Peripheral Nerve Blocks Flashcards
What is a potential complication of a brachial plexus PNB in relation to breathing?
Phrenic nerve blockade which would paralyze the diaphragm
What are risks/contraindications for PNB?
Patient cooperation/participation.
Bleeding disorders and/or pharmacologic anticoagulation.
Sites of infection.
Existing nerve injury (law suit).
What three things need to be considered when choosing a specific LA?
- Desired onset.
- Desired duration.
- Desired sensory/motor block.
Which LA typically does not have a good motor block?
Bupivacaine
What is the maximum dose of lidocaine?
4 to 7mg/kg
What is the maximum dose of bupivacaine?
2.5 to 3mg/kg
What is the maximum dose of ropivacaine?
2.5 to 3mg/kg
What is the duration of action for lidocaine PNB?
Maybe up to 6 hours
What is the duration of action for bupivacaine or ropivacaine PNB?
12-18 hours
How many mg/ml if drug is 3%?
0.3%
30mg/ml
3mg/ml
How many mcg/ml if drug is 1:50,000?
1:10,000?
20mcg/ml
100mcg/ml
Why might epinephrine not be used with bupivacaine or ropivacaine PNB?
The block my out last the duration of the epinephrine so it may not be useful.
Describe a situation where field block technique is used:
Commonly used in dental procedures and “fan” technique by surgeon.
Which nerves does field block technique target?
Terminal cutaneous nerves.
Describe paresthesia technique:
Use known anatomic relationships and surface landmarks to guide needle. When needle makes direct contact with a sensory nerve, the patient can feel it/movement occurs. Older technique not used much anymore
With nerve stimulation technique, at what mA would it be considered close enough to inject?
0.4-0.5 mA
What mA indicates intraneural needle placement?
0.2 mA
How much LA is injected with nerve stimulation approach?
30-40ml with gentle aspiration and divided doses.
What MHz are used by ultrasound technique?
1 to 20 MHz
T/F: Hard structures will show up white on ultrasound? Empty/fluid filled?
True:
Hard=white
Empty/fluid filled=dark
What is echogenicity?
The degree of efficiency with which sound passes through a substance.
T/F: Hyperechoic is a structure or substance through which sound easiliy passes. Appears dark or black on the ultrasound screen?
False:
Hypoechoic=dark/black=sound easily passes through.
What is anechoic?
No reflection via sound waves.
Ultrasound creates a two-dimensional or three-dimensional grayscale image?
Two-dimensional
Which probe (linear or curvilinear) uses high frequency and offers less tissue penetration?
Linear
Which type of probe is typically used for superficial nerves?
Linear
Nerves are best imaged in short-axis or long-axis mode?
short-axis.
Which needle insertion technique does the needle follow the longitudinal (long axis) plane? Transverse (short-axis plane)?
In-plane needle alignment=long axis, longitudinal.
Out-of-plane alignment=transverse, short-axis
With which needle technique will you be able to see the whole needle?
Long-axis/longitudinal.
What are the 8 advantages of continuous PNB over single injection nerve block?
- Reduction in resting and dynamic pain.
- Reduction in supplemental analgesia requirement.
- Reduction in opioid related side effects.
- Reduction in sleep disturbance.
- Improved patient satisfaction.
- Improved patient ambulation.
- Accelerated resumption of passive joint range-of-motion.
- Reduced time to discharge.
What are the 6 complications of continuous PNB?
- Systemic LA toxicity.
- Cather retention.
- Nerve injury.
- Infection.
- Retroperitoneal hematoma.
- Increased risk of falling.
How is the brachial plexus broken down?
5 Roots>3 Trunks> 6 Divisions> 3 Cords> 5 Branches
Which brachial plexus block is indicated for shoulder surgery?
Interscalene block
What nerve roots are most densely blocked using the interscalene approach?
C5-C7
For complete surgical anesthesia of the shoulder, what must also be done in conjunction with an interscalene block?
C3-C4 cutaneous branches may need to be blocked via superficial cervical plexus block or local infiltration.
What are contraindications for interscalene block?
- Local infection.
- Severe coagulopathy.
- LA allergy.
- Patient refusal.
What other nerve will be blocked if interscalene block is properly performed?
Ipsilateral phrenic nerve
What are some other considerations with interscalene block?
- Horner’s syndrome=stroke like symptoms
- Recurrent laryngeal nerve =induces hoarsness
- Vertebral artery injection
- Accidental spinal or epidural injection.
- Pneumothorax.
What would inadvertent vertebral artery injection cause?
Immediate seizure activity.
What are the three components to Horner’s Syndome?
- Ptosis=droopy eye
- Myosis=pupil constricts.
- Anhydrosis=no sweat/no tears/reddened
What ganglia near an interscalene block innervates the face?
Superior cervical ganglia
Which two muscles is the interscalene block placed directly in between?
In between middle and anterior scalene muscles.
Which brachial plexus block is associated with the highest incidence of pneumothorax?
Supraclavicular block
What is surgical procedures is a supraclavicular block used for?
Usually anything distal to the elbow, not ideal for shoulder.
Why is the supraclavicular block not ideal for shoulder surgery?
It does not reliably anesthetize the axillary and suprascapular nerves
On ultrasound, what will we look for when doing a supraclavicular block?
Stop-light like nerves in a row of three. Between the trunks and divisions.
T/F: Ultrasound will show a stop-light like picture when doing a supraclavicular block that shows the nerves as hyperechoic?
True
What are complications of supraclavicular block?
- Ipsilateral phrenic nerve palsy (50%).
- Horner’s Syndrome.
- RLN palsy.
- Pneumothorax*.
- Subclavian artery puncture.
Which brachial plexus block is of highest risk for bleeding?
Infraclavicular block: You can not place direct pressure at puncture site.
T/F: Infraclavicular block is blocked at the level of the trunks
False; level of the cords.
What surgical procedures is the infraclavicular block appropriate for?
Procedures at or distal to the elbow.
Which nerve is spared with infraclavicular blocks?
Intercostobrachial nerve is spared (T2 Dermatome).
What part of the brachial plexus is targeted for an axillary block?
The terminal branches ulnar, radial, and median
Where is the needle placed for an axillary block?
Just posterior and lateral to the pectoral muscle
Which two branches are not involved in axillary block?
Musculocutaneous and axillary nerves
What are the favored sites for injection for blocking individual terminal nerves?
elbow and wrist.
What block is typically done for carpal tunnel release?
Bier Block
What is the time frame for duration of a Bier block?
45-60 mins
How long must the cuff pressure be maintained after LA injected for Bier block?
15-20mins
