Hemodynamic Monitoring: Overview and Practice Questions

Hemodynamic monitoring is an essential practice for assessing patients’ cardiovascular health, especially in critical care settings.

It involves real-time blood pressure measurements within the heart and blood vessels, alongside other parameters like cardiac output and oxygen delivery.

These metrics help diagnose underlying cardiac issues and play an indispensable role in guiding treatment decisions.

Given its significance, understanding the basics of hemodynamic monitoring is pivotal for both healthcare professionals and those interested in patient-centered care.

What is Hemodynamic Monitoring?

Hemodynamic monitoring is the measurement of blood pressure within the heart and blood vessels, alongside other cardiovascular parameters like cardiac output. Used primarily in critical care settings, it provides real-time data to diagnose cardiac issues and guide treatment decisions, offering insights into a patient’s circulatory and cardiac health.

Types of Hemodynamic Monitoring

Hemodynamic monitoring encompasses a range of techniques and tools to measure different cardiovascular parameters.

Here are some of the most prominent types:

• Mean arterial pressure
• Central venous pressure
• Pulmonary artery pressure
• Pulmonary capillary wedge pressure
• Systemic vascular resistance
• Pulmonary vascular resistance
• Cardiac output
• Cardiac index

Mean Arterial Pressure

Mean arterial pressure (MAP) represents the average blood pressure in the arteries during one cardiac cycle. It’s a crucial indicator of perfusion to vital organs.

While a single blood pressure reading provides systolic and diastolic values, MAP gives a comprehensive view of the overall blood flow, resistance, and perfusion.

Clinicians typically aim for a MAP of at least 60-65 mmHg to ensure adequate organ perfusion.

Central Venous Pressure

Central venous pressure (CVP) measures the pressure within the thoracic vena cava, close to the right atrium of the heart.

It provides insight into the right ventricular end-diastolic pressure and can indicate the patient’s volume status.

An elevated CVP might suggest fluid overload or right heart dysfunction, while a low CVP could indicate hypovolemia.

Pulmonary Artery Pressure

Pulmonary artery pressure (PAP) reflects the pressure in the pulmonary artery and is crucial for assessing the function of the left side of the heart and the pulmonary circulation.

It is typically measured using a pulmonary artery catheter.

The PAP reading is bifurcated into systolic and diastolic values. Elevated pulmonary artery pressures can be indicative of conditions like pulmonary hypertension or left heart failure.

Pulmonary Capillary Wedge Pressure

Pulmonary capillary wedge pressure (PCWP) indirectly measures the left atrial pressure.

It is obtained by inflating a balloon on the tip of a pulmonary artery catheter, which then ‘wedges’ in a branch of the pulmonary artery.

This pressure reflects the left ventricular end-diastolic pressure under normal conditions, making it a valuable metric in diagnosing left ventricular dysfunction and distinguishing between cardiac and non-cardiac causes of pulmonary edema.

Systemic Vascular Resistance

Systemic vascular resistance (SVR) represents the resistance to blood flow within the systemic circulatory system.

It measures the afterload or the resistance the left ventricle must overcome to circulate blood throughout the body. SVR is crucial in evaluating and managing conditions like shock.

Elevated SVR can be seen in conditions like hypertensive crisis, while reduced SVR might indicate conditions like septic shock.

Pulmonary Vascular Resistance

Pulmonary vascular resistance (PVR) is the measure of resistance to blood flow within the pulmonary circulatory system. It represents the afterload of the right ventricle.

An elevated PVR can be seen in diseases like primary pulmonary hypertension and chronic thromboembolic pulmonary disease.

It’s essential in assessing the suitability for cardiac surgeries, lung transplant candidates, and managing right heart failure.

Cardiac Output

Cardiac output (CO) quantifies the volume of blood pumped by the heart per minute. It’s a fundamental measure of the heart’s efficiency and function.

CO is calculated by multiplying the heart rate (number of contractions per minute) by the stroke volume (amount of blood pumped with each contraction).

It’s essential in assessing the overall cardiac performance and determining the adequacy of tissue perfusion. Abnormal CO can result from conditions like heart failure, valve disorders, or arrhythmias.

Cardiac Index

Cardiac index (CI) is the cardiac output adjusted for the body surface area of a patient. This normalization allows for a more personalized assessment of cardiac function.

CI is vital as it provides a more tailored view of the heart’s pumping capability in relation to the individual’s body size.

A normal CI suggests that the heart efficiently supplies blood to meet the body’s needs, while deviations (either high or low) may indicate a need for medical intervention.

Note: These metrics, when used appropriately and in combination, provide a comprehensive assessment of a patient’s hemodynamic status, guiding clinicians in making informed therapeutic decisions.

