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ACVS Phase I Master Deck *Use This* > Chapter 21: Anesthesia Principles and Monitoring > Flashcards

Chapter 21: Anesthesia Principles and Monitoring Flashcards

1
Q

A small animal’s metabolic oxygen demand is what?

A

5ml oxygen/kg/min depending on temperature and metabolic factors

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2
Q

Saturated vapor pressure is what?

A

Point at which the gas of the anesthetic agent is in dynamic equilibrium with the liquid agent

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3
Q

How are vaporizers classified?

A

Vaporizer output
method of vaporization
location in the circuit
temperature compensation
agent specificity

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4
Q

Name two methods of vaporizer output?

A

variable bypass or measured flow (rare)

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5
Q

Name three methods of vaporization?

A

Flow over
bubble through
direct injection (desflurane)

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6
Q

Which method of vaporization is used for desflurane?

A

direct injection

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7
Q

What is meant by “in-“ or “out of circuit” vaporizer location?

A

In: within the patient circuit - so dose depends on patient’s minute volume

Out: before the common gas outlet = constant dose of gas regardless of minute volume (most common)

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8
Q

When should CO2 absorbent be changed?

A

When rebreathing is seen on capnography

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9
Q

Fresh gas flow for a nonrebreathing system is at least ____ times the patients respiratory minute volume (MV)?

A

3 times MV
Minute volume is tidal volume (15 mL/kg) x resp rate

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10
Q

What should your O2 flow rate be for preoxgenation?

A

4-5 L/min

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11
Q

What is the I:E ratio min and max?

A

1:1 to 1:4

** Ideal is 1:2

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12
Q

Regulators on anesthetic machines reduce the carrier gas pressure from that in the tank or wall outlet to what PSI?

A

45-50 PSI

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13
Q

Initial tidal volume for ventilator setup is calculated as what?

A

10-15ml/kg for each breath

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14
Q

Which type of ventilator is best for pulmonary disease / patients with changing compliance?

A

Pressure cycled

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15
Q

What is a general starting peak inspiratory pressure for ventilator setup?

A

12mmHg

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16
Q

Below what Pa02 - does the oxygen content in blood decrease rapidly?

A

70mmHg

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17
Q

How do you calculate MAP?
What are normal values?

A

MAP = DAP + ((SAP-DAP)/3)
Normal pressures are 125/85 (98)

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18
Q

Poor MAP <60mmHg may indicate/cause what?
Poor DAP < 40mmHg may indicate/cause what?

A

MAP <60 perfusion and O2 delivery unlikely to meet requirements of aerobic metabolism -> prolonged causes brain function alterations or AKI

DAP <40 Poor coronary artery perfusion and may result in cardiac ischemia

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19
Q

In cats the Doppler tends to underestimate the SAP by what?

A

25mmHg

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20
Q

Is doppler BP affected by tachycardia, or bradycardia or irregular heart beats?

A

NO
but oscillometric is affected

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21
Q

What is photoplethysmography?

A

Using SpO2 wave instead of doppler crystal but using cuff - inflate cuff, when wave comes back is SAP
No advantage over doppler

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22
Q

In oscillometric BP - they tend to underestimate what in cats?
In dogs?

A

Cats - SAP
- Relatively precise for MAP and DAP
Dogs - Underestimate all S/M/D AP

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23
Q

What is needed for direct BP measurement?

A

Arterial catheter, transducer with wheatstone bridge and monitor for wave form

24
Q

What mmHg of PaCO2 is termed hypercarbia? Above what mmHg doe we see adverse consequences of hypercarbia

A

55 mmHg
65mmHg - effects

25
Q

Why can end tidal (end expiratory) CO2 be used as an accurate reliable continuous estimate of arterial CO2?

A

at end of expiration should just be alveolar gas only - this effectively mimics that in the pulmonary blood - and approximates the arterial CO2

26
Q

How do you work around the dilution of ETCO2 in nonrebreathing systems?

A

Use a side stream monitor so it aspirates a sample more proximal in the ETT

27
Q

Apart from measuring CO2, what other benefits can ETCO2 be used for?

A

rapid diagnosis of cardiac arrest
confirm intubation
assessment of CPR effectiveness

28
Q

Describe the ETCO2 trace for hypoventilation?
For hyperventilation?
A leak in the circuit?
Rebreathing of CO2?
Cardiopulmonary arrest?

A

hypoventilation - progressive increase in height of the plateau
hyperventilation - progressive decrease of height of plateau
leak - shark fin
rebreathing - progressive elevation of the baseline
Arrest - Sudden decrease in CO - could also be a circuit disconnect

29
Q

A patient breathing 100% oxygen should have a PaO2 of what?

A

500mmHg and HGB saturation of 100%

30
Q

PaO2 of 80mmHg is what SpO2

A

95%

31
Q

Anemia will not affect the SpO2 until HCT is less than what %?

