3 - Peripheral Nerve Anesthesia Flashcards
What is “soak time”
time it takes for local anesthetics to cross the cell membrane, block action potentials, and produce either analgesia or surgical anesthesia
What is LAST?
Local Anesthetic Systemic Toxicity
Why is interlipid used in LAST?
mitigates the toxic effects of local anesthetics and can reverse both neurologic and cardiac toxicity
What is the minimum required monitoring for a patient to get a block?
ECG, NIBP, Pulse Ox
The use of ________ is contraindicated in children receiving peripheral nerve blocks with NS guidance
muscle relaxants
What is the high range of a NS used for?
The low range?
Monitoring neuromuscular blockade
Localizing peripheral nerves
The general rule with NS is to use ________ currents of _________ for peripheral NS
short duration
No more than 100 microseconds
In NS, the needle is in proximity to the nerve when the threshold for motor response is between ________ mA
0.3-0.5 mA
What is the “pulse width”?
the length of time of each NS electrical pulse
What happens when you place a PNS needle in saline?
D5W?
Reduces the curent density at the needle tip
If you need to dilate the perineural space, what should be used?
D5W, so that you don’t alter the needle’s ability to stimulate the nerve
What is the definition of Ultrasound?
Any sound with above 20 kHz, but in medicine we use 5-15 kHz
On US, high impedance creates __________ images
Low impedance creates _________ images
light
dark
Higher U/S frequencies are useful for ____________
Lower U/S frequencies are useful for ____________
superficial locations (brachial plexus)
Deep locations (subgluetal region)
What is the most common reason for poor visualization with US?
not enough gel
Anatomic landmark for interscalene block
subclavian artery
scalene muscles
Anatomic landmark for supraclavicular block
subclavian artery
Anatomic landmark for infraclavicular block
subclavian/axillary artery and vein
Anatomic landmark for axillary block
axillary artery
Anatomic landmark for lumbar plexus block
lateral aspect of transverse process
Anatomic landmark for radial nerve at anterior elbow
humerus at spiral groove
deep brachial artery
anatomic landmark for median nerve at forearm
brachial artery
Anatomic landmark for ulnar nerve at forearm
ulnar artery
Anatomic Landmark for tibial block
posterior tibial artery
Anatomic landmark for deep peroneal block
anterior tibial artery
Anatomic Landmark for subgluetal block
greater trochanter and ischial tuberosity
When using US, once the needle is seen next to the nerve, what happens next?
a 1- to 2-mL test dose of D5W can be injected to visualize the spread
Describe a combined US/NS approach to PNS
- nerve stimulator set at 0.3 to 0.5 mA
- the nerve is sought primarily using visualization under US
- nerve stimulator serves as an alert when the insulated needle tip is too close to nerve (i.e., contacting or inside the nerve).
What type of needles are generally required for PNB?
22-24 gauge insulated short bevel needles
What is CAIT?
What does it prevent?
Compressed Air Injection Technique
Limits generation of excessive pressure during block administration
How is CAIT used?
air is drawn into the syringe and compressed by 50% during entire injection to maintain pressures @ 760 mmHg
well below the 1,300 mmHg threshold considered to be an associated risk factor for clinically significant nerve injury
What objective tools are available to assess ongoing PNB?
Infrared Thermal Imaging
Current perception threshold measurement
What is an objective measure of motor blockade in PNB?
strength testing using a force transducer
What subjective scale is used to assess motor blockade in PNB?
Bromage Scale
What is an absolute contraindication to regional anesthesia?
Refusal by the patient or parent/guardian
When should schizophrenic patients receive PNB?
Only when general anesthesia is also being performed
What are three relative contraindications to PNB?
- Local Infection
- Systemic anticoagulation
- Severe systemic coagulopathy
If you need to administer a large amount of volume of local, you should use __________ concentration
a lower
to prevent systemic toxicity
What is systemic toxicity with PNB usually attributed to?
Accidental intravascular injection
NOT to an excessive quantity of local anesthetic at an appropriate site
The highest blood levels of local anesthetic occur after:
- Intracostal
- Caudal
- Epidural
- Brachial
When is the use of epinephrine combined with local not appropriate?
- in the vicinity of “terminal” blood vessels, such as in the digits, penis, or ear
- intravenous regional technique
When do peak blood levels occur after PNB administration?
30 minutes
What two factors increase the risk of nerve damage r/t PNB?
- High pressure injection
- highly concentrated agents
How concerning is a hematoma in the epidural space?
In the peripheral nerve space?
Extremely
Not very
Sensory and motor innervation of the face are provided by the __________
CN 5 trigeminal nerve
What are the three main branches of the trigeminal nerve
- Opthalmic
- Maxillary
- Mandibular
What is the only branch of the trigeminal with motor fibers?
Mandibular
In the neck, the vagus nerve passes between which two anatomic landmarks?
The carotid artery and the IJ
What spinal nerve exits above the atlas?
C1
What spinal nerves exits below the atlas?
C2
Where does spinal nerve C8 exit the spinal cord?
Between C7 and T1
How many pairs of spinal nerves are there?
