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Anesthesiology > 11/12: Induction Agents & Techniques > Flashcards

11/12: Induction Agents & Techniques Flashcards

1
Q

What is stage I of anesthetic depth?

A

Stage of voluntary movement; from initial admin of drugs to loss of consciousness

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2
Q

What is stage II of anesthetic depth?

A

Stage of delirium and involuntary movement; disinhibition; react to stimuli, struggle, vocalize

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3
Q

T/F: Intubation should be attempted at stage II of anesthetic depth

A

False;

There is risk of vomiting/regurgitation

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4
Q

What is stage III of anesthetic depth?

A

Progressive loss of reflexes/muscle tone (light, medium, deep)

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5
Q

Where are eyes located in the light plane of stage III?

A
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6
Q

Where are eyes located in the medium plane of stage III?

A
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7
Q

Where are eyes located in the deep plane of stage III?

A
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8
Q

What is a good way to check if an animal is too light or too deep?

A

Check palpebral reflexes

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9
Q

Which is the most important stage and where do you want your patient to be?

A

Stage III;

Want to be somewhere between plane 1 and plane 2

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10
Q

What is stage IV of anesthetic depth?

A

Extreme CNS depression;

Pulses weak/not palpable, resp may cease;

eyes central, pupils dilated

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11
Q

What are the 5 criteria of general anesthesia?

A
  1. Analgesia (loss of response to pain)
  2. Amnesia (loss of memory)
  3. Immobility (loss of motor reflexes)
  4. Hypnosis (unconsciousness)
  5. Paralysis (skeletal m relaxation and normal m relaxation)
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12
Q

What is pharmacokinetics?

A

What the body does to the drugs

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13
Q

What is pharmacodynamics?

A

What drugs do to the body

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14
Q

Why does it take some time for a drug to circulate to the brain after it is given?

A

Depends on circulation time and equilibrium time;

Has to cross BBB and interstitium

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15
Q

What is the % CO to the brain?

A

14%

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16
Q

What is the % CO to the kidney?

A

23%

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17
Q

What is the % CO to the liver?

A

5.8%

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18
Q

What is the % CO to the muscles?

A

16%

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19
Q

What is the % CO to the skin?

A

5%

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20
Q

What is the % CO to the fat?

A

2%

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21
Q

Why does drug [] decrease over time (after initial increase)?

A

Because it is distributed to the fat and muscle and away from the brain

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22
Q

What is the ideal administration rate?

A

Not too fast, not too slow

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23
Q

What can happen if a drug is administered too fast?

A

Overdose

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24
Q

What can happen if a drug is administered too slowly?

A

Stage 2 or not anesthetized at all

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25
Q

Concentration = solute/solution = _____/_____

A

Drug (X) / Volume of distribution (Vd)

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26
Q

Why is the apparent volume of a drug not the actual volume?

A

Due to distribution

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27
Q

What drug characteristics influence distribution?

A

Lipophilicity, protein binding, tissue binding, charge, pKa, size

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28
Q

What patient characteristics influence distribution?

A

Age, breed, body composition, pH, plasma protein, tissue inflammation

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29
Q

Larger Vd = _____ _____

A

longer duration

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30
Q

Which of these drugs have the largest Vd?

A

C > A > B

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31
Q

How do you calculate the loading dose?

A

C x Vd

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32
Q

Calculate the loading dose of propofol in dogs:

Vd = 0.78 L/kg, Induction [] = 8 µg/mL

A

Dose = C x Vd

Dose = 8 µg/mL x 0.78 L/kg

Dose = 8 mg/L x 0.78 L/kg

Dose = 6.14 mg/kg

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33
Q

What does this graph represent?

A

First-order kinetics

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34
Q

What does this graph represent?

A

Zero-order kinetics

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35
Q

What is plasma/blood clearance?

A

Volume of a totally cleared substance per unit of time

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36
Q

What is the equation for clearance?

A

Clearance = k x Vd

(k = elimination constant)

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37
Q

What are the phases of half life?

A

Distribution and elimination

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38
Q

What is the equation for half life?

A

t1/2 = 0.693/K

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39
Q

How is infusion rate calculated?

A

C (ss) x K x Vs (ss)

= C (ss) x Cl

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40
Q

Calculate infusion rate of propofol in dogs:

Vd (ss) = 4.5 L/kg, Cl = 54 ml/kg/min, t1/2 = 57 minutes, K = 0.012 minute-1, maint [] = 4 µg/ml

A

IR = C (ss) Cl

IR = 4 µg/ml x 54 ml/kg/min

IR = 208 µg/kg/min

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41
Q

What does one vial of propofol contain?

A

1% propofol, soybean oil, egg phasphatide, glycerol, NaOH

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42
Q

Propofol is ____ at room temp and is not tissue ____.