A

10%

32
Q

What can affect a pulse oximeter reading?

A

vasoconstriction - pain, alpha 2 agonist, hypothermia
profound anemia
profound hypoxemia

33
Q

Can pulse oximeter be normal in a hypotensive, anemic and hypoventilating patient?

A

yes - so cannot be relied on for assessment of respiration, can be normal in hypoventilation

34
Q

When should you reverse nerve blockage?

A

Do not reverse until all 4 of the twitch responses on your train of four stimulator have returned.
- This signifies that the level of the drug at the neuromuscular junction is low enough that it may be overcome by increasing acetylcholine at the junction (ACHesterase inhibitors)

35
Q

What is normal central venous pressure in mmHg and cmH20?

A

0-5 mmHg
0-8 cmH20

36
Q

Response to a fluid bolus is more indicative of volume status than a CVP measurement. What is the response to a fluid bolus:
when there is hypovolemia ?
when there is hypervolemia?

A

Hypovolemic: a bolus of 5-10 ml/kg might not change CVP
Hypervolemic: CVP will increase by 3-4mmHg and very slowly if at all return to baseline

37
Q

How does a thermodilution catheter work for CVP?
Does it give continuous readings?

A

A thermistor-tipped catheter is placed in the pulmonary artery via the jugular - then a saline bolus is administered, the heart pumps it out and a temperature change is noted -> a curve is formed and CO is area under the curve

No, not continuous. Reads only when the saline injection is given.

38
Q

Cardiac output monitoring techniques?

A

Thermodilution
lithium dilution CO
pulse contour analysis
Noninvasive CO device

39
Q

Name three ways of determining anesthetic depth?

A

Clinical signs
ETCO2
Brainwave activity - electroencephalogram - not good for dogs or cats

40
Q

Which receptors do opioids work on?

A

Mu (μ), kappa, delta
μ is most analgesic
k is also analgesic
delta is modulating of μ

41
Q

How do opioids work?

A

Bind to receptor which are all G-coupled proteins - decreasing the release of substance P and glutamate

activation = influx of K+ and calcium into the presynaptic cell and causes hyperpolarization of the post synaptic cell - resulting in a net decrease in neuronal activity and transmission of pain signals

42
Q

How much can opioid pain relief reduce anesthetic inhalant requirements?

A

40-60%

43
Q

Why might opioids increase regurgitation?

A

May increase pyloric sphincter tone/ileus

44
Q

Which opioids cause histamine release -> causing vasodilation, tachycardia and hypotension more often?

A

Meperidine and morphine lesser extent

45
Q

Potency compared to morphine?
- hydromorphone
- oxymorphone
- meperidine
- methadone
- Fentanyl
- Buprenorphine

A
  • hydromorphone 8x
  • oxymorphone 10x
  • meperidine 1/10th (morphine is 10x meperidine)
  • methadone 2x
  • Fentanyl 100x
  • Buprenorphine 40x
46
Q

Therapeutic plasma concentrations are achieved in dogs in how long after fentanyl patch placement?

A

18-24 hours

47
Q

Remifentanil is unique in the way it is metabolized, how is it metabolized?

A

Metabolized by plasma esterases - so does not need hepatic or renal to be metabolized

48
Q

What can occur rarely with fentanyl or its derivates?

A

Chest wall rigidity - “wooden chest” - treat with naloxone

49
Q

What is serotonin syndrome and which opioids can it be seen in and with use of what drugs?

A

Meperidine and tramadol
when used with monoamine oxide inhibitors (MAOIs) or TCAs (Trazodone)
Result of excess serotonin in the body -> anxiety, hyperthermia and in more severe cases shock, rhabdomyolysis and subsequent renal failure

50
Q

What is Acepromazine?

A

phenothiazine tranquilizer depressing dopamine activity in the RAS - acts as an alpha 1 receptor antagonist

51
Q

Alpha 2 antagonists result in decreases of what?
Adverse effects?

A

norepinephrine
hyperglycemia, respiratory depression, vasoconstriction
hypertension then hypotension due to bradycardia and decreased central sympathetic output
side effects usually seen due to peripheral effects on alpha 1

52
Q

What is trazodone?

A

A phenylpiperazine antidepressant - serotonin antagonist and reuptake inhibitor
peak plasma concentration after oral admin is 7 hours

53
Q

What does etomidate induce?

A

Adrenal suppression which can last for 6 hours - risk of adrenal insufficiency e.g. septic shock patients
- if must be used can give a physiological dose of corticosteroids in postop period

54
Q

MAC for surgically anesthetized patients is?

A

1.2-1.5x published MAC

55
Q

What is electromechanical dissociation?

A

Pulseless electrical activity on your EKG - A plausible wave form on monitor but actually no coordinated muscular contraction by the heart.
ETCO2 and Doppler are better for assessing actual circulation of blood by the heart.

ACVS Phase I Master Deck *Use This* (88 decks)

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