Mod1: Monitoring for Cardiac Surgery - BLOOD PRESSURE MONITORING Flashcards

1
Q

BLOOD PRESSURE MONITORING​

What is the Most frequently monitored hemodynamic variable?

A

BLOOD PRESSURE

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2
Q

BLOOD PRESSURE MONITORING​

Which information is made available to us via the MAP?

A

Organ perfusion

(Especially Brain, Liver and Kidneys)

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3
Q

BLOOD PRESSURE MONITORING​

Which information is made available to us via the diastolic blood pressure?

A

Coronary perfusion

(Coronaries feel during diastole)

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4
Q

BLOOD PRESSURE MONITORING

Which information is made available to us via the Pulse pressure?

A

Stroke Volume

(Volume status)

CO

SVR

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5
Q

BLOOD PRESSURE MONITORING

Why is Noninvasive BP not typically used as primary BP monitoring during CPB?

A

Inadequacy of monitoring hemodynamic parameters

Inaccurate at extreme pressures

Intermittent data, not continuous

Requires pulsatile flow (which is not available during CPB)

Often used merely as adjunct to direct arterial blood pressure monitoring

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6
Q

BLOOD PRESSURE MONITORING

What remains the “Gold Standard” for monitoring BP during cardiac surgery?

A

Direct arterial blood pressure

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7
Q

BLOOD PRESSURE MONITORING

What are advantages of Direct arterial blood pressure monitoring?

A

Displays real-time blood pressure monitoring

Allows for pharmacological or mechanical BP manipulation while maintaining awareness of beat to beat BP

Allows for analysis of waveform can give information on SVR, SV, and cardiac output

Allows for close monitoring of ABG’s, coagulation (ACT’s), and electrolytes

Allows for Direct ABP monitoring possible during non-pulsatile CPB

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8
Q

BLOOD PRESSURE MONITORING

Which information can be gathered via analysis of direct arterial BP waveform?

A

Cardiac Output

SV

SVR

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9
Q

INTERPRETING ARTERIAL WAVEFORM

Which wave on the QRS complex represents the begining of systole?

A

The R-wave

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10
Q

INTERPRETING ARTERIAL WAVEFORM

When does the arterial pulse wave occur in reference to the ECG tracing?

A

160-180 milliseconds after the R-wave

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11
Q

INTERPRETING ARTERIAL WAVEFORM

What happens during the Systolic phase or Systolic upstroke?

What is it associated with on the ECG tracing?

A

Begins with a Rapid increase of pressure to a peak

Opening of the Aortic valve

Blood ejecting into the aorta from LV

Peak systole = Systolic BP

Follows the R-wave on EKG

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12
Q

INTERPRETING ARTERIAL WAVEFORM

What happens during the Systolic runoff?

A

Represents the time when

the eflux of blood out of the ventricle is lower than

the influx of blood into the aorta

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13
Q

INTERPRETING ARTERIAL WAVEFORM

What does the Dicrotic notch represents?

A

Closure of the aortic valve

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14
Q

INTERPRETING ARTERIAL WAVEFORM

What happens during the “diastolic runoff”?

A

Drop in pressure that occurs after the aortic valve closes

Blood is now going into the peripheral circulation

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15
Q

INTERPRETING ARTERIAL WAVEFORM

What does End-Diastolic-Blood-Pressure (EDBP) also referred to as “Aortic Diastolic Pressure” represents?

A

Pressure exerted by the vasculature back onto the aortic valve

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16
Q

INTERPRETING ARTERIAL WAVEFORM

What reflects DBP on the arterial waveform?

A

Lowest reading before the next systolic upstroke

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17
Q

INTERPRETING ARTERIAL WAVEFORM

What reflects MAP on the arterial waveform?

A

Area under the curve

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18
Q

INTERPRETING ARTERIAL WAVEFORM

How is Pulse pressure calculated?

What is its normal value?