Hemodynamic Monitoring Normal Values

Recognizing the normal values for various hemodynamic parameters is crucial for identifying abnormalities and guiding therapeutic decisions. This includes:

• MAP: 93 mmHg
• CVP: 2-6 mmHg
• PAP: 25/8 mmHg
• PCWP: 4-12 mmHg
• SVR: 900-1,400 dynes/sec/cm
• PVR: 150-300 dynes/sec/cm
• CO: 4-8 L/min
• CI: 2-4 L/min/m2

Note: While these are general guidelines, the exact “normal” range may differ slightly based on the reference source and individual patient factors. It’s always essential to interpret these values in the context of the patient’s clinical picture. Moreover, continuous changes in these values or trends rather than isolated readings often provide more meaningful information regarding patient status.

How is Hemodynamic Monitoring Performed?

Hemodynamic monitoring is typically performed using specialized catheters and pressure transducers.

The most common method involves inserting a pulmonary artery catheter (often called a Swan-Ganz catheter) into a central vein. This catheter is threaded through the heart and into the pulmonary artery.

By connecting the catheter to electronic monitoring equipment, healthcare providers can continuously measure various pressures in the heart and lungs, as well as calculate cardiac output.

Other non-invasive methods, such as Doppler ultrasound, can also be used for specific measurements.

Risks of Hemodynamic Monitoring

While hemodynamic monitoring provides invaluable data, it is not without risks. Some potential complications include:

• Bleeding or hematoma formation at the catheter insertion site
• Infection at the insertion site or bloodstream infection
• Pneumothorax (collapsed lung) if a central line is incorrectly placed
• Cardiac arrhythmias due to catheter movement within the heart
• Pulmonary artery rupture or perforation
• Thrombosis or blood clots
• Air embolism

Note: While these risks exist, they are relatively rare, and the procedure is generally safe when performed by trained professionals.

Hemodynamic Monitoring Practice Questions

1. What three values are used to evaluate the forces influencing blood pressure?
1) Central venous pressure (CVP), 2) Pulmonary artery pressure (PAP), and 3) Pulmonary capillary wedge pressure (PCWP).

2. What three factors affect blood pressure?
1) The condition of the left ventricle, 2) The volume of blood in the cardiovascular system, and 3) The relative size of the intravascular space.

3. Which ventricle is composed of more muscle?
The left ventricle

4. Where is most of the systemic blood stored in the body?
The veins

5. What happens during inspiration?
A drop in negative pressure in the thorax from -2 to -5 helps suck blood back toward the heart.

6. What is a Swan-Ganz catheter?
An invasive method of measuring pressure within the heart and lungs.

7. What is another name for the Swan-Ganz catheter?
The triple lumen catheter.

8. What is shock?
A lack of blood flow to tissues/organs in the body.

9. What is the distal lumen?
The fluid-filled line that transmits a wave of pressure from the tip of the catheter to the transducer.

10. What is a transducer?
A device that converts one form of energy to another; it converts the pressure signal to an electrical signal and then sends it on to the monitor.

11. What does the monitor amplify?
It amplifies the signal and displays digital readings and/or a waveform.

12. What does the distal port communicate with?
The pulmonary artery.

13. Which chamber of the heart does the pulmonary artery come out of?
The right ventricle.

14. If the catheter is properly inserted, where does it rest?
In a pulmonary arteriole.

15. What can the distal port help us measure?
Problems that originate in the lungs (e.g., pulmonary edema).

16. What is PCWP?
It stands for pulmonary capillary wedge pressure and reflects what is going on with the left side of the heart.

17. What happens when the balloon is inflated?
It wedges in an arteriole and is able to obtain a pressure reading.

18. Where is the closest location that we can get to the left side of the heart?
The pulmonary arteriole.

19. The proximal port is also known as what?
The central venous pressure port.

20. Where is the CVP port located?
At the top of the right side of the heart, where the superior vena cava goes into the right atrium.

21. The lumen opens how many centimeters from the catheter’s port?
30 cm

22. How is cardiac output measured?
Injecting a bolus of saline at a known temperature less than the body’s into the proximal lumen.

23. What does the SVO2 measurement tell us?
How much oxygen the body is using.

24. What is a normal SVO2 value?
70%

25. What measurement is the closest to the left side of the heart?
PCWP

26. What is the formula for cardiac output?
CO = HR x SV

27. Where can you obtain the PaO2?
In an arterial blood gas (ABG) sample.

28. Where can you find the PVO2?
Mixed venous blood obtained from the distal (PA) port of a Swan-Ganz catheter.

29. Where is the SVO2 obtained from?
The optical module connector in the top-of-the-line Swan-Ganz catheter.

30. VO2 is the amount of what?
Oxygen that the body extracts from the blood every minute in order to feed the tissues.

32. What blood vessel comes in at the top of the right heart?
Superior vena cava

33. What drains into the superior vena cava?
Internal jugular vein

34. Where would the first choice be to insert a Swan-Ganz catheter?
The internal jugular vein and subclavian vein because they are a direct shot into the right atrium (veins closest to the right side of the heart).

