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24 Principles of Anesthesia I > Exam 1- Clinical Monitoring (6/12/23) > Flashcards

Exam 1- Clinical Monitoring (6/12/23) Flashcards

1
Q

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

A
  • Elbow
  • Y-piece
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2
Q

What are the two types of gas sampling systems?

A
  • Side-stream/ diverting analyzer
  • Mainstream/ non-diverting analyzer
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3
Q

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

A
  • Side-stream/ diverting analyzer
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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.

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5
Q

Side-stream responses is dependent on what 3 factors?

A
  • Sampling tubing inner diameter
  • Length of tubing
  • Gas sampling rate (50 - 250 mL/min)
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6
Q

What are 4 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 5 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
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9
Q

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

A
  • 760 mmHg
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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

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

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14
Q

What is typically used in anesthesia machines to determine the concentration of gas?

A
  • IR Analysis
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15
Q

What is the most common gas analyzer?

A
  • Non-dispersive IR analyzer

IR analysis measures energy absorbed from a narrow band of wavelengths of IR radiation as it passes through a gas sample

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16
Q

What gases are measured using a non-dispersive IR analyzer?

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

O2 does not absorb IR radiation

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17
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
  • 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
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18
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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19
Q

What are the two types of oxygen analyzers?

A
  • Fuel or Galvanic Cell O2 Analyzer
  • Paramagnetic O2 Analyzer
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20
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 (best to measure O2 in the inspiratory limb)
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21
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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22
Q

Purpose of gas sampling inside the inspiratory limb.

A
  • Ensures oxygen delivery
  • Analyzes hypoxic mixtures
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23
Q

Purpose of gas sampling inside the expiratory limb.

A
  • Ensure complete pre-oxygenation/ “denitrogenation”
  • ET O2 above 90% adequate
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24
Q

What can trigger a low O2 alarm?

A
  • Pipeline crossover
  • Incorrectly filled tanks
  • Failure of a proportioning system
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25
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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26
Q

What can airway pressure monitoring detect?

A
  • Circuit disconnections
  • ETT occlusions
  • Kinking in the inspiratory limb
  • Fresh gas hose kink or disconnection
  • Circuit leaks
  • Sustained high-circuit pressure
  • High and low scavenging system pressures
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27
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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28
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
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29
Q

What are the characteristics of electrical pressure gauges?

A
  • Built within ventilator or anesthesia machine
  • Alarm system integrated
  • Sensitive to small changes
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30
Q

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

A
  • Identification of circuit disconnection or leaks
  • Monitors airway or circuit pressure and compares it with a preset low-pressure alarm limit.
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31
Q

Where do most of the circuit disconnections occur at?

A
  • 70% of disconnections occur at the y-piece.
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32
Q

What is the normal peak airway pressure?

A
  • 18-20 cmH20

Low-pressure limit should be set just below this.

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33
Q

What does the sub-atmospheric pressure alarm measure?

A
  • Measure and alerts negative circuit pressure and potential for the reverse flow of gas
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34
Q

What can negative pressure cause the patient to have?

A
  • Pulmonary Edema
  • Atelectasis
  • Hypoxia
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35
Q

What can cause negative pressure 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
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36
Q

What are the causes of high-pressure alarms?

A
  • Obstruction
  • Reduced compliance
  • Cough/straining
  • Kinked ETT
  • Endobronchial intubation
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37
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
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38
Q

What are causes of continuing pressure alarms?

A
  • Malfunctioning adjustable pressure relief valve
  • Scavenging system occlusion
  • Activation of oxygen flush system
  • Malfunctioning PEEP
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39
Q

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

A
  • Ulnar Nerve

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

40
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.

41
Q

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

A
  • Corrugator Supercilii
42
Q

Define a single twitch stimulation.

A
  • Single stimuli applied from 1.0 Hz (every second) to 0.1 Hz (every 10 seconds)
43
Q

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

A
  • Train of Four
44
Q

How do you calculate TOF Ratio?

A
  • 4th Response:1st Response
45
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)
46
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

47
Q

Describe tetanic stimulation.

A
  • Tetanic stimulation given at 50 Hz for 5 seconds
48
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
49
Q

What stimulation is used for a deep/surgical blockade?

A
  • Post-tetanic stimulation

Performed every 6 minutes

50
Q

What kind of blocks are in columns A, B, and C?

