercles. The spinal nerves which

form the brachial plexus run in an inferior and anterior direction within

the sulci formed by these structures.

The dorsal scapular nerve arises from the C5 root and passes

through the middle scalene muscle to supply the rhomboidus and levator

scapulae muscles. The long thoracic nerve to the serratus anterior arises

from the C5,6 and 7 roots and also pierces the middle scalenus as it

passes posterior to the plexus.[6]

Trunks and divisions:

The trunks of the brachial plexus pass between the anterior and

middle scalene muscles.The superior trunk lies closest to the surface and

is formed by the C5 and C6 roots.The suprascapular nerve and the nerve

to the subclavius arise from the superior trunk. The suprascapular nerve

contributes sensory fibers to the shoulder joint and provides motor

innervation to the supraspinatus and infraspinatus muscles. The C7 root

continues as the middle trunk and the C8 and T1 roots join to form

inferior trunk. The trunks divide into anterior and posterior divisions,

which separate the innervations of the ventral and dorsal halves of the

upper limb.[6]

The phrenic nerve (C3, 4, 5) passes between the anterior and

middle scalenes and continues over the surface of the anterior scalene

muscle, thus a diaphragmatic twitch during interscalene brachial plexus

performed with a nerve stimulator may indicate placement of the needle

anterior to the plexus.[6]

Chapter (1)

- 6 -


The spinal accessory nerve (CN XI) runs posterior to the brachial

plexus over the surface of the middle and posterior scalenes. Contact with

spinal accessory nerve with a nerve stimulator (stimulating twitch in the

trapezius) indicates placement of the needle posterior to the plexus.[6]

Cords and Branches:

The cords are named the lateral, posterior, and medial cord

according to their relationship to the axillary artery. The cords pass over

the first rib close to the dome of the lung and continue under the clavicle

immediately posterior to the subclavian artery. The lateral cord receives

fibers from the anterior divisions of the superior and middle trunks, and is

the origin of the lateral pectoral nerve (C5,6,7). The posterior divisions of

the superior, middle and inferior trunks combine to form the posterior

cord.[6]

The upper and lower subscapular nerves (C7, 8 and C5, 6

respectively) leave the posterior cord and descend behind the axillary

artery to supply the subscapularis and teres major muscles respectively.

The thoracodorsal nerve to the latissimus dorsi, also known as the middle

subscapular nerve (C6, 7, 8) arises from the posterior cord. The inferior

trunk continues as the medial cord and gives off the median pectoral

nerve (C8, T10), the medial brachial cutaneous nerve (T1) and the medial

antebrachial cutaneous nerve (C8, T1). The lateral cord divides into the

lateral root of the median nerve and the musculocutaneous nerve. The

musculocutaneous nerve leaves the brachial plexus sheath high in the

axilla at the level of the lower border of the teres major muscle and passes

into the substance of the coracobrachialis muscle.[6]

Chapter (1)

- 7 -


The posterior cord gives off the axillary nerve at the lower border

of the subscapularis muscle and continues along the inferior and posterior

surface of the axillary artery as the radial nerve. The axillary nerve

supplies the shoulder joint, the surgical neck of the humerus, the deltoid

and the teres minor muscles before ending as the superiorlateral brachial

cutaneous nerve.[6]

The radial nerve continues along the posterior and inferior surface

of the axillary artery. The medial cord contributes the medial root of the

median nerve and continues as the ulnar nerve along the medial and

anterior surface of the axillary artery. The medial and lateral roots join to

form the median nerve which continues along the posterior and lateral

surface of the axillary artery.[6]

The connective tissue of the prevertebral fascia and the anterior and

middle scalenes envelops the brachial plexus as well as the subclavian

and axillary arteries in a neurovascular "sheath". The tissue is densely

organized as it leaves the deep cervical fascia proximally, but becomes

more loosely arranged distally. The sheath blends with the fascia of the

biceps and brachialis muscles distally.[7]

The Brachial Plexus "sheath"

Anatomic dissection, histological examination, and CT scanning

after injection of radio contrast into the brachial plexus sheath

demonstrate the presence of connective tissue septae which extend inward

from the fascia surrounding the sheath. These thin filamentous connective

tissue septae frequently adhere to nerves and vessels leaving no free space

between layers and compartmentalizing the components of the sheath.

Chapter (1)

- 8 -


Injection into the sheath in cadavers results in the filling of multiple

discrete interconnecting "grape-like" bubbles.[8]

Some controversy exists as to what degree the septae limits the

spread of local anaesthetics within the sheath.Some investigators propose

that the septae significantly limit the spread of solutions when a single

injection technique is used to perform brachial plexus block, and suggest

that the term "sheath "has been misapplied to the connective tissue

surrounding the brachial plexus.This may explain why anaesthesia

occasionally is complete and rapid in onset in some nerves, but delayed

and incomplete or completely absent in others.Other investigators have

demonstrated the existence of communications between the

compartments within the sheath. Methylene blue and latex solutions

injected in cadavers stain and surround the median, radial and ulnar

branches despite the presence of septae.The presence of communications

may explain why single injection techniques have success rates

comparable to multiple injection techniques. Complete spread of local

anaesthesia through a single injection technique possibly occurs through

many routes, such as spread of local anaesthesia through channels

between compartments, spread through communications at proximal

levels in the sheath, and diffusion through the thin septae between

compartments.[8]

