ANESTHESIA Flashcards
why are general anesthetics typically given via inhalational & intravenous route?
offer more immediate control over dose & hence duration of action
term for the concentration in the inspired gas required to render half of a group of pts unconscious, that is unresponsive to painful stimulus
minimum alveolar concentration (MAC)
what is the oil gas partition coefficient?
describes relationship b/w lipid solubility & potency of the drug in producing unconsciousness (the larger the number the more lipid soluble the drug)
what is the meyer-overton hypothesis?
states that anesthetic activity is directly linked to lipid solubility
which inhaled anesthetic has the highest min. alveolar concentration?
N2O
what is the general mechanism of action for the inhaled anesthetics?
reinforce of GABA & glycine inhibitor signaling, reinforcement of two more potassium channel activity & inhibition of glutamatergic signaling
Remember that loss of memory and perceptive awareness can precede the production of what?
analgesia (customary in anesthesia to rely upon analgesics to make sure the pt is pain free)
why do you add a fluorine molecule to the inhaled anesthetics?
removes the explosive nature of the drug product
the volatile anesthetics are most commonly administered in conjunction w/ what and oxygen?
nitrous oxide
which inhaled anesthetic has the highest blood:gas partition coefficient?
isoflurane
which inhaled anesthetic has the lowest blood gas partition coefficient?
nitrous oxide
which inhaled anesthetic drug has has very low hepatic metabolism?
nitrous oxide
the newer agents like (name the two) equilibrate more rapidly into the brain and produce a faster onset of unconsciousness than does halothane.
desflurane & sevoflurane (also when turned off these re-equilibrate from the brain to blood and then to alveoli flooding back into lungs and permitting a more rapid recovery of consciousness)
equilibration occurs most rapidly with high flow organs like the ___________ and less rapidly into skeletal muscle and adipose tissue
brain
once the anesthetic is turned off, elimination of drug is most rapid again in high flow organs, but overall duration of elimination is governed by the rate of release from __________tissue
adipose
what are the two factors that the anesthesiologist can control to adjust the speed of onset of unconsciousness?
can increase the percentage of anesthetic delivered with each breath
can adjust RR (more profound effect on N2O, which doesn’t block the reflex response to PaCO2)
with increasing delivery of anesthetic and thus depth of unconsciousness, there is both a loss of _______________ & reduction in tidal volume
loss of responsiveness to rising carbon dioxide levels
what are the two main respiratory effects of inhaled agents?
increased RR
decreased tidal volume
reflex response to PaCO2 is blocked by all inhaled agents except what?
N2O
when used alone which inhaled agent has no effects on the CV system?
N2O
what are some of the effects of CV depression by inhaled agents?
direct depression -decreased symp. outflow Peripheral ganglion blockade -decreased adrenal catecholamine release Baroreceptor attenuation -decreased Ca2+ flux Vagal stimualation
name two inhaled agents that have irritating odor?
desflurane
isoflurane
none of the inhaled agents except for which drug produce analgesia?
N2O
none of the inhaled agents have effects on muscle relaxation except?
isoflurane
which inhaled agent is protective in that reflexes are maintained if this agent is used alone?
nitrous oxide
which inhaled agent is teratogenic?
N2O (spontaneous abortions)
N2O is an inhibitor of what vitamin?
vitamin B12
what is the second gas effect for N2O?
high volume of N2O + relative insolubility = rapid uptake of gas from alveoli including any accompanying anesthetic agent for O2
what is diffusional hypoxia with N2O?
that brief period of time when the anesthetic is turned off and large quantities of anesthetic gas exit the body by being exhaled (important that anesthesiologist applies oxygen by mask during this critical period)
increase pressure with N2O could give rise to what adverse outcome?
eardrum perf. (N2O has 34x solubility that of nitrogen)
why do we use N2O?
vapor sparing effect (reduced requirement for expensive volatile agent) reduced inspired volatile concentration -reduced resp. depression -reduced CV effects -smoothens the anesthetic procedure cheap
the need to accomodate such a high volume of nitrous oxide compromises the ability to provide high levels of what?
oxygen
which two drugs have actions on NMDA receptor system for glutamate?
propofol
ketamine
which IV anesthetic is unusual in that it can function like GABA itself?
propofol