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Principles of Anesthesia I > E1 > Flashcards

E1 Flashcards

1
Q

What is pulse oximetry dependent on to obtain a measurement?

A

Pulsatile expansion

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2
Q

Automatic BP standards and important considerations

A

Average difference +/- 5 mmHg
In reality
• Large variances
• Underestimate MAP during HTN
• Overestimate MAP during HoTN
• Ankle, thigh, calf cuffs  never validated
Averaging/trending for measurements reliability

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3
Q

What information is provided by EtCO2

A

PRIMARY= ventilation

  • Pulmonary blood flow
  • Aerobic metabolism
  • Placement of endotracheal tube/LMA
  • Integrity of breathing circuit
  • Adequacy of cardiac output
  • Dead space (VD) to tidal volume (VT)
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4
Q

Causes, solutions, and description of overdampened system

A 
•↓ SBP=underestimated
•↑DBP=over estimated
•	No dicrotic notch
•↓ pulse pressure
•Loss of detail d/t
•	System too rigid
•	System too short
	Fix= extension
•	Problem w/ Fluids/pressure bag
	Not enough pressure on bag
	Bag is empty
	Fix=change bag; ↑ pressure
•	Air bubbles
	Fix=remove bubbles from system
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5
Q

What is the law of absorption

A

Beer-Lambert equation
• If a known intensity of light illuminates a chamber of known dimensions
• then the concentration of a dissolved substance can be determined

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6
Q

Mechanism of metabolic alkalosis

A

increase PCO2

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7
Q

What are causes of respiratory alkalosis

A 
Increased minute ventilation
Over ventilation
Abnormal CNS ventilation
pulmonary insult (PE)
Liver failure
sepsis
pregnancy
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8
Q

Abnormal renal [hco3] reabsorption and [h] elimination is…

A

Metabolic acidosis or alkalosis

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9
Q

Characteristics of Oxyhgb dissociation curve in lungs vs tissues/capillaries

A

O2 uptake in lungs
• Bloody nearly saturated
• Across large range of tensions (LEFT shift)
During passage through systemic capillaries
• Large amount of O2 released (RIGHT shift)
• Relatively small drop in tension
 As long as blood is saturated

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10
Q

What is the diagnostic accuracy of invasive BP monitoring?

A

About 80% accurate
• For color change at 5 second
Pulse oximetry, Doppler doesn’t improve

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11
Q

Describe waveforms of art-line

A 
1: systolic upstroke
•	Pulsatile flow down artery
2: systolic peak pressure
•	As ventricle repolarizes
3: systolic decline
•	Begin diastole
4: dicrotic notch
•	Produced by blood pushing back on aortic valve
•	Diastole
5: diastolic runoff
•	Atrial contraction
6: end-diastolic pressure
•	DBP
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12
Q

Causes of increased PetCO2 d/t decreased alveolar ventilation

A 
Hypoventilation
Resp center depression
NM disease
High spinal anesthesia
COPD
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13
Q

Drawback to sidestream EtCO2 measurement

A

analyzers have a delay time and rise time

the concept being similar to other expired gas analysis

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14
Q

What determines pH in ECF?

A

A-B balance between [HCO3] and [CO2]

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15
Q

What physiologic action alters CO2?

Why is this important?

A
  • lung ventilation

- Can help correct respiratory disorders quickly

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16
Q

AANA monitoring standards
Oxygenation
Ventilation
CV

A 
Oxygenation
	Clinical observation
	Pulse oximetry
	ABG’s as indicated
Ventilation
	Auscultation
	Chest excursion
	ETCO2
	Pressure monitors as indicated
Cardiovascular
	ECG
	Auscultation as needed
	BP and HR q 5minutes
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17
Q

Disadvantages of automatic BP. Rationales

A 
Unsuitable in rapidly changing situations
Patient discomfort
Clinical limitations
•	Extremes of heart rate, pressure
Can cause trauma d/t frequent recycling
•	Coagulopathies
•	Peripheral neuropathies
•	Arterial/venous insufficiency
•	Compartment syndrome
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18
Q

What is the degree of weak acid dissociation determined by?

What are examples of weak acids?

A

pH
Temperature

Examples:
albumin, phosphate

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19
Q

What are symptoms of respiratory acidosis

A

vasodilation
narcosis
cyanosis

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20
Q

Arterial line complications

A 
Distal ischemia or pseudoaneurysm
Hemorrhage, hematoma
Arterial embolization
Local infection
Peripheral neuropathy
•	Nerves and vessels in close proximity
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21
Q

What is the Stewart approach to A-B balance interpretation?

