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Mar: Sem 3 - Principles I > Exam 1 Clinical Monitoring Part 2 [6/10/24] > Flashcards

Exam 1 Clinical Monitoring Part 2 [6/10/24] Flashcards

1
Q

What are the two sampling sites depicted by the two arrows?

A
  • Elbow
  • Y-piece

S47

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2
Q

What are the two types of gas sampling systems?

A
  • Side-stream/ diverting analyzer
  • Mainstream/ non-diverting analyzer

S48

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3
Q

Which gas sampling system will have more lag time (transit time)?

A
  • Side-stream/ diverting analyzer

S48

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4
Q

What is rise time in terms of the gas sampling system?

A
  • The time taken by the analyzer to react to the change in gas concentration

The mainstream analyzer will have a faster rise time.

S48

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5
Q

Side-stream response time is dependent on what factors?

A
  • Sampling tubing inner diameter
  • Length of tubing
  • Gas sampling rate (50 - 250 mL/min)

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6
Q

What are gas sampling challenges with mainstream analyzers?

A
  • Water vapor (can block IR waveforms)
  • Secretions
  • Blood
  • More interfaces for disconnections

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7
Q

What are gas sampling challenges with side-stream analyzers?

A
  • Kinking of sampling tubing (can’t break over time)
  • Water vapor (can block IR waveforms)
  • Failure of sampling pump
  • Leaks in the line
  • Slow response time

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8
Q

The total pressure exerted by a mixture of gases is equal to the sum of the partial pressures exerted by each gas in the mixture. What law is this?

A
  • Dalton’s Law

S50

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9
Q

At sea level, what is the total pressure of all anesthetic gases in the system?

A
  • 760 mmHg

S50

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10
Q

Calculate the partial pressure of O2 at room air

A
  • 159.6 mmHg

760 mmHg x 21% = 159.6 mmHg

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11
Q

Calculate the partial pressure of inspired O2 at room air.

A
  • 149.7 mmHg

PIO2 = FIO2 (PB -PH2O)

21% (760 - 47) = 149.7 mmHg

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12
Q

____ is an instrument that allows the identification and quantification, on a breath-by-breath basis, of up to eight of the gases commonly encountered during administering an inhalational anesthetic.

A
  • Mass Spectrometry

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13
Q

Mass Spectrometry:
* How is the concentration determined?
* Abundance of ions at specific mass/charge ratio is determined and related to what?
* How many gasses can it calculate?

A
  • Concentration is determined according to mass/charge ratio
  • Abundance of ions at specific mass/charge ratio is determined and r/t to the fractional composition of gas mixture
  • Can calculate up to 8 different gasses.

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14
Q

This tool uses a high-powered argon laser to produce photons that collide with gas molecules in a gas sample. The scattered photons are measured in a spectrum that identifies each gas and concentration.

A
  • Raman Spectrometry (Raman Scattering)

No longer in use

S51

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15
Q
  • What is Infrared [IR] analysis?
  • What does it measure?
A
  • IR analysis measures energy absorbed from a narrow band of wavelengths of IR radiation as it passes through a gas sample
  • It measures the concentration of gasses.
  • Assymetric, polyatomic molecules of various gasses absorb IR light at specific wavelengths.

S52

similiar to how different wavelength of lights read the pulse ox.

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16
Q

What is the most common IR gas analyzer?

A
  • Non-dispersive IR analyzer

S52

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17
Q

What gases are measured using Infrared analysis?

A
  • CO2
  • Nitrous Oxide
  • Water
  • Volatile Anesthetic Gases

O2 does not absorb IR radiation

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18
Q

How does Infrared Analysis (IR Analyzer) work?

A
  • Gas will enter the sample chamber
  • Each gas has a unique IR transmission spectrum absorption band
  • Strong absorption of IR light occurs at specific wavelengths
  • IR light is transmitted through the gas sample and filtered via narrow-band pass filter.
  • The amount of IR light that reaches the detector is inversely related to the concentration of the gas being measured
  • Less light = high concentration of gas

S53

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19
Q

Do side-stream analyzers take into account of water vapors?

A
  • No
  • Side-stream analyzers report ambient temperature and pressure dry values (ATPD).