Chapter (2)

- 9 -

Basic Principles & Physics of Ultrasound

Basic Principles and Physics of

Ultrasound

Introduction:

Ultrasound is a form of mechanical sound energy that travels

through a conducting medium (e.g., body tissue) as a longitudinal wave

producing alternating compression (high pressure) and rarefaction (low

pressure). Sound propagation can be represented in a sinusoidal

waveform with characteristic pressure, wavelength, frequency, period and

velocity.[9]

The velocity of sound (speed + direction of sound transmission)

varies for different biological media but the average value is assumed to

be 1,540 m/sec (constant) for human soft tissues. The frequency (ƒ) of

medical ultrasound is usually in the range of 2-15 MHz (cycles per sec)

and is inaudible to the human ear.[9]

Because the speed of sound (c) = ƒ x λ, higher frequency waves have

shorter wavelengths (λ) and vice versa.

Transducer Properties:

Linear and curvilinear (or curved) transducers are most useful for

nerve imaging to provide high resolution images. Sector phased array

transducers are less suitable because of the resultant "grainy" images.

Broad bandwidth transducers are designed to generate more than one

frequency. However there is one frequency at which the piezoelectric

transducer is most efficient in converting electrical energy to acoustic

energy and vice versa. This is called the resonance frequency and is

Chapter (2)

- 10 -


determined by the thickness of the piezoelectric element. With broad

bandwidth transducers, the operator can select the examination frequency

to match the target requirement.[9]

Tissue Penetration:

As the ultrasound beam passes through tissue layers, amplitude of

the original signal becomes attenuated with depth of penetration as a

result of certain factors as:

1. Reflection and scatter at interfaces.

2. Absorption (conversion of acoustic energy to heat).

3. Beam divergence.

4. Refraction.[9]

Attenuation indicates a change in signal intensity level in decibel

(dB) and a reduction in 3 dB corresponds to diminution of the original

intensity by half. Signal attenuation is closely related to the ultrasonic

frequency and the type of tissue medium.[10]

To compensate for attenuation, it is possible to amplify the echo

signals detected by the transducer before display. The degree of receiver

amplification is called the gain. Increasing the gain will amplify only the

returning signal and not the transmit signal. An increase in the overall

gain will increase brightness of the entire image, including the

background noise. Preferably, the time gain compensation is adjusted to

selectively amplify the weaker signals arriving from more distal and

deeper locations.[10]

Echo Reflection and Scattering:

Chapter (2)

- 11 -


The amplitude of a reflected echo to the transducer is determined by

the difference in acoustic impedances of the two tissues at the interface

(the degree of impedance mismatch). Acoustic impedance is the

resistance of a tissue to the passage of ultrasound. Mathematically, it is

the product of the medium density and speed of sound.[11]

Major impedance mismatch exists at a soft tissue-air interface. For

this reason, it is clinically important to apply sufficient conducting gel (an

acoustic coupling medium) on the transducer surface to eliminate any air

pocket between the transducer and skin surface. Otherwise much of the

ultrasound beam will be reflected and tissue penetration will be

limited.[11]

The angle of the incident beam also has a major influence on the

signal amplitude returning to the transducer. Specular reflection refers to

a perpendicular reflection after a beam hits a smooth mirror like interface

at a 90 degree incidence. An incident beam hitting the interface at an

angle will result in a beam being deflected away from the transducer at an

angle equal to the angle of incidence but in the opposite direction (angle

of reflection). When this happens, the returned signal is weakened and a

diminished image is displayed. Examples of a specular reflector are block

needles, fascia sheath, diaphragm and walls of major vessels.[11]

Refraction:

After reflection and scattering, the remainder of the incident beam is

refracted with a change in the transmitted beam direction. Refraction

occurs only when the speeds of sound are different on the two sides of the

interface. The degree of beam change (bending) is dependent on the

change in the speed of sound traveling from one medium on the incident

Chapter (2)

- 12 -


side to another medium on the transmitted side (Snell’s Law). With

medical imaging, fat contribute to serious refraction, image distortion and

some of the difficulties encountered in obese patients. Refraction

encountered with bone imaging is even more serious leading to a major

change in the direction of the incident beam and image distortion.[11]

Image Display:

When the echo returns to the transducer, its amplitude is represented

by the brightness of a dot on the display. Its position on the display is

determined by the depth from which the returning echo is originated. The

depth (D) is determined by the time (T) it takes for a wave to travel to and

from a structure (return trip thus 2 times) and can be expressed

mathematically as D = c T /2 where the speed of sound (c) is assumed to

be 1,540 m/sec (average).

Combination of all the dots forms the final image. Strong reflections

give rise to bright dots (e.g., diaphragm, gallstone, bone are hyperechoic).

Weaker reflections produce grey dots (e.g., solid organs) and no

reflection produces dark dots (e.g., fluid and blood filled structures are

hypoechoic or anechoic); this information is then translated onto a

monitor.[12]

Hypoechoic structures appear black on the screen when ultrasound

waves are not returned to the transducer. This can be due to significant

beam attenuation or transmission. Veins and arteries appear very dark

(anechoic) because the beam passes easily through fluid filled structures

without significant reflection. Arteries can be differentiated from veins

since arteries are pulsatile and difficult to collapse while veins are non-

pulsatile and easily collapsed (disappeared from the screen) under

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