Anesthetics

Question 1

Local anesthetics

Answer 1

Transient analgesia, w/out loss of consciousness.
Block nn conduction (thro Na+ channels).

Esters:

• procaine
• chloroprocaine
• cocaine
• tetracaine
• dibucaine
• benzocaine
• proparacaine

Amides:

• lidocaine
• articaine
• mepivacaine
• prilocaine
• bupivacaine
• ropivacaine
• etdocaine

Others:

• dyclonine
• pramoxine

Question 2

General Anesthetics

Answer 2

Induce loss od consciousness, analgesia, amnesia, skeletal mm relaxation and inhibition of autonomic and sensory reflexes.

• analgesia -> inhibition of pain inputs at spinal level
• loss of consciousness -> action on RAS and thalamocortical tr.
• short-term amnesia -> action on hippocampus

Question 3

Stages

Answer 3

1. inducation
   
   • from onset adm to effective surgical anesthesia
   • i.v. thiopental (30-40s)
   • children w/put i.v. -> halothane / sevoflurane
2. maintenance
   
   • oustained surgical anesthesia
   • opioids (fentanyl)
3. recovery
   
   • time from discontinuation of adm until consciousness

Question 4

Stages of depth

Answer 4

I - analgesia, amnesia
II - loss of consciousness; excitement (increase BP and respiration)
III - surgical anesthesia w/ decreased reflexes
IV - medullary paralysi

Question 5

Inhalation anesthetics

Answer 5

Do not have a specific R.

They act by:
- inhibition of excitatory transmission (via inhibition of glutamatergic and nicotinic neurons)
- potentiation of inhibitory transmission by activating
GABA Rs (Cl/K channels).

Their potency is related to their lipid solubility (increase liposolubility, increase anesthetic effect).

All are hallogenated ethers / hallogenated hydrocarbons, EXCEPT nitrous oxide!

• nitrous oxide
• halothane
• enflurane

Question 6

Nitrous oxide

Answer 6

Doesn’t produce surgical anesthesia (decrease potency).

Powerfull analgesic!

Used together w/ other agents -> allow them to be administered at decreased [ ]s and thus decrease their AE.

Question 7

Halothane

Answer 7

Potent, non-irritant, non-volatile anesthetic, limited analgesic.

Used for maintainance if anesthesia.

Question 8

Enflurane

Answer 8

Similar to halothane in potency and speed of action.

Used to maintain anesthesia in combination w/ nitrous oxide.

Question 9

Intravenous anesthetics

Answer 9

They act by:

• potentiation of action of GABA Rs (barbiturates, propofol, etamidate)
• decrease neuronal excitability by blocking NMDA Rs (ketamine)

Used for rapid induction of anesthesia, then anesthesia is maintained by inhalation agents.

Question 10

Barbiturates

Answer 10

Thiopental
No analgesic action
Low safety margin bc it causes cardioresp depression
Induce some CNS depression postoperatively

Question 11

Etomidate

Answer 11

Little analgesic action

Less cardioresp depression and less hangover

Question 12

Propofol

Answer 12

Rapidly metabolized, avoid thiopental hangover

To maintain anesthesia, usefull in day-case surgery

Question 13

Ketamine

Answer 13

Can produce surgical anesthesia
Suitable for brief surgeries
Suitable for minor pediatric surgeries bc children do not suffer from the adult side-effects

Question 14

Preoperative drugs

Answer 14

Before surgery = premedication:

• decrease anxiety -> BZP (diazepam, lorazepam, midazolam)
• decrease pain -> opioids (morphine, fentanyl; at time of induction)
• decrease undesired effects of subsequent adminestered drugs -> cholinergic antagonists (atropine, hyoscine)

After induction of surgical anesthesia -> aid intubation -> neuromuscular blockers (vecurunium, suxamethonium)

During recovery -> to control postoperative emesis -> antiemetics (metoclopramide, droperidol)