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20
Q

What is the recommendation on how gas analyzers should report results?

A
  • Analyzers should report results at body temperature and pressure saturated [BTPS] values.

S54

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21
Q

What are the two types of oxygen analyzers?

A
  • Fuel or Galvanic Cell O2 Analyzer
  • Paramagnetic O2 Analyzer

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22
Q

How does the fuel or galvanic cell operate?

A
  • It has an oxygen battery that measures the current produced when oxygen diffuses across a membrane
  • The current is proportional to the partial pressure of the oxygen in the fuel cell

S55.

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23
Q

What are the drawbacks of a Fuel/ Galvanic Cell O2 Analyzer?

A
  • Short life span (months) depending on the length of O2 exposure
  • Slow response time of approximately 30 seconds
    • best to measure O2 in the inspiratory limb

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24
Q

How does the paramagnetic O2 analyzer operate?

A
  • Oxygen is a highly paramagnetic gas d/t the magnetic energy of unpaired electrons in their outer shell orbits
  • Detects the change in sample line pressure resulting from the attraction of oxygen by switched magnetic fields
  • Signal changes during switching correlates withO2 concentration

S55

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25
Q

What oxygen analyzer is used in most side-stream sampling multi-gas analyzers?

What is the benefit of this analyzer?

A
  • Paramagnetic O2 Analyzer
  • Benefit: Rapid response, breath-by-breath monitoring

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26
Q

Purpose of gas sampling inside the inspiratory limb.

A
  • Ensures oxygen delivery
  • Analyzes hypoxic mixtures

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27
Q

This is arguably the most important of all monitors. It Must be calibrated for high and low concentrations

A

Oxygen monitoring

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28
Q

Purpose of gas sampling inside the expiratory limb.

A
  • Ensure complete pre-oxygenation/ “denitrogenation”
  • ET O2 above 90% adequate

S56

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29
Q

Can we have oxygen monitoring at auxillary sites?

A

No oxygen monitoring at auxiliary sites

S56

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30
Q

What can trigger a low O2 alarm?

A
  • Pipeline crossover
  • Incorrectly filled tanks
  • Failure of a proportioning system

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31
Q

What patient population must we be wary of for high O2 alarms?

A
  • Premature infants (high O2 can cause blindness)
  • Patients on chemotherapeutic drugs (ex: bleomycin)

Bleomycin has been associated with pulmonary toxicity, which can cause lung damage. Supplemental oxygen may exacerbate this toxicity.

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32
Q

This is a key component in measuring ventilation. Its noninvasive. It assess mechnical or spotaneous ventilation.

A

Airway pressure monitoring.

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33
Q

What can airway pressure monitoring detect?

A
  • Fresh gas hose kink or disconnection
  • High and low scavenging system pressures
  • Sustained high-circuit pressure
  • Circuit disconnections
  • Circuit leaks
  • ETT occlusions
  • Kinking in the inspiratory limb

S58

Starting from the pipes then vent then the pt [out to in]

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34
Q

What are the two types of pressure gauges used in airway pressure monitoring?

A
  • Mechanical Pressure Gauges
  • Electronic Pressure Gauges

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35
Q

What are the characteristics of mechanical pressure gauges?

A
  • Requires no power, always on, and have high reliability
  • No recording of data
  • No alarm system
  • Must be continually scanned

S58

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36
Q

What are the characteristics of electrical pressure gauges?

A
  • Built within ventilator or anesthesia machine
  • Alarm system integrated
  • Sensitive to small changes

S58

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37
Q

List the types of different airway pressure alarms

A
  • Breathing circut low pressure alarm
  • Sub atmospherrc pressure alarm
  • High pressure alarm
  • Continuing pressure alarm

S59-61

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38
Q

What is the purpose of the breathing circuit low-pressure alarms?

A
  • Identification of circuit disconnection or leaks
    • Does not detect some partial disconnections
    • May not detect misconnections or obstructions
  • Monitors airway or circuit pressure and compares it with a preset low-pressure alarm limit.
    • Low-pressure limit should be set just below the normal peak airway pressure

S59

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39
Q

Where do most of the circuit disconnections occur at?

