Term
| desired components of general anesthesia |
|
Definition
unconsciousness
amnesia
analgesia
intact, stable autonomic reflexes
muscle relaxation
prompt reversal/recovery
-->no one drug can do all of this |
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Term
|
Definition
no one drug can do all the goals of anesthesia, so concomitant use of a variety of primary and supplemental drugs is used
adjuncts/supplements: sedatives, amnestics, anxiolytics, opiods, NM blockers, etc |
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Term
| classes of general anesthetics |
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Definition
different classes based on mode of administration:
inhalation agents
-volatile liquids
-gas
IV agents |
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Term
| general principles of inhaled anesthetics |
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Definition
minimum alveolar concentration
water/lipid solubility
elimination |
|
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Term
minimum alveolar concentration
(MAC) |
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Definition
the minimum concentration of anesthetic (expressed as % of inhaled gas mixture) needed to abolish specific painful stimulus in 50% of subjects
similar to ED50; a measure of the drug's potency
1/MAC ~ potency |
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Term
|
Definition
MAC is altered by many factors:
-some controlled by the doc (pulm ventiliation, pulm blood flow, use of supplemental rx)
-some intrinsic to the patient (overall health, other meds, etc) |
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Term
| solubility of inhaled anesthetics |
|
Definition
pharmacokinetic property that affects onset and duration of action
dramatically affected by solubility of the inhaled substance in water versus lipid
blood is like a sponge for inhaled anesthetics but getting effective anesthetic concentration in the brain, not blood, is what's important |
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Term
inhaled anesthetics
water solubility |
|
Definition
water solubility compares roughly to the drugs solubility in blood
the more water soluble the drugs, the slower its induction (onset)
need the blood to be "saturated" with drug before it can spill over into the CNS
low solubility in blood - blood compartment quickly saturates and anesthetic quickly diffuses nto brain |
|
|
Term
inhaled anesthetics
lipid solubility |
|
Definition
drugs more soluble in lipids have faster induction, work quickly
brain - the major target of action - in lipid~ |
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Term
| elimination of inhaled anesthetics |
|
Definition
when administration stops, get passive diffusion out of CNS
rate depends on: lipid/water solubility, rate/depth of respiration
elimination via lungs w/o prior metabolism is main route |
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Term
| postulated mechanisms of inhaled anesthetic action |
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Definition
GABA-A receptor chloride channel is the most likely molecular target of most inhaled and parenteral agents
[low] facilitate GABA actions; [high] levels directly activate GABA receptors
maybe some potassium channel activation too (hyperpolarization of nerve membranes) |
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Term
| volatile liquid halogenated hydrocarbon agents |
|
Definition
liquids at STP - heated and volatilized in special anesthesia devices
"-anes" (desflurane, halothane, isoflurane, ...) |
|
|
Term
volatile liquid halogenated hydrocarbon agents
MAC |
|
Definition
all are very potent: MACs from <1% - 6%
extremely LOW therapeutic index |
|
|
Term
volatile liquid halogenated hydrocarbon agents
differences among agents |
|
Definition
side effects profiles var somewhat
different dependence on metabolism before elimination |
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Term
| usual use of inhaled anesthetics in balances anesthesia |
|
Definition
usually used to maintain surgical anesthesia
NOT a required element in surgical/general anesthesia procedures |
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Term
| common DDIs affecting some or all halogenated hydrocarbon anesthetics |
|
Definition
*succinylcholine: increase risk of malignant hyperthermia*
cathecholamines
beta blockers
CCB
opioid/other CNS dep
non-depol NMJ blockers |
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|
Term
|
Definition
#1 overall inhaled anesthetic in US
stable CO, BP falls in dose-dependent fashion
systemic and coronary vasodilator |
|
|
Term
|
Definition
very insoluble in blood, very potent
complete elimination in expired air
cons: $$$, smells bad, poor as induction agent, risk of tachycardia and increased ICP |
|
|
Term
malignant hyperthermia
background |
|
Definition
can happen with ANY volatile liquid anesthetic, NMJ blockers...but SUCCINYLCHOLINE is biggest offender
highly fatal
autosomal dominant trait with variable penetrance (mutation in ryanodine receptor gene)
patient history is important!
can happen intra or post-op |
|
|
Term
malignant hyperthermia
mechanism/treatment |
|
Definition
-sarcoplasmic reticulum looses its ability to take up calcium
-skeletal muscle contracture
-metabolic heat production
-fever
-rapidly developing fever can causes seizures, ventilatory impairment
-skeletal muscle damage leads to hyperkalemia, arrhythmias, myoglobin leakage (rhabdomyolysis) and renal failure |
|
|
Term
malignant hyperthermia
treatment |
|
Definition
dantrolene, oxygen, decrease temp
other drugs as needed |
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|
Term
anesthetic gas
nitrous oxide |
|
Definition
MAC ~ 105%
fast onset and recovery
good analgesia (main use)
no skeletal muscle relaxation, some CV depression, no uterine effects |
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|
Term
|
Definition
rapid effects (sedation, unconsciousness) speed induction, more comfortable than inducing with inhaled anesthetics
most lack analgesia, skeletal muscle relaxation |
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Term
| induction/maintenance IV agents |
|
Definition
BZDs, propofol, opiods,
barbituates, katamine, etomidate
can't use LOCAL anesthetics for general anesthesia at all! |
|
|
Term
|
Definition
benzodiazepine
rapid induction/sedation, excellent antegrade amnesia
fast, smooth recovery
no skeletal muscle relaxation or analgesis
often used for "conscious sedation" (combined with fentanyl) |
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|
Term
|
Definition
most common parenteral anesthetic (induction or maintenance)
fast onset (unconscious in <60 seconds), short duration (can be overcome with intermittent injections or longer infusion)
no analgesia or muscle relaxation
depression of CV, CNS function; largely barbiturate-like |
|
|
Term
ultra short acting IV barbiturates
thiobarbiturates (thiopental, thiamylal) |
|
Definition
render unconscious very quickly
high abuse potential
CV dep, laryngospasm risks
decreased ICP, CBF, CMR |
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|
Term
|
Definition
"dissociative" anesthetic - causes excellent amnesia, profound analgesia, overall cataplectic state
abuse potential - psychomimetic
bronchdilator, increase CBF, ICP
often used in trauma, burn victims getting skin grafts, etc |
|
|
Term
| opioids for induction or maintenance |
|
Definition
fentanyl, sufentanyl
morphine-like opioid agonists
MUCH more potent than morphine |
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Term
| typical process of balanced anesthesia |
|
Definition
IV AGENT: induce anesthesia, or sedate patient, cause short term amnesia
NM BLOCKER: (if needed) for intubation, intra-op skeletal muscle paralysis
mainenance of surgical anesthesia
-INHALED/IV ANESTHETICS
-DRUG FOR PAIN
-O2
allow recovery spontaneously, use drugs (as needed) to reverse skeletal muscle paralysis/ventilatory depression |
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