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Anesthesia & Analgesia > Lecture 10: Maintenance of Anesthesia (Exam 2) > Flashcards

Lecture 10: Maintenance of Anesthesia (Exam 2) Flashcards

1
Q

What are some currently used inhalants

A
  • Isoflurane
  • Sevoflurane
  • Desflurane
  • N2O
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2
Q

What are the characteristics of a desirable inhalant

A
  • Less reactive
  • more potent
  • nonflammable (halogenated by adding Fl, Cl, or Br)
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3
Q

What properties determine the method of admin

A
  • Boiling point
  • Liquid density (specific gravity)
  • Vapor pressure
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4
Q

What properties help to determine kinetics in the px

A
  • Blood/gas partition coefficient
  • Oil/gas partition coefficient
    Both are used to determine the solubility of the gas
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5
Q

Define a gas

A

Agent that exists in gaseous form @ room temp & sea level pressure

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6
Q

What is an example of a gas

A

N2O

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7
Q

Define a vapor

A

Gaseous state of a substance that @ ambient temp & pressure is a liquid

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8
Q

What are some examples of a vapor

A
  • Isoflurane
  • Sevoflurane
  • Halothane
  • Desflurane
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9
Q

What gases laws are used to predict the behavior of a gas

A
  • Boyle’s law
  • Charle’s law
  • Gay-Lussac’s law
  • Dalton’s law of partial pressure
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10
Q

Define Boyle’s law

A

For a fixed amount of gas @ a constant temperature, the pressure exerted by the gas inversely proportional to its volume

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11
Q

Define Charle’s law

A

The volume of a fixed amount of gas is directly proportional to its absolute temperature when the pressure remains constant

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12
Q

Define Gay-Lussac’s law

A

The pressure of a gas increases as the temperature increases if the volume of the gas remains constnat

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13
Q

define Dalton’s law of partial pressure

A

The total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of each individual gas in the mixture

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14
Q

What is vaporization

A

Change in state from a liquid to a gas

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15
Q

At what point is the gas saturated

A

When the equilibrium is reached & no further loss of molecules to the gas phase occurs

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16
Q

Define the vapor pressure of an anesthetic

A

The measure of the ability to evaporate (enter the gas phase)

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17
Q

Saturated vapor pressure = what

A

Max concentration of molecules in vapor state

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18
Q

What is the saturated vapor pressure (SVP) dependent on

A

The temperature which is unique for each anesthetic agent

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19
Q

What happens when the temp of a liquid increases

A
  • More molecules escape liquid phase & enter the gas phase
  • Higher vapor pressure
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20
Q

What happens if the temp of a liquid decreases

A

Lower vapor pressure/concentration

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21
Q

T/F: The SVP of most anesthetics is safe for clinical use

A

False; it is not safe

22
Q

What are the two streams that gases are diverted into

A
  • By pass
  • Vaporizing chamber
23
Q

Describe modern vaporizers

A
  • Variable-bypass
  • Concentration-calibrated
  • Agent-specific
  • Temperature compensated
24
Q

What affects the speed of induction & recovery

A

The rate of uptake & distribution in the body that is effected by the gas in tissues and “in the blood” (AKA the blood/gas coefficient)

