Unit 6 - Misc. Monitors and Equipment

Question 1

how does train of four work

Answer 1

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)

Question 2

what is the BEST method of assessing a deep neuromuscular block

deep block = no twitches present

Answer 2

post-tetanic count

Question 3

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

Answer 3

90%

Question 4

fade occurs when T4/T1 ratio is less than:

Answer 4

1.0

Question 5

what is the advantage of double burst stimulation

Answer 5

easier to detect fade than with TOF

Question 6

describe double bust stimulation

Answer 6

2 short bursts of 50 Hz tetanus 0.75 seconds apart

Question 7

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

Answer 7

> 0.4

Question 8

clinical recovery from blockade achieved when TOF ratio:

Answer 8

> 0.9

reversal agent indicated when ratio < 0.9

Question 9

% receptors blocked to lose T4 with TOF

Answer 9

80-85%

Question 10

describe tetanus

Answer 10

rapid sequence of 50 Hz for 5 seconds

Question 11

how long is TOF assessment affected after tetanus

Answer 11

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

Question 12

describe single-twitch

Answer 12

delivers stimulus ranging from 0.1-1 Hz

Question 13

what is post-tetanic potentiation

Answer 13

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

Question 14

Can assess depth of NM blockade when no twitches are present

Answer 14

Post-Tetanic Count

Question 15

PTc that suggests T1 will return soon

Answer 15

6-10

Question 16

PTc that suggest a deep block

Answer 16

3 PTc or less

Question 17

how does cerebral oximetry work

Answer 17

Uses near infrared spectroscopy (NIRS) to measure cerebral oxygenation

Measures venous oxygen saturation

Question 17

how does cerebral oximetry work

Answer 17

Uses near infrared spectroscopy (NIRS) to measure cerebral oxygenation

Measures venous oxygen saturation

Question 18

where are cerebral oximetry stickers placed

Answer 18

Placed on patient’s scalp, generally over frontal lobe

Question 19

when is post-tetanic count useful?

Answer 19

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

Question 20

what makes up cerebral blood volume

Answer 20

1 part arterial to 3 parts venous

Question 21

____% of blood in brain is venous

Answer 21

75

Question 22

suggests reduction in cerebral oxygenation

Answer 22

25+% change in baseline

Question 23

what does EEG measure

Answer 23

the differences between electrical potentials in multiple brain regions

Question 24

EEG provides information about electrical activity of:

Answer 24

cerebral cortex

Question 25

light sensors used by cerebral oximetry

Answer 25

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

Question 26

what type of brain waves

Answer 26

beta

Question 27

brain waves increased with anesthesia induction

Answer 27

beta

Question 28

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

Answer 28

beta

Question 29

brain waves from highest to lowest frequency

Answer 29

* beta * alpha * theta * delta

Question 30

characteristics of beta brain waves

Answer 30

high frequency, low voltage

Question 31

brain waves assoc with awake but restful state with eyes closed

Answer 31

alpha

Question 32

Answer 32

alpha brain waves

Question 33

Answer 33

theta brain waves

Question 34

Answer 34

delta brain waves

Question 35

Answer 35

burst suppression

Question 36

what are theta waves associated with

Answer 36

* general anesthesia * children during normal sleep

Question 37

what are delta brain waves assoc. with

Answer 37

* general anesthesia * deep sleep * brain ischemia/injury

Question 38

brain waves predominant under GA

Answer 38

theta delta

Question 39

what is burst suppression assoc. with

Answer 39

* general anesthesia * hypothermia * CPB, cerebral ischemia (esp. unilateral)

Question 40

MAC assoc. with isoelectricity on EEG

Answer 40

1.5-2

Question 41

how does N2O affect brain waves

Answer 41

alone increases beta wave activity

Question 42

how can sevo affect brain waves

Answer 42

can increase epileptiform EEG activity

Question 43

how can etomidate affect brain waves

Answer 43

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

Question 44

how can ketamine affect brain waves

Answer 44

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

Question 45

Provides a sensitive measure of brain tissue at risk of infarction

Answer 45

EEG

Question 46

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

Answer 46

O2 & glucose

Question 47

EEG changes that mays signify brain at risk for ischemia

Answer 47

Development of new delta waves during anesthesia

Question 48

conditions that mimic cerebral ischemia

Answer 48

deep anesthesia, hypothermia, hypocarbia

Question 49

how does BIS work

Answer 49

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

Question 50

target BIS for general anesthesia

Answer 50

low probability of explicit recall

Question 51

BIS waveforms as anesthesia gets deeper

Answer 51

* Lower frequency (slower) * Higher amplitude (taller)