A

stable, irritating

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43
Q

How long after opening does propofol have to be discarded and why?

A

6 hours - adjuvant promotes bacterial growth

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44
Q

What does Propofol 28 contain and why is it problematic?

A

Benzyl alcohol - toxic to cats;

Can cause hemolysis, may be able to use for a single injection only

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45
Q

What is the shelf life of propofol 28?

A

28 days from opening

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46
Q

Propofol 28 is bacterio_____.

A

static

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47
Q

What is unique about fospropofol?

A

It is transparent due to not having a lipid carrier

48
Q

What is the onset and duration of fospropofol compared to Propofol 28?

A

Longer

49
Q

What is fospropofol used for?

A

Long-term sedation in humans; studied extensively in vet med

50
Q

What is the onset and duration of propofol?

A

Onset rapid = ~30 seconds

Duration short due to redistribution

51
Q

Where is propofol metabolized and excreted?

A

Metab in liver, excreted thru kidney

52
Q

Propofol causes _____ recovery in cats.

A

prolonged

53
Q

What is the MOA of propofol?

A

Acts on GABAA receptor –> open Cl channel –> hyperpolarization;

Cell cannot mount action potential so brain becomes very depressed

54
Q

Other than propofol, what other 2 drugs have major potentiation at GABAA receptors?

A

Barbiturates, etomidate

55
Q

What is the relationship of ketamine with GABAA receptors and NMDA?

A

GABAA = minor potentiation

NMDA = major inhibition

56
Q

Propofol _____ brain oxygen demand (CMRO2) and brain blood flow (CBF), hence _____ intracranial pressure (ICP).

A

decreases, decreasing

57
Q

What is the concern with propofol and hypotension?

A

Prop can cause hypotension, so cerebral perfusion might be decreased;

Need to be careful that patient doesn’t become ischemic

58
Q

What is dystonia?

A

NOT SEIZURE

Paddling, muscle twitching, opistothonus;

Common during induction and recovery with propofol, multiple potential mechanisms

59
Q

How can you differentiate between dystonia and a seizure?

A

Give something to treat a seizure and if symptoms don’t stop then it is likely dystonia

60
Q

CV depression due to propofol is _____ dependent.

A

dose

61
Q

Other than CV depression, what other CV effects can propofol have?

A

Vasodilation (direct or indirect), decreased contractility

62
Q

What effects does propofol have on the respiratory system?

A
  1. Dose-dependent depression
  2. Dose, speed of injection, dependent apnea
63
Q

What are other side effects that propofol can cause?

A
  1. Oxidative stress to RBC in cats (from phenol structure)
  2. +/- pancreatitis
    1. Prolonged infusion in humans
    2. Dog = increase triglyceride only
64
Q

What are advantages to co-induction with propofol?

A

Improve quality, decrease adverse effects

65
Q

What are disadvantages to co-induction with propofol?

A

Potential excitement, extra steps, cost, skill/experience

66
Q

What drugs can be used as co-induction agents with propofol?

A

BDZ, ketamine, lidocaine, opioids (fentanyl)

67
Q

Diazepam is _____ potent and _____ lipophilic than propofol, resulting in _____ “time lag”

A

less, less, more

68
Q

When should diazepam be administered if given with propofol?

A

Prior to propofol

69
Q

Midazolam is _____ potent and _____ lipophilic than propofol, resulting in _____ “time lag”

A

more, more, less

70
Q

When should midazolam be administered if given with propofol?

A

Immediately prior to or after propofol

71
Q

Co-induction of propofol with BDZ does not help with _____.

A

BP

72
Q

What are the advantages of Total IV Anesthesia (TIVA)?

A

Potential benefits for intracranial hypertension patients, less hypotension and use of vasopressor.

73
Q

What are the disadvantages of Total IV Anesthesia (TIVA)?

A

Cost, accumulation?

74
Q

What is alfaxalone?

A

Basically a transparent propofol that can be given IM

75
Q

What are Althesin/Saffan?

A

Steroid anesthetics alfaxalone + alphadolone in cremophor EL;

Alfaxalone may provide hypnosis, alphadolone may provide analgesia

76
Q

What was a big disadvantage of Athesin/Saffan?

A

Reactions to cremophor EL led to withdrawal (swollen paws, ears, larynx, pulm edema)

77
Q

What drug are the pharmacokinetics of alfaxalone similar to?

A

Propofol

78
Q

What breed has a difference in alfaxalone metabolism?

A

Greyhounds

79
Q

What does alfaxalone use cause animals to be sensitive to?

A

SOUND! and touch

80
Q

What CV effect seems to be better reserved with alfaxalone than propofol in dogs?

A

baroreflex

81
Q

Alfaxalone has a _____ Apgar score than propofol but _____ difference in mortality in c-section.