25
Is a lower or higher blood/gas partition coefficient more desirable
Lower number
26
What is the oil/gas partition coefficient
The solubility of the gas in a lipid (oil) correlates w/ the anesthetic potency
27
(more/less) gas dissolves in solvent as temperature increases
Less
28
What increases alveolar delivery (Pa)
* Increased inspired anesthetic concentration * Increased alveolar ventilation
29
What increases inspired anesthetic concentration
* Increased vaporization of agent * Increased vaporizer dial setting * Increased fresh gas flow * Decreased gas volume of patient breathing circuit
30
What increases alveolar ventilation
* Increased minute ventilation * Decreased dead space ventilation
31
What factors decrease removal from alveoli
* Decreased blood solubility of anesthetic * Decreased cardiac output * Decreased alveolar-venous anethetic gradient
32
Define minimum alveolar concentration (MAC)
* The min alveolar concentration of inhaled anesthetic @ 1 atmosphere that produces immobility in 50% of subjects exposed to a supramaximal noxious stimulus * Corresponds to ED50
33
What is the relationship between potency & MAC
Inverse relationship (the higher the potency the lower the MAC)
34
At what MAC is ED95 achieved (95% of px are anesthetized)
1.2 to 1.4
35
What MAC is surgical anesthesia
1.5 MAC
36
Fill out the MAC Values for these species:
37
What factors can increase MAC
* Hyperthermia * Drugs that cause CNS stimulation * Increased metabolic rate &/or stress (like hyperthyroidism)
38
What Factors decrease MAC
* Blood pressure < 50 mmHg * Hypothermia * Drugs that cause CNS depression * Smaller body weight/size * Age of animal * Hyponatremia * PaO2 < 40 mmHg or PaCO2 > 95 mmHg * Pregnancy * Disease state
39
What factors do not effect MAC
* Blood pressure > 50 mmHg * Anticholinergics * Duration of anesthesia * Gender * Abnorm potassium * Metabolic alkalosis or acidosis (paO2 > 40 mmHg or PaCO2 of 10-95 mmHg)
40
Describe Isoflurane
* Stable in storage (no preservative needed) * Low blood-gas solubility * More potent than sevoflurane * Fairly rapid induction & recovery (good muscle relaxation) * < 1% metabolized in body (mostly in the lungs) * Reasonable cost * Mask induction (noxious odor may lead to breath holding & bronchoconstriction) * Produces carbon monoxide when exposed to desiccated CO2 absorbent * Hypoventilation is common
41
What causes hypotension when using Isoflurane
Due to vasodilation & decreased myocardial contractility
42
Describe sevoflurane
* Lower-blood gas partition coefficient than isoflurane (more rapid induction & recovery) * Lower potency than isoflurane * Similar cardio-respiratory depression to isoflurane * Good muscle relaxation (could trigger malignant hyperthermia * Mask induction has less odor & smoother induction * ~ 3% metabolized in the body (rest is eliminated via lungs) * Can be degraded by CO2 absorbents to produce compound A
43
What are the pharmacodynamics of inhalant anesthetics
* MOA: multiple cell receptors & ion channels; spinal cord & brain involved * Reversible immobilization results in all species even plants & protozoa
44
What are the effect of inhalant anesthetics on the CNS, Resp, & CV system
* CNS - decrease cerebral metabolic rate (oxygen consumption); either no change or an increase in cerebral blood flow; decrease in cerebral BF; decrease in cerebral perfusion pressure; increase in ICP * Resp - drug & species specific depression of ventilation causes increased CO2; bronchodilation; desflurane irritates the airway * CV - can decrease cardiac output & BP; arrhythmias associated w/ certain drugs may be exaggerated
45
What is TIVA & PIVA
Anesthetic techniques utilizing IV infusion of one or more drugs to produce a suitable anesthetic state
46
Why should TIVA be limited to 1 hour
B/c of prolonged recovery times associated w/ longer TIVA time
47
T/F: Supplemental O2 is still provided during TIVA & PIVA
True
48
What is an example of TIVA
"Triple drip" infusion of ketamine, xylazine, & guaifenesin to produce general anesthesia in a horse having a castration
49
Give an example of PIVA
"MILK" + reduced isoflurane concentration for a dog having a TPLO
50
Describe Guaifenesin (GG)
* Centrally acting muscle relaxant w/ sedative props * Co-admin w/ other anesthetic agents for the IV induction &/or maintenance of anesthesia * Used in horses & ruminants * MOA is unclear but likely effects sites in the brain & spinal cord * No analgesic props * Wide therapeutic margin but OD can result in cardio-resp depression * Hepatic metabolism & renal excretion (more rapidly eliminated in female ponies) * Precipitates out of solution when stored below room temp & should be rewarmed before us * Prepared as a 5 to 15% solution in .9% NaCl or 5% dextrose

Anesthesia & Analgesia (29 decks)

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