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Terms in this set (128)
What is resolution?
the ability to separate two points or resolve them
What is axial resolution?
the ability to resolve or separate two points parallel to the ultrasound beam
What is lateral resolution?
the ability to resolve two or more objects perpendicular to the ultrasound beam
What is temporal resolution?
The ability to detect that an object has moved over time
Synonymous with frame rate
Frame rate has a tradeoff between what two factors?
Ultrasound frequency has a tradeoff between what two factors?
(Image Quality) Resolution vs (Tissue Penetration) Attenuation
The higher the frequency, the higher the resolution and lower the penetration
Higher frequencies will increase/decrease resolution and increase/decrease scan depth?
Higher frequencies will have increased resolution with a decrease in scan depth
Lower frequencies will increase/decrease resolution and increase/decrease scan depth?
Lower frequency will have a lower resolution and increased scan depth
What is a hyper echoic tissue?
Hyperechoic tissues reflect a large amount of the ultrasound waves back to the probe and therefore appear white. E.g. bone, air
What is a hypo echoic tissue?
Hypoechoic tissues reflect fewer ultrasound waves and therefore appear as shades of gray. E.g. muscle, liver
What is an anechoic area?
Anechoic areas do not reflect ultrasound waves and therefore appear black. E.g. Veins, injectable fluids, local anesthetic
What 4 factors can be adjusted to optimize your ultrasound scan?
How do you adjust the depth of the ultrasound machine for an optimal picture?
Adjust the depth to 1 cm below the structure of interest
What is the focal zone?
The area with the highest lateral resolution denoted by a triangle on the ultrasound screen
What is gain?
Gain is a uniform amplification of the ultrasonic signal that is returning to the transducer after it travels through the tissue
Increasing gain = increases overall brightness of picture
Decreasing gain = decreases overall brightness of picture
What is dynamic range?
a function of contrast and basically determines how white is white and how black is black
What is anisotropy?
property of being directionally dependent
What is isotropy?
homogeneity in all directions aka looks the same no matter how you look at it
What is an in-plane approach?
Needle is inserted parallel to the probe
In-plane approaches allow the needle to be best visualized but may not always be practical due to anatomical constraints (e.g. regional blocks)
What is an out of plane approach?
Needle is inserted perpendicular to the probe
The out-of-plane approach offers better visualization of two objects at once (e.g. arterial line, central line)
What is the transverse plane?
axial plane runs parallel to the ground and separates the head from the feet
What is the sagittal plane?
Perpendicular to the ground separates right from left
What is the coronal plane?
separates anterior from posterior, front from the back
What is the oblique plane?
between the transverse and sagittal planes (on an angle)
What is reverberation?
occurs when the sound pulse is reflected back into the patient and again returns to the probe.
What is shadowing?
seen when a strongly attenuating substance is proximal to the probe blocking the view
Shadowing caused by poor skin to transducer contact or when air or bubbles are injected into the field obscuring deeper structures.
What is enhancement?
a hyperechoic region appears beneath an object with low attenuation i.e. below a blood vessel
What is the difference between shadowing and enhancement?
Shadowing involves a strongly attenuating object vs enhancement involves a low attenuating object
The degree of attenuation refers to how much it dampens the ultrasound waveform
What part of the nerve are you targeting when you are performing a block?
Perineural space around the epineurium
What components of resolution are inverse?
Resolution and penetration
Upper part of the ultrasound screen is referred to as?
Near field aka Fresnel
To optimize an ultrasound scan use the following?
Focus, gain, depth and dynamic range
Which plane separates the anterior and posterior planes?
Beneath the internal jugular a very hyperechoic region is observed. What is it?
The radial artery is observed by the CRNA while tilting the probe towards the body with the color flow Doppler, what color will be
Which approach allows the CRNA to see structures that are lateral to each other?
Out of plane
Name the parts of the nerve medial to lateral
"Real texans drink cold beer"
Roots --> trunks --> divisions --> cords --> branches
How many roots, trunks, divisions, cords and branches are there?
What block targets the brachial plexus roots and trunks?
What block targets the brachial plexus divisions?
What block targets the brachial plexus cords?
What block targets the brachial plexus branches?
What is the radial nerve test?
Push their forearm against light resistance as they try to extend their arm
Radial nerve supplies the dorsal extensor muscles aka the triceps
What is the motor response of the radial nerve?
Extension of all digits
Extension of wrist and forearm at the elbow
Supination of the forearm
You can differentiate this one from the others (ulnar, median and musculocutaneous) since it involves extension and supination which none of the others do.
What is the musculocutaneous nerve test?
Pull or flex their arm towards their nose with light resistance
What is the motor response of the musculocutaneous nerve?
Flexion of the forearm at the elbow
What is the median nerve test?
