Flashcards in Induction Agents Deck (24)
what are general anesthetics?
they produce unconsciousness but do not stop AP potential, therefore large [pain] can awaken patients, and are normally inject via IV.
name 7 properties of an ideal induction agent
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
what are the 3 major classes of the intravenous anesthetics?
what is the biological mechanism barbiturates?
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
what is the metabolism of barbiturates?
slow hepatic metabolism by p450 enzymes- avoid in patients with pre-exsiting hepatic disease.
what is thipental sodium
one of the only barbituates still used clinically. ultra-soft duration.
describe the recovery for barbituates.
single doswe= rapid recovery
slow hepatic metabolism follows
pateints usually experience disorientation, restlessness, and nausea
recoveries get harder and longer the more doses given.
what is the physiological effect on the CNS due to barbituates
1. dose-dependent depression in 15-30 s,
2. partial dose =cause excitement
3. enhance pain sensitivity
what are the physiological effects on the respiratory tract due to barbituates?
20-40s of apnea following a bolus, then deep breathing resumes
what are the physiological effects on the CVS
directly depress cardiac contractility & decreases venous tone -> hypotension.
blood pools in visceral vessels
-> decreases flow to brain
worsens if injection to fast
whats a common symptom for barbituates overdose?
what are the main adverse effects of barbituates?
hypotension from venodilation
what are the main clinical uses for barbituates?
induction *sedative decrease the dose needed
short term anesthesia
what are the characteristics of the most popular intravenous anesthetic Propofol?
sedation and anesthesia (poor analgesia)
smooth onset of hypnosis
duration 2-4 mins
IV or inhalant
what is the mechanism of propofol?
facilitates the effect of GABA at GABAa receptors in the brain -> inhibits APs (can be used in absence of GABA)
what are the advantages of using propofol
fast, smooth, complete recovery, even after repeat dosages
no grogginess (rapid hepatic metabolism)
good for patients with moderate hepatic disease
what are the physiological effects of propofol on the CNS system?
dose-dependent sedation -> anesthesia
away in 3 mins, full recovery in 20
what are the physiological effects of propofol on the respiratory system?
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
what are the physiological effects of propofol on the CVS system?
direct myocardial sepression & peripheral vasodilation
- hypotension is greater
what is ketamine?
a "dissociative" anesthetic derived from PCP
inhibits perception of signals associated with the sense, without completely abolishing consciousness
gives a dream like state
what is the mechanism of action of phencyclidines?
NMDA receptor bloackade also inhibits GABA receptors and causes CNS overstim. -> CVS effects
what are the physiological effects of phencyclidines on the CNS system?
moderately good analgesia
what are the physiological effects of phencyclidines on the CV?
it causes increases HR and BP due to SNS stimulation, this is advantageous in shocky patients.