Theory, Technique, and Knobology · Tissue Distraction by needle Needle is near. Move PROBE to find it ... The Language of Probe Movement ... Chin et al, Regional Anesthesia and Pain

UltrasoundTheory, Technique, and Knobology

Jerry Jones M.D.

Assistant Professor

Director, Acute Pain Service

Division Chief, Regional Anesthesia & Acute Pain Medicine

UTHSC/Regional One Health

Memphis, Tennessee

Disclosures

▪ Honoraria/Speakers Bureau – B Braun Medical, Avanos, Pacira

▪ CPNB Consulting LLC – Owner

▪ Cal Tenn Innovation Inc – CEO/patent holder

What is ultrasound …?The transmission of mechanical sound energy

If there is no material, nothing can vibrate → NO SOUND

Air/gas is NOT dense enough to transmit ultrasound waves

SOUND = vibrations passing through a conducting medium

• Electrical field applied to crystals

• Mechanical distortion of crystals results in

vibration and production of sound waves

(mechanical energy)

• Each piezoelectric crystal produces an US

wave → summation of all waves forms US

beam

• Also coverts reflected, incoming sound

waves to electrical energy

Lead Zirconate

Titanate (PZT)

D

I

Generation of US wave

• Ultrasound waves are generated in PULSES

- Each pulse commonly consists of 2-3 sound cycles of same frequency

• Pulses MUST be spaced with enough time to permit sound to reach target

and return to transducer before next pulse is generated

Frequency

• Frequency = rate of vibration

• Hertz (Hz) is the basic unit used to specify frequency, # of cycles per second

• 1 Hz = 1 vibration/sec.

• Ultrasound is anything > 20,000 Hz

• Most diagnostic ultrasound falls into the

range of 2-20 MHz (million cycles/sec)

1 cycle

How does it work again …?US transducer emits and receives signals

• Emits a short ultrasound pulse when electrical field applied to it.

• Listens a “LONG” time for returning echoes.

• Can only do ONE at a time

• Converts returning echoes to electrical energy → processed into an

image = PIEZOELECTRIC EFFECT (Pierre Currie 1880)

Speed of Ultrasound

Luckily, the speed of

US is nearly the same

for most body parts

Types of ultrasound

▪ B-mode (brightness mode)

▪ 2D, grey scale image that can be manipulated by adjusting GAIN.

▪ M-mode (motion mode)

▪ Monodimensional view

▪ Common in cardiology and thoracic imaging

▪ Time motion display of ultrasound wave along a chosen line.

▪ Doppler

▪ For imaging motion, specifically flowing blood

▪ RED = TOWARDS and BLUE = AWAY

Acoustic Impedance= the resistance of a tissue to the passage of ultrasound

The degree of acoustic impedance mismatch between two tissues → extent of reflection

The HIGHER the impedance mismatch, the GREATER the amount of reflection

Degree of reflection for air is high d/t VERY LOW acoustic impedance → AIR ARTIFACT

Echoes = bright spots

Produced by surfaces/boundaries between two tissue types

No reflecting

surfaces within fluid

–

ANECHOIC

Grey scale image (sometimes called a “B mode” image) is

due to the “mixture” of different tissue types within an

anatomic area

HYPERECHOIC

HYPOECHOIC

Which one do I pick …?

Sector/phased – crystal

arrangement in footprint is

bundled around the center and

fans out creating a pie-like

image on US screen.

Curvilinear

Linear

Intracavity

Selection is largely based upon:

• Imaging modality

• Depth and/or type of target

structure

• Desired field of view

Curvilinear Transducer

= Wider Field of View

8 MHz Transducer12 MHz Transducer

Interscalene block at approximately 1-2 cm depth.

Higher frequency transducer provides superior image resolution for superficial structures.

Linear Transducer

= Superior Image (higher frequency)

Modern transducers are broad

bandwidth – generate > 1 frequency

HIGH Frequency = HIGH spatial resolution but limited depth of penetration

LOW frequency = LOW spatial resolution but GREATER depth of penetration

- Superficial blocks (interscalene, supraclavicular, axillary, …)

• High frequency transducer 10-15 MHz preferred

- Intermediate depth blocks (infraclavicular and popliteal-sciatic)

- Lower frequency transducer less than or equal to 7 MHz

- Deep blocks (lumbar plexus, sciatic, …)

• Curvilinear transducer 2-5 MHz

Compound Imaging

• Reduces speckle artifacts

• Improves contrast resolution

Impact of the Depth Setting on Image Quality

• Median nerve in the forearm

(arrowhead) gets smaller and

smaller as depth is increased.