35. What pressure can be taken when the catheter is in the right atrium?
Central venous pressure (CVP)

36. What is a normal CVP?
2-6 mmHg

37. After the catheter is in the right atrium, where does it go next?
Through the tricuspid valve into the right ventricle.

38. Why does the waveform change when the catheter moves through the tricuspid valve?
Because the pressure recorded within the right ventricle is dramatically higher than within the right atrium.

39. What is a normal right ventricle pressure for systolic?
15-28 mmHg

40. What is a normal right ventricle pressure for diastolic?
0-8 mmHg

41. What is the normal systolic pulmonary artery pressure?
15-30 mmHg

42. What is the normal diastolic pulmonary artery pressure?
4-12 mmHg

43. What is the normal mean pulmonary artery pressure?
6-18 mmHg

44. What does the dicrotic notch represent?
The closure of the aortic and pulmonic valves at the end of systole.

45. What does it indicate when there is no dicrotic notch?
You may have to reposition the catheter, or the patient was possibly moving.

46. What happens each time the mitral valve opens?
There is direct communication between the catheter tip and the left ventricle via the pulmonary capillary bed.

47. What is the normal mean of PCWP?
4-12 mmHg

48. How do we know if someone is in shock?
They will demonstrate the following: decreased urinary output, decreased blood pressure, cyanotic, temperature changes of the skin, and cerebral perfusion compromise.

49. What does cardiogenic mean?
Beginning at the heart.

50. What is cardiogenic shock?
Left ventricular failure to pump.

51. What pressure is closest to the left ventricle?
PCWP

51. Patients with CHF will have what?
An increased PCWP

52. What is the most common cause of shock?
The inability of the left ventricle to produce adequate stroke volume.

53. What is stroke volume?
The amount of oxygenated blood pumped out of the heart during systole.

54. In adults, what is the average volume for each heartbeat?
60-130 mL/beat

55. What is an infarction?
Dead muscle

56. What are some disorders that can cause cardiogenic shock?
1) Infarction of more than 40% of the left ventricular muscle, 2) CHF, 3) Cardiac tamponade, 4) Chest trauma.

57. What is cardiac tamponade?
Air or fluid in the pericardial sac.

58. How do you know a patient has CHF based on their chest x-ray?
Measure the CT ratio; if it is > 50%, CHF is likely.

59. What happens when left ventricular failure gets worse?
Blood begins to back up into the left atrium.

60. What pressure is measured in the pulmonary arteriole?
PCWP

61. Which factors are not affected by cardiogenic shock?
The skin’s color and temperature.

62. What does peripheral edema cause?
An increase in heart rate.

63. What can happen if you give a patient too much positive pressure on a ventilator?
It can cause cardiac tamponade (because it will squeeze the heart), among other things.

64. How is cardiac output affected in cardiogenic shock?
The left ventricle is failing, so cardiac output is decreased.

65. What drugs would you give to increase cardiac output?
Positive inotropes (e.g., digitalis, digoxin) to increase the contractility of the heart.

66. What is the total amount of blood volume in the venous system?
64%

67. Venous return is the amount of blood volume returning to the?
Right heart

68. A patient’s cardiac index is the cardiac output based on what?
Actual body size

69. What is end-systolic pressure?
The amount of blood in the ventricle after ejection.

70 What is end-diastolic pressure?
The amount of blood in the ventricle after filling.

71. What does cardiac tamponade do to blood entering the heart?
It restricts the blood entering the heart.

72. What is the Fick equation?
CO= VO2/C(a-v)O2 x 10

73. What is the normal right atrial pressure (RAP)?
2-6 mmHg

74. In general, PAP is concerning what?
The lungs

75. In general, PCWP is concerning what?
The left heart

76. In general, CVP is concerning what?
The right atrial pressure and fluid levels.

77. The systemic artery blood pressure (SABP) generally looks at what?
The blood pressure throughout the body.

78. What is preload?
The stretch on the ventricle muscle fibers before contraction.

79. What is afterload?
The resistance of external factors that oppose ventricular contraction.

80. Stroke volume is determined by what?
Preload, afterload, and contractility.

81. A decrease in potassium and sodium causes what?
Atrial fibrillation.

82. What is the procedure for placing an arterial line?
Assemble all equipment, perform the modified Allen test, drape the patient, inject 1% lidocaine, insert the catheter at a 30-degree angle, hold the needle and advance the catheter, remove the needle and secure, attach drip, and observe the waveform.

83. What is the procedure for placing a pulmonary catheter?
It is done by the physician; check the balloon for patency; it is inserted into a selected sight until it reaches the right atrium; then, inflate the balloon.

