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Ideal Inhalational Anesthetic:
- Non-toxic to all tissues
- Non-Flammable
- Non-reactive w/ metal, rubber or soda lime
- Inert (not absorbed/metab by body)
- Pleasant to inhale
- Stable in light and heat
- Min CVS/Resp depression
- Easily and quickly alter anesthetic depth
- Potent, with large safety margin
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Saturated Vapor Pressure, is when...
- The number of molecules leaving liquid = number of molecules entering liquid
- Vapor Pressure is at a maximum for a liquid
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MAC-
- Minimum concentration of an anesthetic agent, which will prevent purposeful movement in response to a supramaxiaml stimulus in 50% of P
- Minimal Alveolar Concentration
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What is the MAC for...
Halothane:
Iso:
Sevoflorane:
Desoflorane:
- Halothane: 0.8-0.9
- Iso: 1.5
- Sevoflorane: 2.4
- Desoflorane: 8.0
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A higher MAC indicates...
- Decreased Potency
- low Blood Gas Solubility= Rapid Uptake and Removal
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Desofluranehas a high ____ , but a low ___
- High MAC
- Low Solubility Partition Coefficient
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The Partition Coefficient is an indication of...
- the relative affinity of two tissues in contact have for the same substance
- (higher partition coefficient=> higher affinity)
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Saturated Vaporization Pressure is an indication of...
degree of solubility and ability to evaporate
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As a general rule, the more ____ a gas is, the faster it works for induction and recovery
insoluble
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The Blood:Gas coefficient influences...
The magnitude of the effect of the an individual anaesthetic
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What influences the uptake into the blood?
- Blood:Gas Coefficient
- CO
- Aveolar to Venous Partial Pressure Difference (Pa-Pv)
- (Increased Pulmonary Ventilation and Decreased CO, as in shock, -> ++ uptake)
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Degredation of Halogenated ethers, vs halothane:
- Halogenated ethers undergo 0.2-5% hepatic degredation
- Halothane undergoes 20%
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Which gas is poorly soluble?
N2O
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N2O shuld not be used in animals with....
- Head Trauma
- Cerebral Edeam
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When is N2O used?
- Adjunctive anesthetic
- (especially when hypotension is a concern)
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N2O can reduce ___ by 20-25%
MAC
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Dangers of N2O:
- Distention in gas filled spaces of the body
- Diffusion Hypoxia
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Where does N2O accumulate?
- Rumen
- Gastric Dilation/volulvus
- Pneumothorax
- Eye
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Why does Nitrous Oxide cause hypoxia?
Less soluble than O2, so it diffuses out of the blood, into alveoli
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With which gas should O2 be admin for 5-10 mins post op?
Nitrous Oxide
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Isoflurane is classified as a ____
Halogenated Ether
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Respiratory Fx of Iso:
- Respiratory Depression (more than halothane)
- Irritant
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When exposed to Carbond Dioxide Absorbant, _____ produces Compoune A
Sevo
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Sevo isn't rec for P with...
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Desflurane is classified as a____
Highly fourinated methyl ether
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Desflurane solubility partition coefficient...
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Hepatic Metabolism of Iso: Sevo: Deso:
- Iso: >1%
- Sevo: 3-5%
- Halothane: >20%
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Soluble anesthetic => ___ Blood:Gas Coeffiecient => ____induction/recovery
- Low Blood:Gas
- Rapid induction/recovery
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The vessel rich group, which reaches equilibrium first, includes:
- Brain
- Heart
- Liver
- Kidney
- Splanchnic Bed
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Relevant Pressures as the anesthetic flows from the liquid phase and through the P
- P Delivered
- P Circuit
- P Inspired
- P Alveolar
- P Arterial
P Brain
- P Arterial
- P Alveolar
- Exhaust
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What two factors determine the rate at which the alveolar concentration increases to the concentration being inspired?
- Inspired Concentration
- Alveolar Ventilation
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Solubility of O2 and N2O relative to anesthetics?
Why is this relevant to induciton?
- O2 & N2O are MORE soluble
- Increases transfer of anesthetics into the blood stream
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Factors that influence anasthetic uptake into the blood:
- Blood:Gas Solubility
- CO (Q)
- Alveolar to Venous Partial Pressure (PA-PV)
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How does shock affect anesthesia uptake into blood?
- Increased Pulmonary Ventilation
- Decreased CO
- => increases uptake
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Decreased CO and Increased pulmonary ventilation can accelerate induction in agents w/...
Examples include(2):
Intermediate Gas Solubility
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What anesthetic property affects recovry?
Solubility
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Hepatic Degredation...
Halogenated Ethers= ____%
Halothane= ____%
- Halogenated Ethers= 0.2-5%
- Halothane= 20%
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What factors Decrease MAC (5)?
- Narcotics/Sedatives/Tranquilizers
- Age
- Hypothermia
- Pregnancy
- Hypoxia
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Factors that increase MAC (2):
- Hyperthermia (increases cerebral metabolic rate)
- Neurotransmitter Release
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When is N2O used (2):
- Adjunctive Anesthetic
- When Hypotension is a concern (reduce cardio depressant anesthetics)
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Benefits of N2O (3):
- Good Analgesia
- MAC sparing (for other drugs)
- Second Gas effect (Accelerates uptake of volatile anesthetics)
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Disadvantages of N2O (5):
- Low potentcy
- Expensive
- Abuse
- Hypoxia if wrong concentration
- Diffusion Hypoxia at recovery
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Solubility of O2 VS N2O:
- O2 MORE Soluble
- N2O LESS Soluble
- (both are less soluble than other anesthetics)
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How can N2O => Hypoxia?
Upon recovery, N2O diffuses more rapidly from blood to alveoli
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Which gas => Compound A when exposed to CO2?
Sevo
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