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Principles of Anesthesia > Clinical Monitoring Lecture 1 > Flashcards

Clinical Monitoring Lecture 1 Flashcards

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1
Q

What monitors are included in AANA monitoring standards?

A
  • Oxygenation: clinical observation, Pulse Ox, ABG as indicated
  • Ventilation: Auscultation, Chest excursion, ETCO2, Pressure monitors as indicated
  • CV: ECG, Auscultation as needed, BP and HR Q5 min
  • Thermoregulation
  • Neuromuscular: with NMBD
  • Positioning/protective measures
    Omission with reason must be charted
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2
Q

What is the minimum ventilation monitors for AANA standards?

A
  • Auscultation
  • Chest excursion
  • ETCO2
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3
Q

How is pulse ox used to measure SPO2?

A

Absorbance of light through matter→ transmitted, absorbed, or reflected

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4
Q

What law/principle is the pulse ox built based on?

A

Beer-Lambert Law→ Law of absorption; A beam of visible light passing through a chemical solution of fixed geometry experiences absorption proportional to the concentration of the solute

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5
Q

What does Beer-Lambert Law predict for light absorption in a solution with more solute vs less solute?

A

More solute= More light absorption
Less solute= less light absorption

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6
Q

What types of hemoglobin are found normally in a healthy adult?

A
  • Oxyhemoglobin (HbO2)
  • Reduced HB
  • Methemoglobin (metHb)
  • Carboxyhemoglobin (COHb)
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7
Q

What is the gold standard pulse ox if 2 wavelength is innaccurate?

A

Co-oximetry (4 wavelength)

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8
Q

What wavelength does pulseox work on?

A

660nm
940nm
difficult to differentiate different Hb when more than one crosses at the same point at these wavelengths

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9
Q

What are the operating principles of a pulseox?

A
  • Light transmitted through skin, soft tissue, venous blood, arterial blood, or capillary blood
  • Pulsatile expansion of the artery increases length of light path→ increases absorbency
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10
Q

Pulse oximetry is transmitting info about ___________ blood

A

Arterial → oxygenated blood and pulsatile

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11
Q

What happens to the artery as blood travels through it and how does this affect pulse ox reading?

A
  • Artery expands as blood comes through and collapses
  • Expansion of artery is picked up by nm wavelengths and by computer data of pulseox (seeing pulsatile absorptions)
  • Artery expands with pulse the length the light has to travel increases and absorbency increases (nm)
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12
Q

How does the pulseox machine calculate the correct value?

A

Pulsatile piece / Non pulsatile piece

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13
Q

What is the difference between SaO2 and SpO2?

A

SaO2: Saturation of arterial blood
SpO2: Saturation as detected by the pulse oximeter

Different by 2-3%→ difference usually accounts for type of machine and how old it is

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14
Q

What can cause signal artifact in pulseox?

A
  • Ambient light: solved by alternating red/infrared
  • Low perfusion: Signal and artifact amplified (hypotension, hypovolemia)
  • Venous blood pulsations: Longer signal averaging time and slower to report changes
  • Additional light absorbers: IV dyes cause low pulseox readings if the dye absorbs a lot of light
  • Additional forms of Hb: Fetal Hb in peds
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15
Q

What happens to oxygen tension if the blood is poorly saturated with O2?

A

Small amount of O2 will be released causing large drop in tension

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16
Q

Why is it important to have SpO2 >90-92%?

A

Below that we see very big changes in PaO2

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17
Q

What happens to O2 as blood passes through systemic capillaries?

A

Large amount of O2 released leading to small drop in tension

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18
Q

How does the oxyhemoglobin curve explain lack of change in O2 partial pressure above 90% Spo2?

A
  • Above 90% there is a slow rise to get to 100% (not a lot of change in partial pressure)
  • When below 90% there is a rapid drop between saturation and partial pressure
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19
Q

What causes oxyHb curve to shift to the left?

A
  • Decrease Temp
  • Decrease 2,3 DPG
  • Decrease H+
  • Carbon monoxide
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20
Q

What causes oxyhb curve to shift to the right?

