Exam 2; General Anesthetics Flashcards
When should general anesthetics be used
only for surgery
What were two of the first general anesthetics used
ether
chloroform
What are the eight characteristics of the “ideal/balanced” anesthetic
loss of consciousness amnesia; don't want to remember analgesia inhibition of reflex muscle relaxation rapid onset of and recovery from anesthesia pleasant experience no dangerous side effects
What is the therapeutic index of general anesthetics
very low
the effective dose and lethal dose are VERY close together
What is the broad mechanism of action of general anesthetics
inhibition of neuronal firing
What two neurons do general anesthetics act upon
potentiation of inhibitory GABAnergic neurons
inhibition of excitatory glutaminergic neurons
Which portion of the brain is more sensitive, the cortex or the thalamus
cortex more sensitive than the brain
The higher the what, the more potent the agent
lipid solubility
The concentration at 50% (ED50) of patients unresponsive is what, which describes potency
MAC; minimal alveolar concentration
the lower the MAC the more potent the drug
The speed of induction is related to what
solubility of the agent in the blood
The more soluble the agent is in the blood (high blood/gas coefficient), the what
slower the onset (induction)
In general, the recovery from the general anesthetic is what
symmetrical with induction
rapid induction = rapid recovery
This is a gas at room temperature and is insoluble in blood; rapid onset = rapid recovery, low amnesia, low potency
nitrous oxide
What is the MAC of nitrous oxide
> 100%
not very effective (need to berate more than 100% concentration of air as NO; which is not plausible
Because nitrous oxide is not soluble in the blood, what tends to happen to the patient
the NO leads the blood and enters the body cavity as gas; causing discomfort
Repeated exposure to nitrous oxide can cause what
megaloblastic leukemia and leukopenia
These are used to maintain anesthesia
the halogenated hydrocarbons; the “-fluranes”
What is a consequence of the “-fluranes”
increased incidence of liver disease with repeated exposure
This is a major consequence of halogenated hydrocarbons resulting from a genetic defect
malignante hyperthermia
What causes malignant hyperthermia due to the halogenated hydrocarbons
increased Ca uptake from skeletal muscle
increasing muscle metabolism; 42℃ –> 107℃
These have a more rapid onset than inhaled anesthetics
IV general anesthetics
This is a barbiturate IV-GA
methohexital
Methohexital binds to and activates what
GABAnergic neurons (inhibitory neuron)
Methohexital action is terminated by what
redistribution in from the brain; the minute the concentration decreases, it stops
This is the most commonly used parental anesthetic with a rapid onset and short duration
propofol
Propofol acts to do what
increase GABAnergic activity
Propofol has what effect
anti-emetic
lessens nausea
This is an analog of phencyclidine which causes “dissociative anesthesia” - profound amnesia and analgesia
ketamine
ketamine has what kind of onset/duration
short induction/duration
What is the mechanism behind ketamine
bind to a receptor which inhibits glutamate neurons (activating neurons)
Ketamine can cause what in patients emerging from anesthesia
hallucinations
This is a very rapid, non-analgesic with a high therapeutic index (conscious sedation), causes some post-op nausea
etomidate
What is the mechanism of etomidate
activated GABA receptors
This is a benzodiazepine which binds to benzodiazepine receptors and enhances GABAnergic activity; causes amnesia
midazolam
