What is ultrasound? :

Physics: ____ w/ a frequency >_____ Hz, approx upper limit of ___ ____

Medicine/Medical: application of ____ waves to therapy or diagnostics, as in deep-heat treatment of a joint or ____ of internal structures

Physics: sound w/ a frequency >20,000 Hz, approx upper limit of human hearing

Medicine/Medical: application of ultrasonic waves to therapy or diagnostics, as in deep-heat treatment of a joint or imaging of internal structures

More specifically, US is:

Acoustic energy generated from _____ ____ inside a transducer vibrate at __ frequency in response to ____ current.

Vibration passes into ___, bounces off ____ & returns to _____

This process is repeated over ___ times/sec, processed by computer & produces real-time __ image

Degree of reflection & return of waves determines...?

Acoustic energy generated from piezoelectric crystals inside a transducer vibrate at high frequency in response to alternating current.

Vibration passes into body, bounces off tissues & returns to transducer

This process is repeated over 7000 times/sec, processed by computer & produces real-time 2D image

Degree of reflection & return of waves determines signal intensity on gray scale

What is the MAIN advantage in UGRA?

What is the most imp prerequisite for successful RA?

Another advantage is that watching spread of LA can possibly have what effect? What else can this do?

main advantage=direct visualization of neural & adjacent anatomical structures & needle tip

correct interpretation of real-time 2D images is most imp

Watching spread of LA:

can possibly lower vol required

confirm correct spread of LA

What is a large reason for block failure?

How can UGRA help this?

Variants are a large reason for block failure

US is only bedside method able to accurately detect local anatomy variation before RA

Does onset time w/ UGRA differ from traditional blocks?

Is this imp clinically?

ranges from no difference to 4-6 min

depends on practice circumstance:

if blocks done in separate block room outside OR before Sx, prolly doesn't make a difference

but if done in OR immediately prior to case, can be beneficial

RA outcomes USG vs NS

How do success rate & incidence of complications differ?

both methods equally utilized to successfully perform PNBs especially with experienced practitioner

comparisons of incidence of complications would require large-sized investigations--not done yet

3 big things for use of UGRA

knowledge of ______

______ recognition

getting the ___&____where it needs to be

knowledge of anatomy

pattern recognition

getting the needle & drug where it needs to be

In US, shadow is created by beam's high degree of reflection from surface of dense structure

ie a bone is very hyperechoic and will have an area of "shadow" under it; this could be a problem b/c you cant see what structures are "in" the shadow

In US, attenuation is a decrease in _____ of sound wave traveling thru a medium.

What does this yield?

In US, attenuation is a decrease in intensity of sound wave traveling thru a medium.

yields progressive decr in returning signal intensity as US travels deeper

In US, what is scattering?

When does it occur?

diffusion or redirection of sound in multiple directions

occurs when sound wave is larger than object it contacts

How do arteries appear in US?

Veins?

Are they collapsible?

artery

round anechoic

not collapsible

pulsatile

vein

oval anechoic

collapsible

non-pulsatile

In US, fat has ____ background containing streaks of _____ lines, often _____ in texture & length

The fat layer is the most ______ layer

In US, fat has hypoechoic background containing streaks of hyperechoic lines, often irregular in texture & length

The fat layer is the most superficial layer

In US, muscle has ____ background containing ___ streaks of ____ lines

Outline of mm layer (the ___ sheath) is highly ____.

Bone often shows _____ outline & ____ bony shadow underneath

In US, muscle has hypoechoic background containing short streaks of hyperechoic lines

Outline of mm layer (the fascial sheath) is highly hyperechoic

Bone often shows hyperechoic outline & hypoechoic bony shadow underneath

In US, nerve in longitudinal section has internal echotexture consisting of continuous ____ longitudinal elements (fascicle groups) interspersed w/ ____ perineural connective tissues

A tendon in longitudinal section appears very much like a _____, although tendon has _____ internal echotexture & discontinuous ______ speckles

In US, nerve in longitudinal section has internal echotexture consisting of continuous hypoechoic longitudinal elements (fascicle groups) interspersed w/ hyperechoic perineural connective tissues

A tendon in longitudinal section appears very much like a nerve, although tendon has fibrillar internal echotexture & discontinuous hyperechoic speckles

Are nerves in interscalene & supraclavicular regions hypo- or hyperechoic?

What does the hypoechoic component of this area represent?

Are nerves below clavicle & in LE hypo- or hyperechoic?

