Anesthetics I and II Flashcards
How might Anesthetics interfere w/CNS function?
most likely by reducing communication between neurons (inhibiting excitatory neurons like glutamate, enhancing inhibitory neurons like GABA)
*though volatile anesthetics have also been shown to decrease GABA release too
Which Voltage gated ion channels to anesthetics work on?
Na channels – they inhibit activity at the channel to cause a reduction in NT release at some synapses
What are the 3 receptor types located on ion channels that Glutamate acts on? Which of these are nonselective?
AMPA, Kainate and NMDA.
Kainate and AMPA are non-selective
How to drugs act on NMDA receptors?
NMDA modulate long term synaptic responses (through Na, K and Ca); volatile anesthetics, ketamine and N20 may inhibit NMDA receptors
What are the 3 types of effects that drugs produce on the GABA-A receptor?
1) Potentiation (increased Cl- produced by low [GABA] but no increase if GABA maximally effective
2) Direct gating (activating GABA receptor in absence of GABA through high [drug])
3) Inhibition (preventing GABA from initiating Cl- current at high concentration of anesthetics)
What is the Meyer Overton Rule and the Unitary Theory of Anesthesia?
Meyer Overton says “potency of anesthetic gases directly related to solubility in olive oil”
Unitary Theory says “since variety of structurally unrelated drugs “obey” the rule, they must bind at same hydrophobic site
So, where to anesthetics bind – lipids or protein?
Hydrophobic pockets on proteins
Of the inhaled anesthetics, which are inorganic gases and which are volatile liquids?
Inorganic gas: N2O
Volatile liquids: Halothane, Enflurane, Isoflurane, Desflurane, Sevoflurane
Which of the inhaled anesthetics boils at a much lower temperature and as such has a much higher vapor pressure?
Desflurane (bp = 22.8 around room temp and vapor pressure 669 mmhg)
How does the anesthesia machine deliver isoflurane and sevoflurane? How is desflurane different?
oxygen or oxygen/N2O mixture passes over surface saturated w/the volatile anesthetic and mixes with it; then it’s delivered to lungs.
desflurane boils and goes through a “dual gas blender” where it is added directly to the main gas stream
How are inhaled anesthetics taken up into the body, distributed and eliminated?
Uptake: absorbed from alveoli into pulmonary capillary blood
Distribution: to site of action (brain) and “reservoirs” (vessel rich group, muscle, fat)
Eliminated: by lungs mostly
What is Henry’s Law (partial pressures rule!!)
Concentration of a gas is directly proportional to the partial pressure of the gas above the solution
What is the partition coefficient?
Ratio of solubilities of a gas between 2 compartments (blood:gas, brain:blood) at equilibrium; describes how anesthetics distribute themselves between different tissues at equilibrium
WHat’s the deal w/equilibration, partial pressure and concentration?
Equilibration means that the same PARTIAL PRESSURE of an anesthetic gas exists in both phases; NOT that the same concentration exists in both phases
What does alveolar partial pressure equilibrate with?
pulmonary capillary blood partial pressure and brain partial pressure. Goal = constant brain partial pressure of inhaled gas
