Local Anesthesia Flashcards
what are 2 reasons we should use local anesthesia in food animals?
- ruminants are poor candidates for general anesthesia
- the cost of general anesthesia would be too much
why are food animals poor candidates for general anesthesia?
Risks
- compartment syndrome
- bloat
- regurgitation
- long fasting requirements (24hr at least)
what 2 drugs are most commonly used as local anesthetics in FA?
- lidocaine hydrochloride 2%
- bupivacaine
what is the toxic dose for lidocaine in cattle vs small ruminants?
cattle = 10 mg/kg
SR = 5 mg/kg
You can increase potency and duration of lidocaine or bupivacaine by adding what drug?
epinephrine
but do not use this in spinal cord or at tissue edges because it will cause necrosis.
What is the mechanism of lidocaine as a local anesthetic?
blocks fast voltage-gated Na Channels in the neuronal cell membrane. The channels do not open, therefore an action potential will not be generated.
what is the difference between local anesthesia for dehorning in cattle vs SR?
cattle - block cornual branch of zygomaticotemporal nerve
SR - block cornual branch of zygomaticotemporal nerve and cornual branch of infratrochlear nerve
What are common clinical uses for inverted L, distal paravertebral, line, and proximal paravertebral blocks that anesthetize the PLF and abdominal wall?
c-sections
LDA, RDA
rumenotomy
exploratory
R&A for intussusception
where is the are of anesthesia for an inverted L block?
behind the 13th rib and ventral to transverse processes of the lumbar vertebrae
what size+length needle should you use for most blocks?
18 gauge
1.5 inch
note that this is adjusted based on BCS and site (ie. need for spinal needles)
what are the concerns for local anesthetic blocks in animals with higher BCS?
that you will get incomplete anesthesia of the deeper layers. Ideally, you want to block skin, SQ, ext abdominal obl, int abdominal obl, transversus abdominus, and peritoneum.
If an animal has a higher BCS, maybe you should use a longer needle.
what does the distal paravertebral block anesthetize?
dorsal and ventral rami of spinal nerves T13, L1, and L2 at the distal end of transverse processes L1, L2, and L4.
For a inverted L block, you should use ~ _____ mL lidocaine in an adult cow.
150-200
For a distal paravertebral block, you should infuse ~_____ mLs (split 10-20 mL per site) dorsal and ventral transverse processes.
60-120
what is the most common use for a line block (a block that anesthetizes a specific area of the PLF)?
c-sections or other emergent procedures.