36: General Anesthetic Agents Flashcards
anesthesia =
loss of sensation or a state without any feeling
advantages and disadvantages of general v. local anesthesia
local: minimal system disturbance, but may not be adequate
general: body wide anesthesia, but disturbance of all organ systems
general anesthesia =
clinical state where there is an induced loss of consciousness or total insensibility in a reversible manner
general anesthesia is associated with _____ respiration and __________ blood pressure
decreased; decreased
myocardial depression and vasodilation
“triad of anesthesia”
asleep
pain-free
still
6 characteristics of ideal anesthetic agent
- unconsciousness
- amnesia
- analgesia
- skeletal muscle relaxation
- areflexia
- good minute-to-minute control
why are adjuvant drugs used prior to anesthesia?
to make it more safe and pleasant
- relieve anxiety = benzodiazepines
- prevent allergic reactions = antihistaminics
- prevent nausea and vomiting = antiemetics
- provide analgesia = opiods
- prevent bradycardia and secretion = atropine and glycopyrrolate
what kinds of clinical conditions might be important to know about when a patient is to undergo anesthesia?
**prior anesthetic history of patient and blood relatives
- family history of malignant hypothermia
- cardiovascular problems
- respiratory disease
- allergies to medicine and food
4 phases of general anesthesia
- induction
- maintenance
- emergence
- recovery
4 stages of general anesthesia
I: analgesia
II: excitement
III: surgical anesthesia
IV: medullary depression
what are inhalable anesthetics generally used for?
maintenance of anesthesia
can be used for induction in pediatrics
what are IV or fixed anesthetics generally used for?
induction and short surgical procedures
what ion channels may anesthetics alter?
- increase GABAa receptor Cl- channel activity
- activate voltage-gated K channels
- inhibit glutamate NMDA receptors
advantages of inhalable anesthetic agents over IV
+ easy to control depth of anesthesia
+ readily reversible, minute-to-minute control
- induction not as fast or smooth as with fixed agents
increasing inspired anesthetic concentration in inspired air —> _________ partial pressure in lungs —>
increased
faster achievement of anesthetic concentration in the blood
increasing alveolar ventilation —> ____ gas molecules/time —>
more
faster anesthesia onset; better ventilation results in more rapid onset of anesthesia
partial pressure of anesthetics with higher solubility are affected by _______
ventilation rate
what does the otswald coefficient tell you?
solubility in blood
lower otswald coefficient –> _____ soluble —> ______ rise in partial pressure in blood —> ______ equilibration with brain and induction
less; more rapid; faster
ex: NO which is less soluble reaches a higher partial pressure in the blood faster and thus is able to reach anesthetic concentrations in the brain more rapidly
brain:blood partition coefficient is related to…
solubility in lipid
more soluble = more potent
high pulmonary blood flow = ______
lower pulmonary blood flow = _________
slower onset
faster onset
the greater the uptake of an agent, the alveolar concentration rises _________ —> ____ rate of induction
slower
slower
ex: insoluble agents are taken up slowly –> alveolar concentration rises fast –> fast induction
less soluble per otswald coefficient = ______ elimination
faster
what is minimum alveolar concentration MAC?
the concentration of anesthetic in the inspired air at equilibrium when there is no response to noxious stimulus in 50% of patients
