Local Anesthetics

Question 1

what is a local anesthetic?

Answer 1

A derivative of cocaine that do not produce euphoria, it inhibits pain without being unconscious.

Question 2

what last longer, an ester local anesthetic or an amide local anesthetic?

Answer 2

esters are shorter since they are metabolized locally and in blood plasma by pseudocholinesterase.

Question 3

what is the method of action of a local anesthetic?

Answer 3

bind R on cytoplasmic surface of Na+channels. They blcok the pore so Na+ cannot enter resulting in no AP. 
small fibres (pain) blacked at lower concentrations, and motor fibres are blocked last.

Question 4

what does an analgesic do?

Answer 4

inhibits the generation of pain.

Question 5

how does a local anesthetic work?

Answer 5

inhibits transmission of signals related to sensation and motor activity.

Question 6

what happens when you combine a vasoconstrictor with a Local Anesthetic?

Answer 6

this slows the initial drug removal of the LA. it can also delay healing.

Question 7

what can happen when lidocaine (local anesthetic) and epinephrine (vasoconstrictor) are administered SC?

Answer 7

skin necrosis. This makes some practitioners not want to risk it.

Question 8

what are the systemic effects of local anesthetics on the CNS and CVS?

Answer 8

CNS: as dose ^ ; drowsiness->excitation +seizures
CVS: ˇ excitability of myocardium -> arrhythmias (rare—> cardiac arrest)

Question 9

why is cocaine used mainly in oral/nasal surgery

Answer 9

its used topically, and it inhibits NE re-uptake –> vasoconstriction -> less bleeding -> easier to see
its very irritating to tissues though, and can produce severe CVS toxicity

Question 10

what is procaine?

Answer 10

an ester with a short duration of action, but it is more allergenic than amides. still used sometimes for rapid onset and short-duration needs.

Question 11

what is lidocaine?

what is the overdose?

Answer 11

The most commonly used
^ # routes of admin.
overdose: drowsiness and possible seizures–>posible cardiac arrest

Question 12

what is the time of onset for injectable, infiltration, topical gel and spray for lidocaine?

Answer 12

inject: 30-60 mins
infil: ~3 min
gel (usually for cathaders)
spray: 60s

Question 13

what is bupivacaine?

Answer 13

slow onset but lasts longer than lidocaine

^ CVS toxicity

Question 14

what is levobupivacaine?

Answer 14

does not distribute well to CNS or heart-> safer

IV use

Question 15

what is proparacaine used for?

Answer 15

eyes

Question 16

what is field block in relation to local anesthetics

Answer 16

like infiltration anesthesia but goal is to prevent pain signals coming from up-stream sites

Question 17

what are clinical uses for L.A? (injectable methods)

Answer 17

1. surface- burned skin healing
2. infultration- inject SC
3. Field block
4. nerve block (less drug but harder to administer)
5. intravenous (tourniquet keeps drug in limp)
6. epidural (Spinal)
7. paravertebral (inject where nerve leaves vertebral foramen)

Question 18

what is systemic IV lodicaine?

Answer 18

1. inhibits depolarization of cardiac muscles.
2. premature AP originate in damage cardiac muscles-> blocked at low drug concentrations.
3. ^ dose ->arrhythmia->death
4. ˇ dose-> anesthesia
5. DO NOT USE WITH epinephrine-contraining products!