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.