• Important to select

appropriate depth!!!

Impact of Gain Setting on Image Quality

• Gain compensates for attenuation

as sound travels deep

• Intensity of returning signals

amplified to brighten image

• Excessive gain → “NOISE”

Impact of Focus Setting on Image Quality

ATTENUATION = ENERGY LOSS

• Absorption → heat production

- Accounts for 80% of attenuation

• Reflection

• Scattering at interfaces

• Varies with frequency of US wave

- High frequency wave = high attenuation

Time Gain Compensation (TGC)

Increases overall image brightness, including

background noise

Gain = receiver amplification, ONLY amplifies returning signal

Preferably, TGC is adjusted to selectively

amplify the weaker signals returning from

deeper structures

Practical Introduction to CPNB & US

US BASICSWhat SHOULD the structures look like?

Nerves

Muscle, Fat, Bone

Artery & Vein

Pleura/Peritoneum

Skin/Fascia

Local Anesthetic


US BASICS Nerve Appearance is due to Connective Tissue content

Supraclavicular Image Femoral Nerve Popliteal Sciatic

White (hyperechoic) Shell with Completely White (hyperechoic) Honeycomb Appearance

Black (Hypoechoic) Center Confused with muscle/tendon

Can be confused with artery or vein


US BASICS Fat vs Muscle, Artery vs Vein, Bone

Saphenous Nerve Block Anterior Sciatic Approach

Fat has long wavy lines. Muscle appears ‘marbleized’ like steak Bone is hyperechoic and casts a dark Bone ‘Shadow’

Arteries pulse & Veins are compressible.


US BASICS Pleura & Peritoneum

Thoracic Paravertebral/Intercostal Supraclavicular Image TAP with II/IH

Pleura & Peritoneum are bright white with Comet Tail Effect below and are moving

Notice Bone Shadow below Rib in picture to far left


US BASICS Fascia & Local Anesthetic

Fascia Iliaca – longitudinal images

Fascia is hyperechoic. Sartorius Muscle seen to Right of first image. L.A. is hypoechoic

Cephalad direction is to the left in first two images.


US BASICS - Tools

Tissue Distraction by needle

Needle is near. Move PROBE to find it

Hydro-dissection using local anestheticUse to find/follow needle tip with steep angles

Leave LA ‘marker’, confirm crossed into next tissue plane

Enhancement when local anesthetic injected(Greater difference in Echogenic interface than with adjacent muscle)

Helps confirm that needle tip is accurate & spread is correct


US BASICS - Pitfalls

Air (USUALLY an enemy)Can’t see through air, but spread pattern of air can confirm needle position.

Oh, I thought THAT was the LATERAL side…..Confirm which side needle will approach EVERY time!

Needle direction on screen should be SAME as direction you are driving the needle.

Is that an Artery? Nerve? Muscle? Can appear similarly. Confirm structure: pulsing? Compresses easily? Or use color doppler

Move through space to confirm

Is THAT my Needle Tip?MUST always be aware of needle tip location!

Needle shaft may appear the same as needle tip.


US BASICS - Odd Visual Effects

Contact Artifact

Anisotropy

Reverberation

Shadows (Bone & Steep Needle)

Posterior Acoustic Enhancement

Contact (air) artifact

Poor probe patient interface. Remember acoustic impedance of air is

MUCH LESS than any other body tissue → limits penetration

Anisotropy

Nerves are not seen well as they are seen at a greater (or lesser) than 90 degree angle to the

probe, so tilting the probe slightly will make nerves appear better or worse.

Reverberation

Sound bounces off deepest aspect of needle and returns to probe to display an image. When at a 90 degree angle to probe, some of that sound bounces back off of most shallow aspect of needle and hits deepest aspect again, returning later. This appears as a deeper structure. Multiple bounces creates the repeating image below the needle.