A
  • 70% of disconnections occur at the y-piece.

S59

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40
Q

What is the normal peak airway pressure?

A
  • 18-20 cmH20

Low-pressure limit should be set just below this.

S59

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41
Q

What does the sub-atmospheric pressure alarm measure?

A
  • Measure and alerts negative circuit pressure and potential for the reverse flow of gas

S60

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42
Q

What can negative pressure cause the patient to have?

A
  • Pulmonary Edema
  • Atelectasis
  • Hypoxia

S60

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43
Q

What can cause subatmopsheric pressure alarm on the anesthesia machine?

A
  • Active (suction) scavenging system malfunctions
  • Pt inspiratory effort against a blocked circuit
  • Inadequate fresh gas flow
  • Suction to misplaced NGT/OGT
  • Moisture in CO2 absorbent

SIM-PA

S60

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44
Q

When is high pressure alarm activated?
Who is it valuble in?

A
  • Activated if the pressure exceeds a certain limit
  • User-adjustable or automated
  • Valuable in pediatrics

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45
Q

What are the causes of high-pressure alarms?

A
  • Obstruction
  • Reduced compliance
  • Cough/straining
  • Kinked ETT
  • Endobronchial intubation

CORKE causes high pressure

S61

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46
Q

When are continuing pressure alarms triggered?

A
  • Continuing pressure alarms are triggered when circuit pressure exceeds 10 cm H2O for more than 15 seconds
  • Fresh gas can enter the circuit but can’t leave

S61

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47
Q

What are causes of continuing pressure alarms?

A
  • Malfunctioning adjustable pressure relief valve
  • Scavenging system occlusion
  • Activation of oxygen flush system
  • Malfunctioning PEEP

S61

MAMS [your pressure is alarming]

48
Q
  • What are the types of peripheral nerve monitoring?
  • Which one is most commonly used?
A
  • Electrical and magnetic
  • Electrical nerve stimulation most commonly used

S63

49
Q

Why is magnetic peripheral nerve monitoring not used even though its less painful and requires no physical contact?

A
  • Bulky and heavy
  • No TOF stimulation
  • Difficult to achieve supramaximal stimulation

S63

50
Q

define supramaximal stimulation

A

Reaction of single muscle fiber to a stimulus follows an all-or-none pattern

S63

51
Q

The response of the whole muscle depends on what?

A

how many muscle fibers are activated

S63

52
Q

When picking a site for nerve stimulation, we want what 3 things?

A
  • Easily accessible
  • Allow quantitative monitoring
  • Avoid direct muscle stimulation.

S64

53
Q

What is the gold standard for the site of nerve stimulation? Why?

A
  • Ulnar Nerve
  • The ulnar nerve innervates the adductor pollicis muscle and has the lowest risk of direct muscle stimulation.

S64

54
Q

What skeletal muscle is the most resistant to depolarizing and nondepolarizing NMBDs?

A
  • Our favorite, the diaphragm
  • Diaphragm has a shorter onset than adductor pollicis and recovers quicker than peripheral muscles.
55
Q

If the arms are unavalible, what muscle can be used to assess nerve stimulation?

A
  • Facial nerve orbicularis oculi
  • Facial nerve corrugator supercili

S64

56
Q

What muscle will reflect the extent of the neuromuscular block of the laryngeal adductor and abdominal muscles the best?

A
  • Corrugator Supercilii > Adductor pollicis.

S64

57
Q

Define a single twitch stimulation.
What must be obtained prior to NMBD?
Does this require a monitoring device?

A
  • Single stimuli applied from 1.0 Hz (every second) to 0.1 Hz (every 10 seconds); earliest and simpliest
  • Reference value mandatory prior to NMBD.
  • Yes, needs a monitoring device.

S65

Not used in clinicals more for research lab to establish ED95

58
Q

What stimulation will provide reliable information throughout all phases of neuromuscular blockade w/o a monitoring device?

A
  • Train of Four

S66

59
Q
  • What stimulus is delivered for TOF?
  • How do you calculate TOF Ratio?
  • TOF is a reliable assessment of what?
A
  • 4 supramaximal stimuli every 0.5 seconds - evaluate TOF count or fade in the muscle resposne.
  • TOF ratio = 4th Response/1st Response
  • Reliable assessment of onset and moderate block.

