General anesthetic agents Flashcards
Therapeutic use of IV anesthetics
induction of anesthesia
What is the therapeutic use of benzodiazepines for anesthetics
for sedation and anxiolysis
Main contributor to IV anesthetics duration of action
redistribution out of CNS
MOA of Methohexital
short acting barbituate, acts on GABA-A receptors
Pharmacokinetics of methohexital
onset 30sec, duration 10 min
Therapeutic use of methohexital
induction of anesthesia and procedural sedation
MOA of propofol
GABA-A agonist, sedative and amnestic, but not analgesic
Therapeutic use of propofol
most commonly used in US. general anesthesia induction and maintenance, procedural sedation, post-op anti-emetic
Pharmacokinetics of propofol
onset 40sec duration 6 min
Side effects of propofol
hypotension and respiratory depression
Pain at injection site
MOA of etomidate
potentiation of GABA-A currents. Minimal cardiovascular and respiratory effects, not analgesic
Therapeutic use of etomidate
commonly used for induction and maitenance of general anesthesia, patients with hypotension
Side effects of etomidate
injection site pain, myoclonic movements, post-op nausea and vomiting, adrenal insufficiency with continuous infusion
Ketamine MOA
NMDA receptor antagonist, produces dissociative sedation, analgesia and bronchodilation. Minimal cardiovascular effects
Therapeutic use of ketamine
less often used due to emergence phenomenon. Usefull for induction of pediatric anesthesia.
procedural sedation for brief, painful procedures
patients with airway disease
Side effects of ketamine
CNS psychotomimetic-vivid dreams and hallucinations, can be countered in adults with benzodiazapines
Some nausea/vomiting, tachycardia and hypersalivation
7 properties of an ideal general anesthetic
anesthesia analgesic and anxiolytic amnesia muscle relaxation inhibition of reflex response to trauma rapid, smooth onset and recovery little or no systemic toxicity or hazard to healthcare personenel
Cardivascular effects of anesthesia
decreases mean arterial blood pressure
Respiratory effect of general anesthesia
reduced or eliminated ventilory drive
Emergence effects
vomiting, treated with 5-HT3 antagonists
return of sympathetic tone- tachycardia and hypertension
shivering
MOA of inhalation anesthetics
Enhances GABA-A activity
Inhibition of excitatory glutamate, nicotinic, 5-HT3 receptors
inhibits action potential propagation by Boltage gated ion channels
GPCRs
Factors affecting anesthetic uptake (3)
blood solubility
aveolar blood flow
difference in PP of agent in aveolar gas vs blood
A high blood:gas partition coefficient results in:
slow induction rate
Mixture for second gas effect
70% nitrous oxide and 1% halothane
What factors affect MAC in patients
increase mac in infancy and chronic alcohol intake
decreae MAC in elderly and acute alcohol intake
Therapeutic use of Nitrous oxide
alone as a sedative/analgesic for outpatient dental in combination (70%) for secondary gas effect
Advantages of NO (4)
good analgesia and amnesia
rapid induction and recovery
minimal cardiovascular effects
reduced side effect of other inhalation agents
Disadvantages of NO (5)
Not a complete anesthetic not a good muscle relaxant can cause diffusion hypoxia myelosuppression- not good for chronic use possible teratogen
Therapeutic use of halothane
rarely used in US, low cost in developing countries
Used for children in US due to lack of pungency
Advantages of halothane (4)
Non-pungent
rapid induction and recovery
muscle relaxant
bronchodilator
Disadvantages of halothane (5)
poor analgesic slow elimination significant cardiac depression increased intracranial pressure halothane hepatitis
Isoflurane therapeutic use
comonly used for maintenance at 1-2%
Advantages of isoflurane
good cardiovascular profile, maintains cardiac function
Disadvantages of isoflurane
pungent
Therapeutic use of desflurane
widely used for maintenance 6-8% during outpatient surgery
Advantages of desflurane
very rapid induction and emergence
good cardiovascular profile
Disadvantages of desflurane
pungent, bronchial irritation, used with IV agent for induction
Therapeutic use of sevoflurane
widely used 2-4%
Advantages of sevoflurane
low pungency - good for pediatric patients
good cardiovascular profile
