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47 Cards in this Set

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  • Back
What are the 5 most common Inhalant Anesthetic Agents?
1. Isoflurane
2. Halothane
3. Nitrous Oxide
4. Methoxyflurane (not used)
5. Sevoflurane (newest)
What characteristics would the "Ideal" inhalation agent have?
a) Minimal toxicity (cardio, respir, hepatic, renal, nervous)
b) Minimal toxicity of waste gas vapors to personnel
c) Ease of administration
d) Rapid & gentle induction and recovery
e) Anesthetic depth easily controlled and altered
f) Good muscle relaxation & postoperative analgesia
g) Low cost
h) Adequate potency to achieve surgical anesthesia
i) Nonflammable & nonexplosive (safe to handle)
j) No need for expensive equipment
Is there an "Ideal" Inhalant agent?
There is NO ideal agent!
What is commonly considered when selecting an inhalation anesthetic agent?
5 Things to consider when selecting an inhalation agent:
1. Availablity
2. Cost
3. Preference of anesthetist & surgeon
4. Special needs of the patient
5. Procedure being performed
What are the 3 Classes of Inhalent Anesthetic Agents?
What are the characteristics of Diethyl ether?
a) Maintains realtivley stable cardiac output
b) No sensitization of heard arrhythmias
c) Good muscle relaxation
d) Good analgesia
e) VERY irritating to trachebronchial mucosa
f) Prolonged recovery
g) HIGHLY flamable and explosive
Mechanism of action
Unknown but appear to inhibit GABA breakdown allowing increased inhibition of nervous system tissues
What is occuring in the body during the induction phase?
a) Transferred via air passages to the alveoli
b) Diffuses into the blood stream via the alveolar capillaries
c) Readily leave circulation and enter the bloodstream due to their HIGH LIPID SOLUBLILTY leading to anesthesia
Describe vapor pressure and its importance.
The percentage of inhalation anesthetic that will evaporate at 20 Degrees C. HIGH VAPOR PRESSURE ARE LABLED VOLATILE. Vapor pressure determines to what concentration an anesthetic gas can be present in the patient and effects how it may be delivered.
What is solubility coefficiant?
A measure of the distribution of the inhalation agent between the liquid (blood) and gas (alveoli) phases in the body.
Does high or low solubility coeffiecient produce a rapid induction? Why?
Low solubility coefficient. Tends to remain in the gas phase and do not solubilize in the blood easily; increases concentration in the alveoli, enter the bloodstream rapidly then rapidly exits into brain; this leads to rapid induction & recovery.
What is lipid solubility?
How does that effect "Hangover Time"?
The affinity of the gas for solubilization in lipids.
High lipid solubility - attracted to fats (sponge effect, increased hangover)
Low lipid solubility - Drug will be exhaled (decreased hangover time)*Easier to eliminate-Better*
What is Minimum Alveolar Concentration (MAC)?
Does high or low MAC indicate increased potency
The lowest concentration of anesthetic gas that will yield no response to a painful stimulus in 50% of patients, Indicates the potency of an anesthetic.
Low MAC= increased potency
MAC-Minimum Alveolar Concentration
Low MAC= increased potency
High MAC= decreased potency
1. Dial setting of 1 X MAC=
Light anesthesia
2. Setting of 1.5 X MAC=
Surgical anesthesia
3. Setting of 2 X MAC=
Deep anesthesia
Whats occuring during the Maintenance phase of anesthesia:
By keeping the inhaled anesthetic concentration at a maintaned level, an equilibrium is established between alveoli, blood, & brain, keeping animal anesthetized.
Whats occuring during the Recovery phase:
By decreasing the anesthetic level in the alveoli, concemtration gradients causing the gas to leave the bloodstream and be exhaled, causing the gas to exit the brain and animal to recover.
What type of vaporizer is used?
Wick Vaporizer
-due to low vapor pressure
How potent is it?
-**Most potent of commonly used drugs!
-High solubility coefficient causes the longest induction, longest recovery (although smooth recovery), and slow changes in anesthetic depth.
How much is metabloized?
*50% is metabolized
-High lipid solubility leads to a great amount of metabolism
What type of disease should it NOT be used in?
**Do NOT use in patients with known renal problems!
-May cause renal problems
How does it effect the Cardiovascular/Respiratory Systems?
Cardio/Respiratory effect:
1. *Most potent respiratory depressant.
2. No sensitization to arrhythmias
3. Decreases contractility of the heart up to 40% causing severe decreases in cardiac output.
(marked muscle relaxation)
How much Analgesia does it produce?
*Profound Analgesia, intra & post operatively
What type of vaporizer is required?
-*Precision Anesthetic Vaporizer
(due to high vapor pressure)
What type of Induction/Recovery time does it have?