A

PP = SBP - DBP

Normal value: 40 - 60 mmHg

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19
Q

INTERPRETING ARTERIAL WAVEFORM

Which informations could be gathered via Pulse Pressure?

A

Fluid status and Vascular competence

Via SV, CO, and SVR

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20
Q

INTERPRETING ARTERIAL WAVEFORM

What could a Narrow PP (less than 40mmHg) indicate?

A

Hypovolemia

Cardiac tamponade

Anything that causes a low CO state

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21
Q

INTERPRETING ARTERIAL WAVEFORM

What could a Widened PP (more than 60mmHg) indicate?

A

Worsening aortic valve insufficiency

Usually Aortic Regurgitation

During diastole, the arterial BP will drop to backfill the LV through that regurgitant aortic valve that is supposed to be closed

May also get what’s called Bisferiens pulse which occurs d/t to run off of blood into the periphery and into the LV

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22
Q

INTERPRETING ARTERIAL WAVEFORM

What’s another name for the biphasic-pulse aortic waveform that shows two peaks per cardiac cycle, a small one followed by a strong and broad one? What does it indicate?

A

Bisferiens pulse

It is a sign of problems with the aortic valve, including aortic stenosis and aortic regurgitation, as well as hypertrophic cardiomyopathy causing subaortic stenosis

It is associated with a widened Pulse pressure

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23
Q

INTERPRETING ARTERIAL WAVEFORM

Explain the mechanics of Systolic Pressure Variation (SPV), volume status, and how it affects SBP?

A

PPV causes and increase in intrathoracic pressure which impedes VR, compresses the lungs, and causes blood in the pulmonary vasculature to be pushed to the left side of the heart, and ejected with each beat

This result in increase in BP during inspiration

During expiration, there is no augmentation to the amount of blood pumped out, resulting in a decrease in SBP

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24
Q

INTERPRETING ARTERIAL WAVEFORM

What’s the normal value of Systolic Pressure Variation (SPV)

