Exam 3 Flashcards
influences of age on the PK of volatiles
↓ lean body mass (muscle mas)
↑ fat mass = ↑ Vd for drugs (especially for more fat soluble)- in certain compartments
↓ clearance if pulmonary exchange is impaired
↑ time constraints due to lower cardiac output
Boyle’s Law
Given a constant temperature….
Pressure and volume of gas are inversely proportional
Fick’s Diffusion Law
Once the molecules get to the alveoli, they move around randomly and begin to diffuse into the pulmonary capillary
Diffusion depends on:
Partial pressure gradient of the gas
Solubility of the gas (diffusion)
Thickness of the membrane
Carbon dioxide vs oxygen molecular wt and solubility
Carbon dioxide, molecular wt 44 g
Oxygen, molecular wt 32 g
co2 is more soluble
Graham’s Law of Effusion
Process by which molecules diffuse through pores and channels without colliding
Smaller molecules effuse faster dependent on solubility (diffusion)
Alveolar pressure an indicator of:
Depth of anesthesia
Recovery from anesthesia- if brain is greater than amount to alveoli – waking up / loosing gas from vessel rich group to alveolis.
Solubility
A ratio of how the inhaled anesthetic distributes between 2 compartments at equilibrium (when partial pressures are equal)
***the relative capacity of each compartment to hold volatile
temperature dependent
Blood gas partition coefficient for Halothane
2.54
Blood gas partition coefficient for Enflurane
1.90
Blood gas partition coefficient for isoflurane
1.46
Blood gas partition coefficient for nitrous oxide
0.46
Blood gas partition coefficient for desflurane
0.42
Blood gas partition coefficient for sevo
0.69
des color
blue
sevo color
yellow
iso color
purple
halothane color
red
MAC: Minimum alveolar concentration:
“the concentration at 1 atm that prevents skeletal muscle movement in response to supramaximal, painful stimulation in 50% of patients”
partial pressure/ percentage of volatile anesthetic we will give.
MACawake
(0.3-0.5 MAC)
presumes that all we are giving is 1.3 mac when we turn the mac off and we let them wake up when they get to 0.3-0.5 = wake up.
MACBAR
(1.7-2.0 MAC)
blunts autonomic responses. If we had 2 mac of des on board w/ no pain and we intubated you, hr wouldnt respond, no sns response at mac bar. But will be very hypotensive. Mac bar = not used.
nitrous mac
104%
halothane mac
0.75%
mac enflurane
1.63%