Truncal Blocks (week 6) Flashcards
What are the absolute contraindications to regional anesthesia?
- patient refusal
- uncorrected coagulation deficiencies
- infection at the block site
Nagelhout, pg. 1141
In addition to potentially spreading or seeding the infection, why else should regional anesthesia not be performed when there is an active infection at the site?
- acidic environment will reduce effectiveness of the block
Nagelhout, pg. 1141
Allergies to which class of local anesthetic are more common?
- Ester
ONE EYED ESTER IS A NASTAY BITCH
Nagelhout, pg. 1141
What is the double crush phenomenon as it relates to regional anesthesia?
- The theory that patients with preexisting neurologic disease may experience permanent injury following a second insult
Nagelhout, pg. 1141, 1143
Why are allergies to ester local anesthetics more common?
- The metabolite paraaminobenzoic acid (PABA) is a known allergen
Nagelhout, pg. 1141
Name the truncal blocks that can be utilized for surgeries in the chest/thorax area
- PECS I/II
- Paravertebral
- Intercostal
- Erector spinae
Nagelhout, pg. 1142 - Fig. 50.1
Name the truncal blocks that be utilized for surgeries in the abdominal/back areas
- Transversus Abdominis
- Quadratus Lumborum
- Erector Spinae
Nagelhout, pg. 1142 - Fig. 50.1
Documented complications associated with regional anesthesia include:
* _________
* ________
* _________
* __________
* _________
- direct/indirect nerve injury
- local anesthetic systemic toxicity (LAST) events
- vascular injury
- hematoma
- infection
Nagelhout, pg. 1142
While the overall incidence of severe or permanent peripheral nerve injury (PNI) following a block is extremely low, it is not uncommon in the early postoperative period for as many as 15% of patients to complain of _____________
- paresthesia
aka postoperative neurologic symptoms (PONS)
Nagelhout, pg. 1142
True or false:
The lack of motor response when using a peripheral nerve stimulator is the best way to guarantee that intraneural needle placement has not occured, thus avoiding direct nerve injury
- False - lack of motor response does NOT guarantee that intraneural needle placement has not occured
Nagelhout, pg. 1142
True or false:
All local anesthetics used in clinically relevant concentrations are potentially neurotoxic
- True story
Nagelhout, pg. 1141
Indirect nerve injury refers to nerve injury occuring from local anesthetic toxicity, ____________, or _____________
- ischemia
- inflammation
Nagelhout, pg. 1142
All patients receiving peripheral blocks should have ____________, and blocks should be performed only in areas where ________________ are immediately available
- functional IVs
- patient monitoring, equipment, and drugs to treat LAST
Nagelhout, pg. 1143
Selection of local anesthetic is dependent on what 3 things?
- onset
- duration
- desired density (pain management vs primary anesthetic)
Nagelhout, pg. 1143
In general, the highest concentrations of local anesthetic in the blood are found after _____________ blockade
- intercostal
Nagelhout, pg. 1143
The type of local anesthesia may have a role in the development of neurotoxicity, with _________ being more toxic than ___________
- esters
- amides
Degree of neurotoxicity is dose dependent
Nagelhout, pg. 1143
How long does Exparel provide pain relief?
Up to 72 hrs
Nagelhout 7th, Ch. 50, pg. 1143
What is the maximum dose of Exparel?
266mg
Nagelhout 7th, Ch. 50, pg. 1143
What is the unique characteristic of Exparel that allows for such a long duration of action?
- DepoFoam
basically an extended release “capsule”
Nagelhout, pg. 1143
Because of its delayed onset, it is not uncommon to mix Exparel with _________ to reduce the onset effect time of the block
- standard bupivacaine
Nagelhout, pg. 1143
Exparel should not be adminstered for at least ___________ following any injection of lidocaine
- 20 minutes
Nagelhout, pg. 1143
Other formulations of bupivacaine should not be given for at least ___________ after a procedure using Exparel
- 96 hours
Nagelhout, pg. 1143
Why is it essential for a topical antiseptic to dry before an injection of Exparel?
- antiseptic solutions may cause the liposomes to degrade, releasing toxic amounts of the drug into the plasma
Nagelhout, pg. 1143
Following a peripheral nerve block, patients should be observed for at least _________ for potential signs of LAST or other adverse outcomes as blood levels peak
- 30 minutes
Nagelhout, pg. 1144
What discharge information should patients be given after a peripheral nerve block regarding what to do/expect as the block starts to wear off?
- site may be numb for up to 72 hours
- first sensations will be tingling in the area that was numb
- being taking prescribed pain medication as soon as any feeling comes back
Nagelhout, pg. 1144 - Box 50.1
You are performing a peripheral nerve block and utilizing a nerve stimulator - you have a setting of 0.1 mA and a motor response is elicited. Is this normal/expected? If not, explain why?