Needle shadow

Posterior acoustic enhancement

Supraclavicular Femoral Infraclavicular

Blood returns sound signals much less than adjacent structures do, so there is a relative overabundance of sound at deeper end

of blood vessel which is seen as exaggerated hyperechogenicity of the underlying tissues

▪ Global Rating Scale for Ultrasound

▪ Frame/Reframe Image & Target (“Frame it up”)

▪ How/Why to Avoid touching the nerve

▪ Avoid excessive needle passes

▪ Steady Speed & Intentional Path of Needle

▪ Use sense of FEEL as advance needle

▪ Move slightly off needle to see injection pattern

▪ Elbows in tight, neutral wrist position, finger tips

▪ STABILIZE YOUR HANDS!!!

▪ SMALL ADJUSTMENTS (Fine motor skills)

▪ Air (USUALLY an enemy)

▪ Avoiding secondary failure

▪ Minimize needle passes

▪ The GOOD Assistant!

▪ Ultrasound Artifacts

▪ Helping & Helped by the ALERT Patient

▪ Completely set up first

▪ Archetypal Images

▪ Ergonomics

▪ Orient needle direction to screen

▪ Sidedness: Left/Right screen errors

▪ Probe hand ‘drift’

▪ Never use needle to find probe

▪ Nerve Stimulation as Confirmation/Alarm

▪ Only redirect Needle for Optimal Spread of Local

▪ Use Ultrasound like a VIDEO, not as a picture…

▪ Using Tissue Distraction by needle

▪ Hydro-dissection using local anesthetic

▪ Find/follow needle even if tip with steep angles

▪ Leave a LA ‘marker’

▪ Enhancement when local anesthetic injected

▪ Looking ‘downstream’ or laterally

▪ Overcome Obstacles, Poor Image & Reorienting

▪ Needle +’s & -’s

▪ Gel, condoms and Probe selection

▪ Know EXACTLY where you’re putting your Probe!

Ultrasound Technique Lessons

The Language of Probe Movement

‘tilt’

‘rock’ or

‘dig in heel of probe’

*

*

*

*

US probe manipulation maneuvers “PART” mnemonic for Pressure,

Alignment, Rotation and Tilt as fundamental probe manipulation maneuvers

Int J Shoulder Surg. 2010 Jul-Sep; 4(3): 55–62. Ultrasound: Basic understanding and learning the languageBarys Ihnatsenka and André Pierre Boezaart

Angle of Incidence

Schematic illustration of improving the angle of incidence by

tilting the probe. By tilting the probe from position 1 to position 2,

we obtained the true axial short-axis view of the artery and the

nerve. The shape of the image of the artery and the nerve got

more rounded, and the image of the nerve is much more defined

in position 2 due to a more favorable angle of incidence. Note

the changes in A1 and A2 distance as well.

“The angle at which the US waves

encounter the surface of the

structure, termed, the angle of

incidence, affects the way it is

presented on the screen. If the angle

is perpendicular, or close to

perpendicular, more US waves will

be reflected back to the transducer

and fewer will be “scattered” away,

resulting in a better image. If the US

waves are more parallel to the

surface of the object (more than a

45° angle of incidence), the image

will have less definition. The operator

can improve the image of the target

by tilting or rotating the probe, thus

adjusting the angle of incidence.”

Int J Shoulder Surg. 2010 Jul-Sep; 4(3): 55–62.

Ultrasound: Basic understanding and learning the language

Barys Ihnatsenka and André Pierre Boezaart

Improving needle visualization during “in plane” needle

placement. To improve needle visualization, one can change the

US probe position (from 1 to 2) and the needle approach (from 1

to 2 to 3) to optimize the angle of incidence between US waves

and the needle

YOUR APPROACH & YOUR HANDS:

“Pause for Pulsation” (Look for Arteries)

Compress/Decompress to identify Veins

Optimize View of Target & Choose Entry Anisotropy

Minimize Depth/Adjust Gain/B-steer

Tilt Probe for better needle angle

Choose as Shallow a Needle Angle as possible

Select a Safe Needle Path


Novice BehaviorsCharacterizing Novice Behavior Associated With Learning Ultrasound-Guided Peripheral Regional Anesthesia Sites et al, Regional Anesthesia & Pain Medicine: March/April 2007 - Volume 32 - Issue 2 - p 107–115