Pinch the thumb
Inability to oppose the thumb causing ape hand due to thumb weakness
Difficulty buttoning buttons on a shirt
What is the motor response of the median nerve?
Flexion of the wrist, second and third digits
Opposition of the thumb
Pronation of the forearm
what is the ulnar nerve test?
Pinch the pinky or try to touch your pinky to your thumb
It's the pinky that becomes weak
What is the motor response of the ulnar nerve?
Flexion of wrist, fourth and fifth fingers
Adduction of the thumb
The interscalene block provides analgesia to what parts?
Analgesia to the shoulder and upper arm
What nerve is often missed in an interscalene block?
May miss the ulnar nerve since you do not cover the inferior trunk
What are the risks associated with an interscalene block?
-Phrenic nerve paralysis
-Larger volumes of local anesthetic may increase the spread of local anesthetic within the neck, leading to hoarseness (recurrent laryngeal nerve blockade) or Horner's syndrome (blockade of the stellate ganglion).
-Potential for total spinal with this block even if you have your needle angled down
The supraclavicular block provides analgesia to what parts?
Analgesia to the entire upper extremity distal to the shoulder
What is the major risk of the supraclavicular block?
-Risk of pneumothorax due to the close proximity to the brachial plexus of the lung
-Subclavian artery injection
What risks do the interscalene block and supraclavicular block share?
Pneumothorax and Horner's Syndrome
What risks do the interscalene block and supraclavicular block not share?
Interscalene block has a risk of phrenic nerve paralysis while the supraclavicular block has the risk of subclavian artery injection
The infraclavicular block provides analgesia to what parts?
Analgesia to the elbow and below
What nerve gets missed in the infraclavicular block?
Does not block the intercostobrachial nerve (T2)
What are the major risks of the infraclavicular block?
1. Axillary artery puncture
This block is more painful than the interscalene and supraclavicular block because the needle crosses two muscle fascial planes
What is the risk shared by the interscalene block, supraclavicular block and infraclavicular block?
The axillary block providers analgesia to what parts?
Analgesia distal to the elbow
What is the major risk of the axillary block?
What nerve is missed in the axillary block?
How can you remember the motor differences for radial, musculocuteanous, ulnar and median?
Radial is the only extension and supination one.
Musculocutaneous is the flexion opposite of radial
ulnar is all about the flexion of the pinky and the adduction of the thumb
Median is all about the opposition of the thumb
Which region is most likely to be inadequately anesthetized following an axillary block with a trans arterial technique?
What is the risk associated with a superficial cervical block?
Potential for phrenic nerve blockade
What is the unusual technique specifically used in the axillary block?
1. The arm is bent cephalad at 90 degrees
2. The radial artery is palpated
3. A block needle (short bevel and insulated) is inserted
An assistant aspirates until arterial blood is withdrawn
The needle is advanced until no blood is aspirated. Local is injected on the radial nerve and musculocutaneous nerves 2/3rd of local
4. Withdraw the needle until arterial blood is aspirated and then stops
5. Inject the remaining 1/3 of the local (30-40 mL total) on the median and ulnar nerves to give you a peri-arterial spread
If a block is shallow do you use a high frequency or a low frequency transducer?
High frequency linear
If a block is deep, do you use a high frequency or a low frequency transducer?
Low frequency curved
What artery is most likely to be injected with local anesthetic during an interscalene block?
What artery is most likely to be injected with local anesthetic during a supraclavicular block?
What artery is most likely to be injected with local anesthetic during an infraclavicular block?
Subclavian or axillary artery depending on the block level
What artery is most likely to be injected with local anesthetic during an axillary block?
When compared to the supraclavicular block, the infraclavicular block has a higher risk of ?
When compared to the infraclavicular block, the supraclavicular block has a higher risk of ?
Phrenic nerve inhibition
What is the best landmark for the interscalene block?
What is the best landmark for the supraclavicular block?
What is the best landmark for the infraclavicular block?
What is the best landmark for the axillary block?
axillary artery pulse
During an interscalene block using the nerve stimulator technique, what patient response indicates proper needle placement?
Deltoid (shoulder abduction)
Pectoralis major (internal rotation of the arm)
Biceps (forearm flexion)
Triceps (forearm extension)
Any twitch of hand or forearm
During an supraclavicular block using the nerve stimulator technique, what patient response indicates proper needle placement?
Finger extension or flexion
Wrist extension or flexion
During an infraclavicular block using the nerve stimulator technique, what patient response indicates proper needle placement?
During an axillary block using the nerve stimulator technique, what patient response indicates proper needle placement?
Radial --> finger or wrist extension
Ulnar --> ulnar deviation
Median --> finger flexion
Musculocutaneous --> Biceps flex
What is the most significant risk associated with bier block?
