Mod 1 - Local Anesthetics & Loco-Regional Techniques 8/18 Flashcards
Quiz 2
what do local anesthetics do?
reversibly block generation/propagation of electrical impulses in nerves (sensory & motor blockade)
what was the first local anesthetic ever?
what was the first synthetic derivative of cocaine in 1904?
cocaine
procaine
when was lidocaine developed?
1943, WW2
local anesthetics are used for 1 procedures, to (inc./dec.) systemic drugs in anesthetized animals, and also has benefits in the 2 period.
- awake
dec. - recovery
what are local anesthetics MOA?
reversibly bind to & inactivate Na+ channels
- Na+ influx needed for depolarization of nerve & propagation of impulses along nerve
- nerve can’t depolarize b/c no Na+ influx
- sensation in area lost
what are the two basic classes of local anesthetics?
- amino amides
- amino esters
amino esters are metabolized in the 1. they are (stable/unstable) in solution and are more likely to cause 2 reactions.
- plasma
unstable - allergic hypersensitivity
amino amides are metabolized in the 1. they are (stable/unstable) in solution. Pro tip: all amino amides have 2.
- liver
stable - the letter “i” twice in their name
(lipid/water) solubility is an important characteristic of local anesthetics because it is directly related to ?.
lipid
potency
(inc./dec.) lipid solubility leads to faster nerve penetration & blockade of ? channels.
inc.
Na+
The more firmly the local anesthetic binds to the protein of the Na+ channel, the (shorter/longer) the duration of action.
longer
local anesthetics exist in what 2 forms?
which form is capable of diffusing across nerve membranes to block Na+ channels?
- ionized
- non-ionized
non-ionized = faster onset time
a dec. in pH shifts the equilibrium between the ionized form of a local anesthetic and the non-ionized form toward the ? form.
what does this cause?
ionized
slower onset of action
all local anesthetics (except cocaine) are vaso(constrictors/dilators).
if this inc., then there is (faster/slower) absorption and therefore (shorter/longer) duration of action
vasodilators
faster
shorter
you must block a minimum of ? Nodes of Ranvier consecutively to get an adequate loss of sensation.
3
lidocaine
- (fast/mod/slow) onset
- (short/mod/long) duration
- can cause ? when injected
- IV CRI (inc./dec.) MAC, (inc./dec.) intestinal motility
- can treat what heart condition?
fast
mod
irritation
dec.
inc.
vtach
T/F - cats can metabolize lidocaine well over time.
false!
bupivacaine
- (fast/mod/slow) onset
- (short/mod/long) duration
- popularly used in ?
- there is more of a risk of ?
- do NOT give (route)
- can cause ?
slow
long
epidurals
toxicity
IV
intra-articular chondrotoxicity
what are 5 dose-dependent complications of local anesthetics?
- neurotoxicity
- cardiotoxicity (esp. bupivacaine)
- allergic reaction
- methemoglobinemia
- nerve & muscle injury (due to repeated injections)
what can we give IV to a patient if we are worried about local anesthetic toxicity?
IV lipids - acts like sponge & collects anything lipophilic for excretion
what is the most used technique involving local anesthetics that is used in vet medicine?
epidural administration of local anesthetics
what is the goal of an epidural?
regional analgesia w/o losing motor function
what are 4 advantages of an epidural?
- simple & quick
- improve peri-op analgesia
- MAC/drug-sparing effects
- ideal for C-sections (b/c no effect on offspring)
what are 4 disadvantages of an epidural?
- risk of motor dysfunction
- Horner’s syndrome (if used on face)
- urinary retention (drug choice)
- must use aseptic technique!
what is the gold standard for local anesthetic administration?
ultrasound-guided nerve blocks
T/F - anesthesia is benign.
False - always comes with a risk
- modern techniques & drugs help make it as safe as possible