Error 1 (43.7%) = needle not visualized while being advanced.Error 2 (11.6%) = inadequate equipment preparation. Error 3 (4.7%) = neural target mal‐positioned on ultrasound screen. Error 4 (26.9%) = unintentional probe movement. Error 5 (3.5%) = awkward needle holding.Error 6 (1.7%) = watching hands instead of ultrasound image. Error 7 (7.8%) = poor ergonomics.

http://journals.lww.com/rapm/Fulltext/2007/03000/Characterizing_Novice_Behavior_Associated_With.3.aspx

Novice vs Expert SkillsScanning Phase:

Locate & identify key anatomic landmarks

Obtain optimal plane for needle insertion

Requires familiarity of gross and sonoanatomy &

the ability to manipulate probe to obtain desired images

Needling Phase:

Safely guide needle tip to appropriate location

Subsequently redirect needle for adequate local spread

Maintaining continual needle-beam alignment found to be

the most demanding skill in either phase

Chin et al, Regional Anesthesia and Pain Medicine & Volume 36, Number 3, May-June 2011 Hand Motion Analysis in Ultrasound-Guided PNB

Novice vs Expert SkillsScanning Phase:

Residents: 1 - 6 minutes

Early Fellow: 1 – 5 minutes

Late Fellow: 54 sec – 1 min 36 sec (had performed >50 SS supraclavicular blocks)

Consultants: 24 sec - 1 min 48 sec

Consultants 3x better ‘Dexterity’ scores (time, total distance of path, total movements)

Consultants similar # movements/minute but made shorter movements with probe hand

Needling Phase:

Residents: 4 min 54 sec - 13 min 30 sec

Early Fellows: 6 – 10 minutes

Late Fellows: 3 min 30 sec – 8 minutes

Consultants: 3 min 24 sec – 8 min 12 sec

Consultants 40% better (shorter) all ‘Dexterity’ scores

Consultants made significantly fewer movements of probe hand/minute and made

smaller amplitude movements with probe and needle hand

(Best to worst possible Total Times for block: 3 min 48 sec to 19 min 30 sec)*

Novice vs Expert SkillsNOVICES:

1. When scanning, probe movements are inappropriately large (Use Gross motor skills)

2. When needling, needle movements are inappropriately large (Use Gross motor skills)

3. When needling, unintentional probe movements (Hand positions not secured)

EXPERTS:

1. Make fewer probe movements to obtain image (Use Fine motor skills)

2. Smaller probe movements with scanning and needling (Use Fine motor skills)

3. Able to obtain and maintain alignment of needle & beam (Hand positions secured)

* MY ANALYSIS

Similar number of probe- & needle-hand movements per minute both phases


YOUR APPROACH & YOUR HANDS:Frame/Reframe Image & Target (“Frame it up”)

Do NOT use excessive needle passes

Steady Speed & Intentional Path of Needle

Use sense of FEEL as advance needle

Move slightly off needle to fully see injection pattern

Keep elbows in tight, neutral wrist position

STABILIZE YOUR HANDS!!!

SMALL ADJUSTMENTS with Fingertips (Fine motor skills)


YOUR APPROACH & YOUR HANDS:Nerve-Stimulation as Secondary Confirmation (& Alarm)

Redirect Needle for Optimal Spread of Local

Use Ultrasound like a VIDEO, not as a still picture…

scan through space to recognize patterns of change, orientation of structures

Images provided by:

Dr Jerry Jones

Scan option 1

Feel the Biceps Femoral

Tendon proximally until

it feel like a muscle

Set the lateral edge of

the probe on that

location

This will orient you as to

which muscle is which

Images provided by:

Dr Jerry Jones

Scan option 1

Scan distally & look for

the nerve to split into

the common peroneal &

tibial nerves, the

decrease in muscle size

and the appearance of

the popliteal vessels

Images provided by:

Dr Jerry Jones

Scan option 2

Set the probe in

the popliteal

crease, and locate

the pulsation of the

popliteal artery

The tibial nerve will

be just superficial

to it

Images provided by:

Dr Jerry Jones

Scan option 2

Scan proximally,

watching for the

common peroneal

nerve to join it

from the lateral

aspect while the

artery descends

away

Thank You!

Documents

Theory, Technique, and Knobology · Tissue Distraction by needle Needle is near. Move PROBE to find it ... The Language of Probe Movement ... Chin et al, Regional Anesthesia and Pain