S66

For deep blocks, TOF if hard to assess in patient.

60
Q

Compare TOF Ratio for partial nondepolarizing block and partial depolarizing block.

A
  • Non-depolarizing block: TOF ratio decreases (fade) and is inversely proportional to the degree of block
  • Depolarizing block: No fade. The ratio is 1.0. (If fade, phase II block has developed)

S66

61
Q

This stimulation is composed of 2 short bursts of 50 Hz tetanic stimulation separated by 750 ms w/ 0.2 ms duration of each square wave impulse in the burst.

A
  • Double Burst Stimulation

Not used as much in clinical practice

S67

62
Q

Double burst stimulation

  • What is DBS3,3 mode?
  • What is DBS3,2 mode?
A
  • DBS3,3 mode – 3 impulses in each of the 2 bursts
  • DBS3,2 mode– 1st burst has 3 impulses and 2nd has 2 impulses

S67

63
Q

With double burst stimulation where are we comparing the fade to?

A

Two short muscle contractions with fade in the 2nd burst, 1st is the comparison

S67

64
Q

Describe tetanic stimulation.

A
  • Tetanic stimulation given at 50 Hz for 5 seconds
  • limited value for assessing recovery, very painful.
  • not used as frequently.

S68

65
Q

Compare tetanic stimulation between non-depolarizer and depolarizer.

A
  • Non-depolarizers - one strong sustained muscle contraction with fade after stimulation
  • Depolarizer – strong sustained muscle contraction w/o fade.
    • With phase II block, fade occurs.

S68

66
Q
  • What stimulation is used for a deep/surgical blockade?
  • How often is this performed
A
  • Post-tetanic stimulation
  • Performed every 6 minutes
67
Q

with post tetanic stimulation, what is the response dependent on?

A
  • Degree of blockade
  • Frequency and duration of tetanic stimulation
  • Length of time between the end of tetanic stimulation and first post-tetanic stimulus
  • Frequency of the single-twitch stimulation
  • Duration of single-twitch stimulation before tetanic stimulation

S69

68
Q

describe post tetanic stimulation

A

Composite stimulation pattern – tetanic stimulation (50 Hz for 5 sec) followed by 10 to 15 single twitches (1 Hz after 3 sec post tetanic stimulation)

S69

69
Q
  • Definition of Intense non-depolarizing blockade.
  • How do you reverse?
A
  • Period of no response for about 3-6 min after intubating dose of non-depolarizing NMBD
  • Neostigmine reversal is impossible
  • high dose os sugammadex for reversal (16mg/kg)

slide 70

70
Q
  • Definition of Deep Non-depolarizing blockade
  • How do you reverse?
A
  • Absence of TOF but presence of at least one response to post-tetanic count stimulation
  • Neostigmine reversal usually impossible
  • dose of sugammadex (4 mg/kg) for reversal

slide 70

71
Q
  • Definition of Moderate Non-depolarizing blockade
  • How do you reverse?
A
  • gradual return of the 4 responses to TOF stimulation appears
  • Neostigmine reversal after 4/4 TOF
  • Sugammadex 2 mg/kg for reversal

slide 70

72
Q

What does Phase I in a Depolarizing blockade suggest?

A
  • All 4 responses are reduced, yet equal and then all disappear simultaneously in TOF (ratio is 1.0)
  • No fade or tetanic stimulation; no post-tetanic facilitation occurs
  • Normal plasma cholinesterase activity

slide 71

73
Q

What does Phase II in a Depolarizing block suggest?

A
  • Fade present in response to TOF and tetanic stimulation; occurrence of post-tetanic facilitation
  • Response is similar to non-depolarizing blockade
  • Abnormal plasma cholinesterase activity

slide 71

74
Q

USE IN CLINICAL PRACTICE

For patients recieving NMBD, what should the CRNA keep in mind?

