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Chapter 18 Egans Special Topics > Pilbeams Chapter 11 > Flashcards

Pilbeams Chapter 11 Flashcards

1
Q

The filling pressure of the ventricle at the end of diastole

A

Preload
-Preload reflects the length of the ventricular muscle fibers and thus the ability of the fibers to generate the necessary tension in the next ventricular contraction.

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2
Q

During high ventricular volumes, when the muscle fibers are overstretched and unable to generate the necessary tension to elicit a contraction that will adequately eject the required SV, what is the end result?

A

Ventricle dilation and failure

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3
Q

What is the RVEDP?

A

Right ventricular end-diastolic pressure
-Typically used as an indicator of the right ventricular preload.

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4
Q

What is the LVEDP?

A

Left ventricular end-diastolic pressure
-Typically used as an estimate of left ventricular preload.

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5
Q

How is the RVEDP and the LVEDP measured?

A
  1. RAP (Right Atrial Pressure)
  2. Central Venous pressure
  3. PAOP (equal to the PCWP)
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6
Q

The CVP and the PAOP can accurately reflect the LVEDP and the RVEDP only when the former measurements are made at the end of ventricular diastole and if there is no presence of valve dysfunction. Why?

A

Because they are registering retrograde (backward) pressures in the right and left atria.

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7
Q

The force that the ventricle generates during each cardiac cycle.

A

Contractility
-Can be estimated using the ejection fraction.

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8
Q

How is the ejection fraction calculated?

A

The ratio of the SV and the end-diastolic volume.
Example: 70/140=0.5

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9
Q

What is the (dP/dT) equation used for?

A

An alternative way to estimate the force of ventricular muscle contraction. This equation represents the change in pressure relative to the change in time (dP/dT)

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10
Q

The impedance that the left and right ventricles must overcome to eject blood into the great vessels.

A

Afterload
-Better expressed as systemic and pulmonary vascular resistances.

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11
Q

The impedance that the LV must overcome to eject blood into the systemic circulation.

A

SVR (Systemic Vascular Resistance)

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12
Q

The impedance that the RV must overcome to eject blood into the pulmonary circulation.

A

PVR (Pulmonary Vascular Resistance)

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13
Q

Increases in afterload are associated with what?
(More resistance)

A

A decrease in CO

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14
Q

Decreases in afterload are associated with what?
(Less resistance)

A

An increase in CO

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15
Q

How does Systemic and Pulmonary hypertension affect SVR and PVR?

A

Systemic and Pulmonary hypertension cause SVR and PVR to increase. In both cases the CO will be reduced.

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16
Q

What treatment/medication will cause vasodilation in systemic and pulmonary vascular hypertension? (Vasodilators)

A

Systemic hypertension-Nitroprusside
Pulmonary hypertension-Tolazoline

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17
Q

Hemodynamic Monitoring Systems

A

A catheter is inserted into the peripheral artery, central vein or pulmonary artery. The catheter transmits pressure changes within the vessel through a heparin filled tube to a transducer and converts the pressure changes to a digital signal for display.

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18
Q

This hemodynamic monitoring device uses an electrical circuit to measure pressures.

A

Strain Gauge pressure transducer (Wheatstone)

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19
Q

The pressure exerted by fluid in motion is called what?

A

Dynamic pressure element
-The pressure applied to fluid inside a system by fluid outside a system.
-This has to do with catheter position in relation to the flow of blood within the vessel.

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20
Q

The pressure exerted by fluid at a standstill is called what?

A

Hydrostatic pressure

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21
Q

For an A-line placed in the radial artery to measure to accurately measure the left heart pressures, how should the catheter be placed?

A

With the end of the catheter facing the source of the blood flow.
(Looking upstream toward the LV)

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22
Q

A pulmonary artery catheter that measures the pressure within a vessel (capillaries or left heart chambers) how should the catheter be placed?

A

With the end of the catheter facing down stream

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23
Q

The pressure placed on a transducer as related to the tip of the catheter.

A

Static pressure head
- To measure pressure accurately, the transducer must be at the same height or level as the catheter tip.

-If the catheter tip is placed higher than the transducer, the monitor will read higher than the actual pressure as a result of fluid pushing down stream.

-If the catheter tip is placed lower than the transducer, the monitor will read lower than the actual pressure as a result of fluid flowing away from the transducer toward the catheter tip.

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24
Q

What is the degree of error when measuring?

