Ch 26 Local Anesthetics

Question 1

__ stop nerve conduction by blocking sodium channels in the axon membrane.

Answer 1

Local anesthetics

Question 2

Small, nonmyelinated neurons are __ than large, myelinated neurons.

Answer 2

blocked more rapidly

Question 3

There are two classes of local anesthetics:

Answer 3

ester-type anesthetics and amide-type anesthetics.

Question 4

__ occasionally cause allergic reactions and are inactivated by esterases in the blood.

Answer 4

Ester-type anesthetics (e.g., procaine)

Question 5

__ rarely cause allergic reactions and are inactivated by enzymes in the liver.

Answer 5

Amide-type anesthetics (e.g., lidocaine)

Question 6

Onset of anesthesia occurs most rapidly with anesthetics

that are __.

Answer 6

small, lipid soluble, and nonionized at physiologic pH

Question 7

Termination of local anesthesia is determined in large part by __.

Answer 7

regional blood flow.

Coadministration of epinephrine, a vasoconstrictor, will prolong anesthesia.

Question 8

Local anesthetics can be absorbed in amounts sufficient

to cause __.

Answer 8

systemic toxicity.

Principal concerns are cardiac dysrhythmias and CNS effects (seizures, unconsciousness, coma).

Death can occur.

Question 9

The risk of systemic toxicity from topical anesthetics applied to the skin can be reduced by (4).

Answer 9

(1) using the smallest amount needed,
(2) avoiding application to large areas,
(3) avoiding application to broken or irritated skin, and
(4) avoiding strenuous exercise and use of dressings or heating pads (which can increase absorption by increasing skin temperature).