A
  • Increase 2,3 DPG
  • Increased temp
  • Increased H+
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21
Q

___________ are relatively sensitive to vasoconstriction

A

Fingers (distal digits)

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22
Q

What can inhibit transmission of light from SpO2 probe?

A

Dark polish or synthetic nails

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23
Q

Where should you monitor pulse ox in a patient who is unstable having SpO2 fluctuations?

A

Somewhere close to the trunk→ detection of desaturation and resaturation is slower peripherally

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24
Q

Which finger should we avoid placing SpO2 in a patient sending to recovery?

A

Avoid index finger→ when pt waking up, eyes are itchy could cause corneal abrasion (try pinky finger)

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25
When might SpO2 monitoring on the toe be more reliable?
Epidural block→ increased vasodilation below block helps pulseox pick up well
26
Which central areas are good places for pulseox prob to pick up desaturation quicker?
- Tongue - Cheek - Forehead *Less affected by vasoconstriction*
27
What are advantages of SpO2 monitors?
- Accurate (+/- 2%) when tested against ABGs (sat >70%) - Not affected by volatiles - Noninvasive - Continuous - May indicated decreased cardiac output - Convenient - Tone modulation - Probe variety - Battery operated - Economical
28
What are limitations to pulse oximetry?
- Failure to determine saturation of arterial blood - Poor function with poor perfusion - Difficult in detecting high partial pressures - Delayed hypoxic event detection (esp. in periphery) - Erratic performance with dysrhythmias - Inaccurate with different Hbs - Inaccurate with dyes - Optical interference (bright lights) - Nail polish/coverings - Motion artifact
29
Which dye absorbs light the fastest and gives most inaccurate pulseox reading (moments after giving)?
Methylene blue *Ingido carmine slower to absorb the light and doesnt absorb as much light so doesnt cause as erratic of a change in pulse oximeter- pulse ox readings return to normal pretty quickly*
30
How does carboxyhemoglobin affect SpO2?
- Absorbs as much light in the 660nm range as oxyhemoglobin - Falsely elevates SpO2
31
Each 1% increase in COHb will _________ SpO2 by 1%
Increase
32
Many smokers have >____% COHb
6
33
What does it mean in regards to SpO2 value if a patient is a longer term smoker? What might their actual SpO2 be if oximeter is reading 94%?
- SpO2 will be falsely elevated by 6% - Reading 94% might actually be 88%
34
Which Dr developed understanding of the circulatory system and the correlation between HR and pulse?
Dr. William Harvey (1600s)
35
When was the 1st recorded blood pressure?
1733→ Reverend Hales on a horse
36
When was the 1st sphygmomanometer invented?
1881→ invented by Samuel von Basch
37
When did modern blood pressure measurements with systolic and diastolic pressures (korotkoff sounds) come around?
1905
38
What causes Korotkoff sounds?
Turbulent flow beyond the partially occluded cuff
39
What are the phases of Korotkoff sounds?
- Phase 1: Most turbulent/audible (SBP) - Phase 2-3: Sound character changes - Phase 4-5: Muffled/absent (DBP)
40
What is the formula to calculate MAP?
DBP + [1/3 (SBP - DBP)] OR (2xDP + SP)/3
41
What are limitations to auscultation of BP?
- Decreased peripheral flow (shock, intense vasoconstriction) - Changes in vessel compliance (severe edema, calcified arteriosclerosis) - Shivering - Incorrect cuff size
42
How does a cuff size that is too big impact BP reading?
Low BP reading
43
How does a cuff that is too small impact BP reading?
Higher BP reading
44
What is the max cuff inflation pressure for adults and neonates?
Adults: 300mmHg Neonates: 150mmHg
45
What size should the cuff bladder be?
- 40% arm circumference - 80% of length of upper arm
46
What is Non-invasive BP based on?
Oscillometry→ SBP 20-25% higher than MAP amplitude *DBP is least accurate*
47
When is non-invasive BP about the same as arterial BP?
When MAP is greater than 75mmHg
48
What is common varience is NIBP compared to arterial BP?
- NIBP underestimates MAP during hypertension - NIBP overestimates MAP during hypotension *Trending necessary for NIBP measurements to be reliable*
49
What are advantages of NIBP?
- Automaticity - Simplicity - Noninvasive - Reliable (ish) - Monitor integration w/pulse ox