A

1.86 mm Hg for every cm above the reference point

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25
Q

Where should the transducer be placed?

A

At the level of the mid-thoracic line of the patient (Epistatic line) to measure the CVP accurately.
-This is about 5 com behind the sternal angle.

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26
Q

How is systemic arterial pressure measured?

A

A catheter is placed into a peripheral artery (radial, brachial or femoral)
-Daily inspection of the surgical site for signs of infection, ischemia and bleeding to avoid serious complications.

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27
Q

What can increase the risk of infection in patients with an arterial line?

A

-Surgical cut down
-Prolonged cannulation (longer than 4 days)
-Altered host defense

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28
Q

What is the most common cause of decreased perfusion?

A

Thrombus formation, which occludes the catheter tip.

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29
Q

Hemorrhaging is a distinct possibility if the line is left open, how can this be avoided?

A

The clinician should stabilize the catheterized site by taping the patient’s arm to a board and keeping it above the blankets for easy observation.
-A hematoma is also a common problem when a large-gauge needle is used.

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30
Q

Catheters placed in the vena cava or right atria are called what?

A

Central Venous lines
-Central venous lines are most often used to administer fluids, drugs and nutritional solutions.
-Also, may be used to monitor right heart pressures

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31
Q

During ventricular systole or atrial diastole when the tricuspid valve is closed, what pressure is measured in the right atrium or vena cava?

A

RAP (Right atrial pressure)
-VSAD—Closed

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32
Q

At the end of ventricular diastole and atrial systole and the tricuspid valve is open, the pressure measured in the right atrium is called what?

A

RVP (Right ventricular pressure)
-VDAS—Open

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33
Q

The CVP measured at the end of ventricular diastole is used to monitor what?

A

-IV fluid administration and estimate the filling pressure (Preload) of the RV.
RVEDP.

34
Q

Where are the CVP lines inserted?

A

Percutaneously into a large central vein such as the jugular, the medial basilic or the lateral cephalic vein.

35
Q

CVP Pressure measurements are taken when?

A

During exhalation and when the patient is supine.
-The transducer is zeroed at the level of the right atrium and the normal CVP is 2 to 6 mmHG.

36
Q

Complications with the insertion of CVP catheters include:

A

Pneumothorax, hemothorax and vessel damage
-Other complications include infection, thrombosis and bleeding
-Placement is confirmed using radiography

37
Q

Pulmonary Artery catheterization (Swan-Ganz)A balloon-tipped flow-directed catheter is a multiple lumen catheter.
-The standard adult size is 110 cm and available in 7 and 8 French sizes.
-The standard pediatric catheter is 60 cm in length and available in 4 and 5 French sizes.

A

Pulmonary Artery catheterization (Swan-Ganz)

38
Q

Dual lumen Pulmonary Catheters

A

Lumen 1-Connects to a balloon located near the tip of the catheter.
Lumen 2- runs the length of the catheter and terminates approx. 30 cm for the tip of the catheter or the level of the RA.
Lumen 3-Can be used to measure right atrial pressures or for administration of IV medications.

39
Q

Thermodilution Catheters

A

Thermodilution catheters incorporate a thermistor connector which contains electrical wires located approx. 1.5 inches (3 cm) from the tip of the catheter.
-When measuring CO a bolus of saline or 5% dextrose is injected into the catheter’s 3rd proximal lumen, which is positioned at the level of the right atrium.

40
Q

How is CO measured using a thermistor?

A

The CO is calculated by integrating the change in temperature that is sensed by the thermistor near the tip of the catheter as the injected saline solution mixes with the patient’s pulmonary blood flow.

41
Q

Positioning the Pulmonary Catheter

A

Positioning the catheter can be accomplished by fluoroscopy or monitoring the pressure tracings generated as the catheter is slowly advanced into the right heart and Pulmonary Artery

42
Q

As the pulmonary catheter is inserted and the respiratory fluctuations are absent, what could this mean?

A

-The stopcock is closed
-Catheter is kinked
-Blood clot
-Air is present
Once the catheter enters the intrathoracic vessels, the balloon is fully inflated with air so it can be flow directed by the blood.

43
Q

Balloon volumes

A

Pediatric (4 or 5 French)- 0.8 ml
Adult (7or 8 French)-1.5 ml

44
Q

The PAOP is characteristically lower than or equal to the PA diastolic pressure. The loss of a distinctive waveform indicates a mechanical problem such as what?

