Local Anesthetics Flashcards
influences distribution and excretion
protein binding
influences redistribution and intrinsic LA potency
lipid solubility
racemic mixtures
mepivacaine (50:50 mixture of enantiomers)
bupivacaine (50:50 mixture of enantiomers)
MOA of local anesthetics (LA’s)
Bind to voltage-gated Na+ channels and block Na+ current, therefore reducing excitability of tissues (cardiac, neuronal, CNS)
LAs are weak (acids/bases) that have pKa values (above/below) physiologic pH
LAs are weak bases that have pKa values above physiologic pH
Potency depends on
lipid solubility
Onset depends on
pKa and ionization
metabolism of esters
- hydrolyzed by pseudocholinesterase
- which = short plasma half-life
metabolism of amides
- liver metabolism (therefore hepatic blood flow and function are important!!)
systemic toxicity is more likely in (amides/esters)
amides
fibers most sensitive to blockade
B fibers - SNS
- small fibers
- myelinated fibers
Duration depends on
protein binding
What concept is analogous to ED50 for LAs?
mimimum effective concentration (Cm) is the concentration of LA that is required to block conduction
What are the 3 possible configurations of the voltage gated Na+ channel?
activated - open
inactivated - closed
rested - closed
Order of loss of nerve sensations
- Autonomics
- Pain
- Cold
- Warmth
- Touch
- Pressure
- Vibration
- Proprioception
- Motor function
potentially can cause methemoglobinemia
prilocaine
treatment of methemoglobinemia
methylene blue 1-2 mg/kg IV (max dose 8mg/kg)
LA toxicity of combinations are (additive/synergistic)
additive
Maximum Dose: Lidocaine
Alone: 300 or 4.5 mg/kg
with Epi: 500 or 7 mg/kg
Maximum Dose: Bupivacaine
Alone: 175 or 2.5 mg/kg
with Epi: 200 or 2.8 mg/kg
highest to lowest protein binding
bupi > ropi > mepiva > lido > procaine > 2-chloroprocaine
Local anesthetics primarily block which channels?
voltage gated sodium channels
Immediate treatment of local anesthetic induced convulsions with?
supplemental oxygen therapy
support of ventilation
intralipid 100ml
midaz as needed