What does degree of hyperechogenicity reflect?

Hypoechoic above clavicle

hypoechoic component represents neural tissue

Hyperechoic w/honeycomb appearance below clavicle & in LE

degree of hyperechogenicity likely reflects amount of connective tissue w/in nerve

Characteristics of Difficult Guidance

Deep blocks (obesity) results in degraded image of both __ & __

Potential for serious injury such as _____

Blocks involving ___, difficult to image nerves

Blocks involving nerves lacking _____ US interfaces, yielding trouble separating nerve image from _____ tissue

Deep blocks (obesity) results in degraded image of both needle & US (make it more difficult)

Potential for serious injury such as pneumothorax

Blocks involving small, difficult to image nerves

Blocks involving nerves lacking distinct US interfaces, yielding trouble separating nerve image from surrounding tissue

Clinical pearl:

A distinct advantage exists when target nerve is surrounded by tissue of ...?

Clinical Pearl

Keep needle _____ to US beam to minimize ___ & maximize ____ back toward probe for best needle image

Clinical Pearl

To improve temporal resolution, decrease imaging depth to...?

Clinical Pearl

What is the most imp application of color Doppler technology?

Color doppler

What type of flow is detected when the transducer is perpendicular to radial artery?

When transducer is aimed away from artery?

When transducer is aimed towards artery?

perpendicular

no flow detected

away from artery

(transducer tip on wrist, handle towards elbow; flow moving away from transducer)

blue flow

towards artery

(transducer tip on wrist, handle towards hand; flow moving towards transducer)

red flow

Acoustic artifact involves error in ______

Anatomic artifact involves error in ______

Acoustic artifact involves error in presentation of US info

Anatomic artifact involves error in interpretation by user

Clinical Pearl

Attenuation can yield negative impact on ______.

2 imp adjustments:

Artificially incr signal ___ of ___ echoes from all points in field

Control gain independently at specified depth intervals, known as ___ ____ ______

Attenuation can yield negative impact on image quality.

2 imp adjustments:

Artificially incr signal intensity of returning echoes from all points in field

Control gain independently at specified depth intervals, known as time gain compensation

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 (TGC) is adjusted to selectively amplify the weaker signals returning from deeper structures.

Acoustic shadowing may lead to what erroneous assumption?

Example?

In supraclavicular nerve block, what do we want to visualize? What do we want to avoid?

that no structures of interest exist in anechoic region

Bone shadow deep to a hyperechoic bone outline is the result of beam attenuation when the beam encounters bone with a high attenuation coefficient. Ultrasound beam penetration is severely impeded.

As 1st rib shields pleura from US, no anatomical info is provided.

In supraclavicular nerve block, goal is to visualize subclavian artery, 1st rib, & trunks or divisions of brachial plexus

Avoid contact with the pleura which should exist immediately below 1st rib

Clinical Pearl

Never insert the needle into the ____ region deep to the 1st rib b/c location of the ___ cannot be identified

Clinical Pearl

Search for acoustic shadow when using ____ technique

Appreciate limitations of this technique, primarily inability to confirm real-time ___ location of _____

Search for acoustic shadow when using out-of-plane technique

Appreciate limitations of out-of plane technique, primarily inability to confirm real-time exact location of needle tip

Clinical Pearl

Acoustic shadowing may not only hide imp structures or distort normal anatomy, it may also be a sign of ...?

Calcified arterial plaques act as strong specular ___ that generate distinct acoustic shadows ___ to affected artery

Further clinical eval may be needed to assess for ...?

Acoustic shadowing may not only hide imp structures or distort normal anatomy, it may also be a sign of serious pt pathology

Calcified arterial plaques act as strong specular reflectors that generate distinct acoustic shadows deep to affected artery

Further clinical eval may be needed to assess for significant vascular ds

Clinical Pearl

Acoustic enhancement can make it difficult to ___ visualize either radial N or posterior cord of brachial plexus

What additional confirmation techniques may be of value?

Acoustic enhancement can make it difficult to definitively visualize either radial N or posterior cord of brachial plexus

nerve stimulation

Clinical Pearl

Reverberation artifacts occur more when needle is completely ____ to US beam

How can you decrease artifact in this case?

Reverberation artifacts occur more when needle is completely perpendicular to US beam

adjust needle to less than 90 degrees for less artifact

Clinical Pearl

US may bounce back & forth w/in lumen of an artery, generating a ____ of 2D image of subclavian artery w/ artifact existing __ to actual structure

What is this called?