A

-Air bubble in the tubing
-Protrusion of balloon over the tip of the catheter

45
Q

When would the PA diastolic pressure be greater than the PAOP?

A

Mitral stenosis or mitral regurgitation

46
Q

Measuring the PAOP by other means via left atrium

A

The catheter must be positioned in a zone 3 position in the lung to accurately reflect the pulmonary venous pressure.
-If positioned in zone 1 or 2, the alveolar pressure will exceed the pulmonary venous pressure and cause the vessels distal to the balloon to collapse.
-The pressure reading will reflect the intraalveolar pressure rather than the left atrial pressure.
-This problem is accentuated by PEEP during MV.

47
Q

How does PEEP affect the left atrial pressure reading?

A

When PEEP is applied to the airway during MV, the alveolar pressure rises which can cause the reading to reflect the intraalveolar pressure rather than the left atrial pressure.

48
Q

Table 11.3
Complications associated with Pulmonary artery catheterization

A

Cardiac Arrhythmias, Infection, Pneumothorax, Air embolism, Thrombosis, pulmonary rupture, infarction, perforation, balloon rupture: air embolism, catheter knotting, dampened waveform, catheter whip or fling

49
Q

What can minimize the chances of a pulmonary infarction or rupture?

A

-Prevent a thrombosis by instilling a continuous flushed solution of heparinized solution.
-Ensure the catheter is deflated after PCWP measurements
-Ensure the balloon is inflated for only 15 to 30 sec between each measurement when measuring the PAOP.

50
Q

What factors influence cardiac output?

A

Heart rate, preload, contractility, afterload

51
Q

Heart rates above 220 cause a reduction in CO because

A

Diastolic filling time is reduced

52
Q

Systemic Arterial Pressures with a normal MAP of 70-100

A

Systolic: 90-140
Diastolic: 60-90

53
Q

Hypertension exists

A

Systolic is above 140
Diastolic is above 90

54
Q

Hypotension exists

A

Systolic is lower than 100
Diastolic is lower than 60

55
Q

The difference between the systolic and diastolic

A

Pulse pressure
- A wide pulse pressure is associated with an increased SV and decreased arterial compliance.

  • A narrow pulse pressure is associated with decreased SV and an increased arterial compliance
56
Q

Right Atrial and Pulmonary artery pressures

A

Proper positioning of the balloon catheter allows for continuous monitoring of:
-RAP (proximal lumen or CVP line) and PA pressure (distal lumen of PA)
-Intermittent measurements of PAOP
-Left atrial and ventricular pressures can be measured intermittently during PAOP determinations.

57
Q

How are PAOP determinations made?

A

PAOP measurements represent retrograde pressure measurements that are obtained by inflating the balloon of a PA catheter until it occludes a small PA and wedges to block blood flow past the catheter tip.

58
Q

Measurements of the right ventricular pressures

A

Usually obtained during insertion of the catheter
-If the right ventricular pressure waveform is seen during continuous monitoring, this indicates that the catheter has slipped into the right ventricle.
-It should be repositioned by reinflating the balloon and allowing the blood flow to carry it back to the PA.

59
Q

Atrial pressures

A

Normal RAP- 2 to 6 mm HG
Normal LAP- 5 to 12 mm HG
-PAOP and CVP measurements are used to determine overall fluid balance.
Low CVP or PAOP=hypovolemia
High CVP or PAOP=hypervolemia or ventricular failure

60
Q

PAOP in assessing pulmonary hydrostatic pressure in the formation of pulmonary edema

A

PAOP can help distinguish cardiogenic pulmonary edema.

61
Q

Causes of elevated RAP

A

Volume overload, RV failure, Tricuspid stenosis or regurgitation, cardiac tamponade, constrictive pericarditis, chronic LV failure

62
Q

Causes of elevated PAOP

A

Volume overload, LV failure, Mitral stenosis or regurgitation, cardiac tamponade, high PEEP

63
Q

Low RAP or PAOP

A

Hypovolemia

64
Q

PA pressure

A

The PA pressure is much lower than the systemic pressure
PA systolic pressure=15-35
PA diastolic pressure=5-15
-PA pressure is measured at end expiration because

65
Q

How does MV affect hemodynamic measured hemodynamic parameters?

A

The lower mean inspiratory pressures present with IMV and pressure support minimize the hemodynamic effects of positive intrathoracic pressure and help maintain right heart preload and CO.

