Anesthesia MidTerm (LS) Flashcards
U.S. recommended trace limits for the
inhalant anesthetics
- 25 ppm N2O
- 2 ppm all others
Women should be particularly careful when using what inhalant anesthetic?
N2O
(miscarriages, decr. fertility)
List methods to reduce exposure to Inhalants.
- Gas scavenger
- Regular inspection of anesthethic equipment
- No N2O w/ activated charcoal scavenger
- Minimize use of face mask & induction chamber
- Adequate ventilation
- Inflate cuffs appropriately
- Low flow anesthesia (when possible)
- Keep distance during recovery
- Vaporizer with key-filler system
2nd Gas Effect?
one gas accelerates the inital uptake of a different anesthetic gas when given together
What is the MOA of Inhalants?
Not clear!
suggestions:
- Meyer-Overton theory
- Protein-receptor hypothesis
- Activation of GABA receptors
- Inhibition of certain Ca2+ channels
Factors DECREASING MAC?
(8)
- Pre-meds
- N2O
- Increasing age
- Hypothermia
- Pregnancy
- Severe hypoxia (PaO2 < 40 mm Hg)
- Severe hypercapnia (PaCO2 > 90 mm Hg)
- Concurrent illness
Which measurement reflects the inhalant agent’s tension in the brain?
Exhaled Conc.
a.k.a
End Tidal or ET
What is used as the standard index of anesthetic potency?
MAC
(Min. Alveolar Conc)
Definition of MAC?
the minimum concentration of anesthetic in the alevoli that produces immobility in 50% of subjects exposed to a supramaximal noxious stimulus @ 1 atmosphere
MAC is _______ related to Potency.
INVERSELY
5 factors affecting recovery from Inhalants?
- Alveolar ventilation
- Solubility
- CO
- Duration of anesthesia
- Metabolism
How can you accelerate “Washout” of Inhalants?
(2)
- High FGF
- Empty reservoir bag
What influences the rate of [inhalant] rise in blood?
(4)
- Inhaled conc. → FGF
- Alveolar ventilation
- Solubility in blood
- CO
When will an inhalant agent cross from the blood into the brain?
when there is an equilibrium btwn alveolus, blood & the brain
Which coefficient describes how quickly an agent moves from the alveoli → blood?
Blood-Gas Coefficient
Which coefficient determines how quickly an agent passes from the blood → brain?
Oil-Gas Coefficient
Oil-Gas Partition Coefficient is _____ correlated to anesthetic Potency.
DIRECTLY
List the Inhalants in order from High→Low based on their Oil-Gas Partition Coefficient
- Halothane
- Iso
- Sevo
- Des
- N2O
Blood-Gas Coefficient is ________ related to speed of induction, recovery & change in anesthetic depth.
INVERSELY
List the inhalant agents from High→Low by their Blood-Gas Partition Coefficients.
- Halothane
- Iso
- Sev
- Des
- N2O
@ Equilibrium btwn the different phases (oil, gas, water), the _______ is the same while the ______ may be different.
- Same partial pressure
- Different conc.
3 things about Modern vaporizers
- Agent specific
- Conc. calibrated
- Temp compensated
Saturated Vapour Pressure (SVP) refers to?
- Max. possible conc. of molecules in the gaseous phase at a specific temp.
- Higher the SVP→ more volatile the agent→high [molecules] in the gas phase
Which Local Anesthetics are Esters?
(4)
- Cocaine
- Procaine
- Tetracaine
- Amethocaine
All others are Amides
MOA of LAs?
directly blocks Na+ channels→ prevents Na+ influx → membrane stabilization (can’t depolarize)