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APEX > Unit 6 - Misc. Monitors and Equipment > Flashcards

Unit 6 - Misc. Monitors and Equipment Flashcards

1
Q

how does train of four work

A

Delivers a series of 4 twitches at 2 Hz at 0.5-second intervals for 2 seconds (Hertz = cycles per second)

Height of the 4th twitch (T4) is compared to height of 1st twitch (T1)

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2
Q

what is the BEST method of assessing a deep neuromuscular block

deep block = no twitches present

A

post-tetanic count

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3
Q

what percent of Nm receptors must be blocked to lose T1 (no twitches)?

A

90%

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4
Q

fade occurs when T4/T1 ratio is less than:

A

1.0

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5
Q

what is the advantage of double burst stimulation

A

easier to detect fade than with TOF

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6
Q

describe double bust stimulation

A

2 short bursts of 50 Hz tetanus 0.75 seconds apart

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7
Q

visual/tactile fade with TOF difficult to detect when ratio:

A

> 0.4

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8
Q

clinical recovery from blockade achieved when TOF ratio:

A

> 0.9

reversal agent indicated when ratio < 0.9

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9
Q

% receptors blocked to lose T4 with TOF

A

80-85%

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10
Q

describe tetanus

A

rapid sequence of 50 Hz for 5 seconds

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11
Q

how long is TOF assessment affected after tetanus

A

Results of TOF inaccurate for up to 6 minutes after tetanus assessment

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12
Q

describe single-twitch

A

delivers stimulus ranging from 0.1-1 Hz

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13
Q

what is post-tetanic potentiation

A

twitch response is stronger after a tetanic stimulus than it was at baseline (d/t ACh mobilization in presynaptic nerve terminal)

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14
Q

Can assess depth of NM blockade when no twitches are present

A

Post-Tetanic Count

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15
Q

PTc that suggests T1 will return soon

A

6-10

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16
Q

PTc that suggest a deep block

A

3 PTc or less

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17
Q

how does cerebral oximetry work

A

Uses near infrared spectroscopy (NIRS) to measure cerebral oxygenation

Measures venous oxygen saturation

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17
Q

how does cerebral oximetry work

A

Uses near infrared spectroscopy (NIRS) to measure cerebral oxygenation

Measures venous oxygen saturation

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18
Q

where are cerebral oximetry stickers placed

A

Placed on patient’s scalp, generally over frontal lobe

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19
Q

when is post-tetanic count useful?

A

to assess for depth of blockade when no twitches are present (like with a deep block)

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20
Q

what makes up cerebral blood volume

A

1 part arterial to 3 parts venous

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21
Q

____% of blood in brain is venous

A

75

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22
Q

suggests reduction in cerebral oxygenation

A

25+% change in baseline

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23
Q

what does EEG measure

A

the differences between electrical potentials in multiple brain regions

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24
Q

EEG provides information about electrical activity of:

A

cerebral cortex

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25
Q

light sensors used by cerebral oximetry

A

3:
1. arterial hgb
2. venous hgb
3. rissue cytochromes

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26
Q

what type of brain waves

A

beta

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27
Q

brain waves increased with anesthesia induction

A

beta

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28
Q

brain waves associated with awake mental stimulation and “light” anesthesia

A

beta

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29
Q

brain waves from highest to lowest frequency

A
  • beta
  • alpha
  • theta
  • delta
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30
Q

characteristics of beta brain waves

A

high frequency, low voltage

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31
Q

brain waves assoc with awake but restful state with eyes closed

A

alpha

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32
Q
A

alpha brain waves

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33
Q
A

theta brain waves

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34
Q
A

delta brain waves

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35
Q
A

burst suppression

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36
Q

what are theta waves associated with

A
  • general anesthesia
  • children during normal sleep
37
Q

what are delta brain waves assoc. with

A
  • general anesthesia
  • deep sleep
  • brain ischemia/injury
38
Q

brain waves predominant under GA

A

theta
delta

39
Q

what is burst suppression assoc. with

A
  • general anesthesia
  • hypothermia
  • CPB, cerebral ischemia (esp. unilateral)
40
Q

MAC assoc. with isoelectricity on EEG

A

1.5-2

41
Q

how does N2O affect brain waves

A

alone increases beta wave activity

42
Q

how can sevo affect brain waves

A

can increase epileptiform EEG activity

43
Q

how can etomidate affect brain waves

A

can cause myoclonus (not assoc. with epileptiform EEG activity)

44
Q

how can ketamine affect brain waves

A

can cause ↑ high frequency cortical activity & pt may be deeper than EEG suggests

45
Q

Provides a sensitive measure of brain tissue at risk of infarction

A

EEG

46
Q

the brain can’t maintain electrical function without what 2 things

A

O2 & glucose

47
Q

EEG changes that mays signify brain at risk for ischemia

A

Development of new delta waves during anesthesia

48
Q

conditions that mimic cerebral ischemia

A

deep anesthesia, hypothermia, hypocarbia

49
Q

how does BIS work

A

Uses a computer algorithm to translate raw EEG data into a number between 0-100

50
Q

target BIS for general anesthesia

A

low probability of explicit recall

51
Q

BIS waveforms as anesthesia gets deeper

A
  • Lower frequency (slower)
  • Higher amplitude (taller)
52
Q

how can ketamine affect BIS

A
  • increases high frequency activity
  • can make BIS higher than the level of sedation/anesthesia
53
Q