-Intermediate Induction
**(due to moderate solubility coefficient)
-Intermediate Recovery time
-Moderately fast changes in anesthetic depth
How much is Metabolized?
10-20% metabolized
What disease should it NOT be used in?
Avoid use in Hepatic Disease!
What are the effects on the Cardiovascular/Respiratory Systems?
Cardio/Respiratory effects:
1. Some respiratory depression
2. Sensitizes the heart to catecholamines causing arrhythmias (catecholamines released from pain, adequate anesthetic depth will solve problem)
3. Increases vagal tone & decreases cardiac output causing lowered blood pressure
(adequate muscle relaxation)
How much Analgesia does it produce?
-Moderate analgesia
-Moderate post-surgical analgesia
(can cause hypothermia due to vasodilation & an increase in cranial pressure)
*Associated w/ Malignant Hyperthermia
Malignant Hyperthermia: a rare condition where animals show increased temperature, muscle rigidity, cardiac arrhytmias and possible death! (Greyhounds & Pigs)
*Most Common Drug Used*
What type of vaporizer should be used?
A Precision Anesthetic Vaporizer
(due to a high vapor pressure)
What types of Induction is it commonly used for?
Mask and Chamber Inductions
-Low solubility coefficient allows rapid changes of anesthetic depth
-Rapid Induction and Recovery
How much is metabolized?
0.25% metabolized
What disease should it NOT be used in?
Absolute contraindications: family history of Malignant Hyperthermia
What effects does it have on Cardiovascular/Respiratory Systems?
Muscle relaxation?
Cardiovascular effect:
1. Heart rate, rhythm, blood pressure
2. No sensitization to arrhythmias
3. Depresses respiration (more than halothane, but less than methoxyflurane)
4. Decreased blood pressure
-Good muscle relaxation
How much Analgesia does it produce?
What are undesirable effects?
-Good Analgesia
-Poor Post-Operative Analgesia (due to low metabolism)
-* Chance of increased intracranial pressure
Nitrous Oxide:
Can this be used alone to produce anesthesia?
Why or Why not?
-Unachievable concentrations for anesthetic as a gas by itself* (high MAC)
-Must be used an adjunct to anesthesia w/ other gases
-Used w/ other agents allows decreased concentration of other agents used (MAC of other agent decreased 20-30%)
Nitrous Oxide:
What is "Second Gas Effect"?
Speeds induction & recovery when used at high concentrations (50-70%)
-Extremely low solubility coefficient (enhances uptake of other gases)
Nitrous Oxide:
What are the dangers due to its solubility coefficient?
1. Diffusion into Air Pockets: poor choice w/ intestinal obstruction, GDV, pneumothorax, diaphragmatic hernia, any Ruminant
2. Diffusion Hypoxia: speedy exit at end of anesthesia causes oxygen in alveoli to be replaced by notrous oxide, to avoid, maintain high oxygen flow for 5 min after nitrous turned off.
Nitrous Oxide:
How does it effect muscle relaxation?
What type of Analgesia does it produce?
-Good muscle relaxation
-Good Analgesia
Nitrous Oxide:
What are the undesirable effects?
Undesirable Effects: increased intracranial pressure, reduced liver blood flow, bone marrow suppression w/ chronic exposure, combustable fire hazard, not absorbed by activated charcoal scavenging devices
Nitrous Oxide:
What are its Contraindications?
Patients with or at risk of Cardiac Arrhythmias, AVIAN Anesthesia, Pulmonary Disfunction, patients w/ Increased Intracranial Pressure, Pneumothorax, GDV, Exploratory Laparotomy, Intra-Ocular procedures, Pre-Existing Bone Marrow disease, Unregulated Hyperthyroidism
Nitrous Oxide:
Other Precautions that must be taken
-Mixing Nitrous Oxide w/ Oxygen causes increased risk of *Hypoxia
-Do NOT use in Closed Systems: Oxygen is removed, Nitrous Oxide is not, therefore increasing levels of nitrous oxide will occur w/ prolonged anesthesia
What type of Vaporizer is needed?
*Newest anesthetic agent-requires vaporizer Made for Sevoflurane
How potent is it?
Any reported Toxicity?
-*Least potent of ALL except Nitrous Oxide, Higher concentrations will be necessary (due to Higher MAC)
-*No reported Toxicity*
(Low % Metabolized)
How does it effect Cranial Pressure?
What type of Analgesia produced?
-Slight chance of Increased Cranial Pressure
-Poor Analgesic
What are the Contraindications?
Family history of
Malignant Hyperthermia
How does it effect the Cardiovascular/Respiratory System?
Cardio Respiratory effects:
1. Severe Respiratory Depression
2. Dose Dependent Depression of Cardiac Contractility
3. Vasodilation