GENERAL ANESTHETICS Flashcards
(36 cards)
what are GE
a mixture of drugs administered through the course of surgery
specific goals of GE
. inhibit neurotransmission = make patient unconcious
. induce analgesia
. induce amnesia (forget events during GE)
. muscle relaxation
. anxiolytic (can increase HR/BP)
what is analgesia
pain relief
what is amnesia
memory loss
what is anxiolytic
reduce anxiety
different classes of GE
INHALATION: gaseous state = drugs are inhaled
used to maintain long duration anesthesia
IV: drugs are water-soluble - injected
used to rapidly initiate anesthesia//supplement inhalation anesthetics
classes of INHALATION anesthetics
N20 (nitric oxide) - dental surgery halogenated hydrocarbons inert gases : Xenon (no chemical reaction) /ether /cholorform
what chemical characteristics do the classes of inhalation anesthetics share
nothing
Lipid theory
- VOLUME EXPANSION
ethanol - causes slight expansion of pm = may alter properties of NT R/ion channels - INCREASED MEMBRANE FLUIDITY
some GE can alter the fluidity of membranes = may alter properties of NT R/ion channels
Direct effects on ligand-gated ion channels
increase of inhibitory GABA R
inhibit excitatory glutamate (NMDA R)
activation of two-pore K+ channels in CNS (suppress AP)
inhibit N ACh R
what are 2 proposed mechanisms of actions for GE
lipid theory
direct effects on ligand-gated ion channels
primary targets of GE
GABAa receptor: (multisubunit receptor) halogenated hydrocarbons - gaesous . propofol IV . etomidate Allosteric Agonists . thiopental
Glutamate NMDA receptor:
ketamine - IV
N20
Xenon
most GE bind to at least 2 targets
inhibition synaptic transmission = common feature
why is halothane (halogenated hydrocarbon) not used
oxidized to trifluoroacetate = trigger strong IS reaction
first-time form = sensitized IS - no response
second time = reaction (bronchioles swell up)
where is P450 found and what is its function
enzyme in the liver - bind to 02 and carry out drug metabolism
= inactivation of drug
= increase secretion of drug from body
allosteric agonists
change enhance binding of the agonist
(eg. GABA on GABAa R - binds, channel opens - Cl- enter cell = re/hyperpolarisation - prevent A.P
= GABA can bind at lower conc.
allosteric inhibitor
bind to another site on enzyme- alter confirmation interferes with substrate binding and inhibits the reaction
describe GABAa R
cylindrical 5 protein subunit 2 alpha 2 beta 1 gamma (similar to N ACh R)
GABA binds to the alpha subunit (interface) - similar to ACh
what do photoactivation studies show
specific binding sites for
ISOFLURANE (hydrogenated drugs)
PROPOFOL (IV GE)
stages of anesthesia
- Analgesia - patient conscious but drowsy
- Excitement - patient unconscious but responds to painful stimuli: coughing, gagging, reflex movements, irregular breathing
- Surgical anesthesia - muscle relaxation, slow respiration, elimination of reflex responses
- Medullary paralysis - respiratory/vasomotor failure
= death (AVOID STAGE!)
why are gaseous GE difficult to work with
gases = hard to maintain proper dose
blood: gas partition coefficient:
distribution between air in lungs and bloodstream
influences RATE of ONSET / recovery
LOWER = faster onset / recovery
oil: gas partition coefficient:
distribution between lipids and dissolved gases in tissues
influences drug POTENCY / recovery rate
HIGHER = greater potency / slower recovery
MAC
minimal alveolar concentration
= concentration of anesthetic in the blood that eliminates sensitivity to pain + induces an unconscious state in 50% of patients (ED50 of other drugs)
describe the relationship between MAC and oil: gas partition coefficient:
inversely proportional