31 pairs
62 spinal nerves
The cervical plexus arises from which spinal nerves?
C1-C4
(a little bit of C5)
All blocks should be followed by _________
manual compression to prevent hematoma formation
When injecting the mandibular nerve, what should be a high priority?
Avoiding intravascular administration, because this area is highly vascular
Which muscle is a suitable US landmark for deep cervical plexus block?
Longus capitis
What are some life threatening complications that can arise from a deep cervical block?
Injection in vertebral artery
Subarachnoid or epidural injections
Phrenic nerve palsy
What is Horner syndrome?
Ipsilateral:
Ptosis
Miosis
Hyperemia
Nasal Congestion
The brachial plexus arises from which vertebral rami?
C5-T1
Brachial Plexus Roots
C5-T1
Brachial Plexus Trunks
Superior (C5 & C6)
Middle (C6 & C7)
Inferior (C8 & T1)
Brachial Plexus Divisions
Superior Ant & Post
Middle Ant & Post
Inferior Ant & Post
Brachial Plexus Cords
Lateral (from ant of superior and middle division)
Posterior (from post of all three division)
Medial (from anterior inferior division)
In that order
What do interscalene blocks target?
Brachial plexus roots
What do supraclavicular blocks target?
Trunks and divisions of the brachial plexus
What do infraclavicular blocks target?
The cords of the brachial plexus
What are the terminal branches of the brachial plexus?
Ulnar
Radial
Median
Musculocutaneous
What does an axillary block target?
The terminal branches of the brachial plexus
A patient with an interscalene block should be watched closely for what three things?
Horner Syndrome
RLN paralysis
Phrenic nerve paralysis
An intrascalene block goes between which two muscles?
anterior and middle scalene
What are three common surgeries that an intrascalene block is used for?
Shoulder surgery
Elbow Surgery
AV fistula formation
Dyspnea with normal vital signs after an interscalene block is probably due to what?
Phrenic palsy
How often does phrenic nerve palsy occur with interscalene blocks?
About 100% of the time, but only 10% are symptomatic
What kind of patients should not receive an interscalene block?
Patients who can’t tolerate phrenic palsy:
COPD
Bronchospasm
Underlying Diaphragmatic Dysfunction
What percentage of patients with interscalen blocks develop Horner Syndrome?
50-75%
Three hallmarks of the Bezold-Jarisch Reflex
- Hypotension
- Bradycardia
- Syncope
How can you decrease the likelihood of stimulating the Bezold Jarisch Reflex?
Prophylactic B blockers before an interscalene block
What is an anechoic area?
An area that is completely black on the U/S (bone etc)
What is a Bier Block?
arm anesthesia provided by the injection of local anesthetic into the venous system distal to an occluding tourniquet.
What is the most popular anesthetic for a Bier Block?
Preservative 0.5% Lidocaine
30-50 ml
Max 3mg/kg
ANY ANESTHETIC USED MUST BE EPI FREE
Which anesthetics are NOT recommended for Bier Block? Why?
Ropivicaine and Bupivicaine
Much higher toxicity if absorbed systemically
If a patient with a Bier Block complains of pain from the tourniquet, what can be done?
Inflate distal cuff to 2.5x the SBP
Deflate the proximal cuff
provides relief for about 15-20 min
US Axial resolution is determined by
pulse length
US lateral resolution is determined by
transducer beam width
Patients with pre-existing neuropathy are more at risk for: (2)
prolongation of the block
local anesthetic neurotoxicity
Indication for an interscalene block
shoulder and upper arm
Indication for a supraclavicular block
entire upper extremity distal to shoulder
Indication for infraclavicular block
elbow and below
Indication for axillary block
distal to the elbow
Indication for intercostal block
chest and upper abdominal wall
Indication for Transversus Abdominis Plane
anterior abdominal wall
Indication for Psoas block
entire hip, thigh and medial aspect of lower leg
Indication for femoral block
anterior thigh and knee
medial aspect of lower leg
Indiciations for fasia iliaca block
hip, femoral shaft and knee
Indication for sciatic block
below knee, sparing the medial lower leg
Indication for popliteal block
below the knee sparing medial lower leg
When using an electronic stimulator, which lead is attached to the patient? To the needle?
Negative lead to skin
Positive lead to needle
When using nerve stimulators, when should the stimulator be turned on?
AFTER entering the skin
In a short-axis view, nerves and vessels appear _______
In a long-axis view, they appear ________
round
linear
What is short axis?
What is long axis?
transverse, cross-sectional
longitudinal, parallel
What are the ART manuevers?
Alignment: sliding along the skin
Rotation: rotating the probe clockwise or counterclockwise
Tilting
Where to the ventral rami roots of the brachial plexus reorganize into trunks?
As they pass the lateral border of the scalene muscles
Where do the three trunks of the brachial plexus divide into vnetral and dorsal divisions?
lateral border of the first rib
Posterior to the clavicle
The ventral divisions of the brachial plexus generally supply the __________
ventral (flexor) portion of the upper extremity
The dorsal divisions of the brachial plexus generally supply ________
the dorsal (extensor) portions of the upper extremity
In the brachial plexus, where do the ventral and dorsal divisions combine into cords?
