General anesthetics Flashcards
3 components of general anesthesia
induction (loss of consciousness)
maintenance
recovery (elimination of anesthetics)
TIVA stands for
total intravenous anesthesia
refers to the combination of intravenous infusions of anesthetics and analgesics
PIVA stands for
partial intravenous anesthesia
usually to reduce the inspired concentration of inhalational anesthetic by using intravenous as well.
PIVA is very common in vet med.
injectable anesthetics can be divided into 4 broad groups:
dissociative
barbiturates (pentobarbital)
phenols (propofol)
steroid anesthesia (alfaxalone)
cyclohexylamines are
group of injectable dissociative anesthetics: ketamine, tiletamine
are antagonists of NMDA, interact with opioid receptors.
used in combination with tranqs and sedatives
describe dissociative anesthesia
complete analgesia with catalepsy(trance), immobility and superficial sleep, hypertonus
hallucinations in ppl
NMDA stands for
N-methyl-D-aspartate
a type of cellular receptor which are found in the reticular formation of the brain and in the spinal cord
ketamine effect on the heart? (3)
inotropic
vasodilatory of vascular smooth muscle
HR and BP usually increase
ketamine half-life
fairly short circa 30 min
what is zoletil
a tiletamine + zolazepam combo. med
the benzo reduces potential convulsions from the tiletamine but can cause resp. depression from the benzo.
propofol acts on what receptors?
activates GABA receptors.
very short acting, recovery quick too.
alfaxalone acts on what receptors?
GABA in CNS
The potency of an inhalant anesthetic agent is expressed as
the minimum alveolar concentration (MAC)
meaning, the min. alveolar concentration that prevents muscular movement in response to noxious stimuli in 50% of animals (so the potency)
a MAC of 1 will allow 50% of animals to move.
1.3 multiplied by a given MAC value will prevent movement in approx. 95% of animals.
An anesthetic with a lower MAC value is
more potent, meaning it requires a lower concentration to achieve the desired effect compared to an anesthetic with a higher MAC value.
For example, if one anesthetic has a MAC of 1% and another has a MAC of 2%, it means that the second anesthetic is less potent, as it requires a higher concentration to achieve the same level of anesthesia.
Factors that increase MAC (so increased the amount of anesthetic required) (4)
hyperthermia
catecholamines
hyperthyroidism
hypernatremia
why use ketamine and propofol combo? (5)
synergism: ket. antagonizes NMDA, prop. agonizes GABA
lower doses of each
rapid induction
hemodynamic stability(ket improves)
anterograde amnesia form both
The blood:gas solubility coefficient (or partition coefficient) is
a measure of the distribution of the inhalation agent between blood and gas in the body.
The blood:gas solubility coefficient indicates
the speed of induction and recovery.
low blood:gas coefficient means less soluble - more effect on the brain with fast induction and recovery.
high blood:gas coefficient means more soluble - less effect on the brain with slower induction and recovery.
low blood:gas coefficient means
less soluble - more effect on the brain with fast induction and recovery.
A low blood:gas coefficient means that these gases are less soluble in blood and thus are rapidly taken up and eliminated by the body.
For gases with lower solubility, even though they’re less soluble in blood, their uptake is still relatively efficient due to the concentration gradient. When these less soluble gases enter the alveoli during inhalation, they create a high partial pressure in the alveoli compared to the blood. This steep concentration gradient drives the gas into the bloodstream, despite its lower solubility.
high blood:gas coefficient means
more soluble - less effect on the brain with slower induction and recovery.
they dissolve more extensively in the blood, leading to slower changes in the partial pressure of the gas in the blood.
the high solubility of the gas means it takes longer for the concentration of the gas in the bloodstream to decrease. This slower elimination from the bloodstream prolongs the time it takes for the patient to wake up
isoflurane causes what physiological changes (4)
in addition to loss of consciousness; decrease in blood pressure and systemic vascular resistance.
depresses respiration too
induces muscle relaxation
which volatile anesthetic vapor is least irritating to the resp. tract?
sevoflurane
isoflurane blood:gas solubility is
low which results in rapid induction and recovery.
what is malignant hyperthermia
a rare but serious condition where body temperature rapidly rises to dangerously high levels, triggered by certain anesthetics.
It’s caused by an abnormal reaction in the muscles, leading to increased metabolism and heat production.
This can result in muscle rigidity, high fever, and if not treated promptly, it can be life-threatening.