A

Understanding how strong ion difference (SID), weak acid concentration [Atot] and PaCO2 affect AND explain A-B balance

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22
Q

What is SaO2

A

A ratio of reduced (deoxygenated) Hb to all Hb

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23
Q

What are limitations and their causes to auscultating BP

A 
	↓ peripheral flow
•	Shock
•	Intense vasoconstriction
	Changes in vessel compliance
•	Severe edema
•	Calcific arteriosclerosis
	Shivering
	incorrect cuff size
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24
Q

What is systolic pressure variation represent and why does it occur

A

SV changes btwn LH and RH

D/T increased intrathoracic pressure and lung volumes

INC LH and DEC RH SBP d/t end-exp pressure

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25
What happens when lung volume increases from increased intrathoracic pressure to left ventricular preload, afterload, SV
INC LV preload DEC LV afterload INC LV SV
26
Invasive BP monitoring sites
``` Radial Brachial Posterior tibial Axillary Dorsalis pedis Femoral ```
27
Describe the stepwise approach of the traditional A-B analysis. 7 steps
1. Is patient hypoxic? 2. Is the pH normal? 3. Is it respiratory or metabolic? and What are PaCO2 and HCO3 levels? 4. Simple or mixed? 5. Compensated, partially or uncompensated? 6. Suspected or actual cause? 7. Treatment?
28
How is systolic pressure variation measured? Effects of mechanical ventilation
 Min pressure, compared to Max pressure  In mechanically ventilated patients • Normal = 7-10mmHg total
29
Treatment of respiratory acidosis
Increase Vm Ventilator setting changes = increase RR or Vt Treat cause
30
How are arterial waveforms made?
Summation of sine waves Fundamental wave + harmonic wave = typical pressure wave •Fundamental wave = Expansion & contraction of vessel in response to pressure wave • Systolic •Harmonic wave = “echo” or “ripple” effect of wave • Diastolic
31
What happens when lung volume increases from increased intrathoracic pressure to right ventricular preload, afterload, SV
DEC RH preload/VR INC RH afterload DEC RH SV
32
Distal pulse difference in waveforms in periphery
``` As pressure wave moves TO periphery: • Arterial upstroke steeper • Systolic peak higher • Dicrotic notch later • Seen later in waveform  Longer distance for sine wave to travel • End-diastolic pressure lower • Wider pulse pressure ```
33
What are the 3 major causes of decreased PetCO2
Equipment malfunction Decreased CO2 production and delivery to lungs Increased alveolar ventilation
34
Acidic or alkalotic? [H+] > [OH-] [OH-]>[H+]
[H+] > [OH-] = acidic | [OH-]>[H+] = alkalotic
35
What is the bohr equation
(Vd/Vt) = [(PACO2 - PeCO2)/PACO2)
36
What happens to dissociation curve if blood poorly saturated
• Small amounts of O2 released • LARGER drop in tension  Steep slope of dissociation curve
37
What is the treatment for respiratory alkalosis?
Decrease minute ventilation Make ventilator changes (dec RR or Vt) Treat cause
38
What are 3 rules of A-B balance
- Electrical neutrality - Dissociation equilibriums - Mass conservation
39
4 types of adult hb
* Oxyhemoglobin (HbO2) * Reduced Hb (deoxy) * Methemoglobin (metHb) * Carboxyhemoglobin (COHb)
40
Pulse pressure variation equation
PPV=[(PPmax-PPmin)/(PPmax + PPmin)/2] x100
41
EtCO2 monitor requirements
CO2 reading within +/- 12% of actual value Manufacturers must disclose interference caused by ethanol, acetone, halogenated volatiles Must have a high CO2 alarm for inhaled and exhaled CO2 Must have an alarm for low exhaled CO2
42
What are Korotkoff phases?
``` Phase 1 • the most turbulent/audible (SBP) Phase II-III • sound character changes Phase IV-V • muffled/absent (DBP) ```
43
How does HbCO compare to HbO2 at 660 and 940? How does HbCO affect SpO2, especially in smokers?
 Absorbs as much light in the 660 nm range as oxyhemoglobin does  Falsely elevates SpO2  Each 1% ↑ COHb will ↑ SpO2 1%  Many smokers have >6% COHb
44
What is SVV
Computer analysis of arterial pulse pressure waveform Area under the waveform Correlates resistance and compliance  based on age, gender  computes SV
45
Describe the Allen's test
``` Compresses radial and ulnar arteries Patient makes a tight fist • Exsanguinating the palm Patient opens hand Release ulnar artery • Color of palm should return in < 10 seconds ```
46
SV pressure curve and contractility
