Lecture2 Flashcards
What are the three primary effects of Localized anesthetics?
Decreases rate of depolarization
Depolarization is not sufficient enough to reach threshold
Impulse is not propagated, never reaching CNS
What ratio of positive charge to neutral charge do we want in LAs?
75:25
What is the normal pH of tissues? and what direction does it go with inflammation?
7.4 and it decreases (acidic)
What does sodium metabisulfite do to the LA’s and why is it added?
It acidifies to prevent oxidation of the vasoconstrictor
What is the mode of action of LAs?
Decrease the permeability of sodium ions and conduction blockade.
What tissue has the highest perfusion rate and potential of toxicity?
Skeletal muscles (largest mass in the body)
Can LA cross BBB or the placental barrier?
Yes both
The longer it takes to hydrolyze esters, the higher or lower the toxicity?
higher toxicity
Where are amides metabolized? and which one is partially in the lungs?
In the liver, prilocaine
What is the metabolic byproduct of prilocaine?
O-toluidine leading to methemoglobinemia
Amide and ester half lives?
Amides: 90-160 minutes
Esters: .1-.7 hrs
*Increased half life is increased toxicity
Amino esters are metabolized by what?
Plasma pseudocholinesterases
*Benzocaine (topical anesthetic), cocaine (both vasoconstrict and dilate, procaine (used for vastdilation)
What are the amino amides?
articaine, bupivicaine, lidocaine, mepivocaine, prilocaine
Why are LA vasoconstrictors?
decreased perfusion (localized response), lower plasma levels, more LA into the nerve, less bleeding at site
what are the three catecholamines that are vasoconstrictors and what do they bind to?
Epinephrine, norepinephrine, and levonodefrin.
They activate alpha receptors
1:1,000 dilution is what in mg/mL? 1:10,000?
1 mg/mL, 0.1mg/mL
How much LA is in a 2% carpel?
20 mg/mL * 1.8 mL = 36 mg of LA
What are five factors that determine the duration of LA?
Individual accuracy of delivering status of tissues in the area anatomic variation type of block
What are the big five LAs?
2% lidocaine, 3% mepivocaine, 4% articaine, 4% prilocaine, 0.5% bupivocaine.
Stats of lidocaine? onset, duration, max dose, etc
onset: 5 min
duration: 90-120
max: 300 mg per appt
pregnancy risk B
What is the maximum dose of epi a pt can have?
0.2 mg in healthy pt and 0.04 in a CV pt
Stats of mepivocaine? onset, duration, max dose, etc
onset, upper:30-120 seconds, lower:1-4 min
duration: U 20 min L40 min
max: 300 mg per appt
pregnancy risk C
Stats of articaine? onset, duration, max dose, etc
onset: 1-6 minutes
duration: under an hour
Max: 400 mg per appt
Pregnancy risk C
Stats of prilocaine? onset, duration, max dose, etc.
onset: 2-3 minutes
duration: 20 min complete, 1.5 hr IA
Max: 400 mg per appt
Pregnancy risk B
liver and lung toxicity: 0-toluidine =methemoglobinemia
Stats of bupivicaine? onset, duration, max dose, etc.
onset: 1-17 minutes
duration: 2-9 hrs
max: 90mg per appt
Pregnancy risk C
What is the safest LA to use on children and pregnant people?
lidocaine
What LA do you use on pts who can’t have epinephrine?
mepivocaine (short duration though)
Prilocaine (liver and lung toxicity)
What is this methemoglobinemia?
oxidation of Hb to methemoglobin so then there is less oxygen to the tissues = hypoxia.and it is treated with methylene blue and o2 solution.
What LA do you use when lidocaine doesn’t get the pt numb?
Articaine - penetrates bone!
caution with regional blocks
be so careful with kids and articaine
What LA is extremely cardiotoxic and how?
bupivicaine - binds strongly to the sodium channels and causesCV collapse and resistant resuscitation. (never use in kids or preggers)
What goes in the chart for LA?
What type and concentration, # of carpels, and method of administration.
