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RUSVM Anesthesiology > Inhalant Anesthesia > Flashcards

Inhalant Anesthesia Flashcards

1
Q

What are the predictable effects of inhalant anesthesia?

A

Narcosis
Muscle relaxation
Not analgesic

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2
Q

What dis Dalton’s law of partial pressure?

A

Total pressure of a gas mixture is equal to the sum of partial pressure of individual gases

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3
Q

What is vapor pressure?

A

Pressure exerted by vapor molecules when liquid and vapor phases are in equilibrium

Depends on temperature
-increases with increasing temperature

Inversely related to boiling point

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4
Q

What inhalant anesthetic has the lowest boiling point ?

A

Desflurane

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5
Q

Why is an electric heater required for desflurane?

A

Boiling point is 23.5 C (close to room temp)—> warmed to maintain in gaseous form

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6
Q

Vapors have a maximum administration percentage AKA ___________

A

Saturated vapor pressure

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7
Q

How is saturated vapor pressure calculated?

A

Vapor pressure / barometric pressure

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8
Q

What is the partition coefficient?

A

Concentration ratio of an anesthetic in the solvent and gas phases

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9
Q

What is the blood-gas partition coefficient??

A

Amount of anestheric in the blood vs alveolar gas at equal partial pressure

-> anesthetic in the alveolar gas represents brain concentration

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10
Q

T/F: anesthetic dissolved in blood is pharmacologically inactive

A

True

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11
Q

What is the order of these gases from low to high, blood-gas partition coefficient?

Isoflurane
Sevolfuratne
Halothane
Desflurane

A

Desflurane (least soluble) < sevolfurane < isofurane < halothane (most soluble)

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12
Q

At a low blood-gas PC is there more or less anesthetic dissolved in blood at equal partial pressure ?

A

Less (more in alveoli)

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13
Q

T/F: there is a shorter time required to attain a partial pressure in the brain when there is a low blood- as PC

A

True

-> sort induction and recovery

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14
Q

A _________ blood-gas PC will have more anesthetic dissolved in blood at equal partial pressure

A

High

-> longer time required to attain a partial pressure in the brain
—> long induction and recovery

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15
Q

Partial pressure in the brain is roughly equal to that in the alveoli. How can P(A) be increased?

A

Increase anesthetic deliver to alveoli

Decrease removal from alveoli

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16
Q

What are ways you can increase alveolar delivery of anesthetic ?

A

Increase impaired anesthetic concentration

  • increase vaporizer setting
  • increase fresh gas flow

Increase alveolar ventilation
-increase minute ventilation (tidal vol x respiratory rate)

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17
Q

How can you decrease removal form alveoli?

A

Decrease blood solubility of anesthetic

Decrease cardiac output
-patients with a low CO will have a faster rise of P(A)

Decrease alveolar-venous anesthetic gradient

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18
Q

The (lower/higher) the Pi, the more rapidly Pa approaches Pi

A

Higher

Pi = inspired anesthetic concentration

A high Pi is required at the beginning of anesthesia to quickly increase Pa

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19
Q

How can you quickly decrease Pa?

A

Turn off vaporizer

Disconnect patient and flush O2

Turn up O2 flow - dilute anesthetic in circuit as it is exchanged from patient

Increase ventilation (IPPV) - increase fresh gas to alveoli

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20
Q

What is the MAC?

A

Minimum alveolar concentration of an anestheric that prevents movement in 50% of patients exposed to a noxious stimulus

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21
Q

If a MAC of an anesthetic is high, then its potency is ________

A

Low

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22
Q

T/F: alveolar concentration is the same as the vaporizer setting

A

False

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23
Q

Hyperthermia, hypernatremia, and CNS stimulant drugs cause what to the MAC?

A

Increase the MAC

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24
Q

Hypothermia, hyponatremia, CNS depressants cause what to the MAC?

A

Decrease the MAC

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25
Q

MAP < 50mmHg, PaO2 < 40mmHg, and PaCO2 cause what to the MAC

A

Decrease the MAC

26
Q

What effects do inhalant anesthetics have on the cardiovascular system?

A

Decrease CO, BP, SVR, and contractility

27
Q

What effects do inhalant anesthetics have on the respiratory system?

A

Decrease ventilation
Bronchodilation
Irritating odor

28
Q

Respiratory arrest can occur at _________ MAC

A

1.5-3

29
Q

Does inhalant anesthetics cause ain’t increase or decrease in ICP? What about metabolic rate?

A

Increase (MAC> 1) ICP

Decrease metabolic rate

30
Q

Inhalant anesthetics act where to produce immobility?

A

Spinal cord and brain

31
Q

How are inhalant anesthetics associated with decreased glomerular filtration?

A

Reduced renal blood flow due to decreased CO

32
Q

How is compound A produced?