slope directly r/t contractility High slope = high contractility INC stretch = INC contractility = INC CO/SV Low slope = low contractility Less stretch = low contractility = dec CO/SV d/t dec preload
47
What occurs to substances with polar bonds in water
They dissolve or dissociate into component parts
48
Degree of H2O dissociation and [H+] is affected by what 3 things
Strong ions Weak Acids CO2
49
How is light absorption affected by solute concentration?
Light absorption must be measured at wavelengths equal to the number of solutes • More solutes = more light absorbed • Less solutes absorbs less light
50
What are symptoms of respiratory alkalosis?
Vasoconstriction, lightheadedness, visual disturbances, dizziness, possible hypocalcemia
51
Physiologic cause of metabolic alkalosis
Net loss of H+ | addition of HCO3-
52
Causes, solutions and description of underdampened system
``` •↑ SBP = exaggerated •Square wave  Too much oscillation •System TOO responsive (↑ resonance) d/t: • Longer tubing  Transmits extra waveforms  Fix=Decrease tubing length • Tubing too distensible  Fix=Use stiffer tubing ```
53
What is the traditional and stewart interpretation of respiratory
Traditional = increased PaCO2 and decreased pH Stewart = increased PaCO2
54
What factors are considered in the Stewart approach?
- PaCO2 - Strong ion difference (SID) - Total weak acid concentration [Atot]
55
Principles of distal pulse amplification
Arterial pressures measured at different sites will have different morphologies • Due to impedence changes along vascular tree
56
Causes of hypocarbia
Respiratory alkalosis Decreases CBF Potassium shifts to the intracellular space Blunts normal urge to breath
57
Equation for SVV
 SVV= SV max – SV min / SV mean
58
Inflation and bladder standards for BP
``` Maximum cuff pressure • 300mm Hg for adults • 150mm Hg for neonates To prevent extended inflation  Cuff bladder • 40% of arm circumference • 80% of length of upper arm ```
59
Expected PCO2 compensation in metabolic alkalosis
PaCO@ = (0.7 x HCO3-) +20
60
``` What is normal range of PaO2 pH PaCO2 HCO3 Anion Gap ```
``` PaO2= 80-100 mmHg (90) pH= 7.35-7.45 (7.4) PaCO2= 35-45 mmHg (40) HCO3= 22-26 mEq/L (24) Anion Gap= 14-18 mEq/L (16) ```
61
What does and increased SPV indicated? How should it be addressed?
indicates= early hypovolemia Give fluid
62
SpO2 limitations (10)
```  Failure to determine sat  Poor function with poor perfusion  Difficulty in detecting high partial pressures  Delayed hypoxic event detection  Erratic performance with dysrhythmias  Inaccuracy with different hgb Inaccuracy with dyes  Optical interference  Nail polish and coverings  Motion artifact ```
63
Causes of hypercarbia
Respiratory acidosis Increases cerebral blood flow Increases ICP in susceptible patients Increased pulmonary vascular resistance Potassium shifts from intracellular to intravascular
64
How are SID and Atot related?
Inversely Acidosis = DEC SID/INC Atot Alkalosis = INC SID/DEC Atot
65
How is light transmitted when measuring SpO2
``` Via  Skin  Soft tissue  Venous blood  Arterial blood  Capillary blood ```
66
How do changes in SID affect A-B balance? What is normal ECF SID?
- Changes in SID cause changes in [H] and [OH] - INCREASED SID = alkalosis - DECREASED SID = Acidosis -Normal = 40-44 mEq/L
67
Advantages of automatic BP
``` Automaticity Simplicity Noninvasive Reliable Monitor integration • Pulse ox doesn’t alarm if BP monitor inflates ```
68
First knowledge of pulse? First recorded BP ? First sphygmomanometer?
 Ancient China and India had some knowledge of pulse  1st recorded blood pressure: 1733 by Reverend Hales on a horse  1st sphygmomanometer: 1881 invented by Samuel von Basch
69
What are the signs of acute and chronic respiratory alkalosis compensation
Acute = HCO3 will decrease 2 mEq/L for q 10 mmHg decreased CO2 (down to 20) Chronic = HCO2 will decrease 5 mEq/L for q 10 mmHg decreased CO2 (down to 20)
70
Traditional and stewart interpretation of respiratory alkalosis
``` Traditional = decreased PCO2 and increased pH Stewart = Decreased PCO2 ```
71
Accuracy of SpO2 compared to ABG
 Accurate (+/- 2%) • when measured against ABG’s (sat > 70%) • Not as accurate w/ sat<70%
72
How does peripheral vasoconstriction affect SpO2 and what can lead to it.
* Cold or exogenous catecholamines | * Decrease in pulsatile strength
73
Causes of metabolic alkalosis
``` Common = GI loss (excess GI suction and Cl- loss) Diuretics Diarrhea Third spacing bleeding hypokalemia ```