66
Q

How does PEEP or auto-PEEP affect hemodynamic measured hemodynamic parameters?

A

The use of PEEP at levels greater than 15 cm H2O can produce erroneously elevated pressure readings.
-The pressures in the thoracic circulation will rise because of compression of the vessels by the increased lung volumes (FRC)

67
Q

PAOP when assessing PEEP

A

PAOP reflects preload of the left side of the heart, is a valuable parameter to measure when assessing the PEEP.
If the PAOP increases during the study, this could indicate overinflation of the alveoli.

68
Q

The volume of blood that is pumped by the heart per minute

A

Cardiac Output
-Normal CO is 4 to 8 L/min
-Calculated by multiplying the SVxHR
-A decrease in SV or HR can cause a decrease in CO

69
Q

Decreases in SV are associated with what?

A

Reduced preload or contractility with an abnormally high afterload
Vice versa

70
Q

An increase in HR may cause a decrease in ventricular filling (the ventricle does not have enough time to fill) and can cause a reduction in CO

A

Ventricular filling (the ventricle does not have enough time to fill) and can cause a reduction in CO

71
Q

An increase in CO is associated with

A

A increase in HR or SV

72
Q

Ficks principle and CO measurements

A

The gold standard for measuring CO is measuring the VO2 (oxygen consumption) and arterial and mixed venous O2 contents.
Once the measurements are made, they can be calculated using the Fick’s principle.
-VO2/(CaO2-CVO2)x10

73
Q

Hemodynamic Equations

A

-CO=HR x SV
-Ficks principle and CO= VO2/(CaO2-CvO2) x 10
-SVR= (MAP-MRAP)/SBF) x 80

74
Q

Mixed venous oxygen saturations (SVO2)

A

-Mixed venous saturations decline when arterial oxygenation is decreased
-Mixed venous saturations can be higher in normal patients with histotoxic hypoxia, intrapulmonary shunting,

75
Q

Oxygen Delivery (DO2)

A

-The amount of oxygen carried in the blood to the tissues each minute.
-The product of CO and arterial O2 content
-Normal DO2 is 1000 mL/min
-DO2 is increased in situations where the CO or the arterial O2
content is elevated.

76
Q

The Shunt Fraction

A

The portion of the CO that does not participate in gas exchange. (Perfusion without ventilation).
-Anatomical+Intrapulmonary=physiological shunt

77
Q

Anatomical shunt

A

Exists because venous blood that would ideally return to the left side of the heart (deoxygenated) drains into vessels served by the left side of the heart. (Venous admixture)
-Typically represents 2% to 3% of the CO.

78
Q

Intrapulmonary shunt

A

Occurs when blood passes through the pulmonary capillaries that are not ventilated.
-Intrapulmonary shunts can be caused by disorders such as: Atelectasis, pulmonary edema, pneumonia, pneumothorax, complete airway obstruction, ARDS, Fistulas

79
Q

Vascular resistance

A

The impedance to blood flow offered by the pulmonary and systemic vascular bed and it influences the force that the ventricular muscle must generate during cardiac contractions.
-SVR= (MAP-MRAP)/SBF) x 80 Normal SVR=900 to 1500 dynes/sec
-PVR=(MPAP-PAOP/CO) x 80 Normal PVR= 100 to 250 dynes/sec

80
Q

What are the most important factors that influence vascular resistance?

A

The viscosity of blood and the caliber of the blood vessels
-SVR may be increased in polycythemia due to the increase in RBC’s, may be decreased during vasodilation such as in hypoxia.

-PVR increases in hypoxia and PPV. (PVR is reduced by the administration of pulmonary vasodilator drugs such as tolazoline and prostacyclin)
-A low CO can increase PVR due to the derecruitment of the pulmonary vessels.

81
Q

Ejection Fraction

A

The ejection fraction is a derived variable that provides an estimate of ventricular contractility.
-It is calculated by dividing the SV by the end-diastolic volume, valuable measurement in the prognosis of heart failure.
-EF value of 0.5 to 0.7 are considered normal and below 0.3 are associated with compromised cardiovascular function and imminent heart failure.

82
Q

The parts of a Swan-Ganz catheter

A
  1. Ejection Port
    2.Distal ejection port
    3.Balloon inflation valve
    4.Thermistor connector
  2. Proximal injection port
    6.Distal lumen
    7.Balloon
    8.Thermistor
  3. Proximal lumen

Chapter 18 Egans Special Topics (9 decks)

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