A

Sevoflurane breakdown in CO2 absorbent

-nephrotoxic in rats

33
Q

Higher concentrations of compound A are formed during??

A

Prolonged anesthesia
Low fresh gas flows
Desiccated absorbent

34
Q

what inhalant anesthetic causes hepatotoxicity?

A

Halothane

  • increase liver enzymes
  • immune mediated halothane hepatitis
35
Q

T/F: very little of sevoflurane and isoflurane is metabolized in the liver

A

True

—> mostly expired

36
Q

What species have generic predispositions to malignatn hyperthermia?

A

Pig, dog, cat, and horses

37
Q

What is malignant hyperthermia?

A

Uncontrolled muscle contraction —> severe hyperthermia —> death

38
Q

What is the first sign of malignant hyperthermia?

A

Rapid increase in EtCO2

39
Q

What is the treatment for malignant hyperthermia?

A

Discontinue anesthetic, flush with O2

Provide 100% O2

Dantrolene -muscle relaxant

Fluids and active cooling

40
Q

What is the max administration of NO?

A

75% (need > 25% O2)

41
Q

What is the solubility of NO?

A

Low (PC 0.47)

42
Q

T/F: nitrous oxide has minimal CV and respiratory depression

A

True

43
Q

T/F: Nitrous oxide has some analgesic properties

A

True

44
Q

What is transfer to closed gas spaces in regards to NO?

A

Equilibration leads to N2O rapidly accumulating (more soluble in blood), while nitrogen leaves slowly (less soluble)

GI tract, sinuses, middle er, pneumothorax, cuff of ET tube —> avoid in disease states causing increased closed gas states

45
Q

What is diffusion hypoxia?

A

When N2O administration is stopped, it diffuses quickly out of blood into alveoli —> displace O2 for alveoli

46
Q

How can diffusion hypoxia be prevented?

A

When discontinuing N2O, provide 100% O2 for 5-10 minutes

47
Q

How can occupational gas exposure be reduced?

A

Scavenging system
Minimize leaks
Avoid mask/chamber induction
Keep patient attached to circuit after gas is turned off
Minimize exposure to exhaled as from patient
Maximize ventilation
Monitor waste gas concentrations

48
Q

What is the first thing you should do if your patient becomes hypotensive during anesthesia?

A

Evaluate patient and turn down the vaporizer

49
Q

If a patient is light under anesthesia but is also hypotensive, what could you do?

A

Add a MAC-sparing drug (opioid, benzodiazepines, lidocaine, or ketamine) then turn down the vaporizer

-> if still hypotensive, crystalloid bolus?, vasopressor?, inotrope (depends on underlying cause)

50
Q

If PaCO2 is greater than 4mmHg the patient is?

A

Hypoventilating

51
Q

What do you do if your patient is hypoventilating?

A

Check anesthetic depth, and turn down vaporizer

IPPV
-manual or mechanical

52
Q

How can you prevent hypothermia during anesthesia ?

A 
Warm before induction 
Bubble wrap feet 
Keep patient covered, minimize scrub time and exposure to water/alcohol 
Increase room temp 
Forced warm air heating
53
Q

What happens if you close the pop-off value while your patient is connected to the machine?

A

Bag fills —> breathing system pressure increases —> transmitted to lung and thoracic cavity

Decreased venous return -> compressed vessels —> decreased cardiac output

54
Q

What are clinical signs of a closed pop-off valve?

A

Apnea, bradycardia, fading Doppler signal

55
Q

What is the treatment for a closed pop off valve?

A

Pull rebreathing bag off
Start CPR if arrested
Evaluate for pulmonary injury

56
Q

What happens if your inspiratory-expiratory valves are stuck?

A

Causes rebreathing of expired gas —> hypercabia

57
Q

What do the waveforms for exhausted soda lime or stuck inspiratory-expiratory valves look like?

A

Rebreathing CO2 —> capnograph waves gradually increase

58
Q

T/F: tracheal tears are associated with overfilling of the tube cuff and are seen more often in cats

A

True

—> only fill cuff until there is no leak at 15-20cm H2o

59
Q

What signs are associated with tracheal tears ?

A

Subcutaneous emphysema

Pnumomediastinum or pneumoretroperitoneum

60
Q

What is the treatment for tracheal tears?

A

Supportive care-> provide time for trachea to from a fibrin seal and emphysema to resolve

Severe—> surgical repair

61
Q

T/F: Inhalant anesthetics have a very high therapeutic index

A

False

Low therapeutic index —> overdose can happen quickly

62
Q

A very low BP(MAP < 50) indicates inadequate cerebral blood flow for consciousness. What should you do in this case?

A

Turn inhalant off until BP has improved

RUSVM Anesthesiology (32 decks)

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