74
What is dampening in the art-line system
* Decreases system resonance | * Prevents exaggerated waveforms
75
Treatment of metabolic alkalosis
Hypoventilation Fluid replacement treat cause
76
What is the ratio of ratios
R= (AC 660/DC 660) / (AC 940/DC 940)
77
Abnormal CO2 levels primarily causes...
Respiratory acidosis or alkalosis
78
Describe the function of automatic flush, zeroing and leveling the invasive BP monitor
Automatic flush • 1-3ml/hr • prevents thrombus formation Zeroing • References pressures against atmospheric air Leveling • Typically  aortic root • midchest/midaxillary line • Level where you want to monitor
79
Traditional and stewart interpretation of metabolic alkalosis
Traditional= Increased HCO3 and increased pH Stewart= Increased SID, Cations > anions
80
How is [Atot] related to A-B balance?
Increased [Atot] = acidosis | Decreased [Atot]= alkalosis
81
Causes increased PetCO2 due to increased CO2 production/delivery
``` INC metabolic rate Fever/sepsis Sz MH Thyrotoxicosis Inc CO HCO3 admin ```
82
How does equipment malfunction cause decreased Petco@
Vent disconnection Esophageal intubation Complete airway obstruction leak around ETT
83
Describe the square wave test & purpose
``` Fast flush • Waveform becomes square • Flush pressure high matching pressure on bag Release of fast flush • Produces oscillations • No more than 2 oscillations • Subsequent oscillations = 1/3rd height of previous This indicates presence of dampening ```
84
What does degree of dissociation of a substance in water determine?
If the substance is a strong acid or base
85
Causes of increased PetCO2 d/t equipment failure
Rebreathing Exhausted SODA lime Faulty ins/exp valves
86
What does the pulse oximeter actually measure and how
Pulsatile expansion of the artery • ↑ length of light path • ↑ absorbency
87
How is EtCO2 clinically measured
Most commonly relies on IR absorption techniques The greater the CO2 in the sample, the less IR that reaches the detector Samples are extracted by one of two methods… - Mainstream (non-diverting) - Sidestream (diverting)
88
EtCO2 chemical indicator
Semi-quantitative Color change of pH sensitive paper (Litmus) A type of capnoMETER
89
What is the automatic non-invasive BP technique
``` Based on oscillometry • The maximal amplitude is MAP • SBP and DBP calculated from algorithm • SBP usually 25-50% of MAP amplitude • DBP is least accurate Roughly  to directly measured arterial pressure • When MAP = 75 mmHg ```
90
When would monitoring SpO2 on toes be appropriate?
* may be more reliable with epidural blocks | * Vasodilation from block improves pulsatile flow
91
difference in capnometry and capnography
Capnometry -The measurement and quantification of inhaled/exhaled CO2 Capnography -The method of measurement but also a graphic display or time
92
What does increased and decreased SID indicate
Increased = presence of unmeasured ANIONS Decreased = presence of unmeasured CATIONS
93
What are the major causes of increased PetCO2
Increased CO2 production/delivery to lungs Decreased alveolar vent Equipment malfunction
94
Tips for monitoring SpO2 on fingers
• Dark polish or synthetic nails inhibit transmission Absorbs or redirects light • Detection of desaturation and resaturation is slower peripherally • Don’t put on index finger High use = ↑ artifact • sensitive to vasoconstriction
95
How does decrease alv vent cause decreased PetCO2
Hyperventilation
96
Indications for invasive BP monitoring
```  Continuous needed, real-time  Planned pharmacologic manipulation  Repeated blood sampling  Determination of volume responsiveness  Timing of IABP counterpulsation ```
97
What is pulse oximetry
Absorbance of light Light through matter | • Transmitted, absorbed or reflected
98
What are the signs of acute and chronic respiratory acidosis compensation?
Acute = increase 1 mmHg for q 10 mmHg (>40) Chronic= increase 4 mEq/L for q 10 mmHg (>40)
99
What information does EtCO2 give and how does it correlate w/ PaCO2
informs us about PACO2 | Approximates PaCO2 about 4 mmHg
100
If EtCO2 is 36 mmHg what is PaCO2 estimate
PaCO2 = ~40 mmHg
101
Disadvantages of invasive BP monitor at brachial, DP, and femoral sites
``` Brachial • Not used much d/t poor collateral flow Dorsalis Pedis • Much smaller  Femoral • Easy to access • Better in emergency situations • Problems • Much more positional • Infection complications • Ligament injury ```
