Exam 3 (Gas laws / MAC / VAs) Flashcards
Boyles law
at a constant temperature, pressure and volume of gas are inversely proportional
Diffusion is described by ______ Law and describes what 3 factors that influence diffusion
Fick’s Law
1. partial pressure gradient
2. solubility of the gas
3. thickness of the membrane
Effusion is described by ______ law and it describes what process?
Graham’s (cracker lol)
describes the process by which molecules pass through pores and channels without colliding (smaller molecules effuse faster)
Henry’s Law is the gas law that is applied when we ________ to increase the speed of induction
overpressurize
Henry’s Law states that the amount of gas in a liquid is proportional to
it’s partial pressure above the liquid
Halothane B:G Partition Coefficient
2.54
Enflurane B:G Partition Coefficient
1.90
Isoflurane B:G Partition Coefficient
1.46
Nitrous Oxide B:G Partition Coefficient
0.46
Desflurane B:G Partition Coefficient
0.42
Sevoflurane B:G Partition Coefficient
0.69
Which volatile has the highest Fat:Blood coefficient?
A. Isoflurane
B. Desflurane
C. Sevoflurane
C. Sevoflurane
Note: halothane has the highest of the volatiles, but since we don’t use it seems a little silly to include it
From high to low organize the volatiles based on Fat:Blood coefficient Isoflurane, halothane, sevoflurane, desflurane, enflurane
High to low: Halothane, Sevoflurane, isoflurane, enflurane, desflurane
Volatile: Nitrous oxide
MAC: _____
104
Volatile: Halothane
MAC: ___
0.75
Volatile: Enflurane
MAC: ___
1.63
Volatile: Isoflurane
MAC: ___
1.17
Volatile: Desflurane
MAC: ___
6.6
Volatile: Sevoflurane
MAC: ___
1.8
What is the MAC required for general anesthesia?
1.3
What is awake MAC
0.3-0.5
What two factors affect MAC the most?
Body temperature and age
What percentage per decade after the age of 55 should we decrease our MAC?
6%
What 4 factors increase MAC?
hyperthermia, increased catecholamines, hypernatremia, excess pheomelanin production (redheads)
What factors DECREASE MAC
Hypothermia
Preoperative medication, intraoperative opioids
Alpha-2 agonists
Acute alcohol ingestion
Pregnancy
Post partum (early…12-72 hours)
Lidocaine
PaO2 <38 mm Hg
Mean BP < 40mm Hg
Cardiopulmonary bypass
Hyponatremia
Spinal cord depression is achieved by inhibiting what two receptors?
What channels are blocked pre-synaptically?
What neurotransmitter is increased?
NMDA and AMPA (glutamate receptors).
Na+ channel inhibition pre synaptic that decreases release of glutamate
Glycine (inhibitory transmitter) is enhanced
Loss of consciousness is thought to be achieved by increasing _____ in the CNS, particularly in the _______. VAs may also potentiate _____ in the brainstem.
What is not effected in the brain via VAs?
GABA; RAS ;Glycine
No effect of volatiles on AMPA, NMDA, or kainate
Sum of partial pressures = Ptotal is described by ______ law
Dalton’s
Vapor pressure of Halothane
243 torr
Vapor pressure of Enflurane
175 torr
Vapor pressure of Isoflurane
238 torr
Vapor pressure of Desflurane
669 torr
Vapor pressure of Sevoflurane
157 torr
How do you calculate Fi[gas]
P[gas] / P[total]
Flow-over increases vaporization by increasing _____ ____ and achieves this via ____
surface area; wicks
