Induction Agents

Question 1

what are general anesthetics?

Answer 1

they produce unconsciousness but do not stop AP potential, therefore large [pain] can awaken patients, and are normally inject via IV.

Question 2

name 7 properties of an ideal induction agent

Answer 2

compatible with other agents and IV fluids
painless on administration
high potency and efficacy
minimal cardiovascular effects or other toxicity
inhibition of gag reflex to facilitate intubation
rapid and predictable offset of effect
rapid metabolism for minimal grogginess/ hangover

Question 3

what are the 3 major classes of the intravenous anesthetics?

Answer 3

1. barbiturates
2. propofol
3. phencyclidines

Question 4

what is the biological mechanism barbiturates?

Answer 4

it inhibit dissociation of GABA from its receptor and increases percentage of the time that GABAa receptors are in the open state. IE inhibits AP
at ^ [ ] can open GABA channels directly without GABA present
can produce intense CNS depression

Question 5

what is the metabolism of barbiturates?

Answer 5

slow hepatic metabolism by p450 enzymes- avoid in patients with pre-exsiting hepatic disease.

Question 6

what is thipental sodium

Answer 6

one of the only barbituates still used clinically. ultra-soft duration.

Question 7

describe the recovery for barbituates.

Answer 7

single doswe= rapid recovery
slow hepatic metabolism follows
pateints usually experience disorientation, restlessness, and nausea
recoveries get harder and longer the more doses given.

Question 8

what is the physiological effect on the CNS due to barbituates

Answer 8

1. dose-dependent depression in 15-30 s,
2. partial dose =cause excitement
3. enhance pain sensitivity

Question 9

what are the physiological effects on the respiratory tract due to barbituates?

Answer 9

dose-dependent depression

20-40s of apnea following a bolus, then deep breathing resumes

Question 10

what are the physiological effects on the CVS

Answer 10

directly depress cardiac contractility & decreases venous tone -> hypotension.
blood pools in visceral vessels
-> decreases flow to brain
worsens if injection to fast

Question 11

whats a common symptom for barbituates overdose?

Answer 11

enlarged spleen

Question 12

what are the main adverse effects of barbituates?

Answer 12

hypotension from venodilation

extravascular damage

Question 13

what are the main clinical uses for barbituates?

Answer 13

induction *sedative decrease the dose needed

short term anesthesia

Question 14

what are the characteristics of the most popular intravenous anesthetic Propofol?

Answer 14

sedation and anesthesia (poor analgesia)
smooth onset of hypnosis
duration 2-4 mins
induction use
IV or inhalant

Question 15

what is the mechanism of propofol?

Answer 15

facilitates the effect of GABA at GABAa receptors in the brain -> inhibits APs (can be used in absence of GABA)

Question 16

what are the advantages of using propofol

Answer 16

fast, smooth, complete recovery, even after repeat dosages
no grogginess (rapid hepatic metabolism) 
good for patients with moderate hepatic disease

Question 17

what are the physiological effects of propofol on the CNS system?

Answer 17

dose-dependent sedation -> anesthesia
smooth induction
rapid/smooth recover
away in 3 mins, full recovery in 20

Question 18

what are the physiological effects of propofol on the respiratory system?

Answer 18

respiration inhibited in a dose-dependent manner
initial apnea following a bolus is longer than other drugs
prolonged apnea and cyanosis may occur with too fact injection

Question 19

what are the physiological effects of propofol on the CVS system?

Answer 19

direct myocardial sepression & peripheral vasodilation

- hypotension is greater

Question 20

what is ketamine?

Answer 20

a “dissociative” anesthetic derived from PCP
inhibits perception of signals associated with the sense, without completely abolishing consciousness
gives a dream like state

Question 21

what is the mechanism of action of phencyclidines?

Answer 21

NMDA receptor bloackade also inhibits GABA receptors and causes CNS overstim. -> CVS effects

Question 22

what are the physiological effects of phencyclidines on the CNS system?

Answer 22

pseudo-unconsciousness
moderately good analgesia
hypothermia

Question 23

what are the physiological effects of phencyclidines on the CV?

Answer 23

it causes increases HR and BP due to SNS stimulation, this is advantageous in shocky patients.

Question 24

what are side effect of phencyclidines?

Answer 24

minimal respiratory effects
raises intreacranial pressure
excitement common if administered alone -> very rough recovery (needs additional sedative)