What kind of nerve stimulation is performed in rows 1 through 4?

51
Q

Describe an intense non-depolarizing block.
When does this occur?
Reversal?

A
  • Period of no response 3 – 6 minutes after an intubating dose of non-depolarizing NMBD
  • Reversal with high dose of Sugammadex (16 mg/kg)
  • Neostigmine reversal impossible
52
Q

Describe a deep non-depolarizing block.
Reversal?

A
  • Absence of TOF but the presence of at least one response to post-tetanic count stimulation.
  • Dose of sugammadex (4 mg/kg) for reversal
53
Q

Describe a moderate non-depolarizing block.
Reversal?

A
  • Gradual return of the 4 responses to TOF stimulation appears
  • Neostigmine reversal after 4/4 TOF
  • Dose of sugammadex (2 mg/kg) for reversal
54
Q

Describe a phase 1 depolarizing blockade.

A
  • No fade or tetanic stimulation; no post-tetanic facilitation occurs
  • All 4 responses are reduced, yet equal and then all disappear simultaneously in TOF (ratio is 1.0)
  • Normal plasma cholinesterase activity
55
Q

Describe a phase 2 depolarizing blockade.

A
  • Fade present in response to TOF and tetanic stimulation; occurrence of post-tetanic facilitation
  • Response is similar to a non-depolarizing blockade
  • Abnormal plasma cholinesterase activity
56
Q

What are reliable clinical signs for ETT extubation?

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
57
Q

What will EEG help identify?

A
  • Identify consciousness/ unconsciousness
  • Seizure activity
  • Stages of sleep
  • Coma
  • Identify inadequate oxygen delivery to the brain (hypoxemia or ischemia)
58
Q

Describe the following EEG factors:
-Amplitude
-Frequency
-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
59
Q

What kind of waves are present in alert, attentive patients?

A
  • Beta waves (>13 Hz)
  • Higher frequency
60
Q

What kind of waves are present when resting and eyes are closed?

A
  • Alpha waves (8-13 Hz)
  • Present during the beginning of induction (anesthetic effects)
61
Q

What kind of waves are present during depressed, deep anesthesia?

A
  • Theta waves (4-7 Hz)
  • Delta waves (<4 Hz)
  • Slower frequency
62
Q

How many channels are used in processed EEG compared to the gold standard EEG?

A
  • 4 channels vs 16 channels
63
Q

How does a BIS monitor estimate anesthetic depth?

A
  • Computer-generated algorithm/weighting system

Note: BIS monitoring has not demonstrated to be superior to end-tidal agent concentration monitoring

64
Q

What is the BIS range for general anesthesia?

65
Q

What is the most common type of evoked potential monitored intra-op?

A
  • Sensory evoked potential
66
Q

What is sensory-evoked potential?

A
  • Electric CNS response to electric, auditory, or visual stimuli
67
Q

How are sensory-evoked potentials described?

A
  • Latency: time measured from the application of stimulus to the onset or peak of response
  • Amplitude: size or voltage of recorded signal
68
Q

What are the three types of sensory-evoked potentials?

A
  • Somatosensory-evoked potential (SSEP)
  • Brainstem auditory-evoked potential (BAEP)
  • Visual-evoked potential (VEP)
69
Q

What monitors the responses to stimulation of peripheral mixed nerves (containing motor and sensory nerves) to the sensorimotor cortex?

A
  • Somatosensory-Evoked Potential (SSEP)
70
Q

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

A
  • Brainstem Auditory-Evoked Potential (BAEP)
71
Q

What type of latency SSEPs are most commonly recorded intra-op, less influenced by changes in anesthetic drug levels?

A
  • Short-latency
72
Q

Monitors the responses to flash stimulation of the retina using light-emitting diodes embedded in soft plastic goggles through closed eyelids or contact lenses

A
  • Visual-Evoked Potential (VEP)
73
Q

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

A
  • Motor-Evoked Potentials (MEP)
74
Q

What is the most common MEP?

A
  • Transcranial motor-evoked potentials

Monitors stimuli along the motor tract via transcranial electrical stimulation overlying the motor cortex

75
Q

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

A
  • Electromyography

Assesses the integrity of cranial or peripheral nerves at risk during surgery

76
Q

Where is the primary thermoregulatory control center?

A
  • Hypothalamus
77
Q

What fibers are heat and warmth receptors?

