Local anesthetics Flashcards
Where do local anesthetics bind?
To sodium channels in nerves
For what can local anesthetics be used?
Peripheral nerve blocks
Neuraxial anesthetics
Subq anesthetics
Topical anesthetics
How many nodes need to be blocked on myelinated fibers?
3 nodes of Ranvier
What is the easiest type of nerve to block?
Small, myelinated fibers
What three types of fibers are there?
A, B, and C
Subclasses of A fibers
Alpha
Beta
Gamma
Delta
Are A fibers myelinated?
Yes
Alpha fibers have __ function
motor
Beta fibers have __ function
tactile and proprioceptive
Gamma fibers have __ function
muscle tone
Delta fibers have __ function
pain, cold temperature
Are B fibers myelinated?
Yes
B fibers are located __.
on preganglionic sympathetic fibers
Are C fibers myelinated?
No
C fibers function in __.
visceral pain
Local anesthetics preferentially bind to which states of receptors?
Inactivated and open states; frequency dependent blockade
What type of molecule are almost all local anesthetics?
Amides or esters (almost always amides for non-anesthesiologists)
Where do local anesthetics bind?
On the cytoplasmic side of the receptor
What adjunct is added to lidocaine to increase absorption and duration?
Epinephrine
What happens with neurotoxicity of LA?
Seizures
What worsens neurotoxicity of LA?
Acidosis
Direct neural toxicity
Irreversible injury to nerve tissue
Allergic reactions of LA are generally due to this type
Esters
What type of reaction happens?
Type I or type IV
If someone says they have an allergy to an amine, what is it actually generally from?
An additive in the LA
What relationship determines the speed of onset of the LA?
The pH to the pKa: pKa should be higher so there is more uncharge form that can traverse the membrane
How is cardiovascular toxicity treated?
With intralipid; creates a “sink” that LA can be sequestered into