- The goal is to elicit a motor response with minimal amplitude - usually 0.3-0.5 mA
- A setting less than 0.2 mA may indicate that the needle tip has penetrated the nerv’es epineurium - DO NOT PROCEED WITH INJECTION
Nagelhout, pg. 1144
The number of cycles that occur in 1 second is called a __________
- Hertz, Jalen
as reference, humans can detect sound frequencies from 20 to 20,000 Hz
Nagelhout, pg. 1145
In general, high frequency ultrasound (>7 MHz) creates _______ resolution images; these waves degrade/attenuate ___________ and can visualize structures up to depths of _________
- high
- quickly
- ≤ 4 cm
Nagelhout, pg. 1145
Low frequency ultrasound (2-5 MHz) can image ________ structures with _________ resolution
- deeper
- decreased
Nagelhout, pg. 1145
The standardized propagation velocity of sound through tissue is approximately ____________
- 1540 m/second
Nagelhout, pg. 1145
_________ of tissue describes it stiffness, or resistance against the propragation of sound
- impedance
Nagelhout, pg. 1145
Differences in impedance along tissue borders results in:
- reflection
- refraction
- scattering
- attenuation
Nagelhout, pg. 1146
________ of an ultrasound wave is the basis of all diagnostic imaging and occurs when a sound contacts the borders of two tissues with difference densities (acoustic impedance)
- reflection
part of the beam continues through the tissue and part returns
Nagelhout, pg. 1146
The amount of reflection of the US beam is proportional to the ____________
- difference of impedance between the two tissues ( equal impedance gives no echo, large difference gives large echo)
Nagelhout, pg. 1146
Define refraction as it relates to ultrasound imaging
- the reflection of the ultrasound wave when it strikes at an oblique angle - the echoes do NOT return directly back to the transducer
Nagelhout, pg. 1146
True or false:
Scattering occurs when the wave is smaller than the structure it contacts, generating a uniform, low amplitude reflection in all directions
- False - scattering occurs when the wave is GREATER than the structure it contacts
Nagelhout, pg. 1146
What is an example of a hyperechoic structure? How might this appear on the ultrasound image?
- Bone, fascia, needles
- bright/white
Nagelhout, pg. 1147
What is the appearance of a hypoechoic structure on an ultrasound image?
- varying shades of gray
Nagelhout, pg. 1147
Describe the appearance of nerves on an ultrasound image - why do they appear like this?
- They can be either hyper- or hypoechoic
- It depends on their location in the body and the density of the surrounding structures
Nagelhout, pg. 1147
Proximal nerves, such as the roots of the brachial plexus, are _______ dense than the surrounding connective tissue, making them appear ________echoic on ultrasound
- less
- hypo
Nagelhout, pg. 1147
Peripheral nerves, such as the tibial and peroneal nerves, are _______ dense than the surrounding connective tissue, making them appear ________echoic on ultrasound
- more
- hyper
Nagelhout, pg. 1147
What type of structure might appear anechoic on the ultrasound image?
- Fluid-filled (e.g. blood vessels & cysts)
They do not reflect sound waves
Nagelhout, pg. 1147
In diagnostic imaging, Doppler is used to detect and measure __________
- blood flow
Nagelhout, pg. 1147
Color-flow Doppler technology assigns a color to the blood flow based on ___________
- whether or not it is arterial or venous
NO STUPID IDIOT ITS BASED ON DIRECTION OF FLOW IN RELATION TO TRANSDUCER
Nagelhout, pg. 1147
When Doppler ultrasound is oriented over a blood vessel so that blood is flowing toward the transducer it will result in a _____________ Doppler shift
- positive
Nagelhout, pg. 1147
If blood is flowing away from the transducer, it will result in a ___________ Doppler shift
- negative
Nagelhout, pg. 1147
In diagnostic ultrasound imaging, proper orientation is achieved when the orientation indicator is aligned to the provider’s _________ side in a transverse view, or toward the patients _________ in a sagittal view
- left
- head
Nagelhout, pg. 1147
What is the appearance of the needle on the ultrasound image when using the in-plane approach?
- the entire length of the needle is visualized
Nagelhout, pg. 1148
What is the appearance of the needle on the ultrasound image when using the out-of-plane approach?
- the cross section of the needle is seen as a hyperechoic dot where it crosses the plane
When utilizing a continuous catheter technique for peripheral nerve blocks, how far is the catheter threaded beyond the needle tip? What is the rationale for this length?
- 3-5 cm
- insertions > 5 cm have been associated with catheter kinking/knotting
Nagelhout, pg. 1175
