Local Anesthetics Flashcards
(18 cards)
Which is the correct order of blockade of nerve fibers for LAs?
A. Large, myelinated (Aa) fibers, small myelinated (Adelta), small unmyelinated (C)
B. Small myelinated (Adelta), small unmyelinated (C), large myelinated (Aa)
C. Small unmyelinated (C), small myelinated (Adelta), Large myelinated (Aa)
B.
A delta fibers correspond to which? A. Cold perception and pain B. Warmth perception and pain C. Touch, vibration, position perception D. Muscle control
A
C fibers correspond to which? A. Cold perception and pain, B. Warmth perception and pain, heart rate, GIT, GUT, blood pressure, sweating C. Touch, vibration, position perception D. Muscle control
B
C fibers are associated with warmth perception and slower pain conduction, as well as heart rate, blood pressure, GIT, GUT function and sweating (therefore, block these fibers and you can potentially decrease sympathetic firing and lower the HR and BP, as well as maintain GIT motility!)
Aa (A alpha) fibers correspond to which? A. Cold perception and pain B. Warmth perception and pain C. Touch, vibration, position perception D. Muscle control
D. Muscle control
Note: Aa/Ab fibers are for touch, vibration and position perception
T or F: LAs block voltage gated sodium channels, such that the drug in the nonionized form will cross the membrane and the ionized form will bind to the sodium channel from the inside.
True
LAs block voltage-gated sodium channels by binding to channels: A. In the closed, quiescent state B. In the open state C. In the inactivated state D. B and C only E. Only B
D. They will bind to the open and inactivated (immediately after opening)
Which of the following determines the pKa and thus the state of ionization of the LA? A. Ester vs. amide group B. Terminal amine C. Aromatic ring D. B and C
B. The terminal amine can be in the ionized (quaternary) or the nonionized (tertiary) form, effecting its degree of ionization in a given environment.
The following are amide LAs EXCEPT: A. Lidocaine B. Bupivicaine C. Proparacaine D. Benzocaine E. C and D F. Just C
E. C and D: Proparacaine and Benzocaine
These are ester LAs
The following are ester LAs EXCEPT: A. Proparacaine B. Procaine C. Benzocaine D. Mepivicaine
D. Mepivicaine
This is an amide LA
T or F: Ester LAs are metabolized by the liver, and amide LAs are metabolized by plasma pseudocholinesterases.
F. The opposite. Think esters go with -esterases!
LAs generally have a pKa in what range? A. 5-6 B. 6-7 C. 7-8 D. 8-9
D. They have a relatively high pKa, and thus will be relatively nonionized in aqueous tissue solutions such as blood and CSF and will diffuse through them quickly. This will make them slower to diffuse through cell membranes, but will diffuse into the cell relatively fast (lipophilic)
The use of lidocaine for equines to prevent post-surgical ileus is most attributed to what? A. Blockage of the Aa fibers B. Blockage of the Ad fibers C. Blockage of the C fibers D. Unknown; it just helps somehow.
C.
Remember, C fibers are involved with autonomic functions, so if you block them you can see cardiac suppression, hypotension (block sympathetic transmission) as well as increased GI motility, increased salivation, and other muscarinic effects.
What is the reason for using Sodium Bicarbonate with Lidocaine for local infiltration?
A. Causes vasoconstriction, keeping the drug at the site longer.
B. Causes local vasodilation, enhancing the effect and duration of the drug.
C. It reduces pain on injection
D. Both B and C
C
Classify Lidocaine as a LA: A. Fast-acting, long duration B. Slow-acting, long duration C. Fast-acting, short duration D. Fast-acting, medium duration
D
Classify bupivacaine as an LA: A. Fast-acting, long duration B. Slow-acting, long duration C. Fast-acting, short duration D. Fast-acting, medium duration
B. In fact, it can last up to 8 hours! So it might be a good choice for a painful surgery to give this intra-op to keep the patient comfortable throughout recovery.
All of the following are true for bupivacaine EXCEPT:
A. It is the most cardiotoxic of the LAs
B. Diazepam can enhance its cardiodepressant effects
C. Preparations of this drug consist of mostly the S enantiomer of the compound.
D. We don’t tend to use it topically
C. It is a racemic mixture, which is about 50/50 of the R and S enantiomers. In fact, ropivicaine is a similar drug that is made up of the less cardiotoxic S enantiomer (this could potentially be an even better drug then).
T or F: Mepivicaine is considered the lidocaine for horses, and is essentially preferred because it has less of an irritating effect to the tissue.
True
Which of the following is true of tetracaine?
A. It is commonly used as a spray to facilitate endotracheal intubation in cats
B. It is used as an adjunct with lidocaine to enhance its effects
C. It is similar to the topical ophthalmic proparacaine but longer lasting
D. It is similar to the topical ophthalmic proparacaine but does not last quite as long
C.