50
What are disadvantages of NIBP?
- Unsuitable in rapidly changing situations - Pt discomfort - Clinical limitations (extremes HR/BP) - Can cause trauma from repeated cycling (coagulopathies, peripheral neuropathies, art/venous insufficiency, compartment syndrome)
51
What are indications for invasive BP monitoring?
- Planned pharmacologic manipulation (pressors) - Repeated blood sampling - Determination of volume responsiveness - Timing of IABP counterpulsation
52
What is the most common site for art line? what are other sites?
- Most common: Radial→ easy access, complications uncommon - Other sites: Brachial (try to avoid d/t occlusion causing loss of big chunk of arm), Posterior tib, Axillary, Dorsalis pedis, Femoral
53
What is the Allens Test?
Occlude radial and ulnar artery and pt makes tight fist the opens hand-- then release ulnar to see if there would be enough collateral flow if occlusion occurred in radial *color should return to palm in less than 10 seconds for sufficient ulnar flow
54
What is the allen test predictive of?
More predictive of occlusion than ischemia
55
What is Seldingers technique for radial art line insertion?
- Going from something small to bigger and gradually increase size - Needle→ pass guidewire through needle→ removed needle → insert catheter
56
What position do you want to hand in before attempting radial art line insertion?
- Towel under wrist to move artery more superficial - Tape fingers (most importantly the thumb bc it causes the most radial artery movement)
57
What is the transfixtion technique for arterial line placement?
- Intentionally puncture front and back walls of artery → remove needle and pull catheter back until pulsatile blood appears then advance - More hematomas and faulty artlines with this method
58
Where is the leveling point for art line?
Aortic root: Mid-axillary/chest line
59
How do you maximize artline waveform?
- Limit stopcocks - Limit tubing length - Non-distensible tubing *Want stopcock close to insertion point if having frequent lab draws to avoid wasting blood*
60
What are the different waveforms of an art line?
1: systolic upstroke 2: systolic peak pressure 3: systolic decline 4: dicrotic notch 5: diastolic runoff 6: end-diastolic pressure
61
What happens to art line waveform as pressure waves move TO periphery? *reason why arterial pressures measured at different sites have different morphologies*
- Arterial upstroke steeper - Systolic peak higher - Dicrotic notch later - End-diastolic pressure lower - MAP changes very little: systolic and diastolic pressure going opposite directions at the same time and spreading out equally
62
What does distal pulse amplification of an art line mean?
Arterial pressure measured at different sites will have different morphologies d/t impedence changes along vascular tree→ Periphery has steeper peaks and later dicrotic notch with lower EDP
63
How are arterial line waveforms made?
- Summation of sine waves (Fourier analysis) - Based on waveform and amplitude - Fundamental wave + Harmonic wave = typical pressure wave
64
What is the square wave test?
- Way to make sure the art line is correctly calculated (not over or under dampened) - Square wave created when you flush then should see no more than 2 oscillations no greater than 1/3 previous oscillation then return to art waveform - Anything that doesnt have square wave and rapid return of oscillations after flush is probably dampened incorrectly
65
What is the purpose of dampening capability for an art line?
- Decreases system resonance - Prevents exaggerated waveforms
66
What does underdampened look like?
Systolic pressure looks elevated
67
What does over-dampened look like?
Systolic pressure decreases, absent dicrotic notch, narrowed pulse pressure, loss of detail
68
What pathology can cause arterial line waveform changes?
- Age: lack of distensibility - Atherosclerosis (higher pressure) - Embolism - Arterial dissection - Shock (hypotension) - Hypothermia - Vasopressor infusions
69
What is the art line waveform on the right showing?
70
What are complications of arterial lines?
- Distal ischemia or pseudoaneurysm (non healing hole in artery) - Hemorrhage, hematoma - Arterial embolization (if you hit plaque or fistula) - Local infection - Peripheral neuropathy—nerve very close to the artery

Principles of Anesthesia (9 decks)

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