102
How does dec CO2 production/delivery to lund cause dec PetCO2
``` Hypothermia Arrest PE Hemorrhage HoTN ```
103
What are normal up and down variations for SPV
 Normal UP= 2-4mmHg |  Normal DOWN= 5-6mmHg
104
What is strong ion difference (SID)
SID = strong cations - strong anions | SD=(Na + K + Ca2 + Mg2) - (Cl- + lactate)
105
What are causes of SpO2 signal artifact and how are they corrected?
``` -Ambient light solved by alternating red/infrared -Low perfusion if signal amplified, artifact is too -venous blood pulsation Longer signal, slower change -Additional lights IV dyes, New pulse ox w/ 8 wavelengths filters dye -Additional forms of Hb ```
106
What are symptoms of metabolic alkalosis
Widespread vasoconstriction lightheadedness tetany paresthesia
107
What does SVV calculation rely on? | What is normal SVV
Assumes SR, Vt 8 ml/kg, stable respiration normal = 13%
108
Difference between uncompensated, partially compensated and fully compensated A-B disorders?
uncompensated= abnormal pH and CO2/HCO3 Partially compensated = pH abnormal and both CO2 and HCO3 are adjusting in same direction. Fully compensated = pH normal, CO2 and HCO3 abnormal and adjusted in same direction
109
Causes of respiratory acidosis
Primary = lungs fail to eliminate CO2-hypoventilation Drug related resp depression/OD Neuro injury Lung injury/disease (COPD, ARDS etc) NMBD
110
What is the best method to confirm endotracheal intubation
Detection of carbon dioxide breath-by-breath the
111
Which SpO2 monitoring sights are most sensitive and why
Tongue, Cheek, Forehead • less affected by vasoconstriction • reflects desat quicker
112
How is hydrogen ion concentration measured?
pH (negative log of H concentration)
113
Invasive BP placement techniques
1st: Seldinger’s Technique • Use of guidewire passed through needle ``` 2nd: Transfixion Technique • Same positioning and preparation • Front and back walls are punctured intentionally • Needle removed • Catheter withdrawn until pulsatile blood flow appears and then advanced • Difficult with  Long caths  Small & stiff caths  Low BP may not be as pulsatile -not associated w/ more complications ```
114
What pathology can alter art-line waveform (7)
``` Age: lack of distensibility Atherosclerosis • ↑SBP; ↓DBP? Embolism • Clot on cath Arterial dissection Shock Hypothermia Vasopressor infusions ```
115
What is an abnormal pulse pressure variation and what does it indicate? How should it be addressed?
abnormal = >17% Decrease preload and increased intravascular volume Fix= volume resus
116
How can invasive BP monitoring waveform be maximized
``` •Limit stopcocks •limit tubing length • ↑s waveform falsely ↑ BP •non-distensible tubing • Prevents pulsatile expansion  So that waveform isn’t amplified by tubing ```
117
Advantages of SpO2 (10)
``` Accurate Not affected by gas Noninvasive continuous Can indicate decreased CO Convenient Tone modulation Probe variety Battery operated Economical ```
118
What are Korotkoff sounds?
 Series of audible frequencies |  Produced by turbulent flow beyond partially occluding cuff
119
Describe weak acid dissociation in H2O?
Partially dissociates in H2O | Degree of dissociation determined by: pH and temp
120
How is pulse pressure measured and what does it indicate? | What is normal
utilizes max and min pulse pressures over entire respiratory cycle Normal <13% ∆  Maximal difference in arterial pulse pressure  Divided by average of max & min pulse pressures  Normal 13-17%
121
``` AANA monitoring standards Thermoregulation Neuromuscular Positioning and protection Additional Omission ```
-Thermoregulation  When significant ∆ in body temp are anticipated or suspected -Neuromuscular  When NM blocking agents are administered -Positioning and protective measures  Except aspects performed exclusively by other providers  Note no involvement, or check yourself -Additional means  depending on needs of patient, surgical technique or procedure -Omission with reason must be charted  Reason why monitoring wasn’t done
122
What is the Boston approach to A-B analysis?
A-B maps and relationship between CO2 and HCO23
123
What is AC and DC
``` AC = pulsatile DC = non-pulsatile ```
124
Why analyze waveform
 Hemodynamic resuscitation = begins w/ adequate preload |  Who would benefit from ↑ preload ”reserve”

Principles of Anesthesia I (4 decks)

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