A

10 mmHg

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25
INTERPRETING ARTERIAL WAVEFORM What do large variations in Systolic Pressure Variation (\>15 mmHg) indicate? How do this affect ABP?
**Hypovolemia =** ↓ ABP with PPV Patients are said to be hypovolemic when the respiratory variations are more than 15mmHg. It’s the same exact concept as SVV (stroke volume variation) SVV is measured as percent
26
INTERPRETING ARTERIAL WAVEFORM What does the ARTERIAL WAVEFORM reflects?
Changes in pressures over time Qualitative estimates of hemodynamic indices of Contractility, SV, SVR
27
INTERPRETING ARTERIAL WAVEFORM On the following chart, what does "a" represents?
**Contractility** Grossly judged by rate of pressure rise/slope of upstroke during systole The steeper the slope, the quicker the rise, the greater the contractile forces Converly, the shallower the slope, the slower the rise and the weaker the contractile forces *This is a controversial way to the determine the pt's volume status*
28
INTERPRETING ARTERIAL WAVEFORM On the following chart, what does "b" represents?
**Stroke Volume** Area under the aortic pressure waveform Onset of systole to _dicrotic notch_
29
INTERPRETING ARTERIAL WAVEFORM What determines the location of the Dicrotic notch?
Timing of the Aortic closure in the cardiac cycle
30
INTERPRETING ARTERIAL WAVEFORM What charaterizes Aortic closure and dicrotic notch location in pts that are hypovolemic?
Aortic closure occurs slower Consequently the Dicrotic notch occurs farther down the dicrotic limb
31
INTERPRETING ARTERIAL WAVEFORM Why is using arterial waveform interpretation alone to determine volume status controversial?
*The location of the arterial line itself affects where the Dicrotic nocth occurs on the dicrotic limb* Pts with radial arterial line or arterial lines that are more peripheral will have their Dicrotic nocth occur lower on the dicrotic limb vs pts with arterial lines placed more proximal (axillary or sunclavian arteries or aortic root) This is why you cannot necessarily use the location of the Dicrotic notch to determine volume status
32
INTERPRETING ARTERIAL WAVEFORM What on the arterial waveform represents Systemic Vascular resistance?
Position of Dicrotic notch ## Footnote * High on downslope = ↑ SVR* * Low on downslope = ↓ SVR*
33
INTERPRETING ARTERIAL WAVEFORM What value of SVR correspond to a Dicrotic notch High on downslope?
↑ SVR
34
INTERPRETING ARTERIAL WAVEFORM What value of SVR correspond to a Dicrotic notch Low on downslope?
↓ SVR
35
INTERPRETING ARTERIAL WAVEFORM What does the "c" on the chart represents?
**Systolic time**
36
INTERPRETING ARTERIAL WAVEFORM What does the "d" on the chart represents?
**Diastolic time**
37
ARTERIAL BP - SITES OF CANNULATION Why is the Radial artery the most common cannulation site?
Ease of placement Accurate estimation of true aortic pressure
38
ARTERIAL BP - SITES OF CANNULATION What are contraindications for radial arterial line placement?
Positive Allen’s test Radial artery harvest
39
ARTERIAL BP - SITES OF CANNULATION Why is the Allen’s test performed before radial artery line placement?
Too determine whether ulnar artery collateral circulation to the hand is present in the case of arterial thrombosis The test screens for pts with inadequate palmar collateralisation from the ulnar artery
40
ARTERIAL BP - SITES OF CANNULATION How is the Allen’s test performed?
Apply firm pressure over both the radial and ulnar arteries simultaneously while having the pt squeeze their hand to promote exanguination Release pressure over the ulnar artery, keeping the radial artery compressed Measure time for capillary refill of the nail bed
41
ARTERIAL BP - SITES OF CANNULATION What is a _positive_ **Allen's test**? What does a positive Allen's test indicate?
Capillary refill of nail bed **\>10 seconds** Indicates inadequate collateral circulation from the ulnar artery
42
ARTERIAL BP - SITES OF CANNULATION Why should the radial artery line be placed in opposite side if the IMA is to be harvested for graft?
Due to the **dampen** or **obliterate tracing** resulting from compression of chest wall & subclavian artery This slide states that if the IMA is to be harvested for grafting, the radial artery catheter should be placed on the opposite side. This is not practice that you will see. The main reason that the surgeon request that the radial artery catheter be placed on one side over the other is if he plans to harvest the radial artery for one of the bypass grafts. OR if there is some type of blockage in the subclavian that would preclude you from placing a catheter in it and reducing blood flow even more. And the reason is because of compression of the chest wall with the sternal retractor. However, this is not actual practice that you will see, although it theoretically could happen because the internal mammary arteries branch off the subclavian artery proximal to where the subclavian becomes the axillary artery. Here you can see the right subclavian artery and how the internal thoracic or internal mammary artery branches off the subclavian artery. This picture shows it branching off the axillary because the subclavian actually turns into the axillary artery as it passes underneath the clavicle. So theoretically, you could have an obliteration of the pulse with the sternal retractor that’s used to take down the mammary.