US may bounce back & forth w/in lumen of an artery, generating a duplication of 2D image of subclavian artery w/ artifact existing deep to actual structure

vessel reverberation artifact

probe not making good contact w/ skin

get "drop out" (anechoic area) where there is no contact

Anatomic artifacts are tissue structures, either normal or aberrant, that may resemble ___ ___ & mislead operator into ...?

What are 2 common solutions to these pitfall errors?

Anatomic artifacts are tissue structures, either normal or aberrant, that may resemble target nerve & mislead operator into pursuing wrong target

trace target N along its expected anatomic course

use PNS as an adjunct to confirm target's identity

 nerve and a tendon of the forearm in cross section: the nerve is oval and the tendon has an irregular shape

 note that the tendon will merge into a muscle proximally while the nerve does not

1. Nerves are echogenic (hypo or hyper) relative to surrounding tissue

Blood vessels are uniformly anechoic structures

2. Arteries pulsate & resist compression

Veins do not pulsate & are compressible

Nerves are nonpulsatile & are not compressible

3. Color Doppler can detect blood flow, thereby positively identifying blood vessel (but if transducer held perpendicular then it will not pick up flow; transducer needs to be <90 to see flow)

Clinical Pearl

Whenever basic maneuvers (compression), defining features (internal echogenicity), & color Doppler fail to identify a structure of interest, what should we do?

Simple Start List

Relate dot on screen to ________.

Use ____

Think of the US beam in __ even tho you're looking at a __ pic & adjust the needle accordingly

Relate dot on screen to nipple on probe

Use autogain

Think of the US beam in 3D even tho you're looking at a 2D pic & adjust the needle accordingly

Scanning technique--Nerve Localization

Perform complete & systematic ___ ___ in region

Nerves may not be readily visible, but ___, ___ & ___ are easily identifiable under US & help define target N location

Imp to visualize structures that should not be ____or ___.

What can you use to maximize image?

Perform complete & systematic anatomical survey in region

Nerves may not be readily visible, but mm, vessels & bones are easily identifiable under US & help define target N location

Imp to visualize structures that should not be entered or trespassed (ie, 1st rib & pleura in supraclavicular region)

PART maneuvers

What are the components of the PART maneuver?

P: pressure--varying degrees of transducer pressure on skin

A: alignment--sliding motion of transducer to define lengthwise course of nerve

R: rotation--of transducer clockwise/counterclockwise to optimize image

T: tilting--tilt transducer in both directions to maximize angle of incidence of US beam w/ target N

It is imp to have proper ___handling & body ___ when handling transducer & needle, viewing screen, & positioning pt

How do we maximize success?

It is imp to have proper needle handling & body egonomics when handling transducer & needle, viewing screen, & positioning pt

choose proper body location & orientation in relationship to pt

US machine placed directly in front of operator to provide direct line of vision

both hands anchored

see 10 tasks for successful US blocks

ID target on __ axis

T/F: It is imp to inject small vol of test soln to begin, but if we don't see the soln it's ok b/c we used US to find nerve

ID target on short axis

FALSE!!

Need to inject test dose, but unseen soln should be presumed to be IV or out of imaging plane

How can we get desired pattern of LA spread?

Remember to use traditional RA safety when using US, which includes what 6 things?

adjust needle

GA equipment

frequent aspiration

IV test dosing

monitors

pt response

ease of injection

(Fill in the blanks. Parenetheses asking for hyper-, hypo-, or anechoic.)

Strong specular reflections give rise to ___dots (_______). What structures are examples of this? (4)

Weaker diffuse reflections produce ___ dots (_______) e.g., ___ ___.

 No reflection produces ____ dots (_______) e.g.,________. Why do they appear this way?

Deep structures often appear ______ . Why?

Strong specular reflections give rise to bright dots (hyperechoic)

e.g., diaphragm, gallstone, bone, pericardium.

Weaker diffuse reflections produce grey dots (hypoechoic)

e.g., solid organs.

No reflection produces dark dots (anechoic)

e.g., fluid and blood filled structures

because the beam passes easily through these structures without significant reflection.

Deep structures often appear hypoechoic because attenuation limits beam transmission to reach the structures, resulting in a weak returning echo.

USG is rapidly expanding area of anesthesia care:

The major benefits related to ________ & _______.

It is _____ a new gold standard for RA, unlikely that it will be; there are advantages to its use, but the _______ must be understood.

visualizing anatomy

real time block performance

NOT

limitations