Toxicity from the local anesthetic
How many minutes MINIMUM must the tourniquet be inflated in a Bier Block?
What can happen if a Bier Block is deflated before the minimum 20 minutes?
If the cuff is deflated too soon (or the cuff fails), then the local anesthetic is washed into the systemic circulation where it can produce seizures or cardiovascular collapse.
What is the order of operations for applying a Bier Block?
1. Place a double cuff tourniquet on the patient. Do not inflate it.
2. Place a 22g IV in a distal peripheral vein of the operative extremity.
3. Elevate the extremity for 1-2 minutes to allow for passive exsanguination
4. Wrap the besmirch bandage around the extremity to further exsanguinate it. Begin at the distal limb and move proximally until you reach the distal tourniquet cuff
5. Inflate the distal cuff
6. Inflate the proximal cuff
7. Deflate the distal cuff
8. Remove the esmarch bandage
9. Inject the LA
What are good choices for Bier Block LA?
0.5% Lidocaine 50 mL
What's an acceptable additive to the Bier Block LA?
Toradol 15-30 mg which assists with analgesia and does not increase the risk of bleeding
What LA should not be used for Bier Block?
Bupivicaine should be avoided since accidental LAST could cause a difficult cardiac resuscitation
What additive should be avoided in a Bier Block?
1. Epi (due to risk of ischemia)
2. Preservative (due to risk of thrombophlebitis)
What nerves arise from the lumbar plexus?
Lateral femoral cuteanous
"I invariably get lazy on Fridays"
What's the peripheral block max for Ropiviciane?
What is the peripheral block max for Bupivicaine?
What is the peripheral block max for Lidocaine with and without Epi?
Without = 300 mg
With = 500 mg
What part of the leg is blocked in a femoral nerve block?
anterior thigh, anteromedial knee, and the medial aspect of the lower leg, ankle and foot
What is a femoral nerve block used for?
total knee replacement
femoral knee fractures
What two blocks combined provide complete analgesia to the entire lower extremity?
Femoral nerve block + sciatic nerve block
What landmarks are used for the femoral nerve block?
Two pops are felt as the needle in a femoral block passes through what?
What are the borders of the Femoral triangle?
-S = sartorius muscle
-A = adductor longus muscle
-IL = inguinal ligament
What are the structures inside the femoral triangle (medial to lateral)?
-Use "VAN" for the structures INSIDE the triangle (medial to lateral):
-V = vein
-A = artery
-N = nerve
What are the risks associated with the femoral nerve block?
and post op patient falls
The adductor canal block also known as the saphenous nerve block provides analgesia to what parts?
anteromedial knee and the medial aspect of the lower leg, ankle and foot
What is unusual about the adductor canal block also known as the saphenous nerve block?
The adductor canal block is a sensory block and preserves quadriceps motor function
What is the adductor canal block also known as the saphenous nerve block used for?
Frequently used for knee surgery such as total knee arthroplasty
May also be used for saphenous vein stripping and foot surgery (often with a popliteal block)
What structures travel within the adductor canal?
posterior branch of the medial femoral cutaneous nerve
What are the landmarks of the adductor canal block?
The sciatic nerve provides motor innervation to?
What nerve is being blocked in a popliteal block?
What surgeries is the popliteal (sciatic nerve) block used for?
Foot, ankle, and Achilles' tendon repairs
What are the landmarks for the popliteal block?
tendon biceps femoris (lateral)
tendon semitendinosus and semimembranosus
What two nerves make up the sciatic nerve?
common peroneal nerve
What nerve is missed in a popliteal block?
Stimulation of the tibial nerve results in?
Plantar flexion and inversion
This is what you want to see in a popliteal block
Stimulation of the common peroneal nerve results in?
What levels does a TAP block cover?
What surgeries is a TAP block cover?
Used in open hernia surgery, TAH, appendectomy, and other surgeries of the abdomen
Local anesthetic is placed between what layers of the muscle in a TAP block?
internal oblique muscle (IOM)
transversus abdominis muscle
What nerves do wrist blocks target?
Block the radial, ulnar, and median nerves
What are wrist blocks used for ?
Used for hand surgeries that do not require motor block
What is a rectus sheath block?
Local placed under the rectus abdominus muscle
What surgery is a rectus sheath block used for?
Umbilical hernia repair
What is a paravertebral block used for?
Useful for surgeries of the chest wall and breast
What is the significant risk of a paravertebral block?
Carries a significant risk of pneumothorax
What is the erector spinae block?
"Paravertebral block - light"
Local is placed between the erector spinae and the transverse process
Why would you place an erector spinae block instead of a paravertebral block?
Thought to have less risk of pneumothorax than paravertebral blocks
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