Local anesthetics Flashcards
Physiologic pH local anesthetics are
Charged (cationic)
The lower the pKa
The more uncharged species
Most local anesthetics have a higher Pka
more likely to be charged
Mechanism of action
Block open Na+ channels
only in periphery (no loss of consciousness)
Dose dependent effects
Ability to generate AP is dependent on dose
Work best on
Rapidly firing or chronically firing
Order of nerves blocked
CBA
Smaller C and B fibers
Small A-Delta and A-gamma
A-alpha blocked last
Pain blocked first
Sensation fibers
Motor function
same thickness = myelinated > unmyelinated
When block is reversed which sensation returns last?
Pain
Which local ester anesthetic is more potent? Procaine or Tetracaine?
Tetracaine
Which amide anesthetic is more potent?
Mepivacaine or Bupivacaine
Bupivacaine
Which local anesthetic is used for labor?
Bupivacaine
The addition of epinephrine is used to
vasoconstrict at the site
double the duration of action
block that is administered directly to wound
Infiltration
Block that surrounds the wound
Infiltration (surround)
Block that is a peripheral nerve block
Infiltration (peripheral)
Block that is applied to the spine, epidural, or caudal region
Infiltration (spinal)
Which type of local anesthetic is hydrolyzed/metabolized faster? Ester or amide?
Ester (choline esterases breakdown esters in the blood plasma)
Metabolite of ester LA metabolism?
Para-amino benzoic acid
What metabolite causes allergic reactions in many people (allergic dermatitis, asthma, anyphylactic shock)?
Para-amino benzoic acid
due to breakdown of ester LA
Amide LAs are broken down by?
Liver CYP450
Toxicity of LAs
Systemic
Neurotoxicity
Systemic toxicity
Hypersensitivity Para-aminobenzoic acid
CNS effects
Cardiovascular
Which LA causes cardiac effects?
Bupivacaine
How do you prevent cardiac toxicity w/ bupivacaine?
Inject with lipid