43
ARTERIAL BP - SITES OF CANNULATION Where should the arterial line be placed if both IMA’s are to be harvested?
F**emoral artery**
44
ARTERIAL BP - SITES OF CANNULATION Why is the use of the Brachial artery relatively contraindicated as a cannulation site?
Brachial artery has **no benefit of collateral flow** as does the ulnar Brachial artery (medial to the antecubital fossa)
45
ARTERIAL BP - SITES OF CANNULATION In which instances is Brachial artery cannulated?
Invasive BP monitoring is required, but Radial arteries cannot be cannulated for some reason
46
ARTERIAL BP - SITES OF CANNULATION True or False: Brachial arterial line are usually only used for short periods of time
True
47
ARTERIAL BP - SITES OF CANNULATION Why does Brachial arterial line more accurately reflects central aortic pressure than the radial artery?
C**loser to the heart**
48
ARTERIAL BP - SITES OF CANNULATION Why should shortest, smallest gauge (18 or less) cath be used for Brachial artery line cannulation?
To decrease the incidence of **thromboembolism**
49
ARTERIAL BP - SITES OF CANNULATION What's the largest vesselcommonly use to monitor arterial BP with comparable results to all other sites?
**Femoral artery** *Large & superficial making for easy access*
50
ARTERIAL BP - SITES OF CANNULATION Why is the Femoral artery an excellent access to the central arterial tree?
Its waveform more closely resemble aortic pressure waveform than do waveforms from more peripheral sites
51
ARTERIAL BP - SITES OF CANNULATION Why is there a Low risk of distal ischemic sequela with femoral artery cannulation?
Because of its large **Diameter**
52
ARTERIAL BP - SITES OF CANNULATION When is the risk for plaque immobilization and pseudoaneurysm significant with femoral artery line placement?
When initially placing the line
53
ARTERIAL BP - SITES OF CANNULATION Why should the femoral artery be placed below the inguinal line?
To reduce the risk of damaging the **inguinal liguament**
54
ARTERIAL BP - SITES OF CANNULATION True or False: during femoral cannulation, you must be cautious of hitting a hematoma or creating uncontrolled hematomas into the pelvis or retroperitoneal space
**True**
55
ARTERIAL BP - SITES OF CANNULATION Why femoral artery cannulation suggested in pts with expected difficulty weaning from CPB d/t known ↓ EF or severe wall motion abnormalities?
They may require IABP Access may be used should IABP placement become necessary
56
ARTERIAL BP - SITES OF CANNULATION What are contraindications to femoral artery cannulation?
Prior vascular surgery Skin infection
57
ARTERIAL BP - SITES OF CANNULATION What are advantages of Axillary artery cannulation?
More comfortable for the patient Large and superficial Easy access to central arterial tree Provides a central arterial pressure waveform that more closely resemble the aortic root pressure
58
ARTERIAL BP - SITES OF CANNULATION Why is there increased risk of cerebral embolus of air or debris with axillary artery cannulation?
Because cannulation site more centrally located Air or debris can easily enter the circulation during flushing of the catheter
59
ARTERIAL BP - SITES OF CANNULATION Why is left axillary cannulation preferred?
Reduce risk of cerebral embolus of air or debris
60
ARTERIAL BP - SITES OF CANNULATION What could cause nerve damage with axillary catheter placement?
Hematoma formation Traumatic cannulation
61
ARTERIAL BP - SITES OF CANNULATION True or False: Infection at site is a contraindication for axillary artery cannulation
True
62
ARTERIAL BP - SITES OF CANNULATION When is Aortic root cannulation indicated for arterial BP monitoring? Who places it?
When difficulties are encountered in obtaining reliable BP Placed by surgeon
63
ARTERIAL BP - SITES OF CANNULATION Ulnar artery cannulation is rare. The Process for cannulation of the ulnar artery is similar to that of which other vessel?
The radial artery
64
ARTERIAL BP - SITES OF CANNULATION True or False: Ulnar artery provides most of the blood flow to the hand in 90 percent of pt
True
65
ARTERIAL BP - SITES OF CANNULATION In which instances is the ulnar artery cannulated?
