Inhalation Agents Flashcards
Variations in Induction Speed
Machine: air flow rate, absorption into plastic
Lungs: ventilation, concentration, blood gas solubility, v/q problems, second gas effect
Blood: cardiac output
Tissues: oil/gas solubility, metabolism, diffusion hypoxia, obesity, hypothermia
Blood/Gas Coefficient
how fast an anesthetic goes in and out of the body
sevo - 0.6
iso - 1.4
nitrous 0.47
des 0.42
MAC
minimum alveolar concentration required to achieve surgical anesthesia in 50% of patients
sevo - 2%
iso - 1.15%
nitrous 105%
des 5.8%
Oil/Gas Coefficient
potency
sevo - 50
iso - 99
nitrous 1.4
des 18.7
The lower the blood/gas coefficient the _____ the rise of anesthetic in the lungs
faster
fast in, fast out
The faster you breathe, the ____ you go to sleep
faster
The higher the dose and concentration, the _____ it works
faster
A V/Q mismatch ____ the delivery of all anesthetics, affecting the ____ agents more than the _____ agents
slows
fast, slow
Nitrous Oxide
expands in closed spaces - use caution in certain surgery
is an inorganic molecule
contraindicated in pregnancy
inactivates vitamin b12 causing accumulation of homocysteine resulting in inability to copy DNA
Blood Flow
vessel-rich - 75%
muscle - 18%
fat - 5%
vessel-poor - 2%
Increases in cardiac output ____ the onset, affecting the _____ agents more than the _____ agents
slows
slower, faster
Inhalation Gas Metabolism
sevo - 5-7%
iso - <1%
nitrous oxide - trace
des - <0.1%
Children have a ____ MAC dose than adults
higher
MAC awake
the alveolar concentration of anesthetic that inhibits responses to command in half of the patients
MAC bar
the alveolar concentration of anesthetic that blunts the autonomic response to noxious stimuli in half of the patients
approximately 1.6 time higher than MAC
halogenated ethers
all inhaled anesthetics except nitrous oxide and halothane
Inhalation Agents Mechanism of Action
actions on GABA receptors - allows CL- to enter cell
inhalation anesthetics _____ cerebral blood flow
increase
inhalation anesthetics _____ CMRO2
decrease, except nitrous oxide increases?
inhalation anesthetics _____ intracranial pressure
increase, except nitrous oxide decreases
inhalation anesthetics _____ cerebral perfusion pressure
decrease
inhalation anesthetics _____ intro-ocular pressure
decrease
inhalation agents mechanism for decreased blood pressure (5)
CNS depression direct cardiac depression decreased systemic vascular resistance baro-receptor depression hormonal changes (decreased renin and vasopressin release)
*except nitrous oxide where BP stays the same
____ sensitizes myocardium to effect of catecholamines
halothane
