Local Anesthetics Flashcards
how are local anesthetics classified
by bond between hydrocarbon and lipophilic portion
ester -CO-
amide -NHC-
MoA of local anesthestics
blocaks voltage-gated Na channels in neuronal cell membrane
slows rate of depolarization
which fibers are blocked first
smaller diameter fibers
less myelination
sympathetic, pain
T/F with brachial plexus block motor fibers are blocked first
True
motor fibers are on periphery of nerve trunk and sensory fibers in center
local anesthestics are weak acids/bases
bases
acidic tissues (infection) increase ionized portion which is inactive
what are potency, onset and duration affected by
pK
protein binding
lipid solubility
lower pK (closer to tissue pH) →
faster onset
higher protein binding →
longer duration of action
higher lipid solubility→
higher potency
why add bicarbonate
faster onset and prolonged duration
less sting on injection
toxicity is
additive
toxicity
methemoglobinemia
neurotoxicity
chondrotoxicity
systemic
what caused severe methemogloinemia in and was discontinued in vet med
benzocaine + tetracaine
laryngeal spray for intubation
T/F preservative-free versions should be used for epidural and spinal anesthesia
True
what is the first sign of cardiovascular collapse with bupivacaine
death
systemic toxicity with lidocaine
depression/sedation, twitching, seizures THEN cardiovascular signs
which has the worst resuscitation rate after toxic dose in dogs
bupivacaine
50/50
when do allergic reactions most commonly occur
procaine in Procaine Penicillin G (PPG)
less common with amide anesthetics
goals of locl anesthesia
Provides analgesia before, during, and after procedure
May allow decreased dose of systemic drugs (MAC-sparing)
Decreased hypotension and other adverse effects of general anesthesia
Prevents central sensitization
Important part of multimodal anesthesia
oder of nerve blockade
B fibers
A-δ and C fibers
A-γ
A-β
A-α
types of regional anesthesia
- *intravenous regional (IVRA)**
- *peripheral** - individual nerve, plexus, intercostal, paravertebral
central (neuraxial) - epidural, spinal
bier block
intravenous regional anesthesia
tourniquet placed→local anesthetic injected into peripheral vein→released into systemic circulation when tourniquet removed (Lidocaine only)
limit procedure: 60-90 min
T/F epidural anesthesia and spinal anesthesia are the same thing
False
Epidural - space between dura and vertebrae
spinal - space between dura and spinal cord, containing CSF
epidural contraindications
CHINAS
coagulopathy, hypovolemia, infection at injection site, neoplasia at injection site, anatomy, sepsis
main adverse effect
hypotension
block of sympathetic trunk → decreased vascular tone
tools for local anesthesia
palpation
nerve locator
ultrasound