BIS value assoc. with burst suppression

A

0-40

54
Q

BIS assoc. with light to moderate sedation

A

80

55
Q

limitations of BIS monitoring

A
  • 20-30 second lag
  • inaccurate with w/ hypothermia, electromyographic interference (↑ muscle tone), and encephalopathy
  • less accurate in children
56
Q

target range for GA of patient safety index monitor (PSA)

A

25-50

57
Q

how is patient safety index monitor (PSA) similar to BIS

A
  • measures EEG
  • runs data through an algorithm
  • displays a number that indicates level of anesthetic depth

electromotive force (voltage) = current x impedance

58
Q

law obeyed by electricity

A

Ohm’s Law

59
Q

what must occur to cause electrical injury

A

Must be voltage difference for current to flow across an impedance

60
Q

consequences of electrical injury

A
  • arrythmias
  • muscle contractions
  • diaphragmatic paralysis
  • thermal injury
61
Q

threshold for touch perception of electrical shock

A

1 mA

62
Q

max current for a harmless electrical shock

A

5 mA

63
Q

“let go” current occurs before sustained contraction

A

10-20 mA

64
Q

current assoc. with loss of consciousness

A

50 mA

65
Q

current assoc. with V fib

A

100 mA

66
Q

Greatest margin of safety against risk of macroshock

A

isolate ground from main power supply

67
Q

what is a macroshock

A

comparatively larger amount of current applied to external body surface

68
Q

what is a microshock

A

comparatively smaller amount of current applied directly to myocardium

High resistance of skin bypassed - takes significantly smaller amount of current to induce V-fib

69
Q

maximum allowable current leak in the OR

A

10 microA

70
Q

3 things that increase susceptibly to microshock

A

CVL, PAC, or pacing wires provide direct conductive pathway to heart

71
Q

3 things that increase susceptibly to microshock

A

CVL, PAC, or pacing wires provide direct conductive pathway to heart

72
Q

what is electrical grounding

A

OR systems designed to reduce risk of electric shock

OR power supply is not grounded; equipment is grounded

73
Q

what is electrical grounding

A

OR systems designed to reduce risk of electric shock

OR power supply is not grounded; equipment is grounded

74
Q

2 faults in the system for shock to occur in OR:

A

1) After 1st fault, OR power supply becomes grounded. There is no completed circuit and no shock
2) After the 2nd fault, the circuit is complete and electric shock occurs

75
Q

required to supply ungrounded power to OR

A

Isolation transformer

76
Q

purpose of line isolation monitor (LIM)

A

assesses integrity of ungrounded power system in OR

77
Q

Tells you when OR becomes grounded and how much current could potentially flow through you or your pt if a 2nd fault occurs

A

Line isolation monitor (LIM)

78
Q

does a line isolation monitor protect against micro or macro shock

A

nope, not by itself

79
Q

Primary purpose of line isolation monitor

A

alert OR staff of 1st fault (means the OR has become grounded)

80
Q

what should you do if line isolation monitor sounds

A

alert OR staff of 1st fault (means the OR has become grounded)

81
Q

when will line isolation monitor sound

A

alarm will sound if sum of all currents > 2-5 mA but no risk of electric shock in this situation

82
Q

current delivered by electrocautery

A

500,000 – 1 million Hz

83
Q

serves as an exit point for monopolar ESU

A

Functional return electrode

provides large, low impedance surface area for current to exit the body

84
Q

why doesn’t bipolar ESU need a return pad

A
  • Tip of bipolar (forceps) contains active electrode and return electrode
  • Electrical current not dispersed throughout patient’s body
85
Q

factors that increase risk of burns with ESU

A
  • fauly in return electrode
  • electrode malfunction
86
Q

factors that increase risk of burns with ESU

A
  • fauly in return electrode
  • electrode malfunction
87
Q

why is the return pad for ESU so large

A

a large, low impedance surface area needed for electrical current to exit the body

the smaller the area that the electricity exits, the greater the intensity of the burn

88
Q

how are burns at return pad site prevented

A
  • entire surface of electrode should be in direct contact with patient’s skin
  • return pad should not be placed over bony prominences or metal implants
  • make sure gel isn’t dried out
89
Q

how can metal jewelry cause a burn with ESU

A

by “re-concentrating” electrical current from ESU

90
Q

what should be done if the patient can’t remove a piece of jewelry and cautery is going to be used

A
  • site of surgery should be far away from location of jewelry
  • jewelry should not be in direct path between ESU & return pad
  • jewelry should be taped to skin to increase the surface area of contact between jewelry and skin

If capacitance-coupled return electrode used: any metal can form capacitive coupling & cause burns

91
Q

2 drugs that are most likely to reduce reliability of BIS

A
  • ketamine: increases high-frequency activity (can increase BIS)
  • N2O: increases amplitude of high-frequency activity, reduces amplitude of low-frequency activity (doesn’t affect BIS)

APEX (54 decks)

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