Regional Lecture I part II Flashcards
mechanisms of nerve injury?
mechanical
stretch
pressure/compression
chemical
vascular (prolonged disruption of BF to nerve)
are LA drugs neurotoxic?
yes they all are to some degree. Cause histological changes, but usually not clinically significant
how does lidocaine affect blood flow?
inhibits neural blood flow
have neural injury rates changed with introduction of ultrasound?
no
are nerve injuries primarily from intraneural injections?
no, we used to think so though.
does intrafascular injection equal nerve injury?
yes
is it okay to inject into a nerve?
No, it might not cause injury (unless intrafasicular) but we still want to avoid this.
where do axons run?
in the fassicules
what is epinerium?
protective connective tissue forming the outer covering of nerves, as well as inner supportive tissue
how would an intrafasicular injection feel to the anesthesia provider?
there is higher injection pressure
why do risks of nerve injury decrease distally?
there are only a few large fascicles bound by a sheath proximally. these are easy to needle
distally there are many small fascicles without a sheath so needles have a hard time entering the fasicle.
two kinds of vascular nerve injuries?
intrinsic within epineurium and extrinsic around nerve
key factors in post op neuropathy mgmt?
communication (ensure pt you are on it and don’t blow it off)
surgeon - possible procedural component
neurology - involve them earlier than later (can do electrophysiological testing)
when should you immediately involve neurology for post op neuropathy?
motor involvement in nerve injury
how long should you follow patient after post op nerve injuyr?
until symptoms resolve or stabilize
how quickly do sensory symptoms resolve in post-op neuropathy?
95% in 4-6 weeks
99% in 1 year
Techniques for finding nerves?
landmarks
paresthesia
nerve stimulator
ultrasound
fluoroscopy
CT guided
what kind of images to fluroscopy and CT provide?
still and live images
when is fluroscopy for PNB used?
mostly in pain blocks and is expensive
when is CT used to guide PNBs?
rarely in pain blocks, is extremely expensive
What is the paresthesia technique and how is it done?
old technique that creates a feeling of tingling, tickling, burning, prickly or buzzing.
goal is to place needle in direct contact with the nerve to produce a paresthesia, then slightly withdraw the needle and inject.
this has a risk of neural injury and higher block failure rates
should you inject LA if the pat has sharp pain or paresthesia?
NO!!!
how does nerve stimulator technique affect motor or sensory nerves?
motor nerve - muscle twitch
sensory nerve - paresthesia over target nerve distribution
what kind of impulse does nerve stimulator use?
negative polarity impulse
this neutralizes the positive current outside the nerve dropping the membrane potential