A
  • Keep pt warm to prevent delaying nerve conduction
  • Attach electrodes prior to induction, turn on after pt is unconscious
  • Moderate level of blockade is sufficient for surgery with 1 or 2 responses to TOF
  • Reverse when all 4 responses present to TOF
  • Check for neuromuscular recovery prior to extubation post-reversal

Add Warm Mittens Right Now

slide 72

75
Q

Reliable clinical signs for reversal

A
  • Sustained head lift for 5 sec
  • Sustained leg lift for 5 sec
  • Sustained handgrip for 5 sec
  • Sustained ‘tongue depressor test’
  • Maximum inspiratory pressure

slide 72

76
Q

What is an EEG?
How are the electrodes placed?
How many channels does it use to gather information?

A
  • Summation of excitatory and inhibitory post-synaptic potentials in the cerebral cortex
  • Electrodes placed so that surface anatomy relates to cortical regions
  • Uses at least 16 channels of information

Slide 74

77
Q

EEG identifies:

A
  • Consciousness
  • unconsciousness
  • seizure activity
  • stages of sleep
  • coma
  • Inadequate oxygen delivery to the brain (hypoxemia or ischemia)

I-CCUSS

Slide 74

78
Q

EEG Signal description

  • What is amplitude?
  • What is frequency?
  • What is time?
A
  • Amplitude – size or voltage of recorded signal
  • Frequency – number of times per second the signal oscillates or crosses the 0-voltage line
  • Time – duration of the sampling of the signal

slide 74

79
Q

Peri-op uses for EEG

A
  • Identifies inadequate blood flow to cerebral cortex
  • Guides an anesthetic-induced reduction of cerebral metabolism
  • Used to predict neurologic outcome after a brain insult
  • Gauges the depth of the hypnotic state of patients under GA

Slide 75

80
Q

What are the Hz and pt LOC of the following EEG signals:
* Beta
* Alpha
* Theta
* Delta

A
  • Beta (> 13 Hz): Awake -Alert attentive brain
  • Alpha (8 - 13 Hz): Eyes closed or Anesthetic effects
  • Theta (4 - 7 Hz)
  • Delta (< 4Hz): Depressed

BAT Da EEG

slide 76

81
Q

Processed EEG [BIS]
* Contains ____ along with desired EEG signal
* Uses ____ channels of information; ____ per hemisphere
* Necessary to display the activity of both hempspheres; delineates ____ from ____ changes (ex: Regional ischemia d/t carotid clamping (unilateral), EEG depression from anesthetic drug bolus (bilateral)
* There ____ an adequate number of studies comparing EEG vs processed EEG

A
  • Contains artifact along with desired EEG signal
  • Uses < 4 channels of information; 2 per hemisphere
  • Necessary to display the activity of both hempspheres; delineates unilateral from bilateral changes (ex: Regional ischemia d/t carotid clamping (unilateral), EEG depression from anesthetic drug bolus (bilateral)
  • There isn’t an adequate number of studies comparing EEG vs processed EEG

slide 77

82
Q

Bispectral Index (BIS):
* How does the processes EEG signal estimate anesthetic depth?
* What can the BIS help prevent.
* For cases with intraoperative awareness, what is better? the BIS or end tidal agent concentration monitoring?

A
  • Processes EEG signal to estimate anesthetic depth using a computer generated algorithm.
  • BIS is proposed as a method to prevent intraop awareness; has not been demonstrated to be superior to end-tidal agent concentration monitoring
  • In cases with intraoperative awareness, neither technique was found to be completely reliable

slide 78

83
Q

Sensory-Evoked potentials

A
  • most common type of evoked potential intra-op
  • Electric CNS responses to electric, auditory, or visual stimuli
  • Sensory system stimulus with responses recorded at various sites along the sensory pathway to the cerebral cortex
    -Cortical or subcortical

slide 79

84
Q
  • Sensory-evoked responses are described in what 2 terms?
  • ____ is the time measures from the application of the stimulus to the onset/peak of the response
  • ____ is the size or voltage of the recorded signal
  • you need a ____ to reproduce reliable tracings
  • What are 3 types of sensory evoked potentials?
A
  • Sensory-evoked responses are described in terms of latency and amplitude
  • latency is the time measures from the application of the stimulus to the onset/peak of the response
  • amplitude is the size or voltage of the recorded signal
  • you need a baseline to reproduce reliable tracings
  • Include somatosensory-evoked potentials, brainstem auditory-evoked potentials and visual-evoked potentials

slide 79

85
Q

What do somatosensory-evoked potential do?

