Ner 26: Local Anesthetics

Front 1

Define local anesthetic

Back 1

compounds which block nerve impulse conduction reversibly, causing no permanent dysfunction of the nerve.

Front 2

Ideal qualities of a local anesthetic

Back 2

-Not irritating to adjacent tissue
-low systemic tox (and therefore high therepeutic index)
-Rapid onset and recovery.

Front 3

Class A local anesthetic and ex

Back 3

Act at receptor site on the external surface of the nerve membraine.
Ex. Tetrodotoxin

Front 4

Class B local anesthetic and ex

Back 4

Act at receptor sites on the internal analog surface of the membrane
Ex. Quarternary analog of lidocaine

Front 5

Class C local anesthetic and ex

Back 5

Act by receptor independent physico-chemical mechanism.
Ex. Ethanol, Benzocaine

Front 6

Class D local anesthetic and ex

Back 6

Combination of receptor mechanism and receptor independent mechanism.
Ex. Most clinically useful agents.

Front 7

What determine the speed of onset of an anesthetic

Back 7

Lipid solubility speeds up onset
Low pKa speeds up onset
Small molecules have faster onset

Front 8

What determines the duration of an anesthetic

Back 8

Proportional to the contact between drug and neural tissue. Therefore:
-Lipid Soluability (more = longer?)
-pKa (smaller = longer?)
-Size (smaller = longer?)
-Amides longer than esters
-Local blood flow (less = longer)
-Protein binding (Less = Longer?)

Front 9

Metabolism of ester and Amide local anesthetics

Back 9

Esters metabolized primarily by plasma pseudoesterases, and secondarily by liver esterases.
Amides are metabolized exclusively in liver.

Front 10

Infiltration anesthesia

Back 10

Injection into tissue without consideration of nerve proximity

Front 11

Nerve block anesthesia

Back 11

Injection around nerve or nerve plexus, blocking a wider region.

Front 12

Intravenous regional anesthesia (Bier's block)

Back 12

Drug injected into vasculature and a tourniquet is used.

Front 13

Spinal anesthesia

Back 13

Drug delivered through dura into CSF in lumba spinal cord. Onset goes from sympa to para, and from sensory to somatic. Anesthesia works on spinal nerve roots and ganglia.

Front 14

What factors effect the degree of spinal anesthesia

Back 14

-Extent of vertebral diffusion
-Patient Position
-Relation between specific gravity of anesthetic and spinal fluid.

Front 15

SE other than conduction block of spinal anesthetic.

Back 15

-Generalized hypotension
-Regional circulatory effects on brain, liver, and kidney secondary to cardio effects.
-Neurological complications resulting in headaches and sensory/motor function change.

Front 16

Epidural anesthesia

Back 16

Used for regional anesthesia effecting large areas. Needle is passed in between vertebrae into epidural space in thoracic or lumbar regions. Used for birthing. Relieves pain without effecting motor. Less hazardous than spinal anesthetic.

Front 17

CNS toxicity of local anesthetics

Back 17

Can lead to hallucinations, loss of consciousness, siezures.

Front 18

Cardio toxicity of local anesthetics

Back 18

Hypotension, depressed contractility, (cocaine is exception to these), and arrhythmia, cadiac failure.

Front 19

Name ester anesthetics

Back 19

Cocaine
Procaine
Tetracaine
Benzocaine
Chloroprocaine

Front 20

Cocaine

Back 20

Ester local anesthetic. Used topically in upper resp tract.
Is a CNS stimulant, blocks reuptake of monoamines, especially sympathetics.
SE - Seizures, Hyperthermia

Front 21

Procaine

Back 21

Ester local anesthetic. Low potency, short duration.
Used for infiltration and spinal anesthesia.

Front 22

Tetracaine

Back 22

Ester local anesthetic. used for topical, spinal, and ophthalmologic anesthesia.
Longer lasting and more potent than procaine.

Front 23

Chloroprocaine

Back 23

Ester local anesthetic. Used for surgical and OB procedures.
Rapid onset, short acting.

Front 24

Benzocaine

Back 24

Ester local anesthetic. Used in prolonged surface anesthesia. Found in sunburn creams.
Low solubility and pKa

Front 25

List amide local anesthetics (in order of potency)

Back 25

Lidocaine
Prilocaine
Mepivacain
Ropivacine
Bupivacaine
Etidocaine
Dibucaine

Front 26

Prilocaine

Back 26

Like lidocaine but produces methmeglobinemia

Front 27

Bupivacaine

Back 27

More likely to produce arrhythmias

Front 28

Ropivacaine

Back 28

Slightly less potent than bupivicaine but less likely to produce cardio tox.