Pulse Ox, Capnography, Blood Pressure Monitoring Flashcards
(74 cards)
1
Q
Physiologic effects of hypercarbia (hypercapnia)
A
- Respiratory acidosis (decreases pH)
- Central (pulmonary) vasoconstriction (inc PVR)
- Peripheral and cerebral vasodilation (dec SVR, inc CBF, ICP)
- Sympathetic response/catecholamine release (epinephrine release, causes tachycardia and hypertension/vasoconstriction)
- CO2 narcosis (depresses respiratory drive at 70mmHg)
- Possible death
2
Q
PaCO2 equal to 1 MAC of inhalation anesthesia
A
200 mmHg
3
Q
Effects of hypocarbia (hypocapnia)
A
- Respiratory alkalosis (pH increases)
- Central (pulmonary) vasodilation (dec PVR)
- Peripheral and cerebral vasoconstriction (inc SVR, dec CBF and ICP)
4
Q
The rate at which CO2 rises during apnea
A
PaCO2 rises 6mmHg after the first minute of apnea
After each subsequent minute of apnea, PaCO2 rises 3-4 mmHg
5
Q
When the patient starts breathing over the ventilator
A
Curare cleft
6
Q
Treatments for a curare cleft
A
- Suppress the patient’s respiratory drive with propofol
- Redose paralytic or narcotic
- Increase the patient’s minute ventilation (which decreases EtCO2, decreases drive to breathe)
- Turn off vent and let patient breathe spontaneously
7
Q
Treatments of bucking
A
Turn off the ventilator!!
8
Q
EtCO2 waveform with COPD
A
upslope due to not being able to get the air out
9
Q
Esophageal intubation EtCO2 waveform
A
Small waves that fade out
10
Q
Causes of hypocapnea
A
- Hyperventilation
- Hypotension/low cardiac output
- Loose circuit connection
11
Q
Why is capnography important during MAC/sedation?
A
You still know the respiratory rate
You can detect apnea
12
Q
Cerebral autoregulation ranges
A
60-160 mmHg
13
Q
If blood pressure goes above the autoregulation range…
A
blood flow to the head will increase
14
Q
If blood pressure goes below the autoregulation range…
A
blood flow to the head will decrease
15
Q
The cerebral autoregulation curve shifts to the (R/L) in chronically hypertensive patient
A
Right
16
Q
Normal autoregulation for renal blood flow
A
80-180 mmHg
17
Q
Normal autoregulation for coronary blood flow
A
50-120 mmHg
18
Q
Impairment of autoregulation
A
- Ischemia
- Hypercarbia
- Acidosis
- High end tidal concentration of volatile agent
19
Q
A patient’s BP should be within ____ of their pre-op value
A
20-30% MAP
20
Q
Etiologies of hypotension
A
- Hypovolemia
- Vasodilation
- Patient positioning
- Vagal response
- Need for stress dose of steroids
- Decreased cardiac contractility/ejection fraction
- Too large of BP cuff
- Lateral decubitus position (upper arm)
21
Q
Treatments for hypotension
A
- Cause vasoconstriction w/vasopressors or dec inhalation agents
- Increase intravascular volume
- Change patient’s position
- Administer inotropes
- Give stress dose of steroids
22
Q
Types of blood pressure measurements
A
- Auscultation
- Doppler (only measures systolic)
- NIBP (oscillometry) -noninvasive blood pressure
- Noninvasive arterial line (tonometry)
- Arterial line
23
Q
Korotkoff sounds with sphygmomanometry (auscultation)
A
Disappear when artery is completely decompressed
Appears when artery is decompressed (systolic)
Disappear when artery is completely open (diastolic)
24
Q
NIBP cuff sizing
A
Width should be 20-50% greater than the diameter of the extremity
25
If a blood pressure cuff is too large...
underestimation of blood pressure
26
If a blood pressure cuff is too small...
overestimation of blood pressure
27
Systolic is (higher/lower) in the legs than the arm?
10-20 mmHg higher in the legs
28
Diastolic is (higher/lower) in the legs than the arm?
Equal or lower in the legs
29
MAP is (higher/lower) in the legs than in the arm?
Higher
30
Where do you avoid placing a BP cuff?
1. The operative arm
2. AV fistula
3. Same side as mastectomy or prior lymph removal
31
Disadvantage to noninvasive A-line
1. Sensitive to movement and exact placement
2. Requires frequent calibration
3. No arterial access to labs
32
In a patient not lying flat, the higher the measuring site, the (higher/lower) the blood pressure reading?
Lower
33
In a patient not lying flat, the lower the measuring site, the (higher/lower) the blood pressure reading?
Higher
34
How many oxygen molecules can hemoglobin bind?
4 -one for each subunit
35
How many hemoglobin molecules are in a RBC?