A
  • Monitor the responses to stimulation of peripheral mixed nerves (contain motor and sensory nerves) to the sensorimotor cortex
  • Responses consist of short-latency and long-latency waveforms
    • Short-latency SSEPs are most commonly recorded intra-op; less influenced by changes in anesthetic drug levels*
  • Induction, neurological disease or age, and use of different recording electrode locations may alter appearance of SSEPs

slide 80

86
Q

What do Brainstem Auditory-Evoked Potentials do?

A

Monitors the responses to click stimuli that are delivered via foam ear inserts along the auditory pathway from the ear to the auditory cortex

slide 81

87
Q

What do Visual-Evoked Potentials do?

A
  • Monitors the responses to flash stimulation of the retina using light-emitting diodes embedded in soft plastic goggles through closed eyelids or contact lenses
  • Least commonly used monitoring technique intra-op

slide 81

88
Q

What do Motor-Evoked Potentials do?

A
  • Monitoring the integrity of the motor tracts along the spinal column, peripheral nerves, and innervated muscle

slide 82

89
Q
  • Most common MEP?
  • what does it monitor?
A
  • Transcranial motor-evoked potentials
  • Monitors stimuli along the motor tract via transcranial electrical stimulation overlying the motor cortex

slide 82

90
Q

Electromyography is a type of motor evoked potential, what does it do?

A
  • Monitors the responses generated by cranial and peripheral motor nerves to allow early detection of surgically induced nerve damage and assessment of the level of nerve function intra-op
  • Assesses the integrity of cranial or peripheral nerves at risk during surgery

Slide 82

91
Q

what are the 2 types of motor evoked potentials?

A
  • Transcranial motor-evoked potential
  • Electromyography

S82

92
Q

Temperature control:
* Primary thermoregulatory control center is the ____
* ____ fibers are the heat/warmth receptors
* ____ fibers are the cold receptors

A
  • Primary thermoregulatory control center is the hypothalamus
  • unmyelinated C fibers are the heat/warmth receptors
  • A-delta fibers are the cold receptors

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93
Q

Thermoregulatory response is characterized by?

A
  • Threshold
  • Gain
  • Response
94
Q
  • ____ is the temperature at which the response will occur
  • ____ is the intensity of the response
  • ____: sweating, vasodilation, vasoconstriction and shivering
A
  • Threshold – temperature at which a response will occur
  • Gain – the intensity of the response
  • Response – sweating, vasodilation, vasoconstriction, and shivering

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95
Q

Why does core temperature drop with anesthesia?

A

anesthesia vasodialates which diverts blood away from the core, decreasing temperature

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96
Q

Hypothermia in GA goes through 3 phases. List the phases.

A
  1. Initial
  2. Sow linear reduction
  3. plateau phase

S85

97
Q

What happens during the initial stage of hypothemia during GA?

A
  • Initially: rapid decrease of approx. 0.5 to 1.5°C
  • Anesthesia-induced vasodilation
  • Increases heat loss d/t redistribution of body heat
  • Over 30 mins

S85

98
Q

What happens during the slow linear reduction phase of hypothermina in GA?

A
  • Slow linear reduction: approx. 0.3°C per hour
  • GA decreases metabolic rate by 20-30%
  • Heat loss exceeds production
  • Occurs 1-2 hours after anesthesia

S85

99
Q

What happens during the plateau phase of hypothermina in GA?

A
  • Thermal steady state
  • Heat loss equals heat production
  • Occurs 3-4 hours after anesthesia
  • Vasoconstriction prevents loss of heat from core, but peripheral heat continues to be lost

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100
Q

Temperature control can vary due to which factors?

A
  • Anesthesia
  • Age
  • Menstral Cycle
  • Drugs
  • Alchohol
  • Circardiam Rhythm.

S84

101
Q

Hypothermia in Neuraxial anesthesia causes the autonomic thermoregulatory defenses ito be impaired. What are the 4 defences?