A
  • Unmyelinated C-fibers
78
Q

What fibers are cold receptors?

A
  • A-delta fibers
79
Q

The thermoregulatory response is characterized by what three factors?

A
  • Threshold – temperature at which a response will occur
  • Gain – the intensity of the response
  • Response – sweating, vasodilation, vasoconstriction, and shivering
80
Q

What affects the thermoregulatory response?

A
  • Anesthesia type
  • Age
  • Menstrual cycle
  • Drugs/EtOH
  • Circadian rhythm
81
Q

What is the initial decrease in body temperature with hypothermia in general anesthesia?

A
  • Rapid decrease of approximately 0.5-1.5 °C over 30 mins
  • Caused by anesthesia-induced vasodilation
  • Increases heat loss d/t redistribution of body heat
82
Q

How much heat is lost during the slow linear reduction phase with hypothermia in general anesthesia?

A
  • 0.3 °C per hour
  • Caused by the decrease of the metabolic rate of 20-30%
  • Heat loss exceeds production
  • This occurs 1-2 hours after anesthesia has started

Use Bair Hugger to combat heat loss

83
Q

Describe the plateau phase of hypothermia in general anesthesia.

A
  • Thermal steady state
  • Heat loss = heat production
  • Occurs 3-4 hours after anesthesia has started
  • Vasoconstriction prevents loss of heat from the core, but peripheral heat continues to be lost
84
Q

How is central thermoregulatory control inhibited by neuraxial anesthesia?

A
  • Neuraxial anesthesia decreases the thresholds that trigger peripheral vasoconstriction and shivering
85
Q

Why might there not be a temperature plateau with neuraxial anesthesia?

A
  • Neuraxial anesthesia centrally alters the vasoconstriction threshold
  • Vasoconstriction of the lower extremity will be inhibited by the nerve block
86
Q

What are the types of heat transfer?

A
  • Radiation
  • Convection
  • Evaporation
  • Conduction
87
Q

Describe Radiation.
Which patient population is vulnerable to this type of heat transfer?

A
  • Heat loss to the environment, body surface area (BSA) is exposed to the environment
  • Approx. 40% of heat loss in pt
  • Infants have a high BSA/body mass ratio makes them vulnerable
88
Q

Describe Convection.

A
  • Loss of heat to air immediately surrounding the body, approx. 30%
  • Clothing or drapes decrease heat loss
  • Greater in rooms with laminar airflow
89
Q

Describe Evaporation

A
  • Latent heat of vaporization of water from open body cavities and respiratory tract. Accounts for approx. 8-10% of heat loss
  • Sweating is the main pathway
90
Q

Describe Conduction

A
  • Heat loss due to direct contact of body tissues or fluids with a colder material, negligible
  • Contact between skin and OR table; intravascular compartment and an infusion of cold fluid
91
Q

List complications related to hypothermia

A
  • Coagulopathy
  • Increase the need for transfusion by 22%
  • Blood loss by 16%
  • ↓O2 delivery to tissues
  • 3x the incidence of morbid cardiac outcomes
  • Shivering
  • Decrease drug metabolism
  • Post-op thermal discomfort
92
Q

Benefits of hypothermia

A
  • Protective against cerebral ischemia
  • Reduces metabolism… 8% per degree Celsius
  • Improved outcome during recovery from cardiac arrest
  • More difficult to trigger MH
93
Q

Peri-Op Temperature Management

A
  • Prioritize airway/heating in pediatrics
  • Warm IV fluid and blood
  • Cutaneous warming
  • Forced air warming (convection method)
94
Q

How can you perform cutaneous warming?

A
  • ↑ Room Temperature (Liver transplant, trauma)
  • Insulation (blankets reduce heat loss by 30%)
  • Hot water mattress (safer/effective if placed on top of pt)
95
Q

What is the gold standard monitoring site for temperature?

A
  • Pulmonary Artery
96
Q

What are other monitoring sites for temperature?

A
  • Tympanic membrane (ear) - perforation risk
  • Nasopharyngeal - prone to error, nose bleeds
  • Esophagus - place in the distal esophagus, lower third to lower quarter of the esophagus (best site to monitor)
97
Q

OR Temperature

A
  • 65 degree (18°C) to 70 degrees (21°C)

24 Principles of Anesthesia I (27 decks)

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