Around 300 million
36
The percentage of RBCs in blood
Hematocrit
Normal for males: 45%
Normal for females: 39%
Usually 3x Hgb
37
Decrease in Hgb or Hct
Anemia
38
Causes of anemia
1. Blood loss
2. Fluid administration
3. Lysed RBCs
4. Decreased production of RBCs (common w/renal failure)
39
PaO2
```
Partial pressure of oxygen in arteries
1.5% of all oxygen in the body
80-100 mmHg on RA
5x FiO2 in healthy patients
Decreases with age
```
40
PAO2
Partial pressure of oxygen in the alveoli
41
SaO2
Percentage of hemoglobin that is saturated with oxygen
| 98.5% of all oxygen in the body
42
Factors that determine PAO2
1. FiO2 (higher FiO2 = higher PAO2)
2. Barometric pressure (lower elevation = higher PAO2)
3. Minimal determination from minute ventilation
43
Factors that determine PaO2
PAO2, the lower PAO2, the lower the rate of diffusion in the blood, the lower the PaO2
44
Factors that determine SaO2
```
1. Mainly PaO2, hemoglobin soaks up oxygen until it is 100% saturated
Less effect:
2. pH
3. CO2
4. Temperature
5. Anemia
6. 2,3 DPG
7. Carboxyhemoglobin levels
8. Methemoglobin levels
```
45
How does supplementary oxygen affect PAO2, PaO2 and SaO2?
It increases, PAO2, which leads to greater diffusion into the blood and increases PaO2. PaO2 allows hemoglobin to soak up oxygen, increasing SaO2
46
The difference between PAO2 and PaO2
A-a gradient
47
Normal A-a gradient
5-15 mmHg on RA
| 10-110 mmHg on 100% FiO2
48
How does lung disease effect the A-a gradient?
It increases the gradient because oxygen will not have any issues getting into the alveoli, but will not be able to diffuse well into the blood. This does not change PAO2, but will decrease PaO2
49
According to the oxygen dissociation curve, when PaO2 is 60 mmHg, SaO2 will be
90%
50
What happens below a PaO2 of 60 mmHg?
Cerebral blood flow increases rapidly
51
When the PaO2 is 27 mmHg, SaO2 is ___ in adults
50%
52
Meaning and causes of a right shift of the oxygen dissociation curve
Means that a higher PaO2 is required to achieve the same SaO2
Hemoglobin is not holding oxygen well, there is better perfusion to the tissues
Causes:
Acidosis (increased CO2, decreased pH)
Increased 2,3 DPG
Anemia
Hyperthermia
53
Meaning and causes of a L shift of the oxygen dissociation curve
```
Does not require as high of PaO2 to achieve the same SaO2. Hemoglobin has a higher affinity for oxygen, does not release it to tissues well
Causes:
Alkalosis
Decreased 2,3 DPG
Hypothermia
Methemoglobinemia
Carboxyhemoglobinemia
```
54
Normal P50 values for adults
PaO2 = 27 mmHg, SaO2 =50%
55
P50 value for sickle cell anemia
31 mmHg (R shift)
56
P50 value for pregnant mother
30 mmHg (R shift)
57
P50 value for fetal hemoglobin
19 mmHg (L shift)
58
P50 value for packed RBCs
18 mmHg (L shift) caused by depleted 2,3 DPG
59
How to measure SaO2
Direct: arterial blood gas (ABG)
Indirect: pulse ox
60
Explain the physics of the SpO2 monitor
Oxygenated hemoglobin absorbs more infrared (940nm) light, allowing more red (660nm) light to pass through
Deoxygenated hemoglobin absorbs more red light (660nm), allowing more infrared light (940nm) to pass through
61
Bad SpO2 waveform can be caused by
1. Issues with the monitor
2. Low cardiac output
3. Decreased perfusion
62
How accurate is the SpO2 monitor?
95% accurate when the saturation is above 70%
4% error below 70% saturation
15% error below 50% saturation
63
Causes of low SpO2 despite normal SaO2
1. Inaccurate waveform (caused by hypotension/low cardiac output/vasoconstriction/cold patients/misplaced probe)
2. Motion or shivering
3. Diagnostic IV dye
4. Dark nail polish
5. Manual BP cuff inflation if BP is on same arm
64
Causes of low SaO2, despite normal SpO2
1. Carbon monoxide poisoning
| 2. Cyanide toxicity
65
Clinical implications of CO poisoning
CO binds to Hgb, displacing oxygen from it (230x more affinitive to Hgb than O2)
1, SaO2 is decreased
2. SpO2 reading is normal or elevated
3. PaO2 does not change
66
Causes of carboxyhemoglobin formation
1. Smoking/smoke inhalation
| 2. Dried out (dessicated) CO2 absorbant
67
How to diagnose CO poisoning
ABG or co-oximeter, red skin
68
Treatment of CO poisoning
Deliver 100% O2
69
Implications of cyanide poisoning
CN binds to Hgb
causes a decrease in SaO2
Normal SpO2 and PaO2
Diagnosed with ABG or co-oximeter
70
Causes of cyanide poisoning
1. High doses of nitroprusside (Nipride)
2. Smoke inhalation
3. Inhaling chemicals
71
Treatment of cyanide poisoning
1. Sodium Nitrate
| 2. Sodium Thiosulfate
72
Description of methemoglobinemia
```
Iron is oxidized and ends up with +3 charge
SaO2 decreases
SpO2 reads 85%
PaO2 does not change
Pt becomes cyanotic
DIagnosed with ABG or co-oximeter
```
73
Causes of MetHgb
1. High doses of nitroprusside (nipride)
2. High does of NTG
3. Local anesthestic spray in pharynx
4. Chemical inhalation
74
Treatment of MetHgb
Methylene blue