Question 52

how can ketamine affect BIS

Answer 52

* increases high frequency activity * can make BIS higher than the level of sedation/anesthesia

Question 53

BIS value assoc. with burst suppression

Answer 53

0-40

Question 54

BIS assoc. with light to moderate sedation

Answer 54

80

Question 55

limitations of BIS monitoring

Answer 55

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

Question 56

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

Answer 56

25-50

Question 57

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

Answer 57

* measures EEG * runs data through an algorithm * displays a number that indicates level of anesthetic depth | electromotive force (voltage) = current x impedance

Question 58

law obeyed by electricity

Answer 58

Ohm’s Law

Question 59

what must occur to cause electrical injury

Answer 59

Must be voltage difference for current to flow across an impedance

Question 60

consequences of electrical injury

Answer 60

* arrythmias * muscle contractions * diaphragmatic paralysis * thermal injury

Question 61

threshold for touch perception of electrical shock

Answer 61

1 mA

Question 62

max current for a harmless electrical shock

Answer 62

5 mA

Question 63

“let go” current occurs before sustained contraction

Answer 63

10-20 mA

Question 64

current assoc. with loss of consciousness

Answer 64

50 mA

Question 65

current assoc. with V fib

Answer 65

100 mA

Question 66

Greatest margin of safety against risk of macroshock

Answer 66

isolate ground from main power supply

Question 67

what is a macroshock

Answer 67

comparatively larger amount of current applied to external body surface

Question 68

what is a microshock

Answer 68

comparatively smaller amount of current applied directly to myocardium ## Footnote High resistance of skin bypassed - takes significantly smaller amount of current to induce V-fib

Question 69

maximum allowable current leak in the OR

Answer 69

10 microA

Question 70

3 things that increase susceptibly to microshock

Answer 70

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

Question 71

3 things that increase susceptibly to microshock

Answer 71

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

Question 72

what is electrical grounding

Answer 72

OR systems designed to reduce risk of electric shock | OR power supply is not grounded; equipment is grounded

Question 73

what is electrical grounding

Answer 73

OR systems designed to reduce risk of electric shock | OR power supply is not grounded; equipment is grounded

Question 74

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

Answer 74

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

Question 75

required to supply ungrounded power to OR

Answer 75

Isolation transformer

Question 76

purpose of line isolation monitor (LIM)

Answer 76

assesses integrity of ungrounded power system in OR

Question 77

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

Answer 77

Line isolation monitor (LIM)

Question 78

does a line isolation monitor protect against micro or macro shock

Answer 78

nope, not by itself

Question 79

Primary purpose of line isolation monitor

Answer 79

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

Question 80

what should you do if line isolation monitor sounds

Answer 80

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

Question 81

when will line isolation monitor sound

Answer 81

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

Question 82

current delivered by electrocautery

Answer 82

500,000 – 1 million Hz

Question 83

serves as an exit point for monopolar ESU

Answer 83

Functional return electrode | provides large, low impedance surface area for current to exit the body

Question 84

why doesn't bipolar ESU need a return pad

Answer 84

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

Question 85

factors that increase risk of burns with ESU

Answer 85

* fauly in return electrode * electrode malfunction

Question 86

factors that increase risk of burns with ESU

Answer 86

* fauly in return electrode * electrode malfunction

Question 87

why is the return pad for ESU so large

Answer 87

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

Question 88

how are burns at return pad site prevented

Answer 88

* 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

Question 89

how can metal jewelry cause a burn with ESU

Answer 89

by “re-concentrating” electrical current from ESU

Question 90

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

Answer 90

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

Question 91

2 drugs that are most likely to reduce reliability of BIS

Answer 91

* 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)