A
  • vasodialation
  • sweating
  • vasoconstriction
  • shivering

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102
Q

Does hypothermia cause thermal discomfort in neruaxial anesthesia?

A

Hypothermia doesn’t cause much thermal discomfort. Pts do not complain of feeling cold.

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103
Q

Central thrmoregulatory control is inhibited by neuraxial anesthesia, what does this cause?

A

Decreases the thresholds that trigger peripheral vasoconstriction and shivering

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104
Q
  • With hypothermia in neuraxial anesthesia an inital decrease in core temp is caused by?
  • there may not be a plateau phase d/t?
  • what threshold is centrally altered?
A
  • neuraxial blockade-induced vasodilation
  • inhibition of peripheral vasoconstriction
  • vasoconstriction threshold

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105
Q

What are the 4 methods of heat transfer?

A
  • Radiation
  • Convection
  • Evaporation
  • Conduction

S87

106
Q
  • How much heat is lost through radiation?
  • ____ is exposed to environemnt?
  • why are infants more vulnerable?
A
  • heat loss to the environment, approx. 40% of heat loss in pt
  • Body surface area [BSA] exposed to environment
  • Infants: high BSA/body mass ratio makes them vulnerable

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107
Q
  • How is heat loss through convection?
  • what can decrease heat loss?
  • Where is heat loss greater?
A
  • loss of heat to air immediately surrounding the body, approx. 30%
  • Clothing or drapes decrease heat loss
  • Greater in rooms with laminar air flow

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108
Q
  • How is heat loss through evaporation?
  • what is the main pathway?
A
  • latent heat of vaporization of water from open body cavities and respiratory tract, approx. 8-10%
  • Sweating is main pathway

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109
Q

How is heat lost through conduction?
What are examples?

A
  • heat loss due to direct contact of body tissues or fluids with a colder material, negligible
  • Ex: contact between skin and OR table; intravascular compartment and an infusion of cold fluid

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110
Q

What are the 7 hypothermia complications mentioned in class?

A
  • Coagulopathy: Impairs platelet aggregation enzymes involved in coagulation cascade
  • Increases need for transfusion by 22%; blood loss by 16%
  • Decreases oxygen delivery to tissues
    • Increases risk of wound infection, decreases tissue healing
  • 3x the incidence of morbid cardiac outcomes
    • Increased BP, HR, and plasma catecholamine levels
  • Shivering
    • Increases oxygen demand
  • Decreased drug metabolism
    • Increased duration of NMB
  • Post-op thermal discomfort

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111
Q

What are the benefits of hypothermia?

A
  • Protective against cerebral ischemia
  • Reduces metabolism 8% per degree C
  • Improved outcome during recovery from cardiac arrest
  • Neurosurgery when brain tissue ischemia is expected
  • More difficult to trigger MH

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112
Q

What are some methods to heat patient peri-op?

A
  • Airway heating and humidification – infants and children > adults
  • Warm IV fluid and blood
  • Cutaneous warming:
  • Forced air warming:

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113
Q

When using cutaneous warming what are 3 different methods you can use?

A
  • Increased room temperature
    • [Ex: liver transplants, major trauma, pediatrics]
  • Insulation -
    • Single blanket reduces loss by 30%.
    • Doesn’t increase body temperature
  • Hot water mattresses:
    • More effective and safer placed on top of pts

Slide 90

114
Q

What is the most common method to prevent heat loss from radiation?

A

Forced air warming
it uses convection to transfer heat to pt

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115
Q
  • What are 4 temperature monitoring sites?
  • What are the risk/benefits with these sites?
A
  • Pulmonary artery (gold standard)
  • Tympanic membrane: approximates temp at hypothalamus (careful about preforation)
  • Nasopharyngeal: reflects brain temp, but more prone to error and epistaxis
  • Esophagus: safe, easy, no artifact, accurate place in distal esophagus lower 1/3 to 1/4

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116
Q

What is the OR temp (C) when the room is 70F or 65F?

A

70 degrees F = 21 degrees C [usally for PEDS cases]
65 degrees F = 18 degrees C [usually for adult cases]

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Mar: Sem 3 - Principles I (29 decks)

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