Upon entering the axilla
How are the cords of the brachial plexus named?
By their position relative to the axillary artery
Lateral to the artery
Medial to the artery
Posterior to the artery
The lateral cord of the brachial plexus branches into:
musculocutaneous nerve
lateral root of the median nerve
The medial cord of the brachial plexus branches into:
ulnar nerve
medial root of the median nerve
The posterior cord of the brachial plexus branches into:
axillary and radial nerves
Where do the cords divide into branch nerves?
lateral border of the pectoralis minor muscle
What are the four primary approaches for anesthetizing the brachial plexus?
Interscalene
Supraclavicular
Infraclavicular
Axillary
Which brachial block is best for shoulder surgery?
Interscalene
Which brachial plexus block has the highest risk of LAST?
Axillary
Immediately medial to the first rib is the __________
cupola of the lung
Supraclavicular blocks have a high risk of ________
pneumothorax
The cricoid cartilage corresponds with the vertebral body of _____ and ______
C6
Chassaignac’s Tubercle
What can you ask the patient to do to make the scalene muscles easier to see?
Take a fast, deep breath through the nares
If an axillary block is desired, but the patient can’t abduct the arm, which block can be used instead?
Infraclavicular
What is a potential problem with infraclavicular blocks?
You can’t easily compress the axillary artery if it’s punctured
Why are bier blocks usually only useful up to 1 hr?
Patient discomfort from the tourniquet
What is the preferred size and location of an IV for an upper extremity bier block?
23-25 g IV
dorsum of the hand
What are two difference between IVRA of the upper extremity and the lower extremity?
Lower extremity dose is about double
Tourniquet pressure has to be way higher, which increases likelihood of tourniquet pain
When performing an intercostal nerve block the patient should be positioned
supine, with arms above the head
When inserting the needle for an intercostal block, the needle should be placed:
perpendicular to the rib until it makes contact, then walked caudad off the rib
The TAP block places local anesthetic between the _____ and ______
internal oblique
transversus abdominis
The lumbar plexus is formed from the ______
L1-L4 ventral rami
The lumbar plexus is formed between which two muscles?
in front of the quadratus lumborum
Behind the psoas
Immediately after emerging from the _________ the nerve roots form the lumbar plexus
intervertebral foramina
Femoral nerve blocks are not used as ________,
but rather ________
sole anesthetics
postop analgesia options after knee surgery
If a patient is going with a peripheral catheter, what is an absolute requirement?
Must be able to get in contact with someone 24/7 until the catheter is removed
Paralysis of ________ is common in shoulder surgeries
ipsilateral diaphragm
d/t interscalene block
Which of the brachial plexus nerves is lease likely to be covered by an axillary block?
Musculocutaneous. It separates very high in the axilla and often needs to be blocked by itself
What is the max dose of bupivicaine and ropivicaine?
Bupivicaine 2 mg/kg
Ropivicaine 3 mg/kg
All sensory fibers above the knee come from the _______
All sensory fibers below the knee come from the ________
Femoral plexus
Sciatic
What is the terminal branch of the femoral nerve?
Saphenous nerve
The injection of 3-5 mL of local anesthetic into the coracobrachialis muscle will anesthetize what nerve?
Musculocutaneous
On the ultrasound monitor, the femoral nerve will appear:
hyperechoic, triangular, and lateral to the femoral artery
What nerve roots contribute fibers to the ulnar nerve?
C8, T1
What nerve roots contribute fibers to the radial nerve?
C7, C8
What nerve roots contribute fibers to the musculocutaneous nerve?
C5, C6
The popliteal fossa is bounded laterally by the _________ and medially by the__________
the biceps femoris tendon
semimembranosus and semitendinosis tendons
From superior to inferior, the structures in the intercostal neurovascular bundle are positioned:
Vein
Artery
Nerve
The musculocutaneous nerve is situated between what muscles?
pectoralis major
Coracobrachialis
What volume of local anesthetic would you expect to use in an ultrasound-guided popliteal sciatic block?
20 ml
What is the most common cause of hypotension in the postanesthesia care unit?
hypovolemia
Where are the 3 trunks of the brachial plexus located in relation to the subclavian artery?
Lateral
Which of the following is the most common event leading to an anesthesia malpractice claim?
Regional Blocks
Which nerves are anesthetized during an ankle block?
deep peroneal
saphenous
posterior tibial
sural
superficial peroneal
What two muscles form the crease in the axilla in which the ultrasound probe is placed during an ultrasound-guided axillary block?
Pectoralis major
bicep
The largest identifiable and preventable cause of accidents is
fatigue
When performing a brachial plexus block using the axillary approach, it is often necessary to perform separate blocks of which nerves?
Why?
medial brachial cutaneous and intercostobrachial nerves
medial brachial exits sheath below clavicle
intercostobrachial doesn’t travel in the sheath
The injection of a 5-8 mL of local anesthetic subcutaneously near the inferior border of the medial malleolus would anesthetize which nerve?
Saphenous
What is the only additive to the local anesthetic for a Bier block that has been proven effective?
Ketoralac