When radial artery can not be used Positive Allen’s Harvest for graft
66
ARTERIAL BP - SITES OF CANNULATION Allen's test must be performed prior to ulnar catheter placement. How does Allen's test for ulnar artery cannulation differ to that for radial artery cannulation?
*Occlude the ulnar artery* and assess for adequate radial artery collateral flow
67
ARTERIAL BP - SITES OF CANNULATION What are disadvantages of using Dorsalis pedis and posterior tibial arteries as cannulation sites for BP monitoring?
Difficult management in postop period Difficult cannulation Increased risk for ischemic complications Relative contraindication with PVD/DM Distal location increases distortion of waveform
68
ARTERIAL BP - SITES OF CANNULATION In which population is it appropriate to use Dorsalis pedis and posterior tibial arteries as cannulation sites?
Pediatrics
69
Direct Arterial Blood Pressure As cannulation site becomes more peripheral, what happens to **Arterial upstroke**?
Becomes **steeper**
70
Direct Arterial Blood Pressure As cannulation site becomes more peripheral, what happens to **Systolic peak**?
Becomes **higher**
71
Direct Arterial Blood Pressure As cannulation site becomes more peripheral, when does the **Dicrotic notch** appears?
**Later!!!**
72
Direct Arterial Blood Pressure As cannulation site becomes more peripheral, what happens to **Diastolic wave**?
Becomes more prominent
73
Direct Arterial Blood Pressure As cannulation site becomes more peripheral, what happens to **End diastolic pressure**?
Becomes lower
74
Direct Arterial Blood Pressure As cannulation site becomes more peripheral, what happens to **Systolic pressure**?
Systolic pressure increases (as much as **20-50mmHg higher** than central aorta)
75
Direct Arterial Blood Pressure As cannulation site becomes more peripheral, what happens to **Diastolic pressure**?
Becomes lower
76
Direct Arterial Blood Pressure As cannulation site becomes more peripheral, what happens to **Pulse pressure**?
Wider pulse pressure
77
Direct Arterial Blood Pressure As cannulation site becomes more peripheral, what happens to **MAP**?
MAP remains relatively unchanged
78
ARTERIAL BLOOD PRESSURE MONITORING - COMPLICATIONS What are common complications associated with arterial blood pressure monitoring?
Distal ischemia (low) Arterial thrombosis Infection Bleeding
79
ARTERIAL BLOOD PRESSURE MONITORING - COMPLICATIONS What's is the most common site of arterial BP cannulation for CPB?
The radial artery
80
ARTERIAL BLOOD PRESSURE MONITORING - COMPLICATIONS Sometimes, False low of radial artery pressure is seen immediately after CPB. What could be responsible of lower BP immediately after CPB?
Peripheral vasodilation secondary to rewarming Hypovolemia Vasoconstriction *If suspect that peripheral artery tracing is dampened (slow upstroke or loss of dicrotic notch), obtain a direct pressure measurement from central site*
81
ARTERIAL BLOOD PRESSURE MONITORING - COMPLICATIONS Sometimes, False low of radial artery pressure is seen immediately after CPB. What would the surgeon do if this is suspected?​
The surgeon will sometimes place a catheter into the aortic root and transduce it to compare it to the radial artery pressure And if it is in fact lower, an alternate site will be chosen to place an arterial line
82
RECOMMENDATIONS FOR BLOOD PRESSURE MONITORING DURING CPB T/F: Radial artery pressure is usually accurate before and after CPB
True
83
RECOMMENDATIONS FOR BLOOD PRESSURE MONITORING DURING CPB When is Addition of a femoral artery catheter recommended?
Poor LV function is evident Second comparable (central) BP (BP from a more peripheral site is questionable) Ensures arterial access should IABP become necessary
84
RECOMMENDATIONS FOR BLOOD PRESSURE MONITORING DURING CPB If IMA is to be harvested for grafting, why should you place radial artery catheter in opposite side
Compression of chest wall/subclavian artery =\> dampens/obliterates tracing This is not necessarily practice Theoretically, because the IMA branches from the SC artery, occlusion could occur to the radial artery This is rarely seen unless the pt has some sort of blockage in the sc artery
85
RECOMMENDATIONS FOR BLOOD PRESSURE MONITORING DURING CPB If both IMA’s are to be harvested, where should the arterial cannulation be placed?
Place femoral artery catheter
86
RECOMMENDATIONS FOR BLOOD PRESSURE MONITORING DURING CPB If radial artery to be harvested, where should you place arterial line?
Place radial arterial line on **opposite side**
87
RECOMMENDATIONS FOR BLOOD PRESSURE MONITORING DURING CPB When is the only time that the radial artery is cannulated on the opposite side?
Known blockage in the subclavian artery Radial artery is to be harvested