A

better, no

82
Q

Recovery quality with alfaxalone is _____ or _____ than propofol.

A

similar, slightly worse

83
Q

What are the physiochemical characteristics of Etomidate?

A
  1. Water insoluble
  2. 35% propylene glycol
  3. Lipid emulsion
  4. New formulation with cyclodextrin
84
Q

In humans, where is Etomidate primarily metabolized?

A

liver

85
Q

How is Etomidate excreted in humans?

A

85% by kidney, rest through bile and feces

86
Q

What is the method of action of Etomidate?

A

Acts on GABAA

87
Q

What unwanted thing can Etomidate cause, esp if used in a septic patient?

A

Iatrogenic Addison’s (low steroid #s)

88
Q

Etomidate _____ CMRO2, CBF, and ICP.

A

decreases

89
Q

What about CPP (cerebral perfusion pressure) with Etomidate is opposite of propofol?

A

It is maintained or increased –> net increase in oxygen supply to demand ratio

90
Q

What effect can Etomidate have that is associated with the brainstem or deep cerebral acitivity? What is done to mitigate this?

A

Myoclonus;

Commonly combined with midazolam

91
Q

What effect does Etomidate have on the cardiopulmonary system?

A

Minimal

92
Q

What is the effect of Etomidate on baroreflex?

A

It is well-maintained

93
Q

What effect does Etomidate have on the endocrine system?

A

Dose-dependent, temporary suppression

94
Q

What other side effects does Etomidate have?

A

Nausea/vomiting, pain on injection, excitement

95
Q

What type of solution is ketamine prepared in?

A

Slightly acidic (pH 3.5-5.5)

96
Q

What is ketamine’s relationship with water?

A

Freely water-soluble

97
Q

What happens if you give ketamine orally?

A

Animal will foam a lot because it is bitter

98
Q

What is the onset and duration of ketamine?

A

Rapid onset (but slower than other injectables) = 45-60 seconds

Short duration (redistribution)

99
Q

How is ketamine eliminated?

A

Ketamine (active) –> norketamine (active) –> water soluble inactive metabolites

100
Q

What type of drug is Ketamine?

A

NMDA receptor non-competitive antagonist

101
Q

T/F: Ketamine is a monoaminergic –> antinociception

A

True

102
Q

What “state” does ketamine cause and what does this mean?

A

Cataleptic state - dissociation of limbic and thalamocortical system;

Eyes open with slow nystagmic gaze and pupillary dilation, varying degrees of hypertonus;

Salivation, lacrimation common

103
Q

What reflexes stay intact with ketamine administration?

A

Corneal and light reflexes

104
Q

How is recovery from ketamine without proper sedation?

A

rough

105
Q

What effect does ketamine have (bc it is an NMDA R antag) that propofol and like drugs do not?

A

analgesia

106
Q

What can ketamine cause in the CNS and what is used to mitigate it?

A
  1. Intracranial hypertension - can use mechanical ventilation and combo with BDZ
  2. Can also cause seizures
107
Q

What cardio effects can ketamine have?

A
  1. Increased HR, BP, CO
  2. Direct myocardial depression (increased symp tone mitigates this)
108
Q

What effect does ketamine have on respiration?

A

Insignificant depression, but higher dose can cause “apneustic” pattern

109
Q

What is a apneustic pattern?

A

Prolonged inspiratory pause - inhale, hold breath, exhale

110
Q

Ketamine is a muscarinic _____ and can cause _____ and _____.

A

antagonist, bronchodilation, airway secretion/hypersalivation

111
Q

What effect does ketamine have on the eyes?

A

Increases IO pressure due to extraocular muscle contraction

112
Q

Where might we use Telazol?

A

In wildlife and shelter medicine

113
Q

Which component of telazol is metabolized faster by dogs and horses? What does this lead to?

A

Zolazepam –> rough recovery

114
Q

Which component of telazol is metabolized faster by cats and pigs? What does this lead to?

A

Tiletamine –> smooth recovery

115
Q

What is the induction protocol for critically ill patients?

A

Opioid + BDZ

(GDV, septic/hemoabd, severe heart disease)

116
Q

What would be the only indication for using an inhalant anesthetic for induction? What is the exception?

A

Patient is too fractious or wild to be handled for an IM injection (RARE);

Exception = small exotic and avian spp where IV access is not possible

117
Q

What are disadvantages of using an inhalant anesthetic as an induction agent?

A
  1. Slower and stressful induction time (increased symp tone, harder to induce, prone to arrhythmia)
  2. Patient goes thru all stages of anesthesia (risk of injury - thrash, flail, vocalize, urinate, defecate)
  3. Waste gas pollution and exposure

Anesthesiology (12 decks)

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