84. What are the common sites for placing a pulmonary catheter?
Subclavian or internal jugular vein.

85. What are the common sites for placing an arterial catheter?
Radial, brachial, or femoral arteries.

86. What is systemic vascular resistance?
The pressure on the vessels throughout the body (from the aorta).

87. What is pulmonary vascular resistance?
The pressure on the pulmonary artery.

88. What factors affect the contractility of the heart?
Coronary blood flow, sympathetic nerve stimulation, inotropic drugs, physiologic depressants, and damage to the heart.

89. What are the left atrial filling pressures?
Preload and PCWP

90. What are the right atrial filling pressures?
The amount of blood in the right atrium or CVP.

91. What is MAP, and what is the normal range?
It stands for mean arterial blood pressure; the normal value is 93 mmHg.

92. What is CVP?
Central venous pressure

93. What is PCWP, and what is the normal range?
It stands for pulmonary capillary wedge pressure; the normal range is 4-12 mmHg.

94. What is an increased CVP associated with?
Fluid overload, right ventricular failure, hypercapnia, valvular stenosis, PE, cardiac tamponade, pneumothorax, PPV, PEEP, and left ventricular failure.

95. What is associated with an increased PAP?
Pulmonary hypercapnia, left ventricular failure, and fluid overload.

96. What is associated with an increased PCWP?
Left ventricular failure, fluid overload, interstitial edema, alveolar filling, and pulmonary edema.

97. What does an increase or decrease in CVP represent?
An increase represents fluid overload, L-R shunt, and cor pulmonale. A decrease represents hypovolemic shock.

98. Why should all blood pressure measurements be taken at the heart level?
To eliminate the effect of gravity on hydrostatic pressure.

99. What is the definition of stroke volume?
The volume of blood ejected from the heart with each beat.

100. How does heart rate affect diastolic pressure?
It changes the duration of diastole, and the pressure continues to fall until the next systole.

101. What is an early sign of changes in circulating blood volume?
Changes in pulse pressure.

102. Low pulse pressures can indicate what two things?
CHF and shock

103. What is the average driving force in the arterial system throughout the cardiac cycle?
Mean arterial pressure

104. MAP can be used to calculate what?
SVR and PVR

105. What is the normal range for MAP?
70-105 mmHg

106. An MAP below 60 indicates what?
Circulation to vital organs may be compromised, and poor tissue perfusion.

107. What are the indications for arterial cannulation?
It’s indicated for hemodynamically unstable patients, patients on vasoactive drips, patients with IAB, and perioperative patients.

108. What are the hazards of arterial cannulation?
Hemorrhage, thrombus, air embolism, systemic infection, site infection, arterial spasm, and vascular occlusion.

109. Why is invasive hemodynamic monitoring needed?
Because clinical assessment alone may not accurately predict hemodynamics.

110. What must be considered before a catheter is placed in a patient?
The risk-benefit ratio of invasive monitoring.

111. What is hemodynamic monitoring performed to do?
To evaluate the intravascular fluid volume and cardiac/vascular function; and to identify sudden hemodynamic changes.

112. Why is invasive monitoring needed?
To obtain an accurate evaluation of hemodynamics.

113. What type of patient may a physician want to place an arterial catheter in?
Those with significant hemodynamic instability or the need for frequent arterial blood draws.

114. What conditions are likely candidates for arterial pressure monitoring?
Severe hypotension (shock) or HTN; respiratory failure.

115. What patient may benefit from arterial pressure monitoring?
Those in need of medication that affects blood pressure (e.g., vasodilators and inotropic agents).

116. Where is the arterial catheter usually placed?
Radial, ulnar, brachial, axillary, and femoral.

117. Where is the arterial line most often placed, and why?
The radial artery because it is readily accessible and there is adequate collateral circulation.

118. What is low blood pressure a late sign of?
Deficits in blood volume or cardiac function.

119. What are the causes of hypotension?
Low blood volume (bleeding), cardiac failure/shock (heart attack), vasodilation (sepsis).

120. During the administration of what drugs should the diastolic pressure be watched carefully?
Vasodilators, such as sodium nitroprusside.

121. What are the six causes of increased central venous pressure?
Fluid overload, heart failure, pulmonary hypertension, tricuspid valve stenosis, pulmonary embolism, and increased venous return.

122. What are the four causes of decreased central venous pressure?
Vasodilation, reduced circulating blood volume, leaks in pressure system/air bubbles, and spontaneous inspiration.

123. When can pneumothorax occur during hemodynamic monitoring?
When the catheter punctures the pleural lining.

124. What can the accidental opening of the central venous line stopcock allow and result in?
Air to enter the vein, which can cause an air embolus.

125. What does the PAC allow the assessment of?
It allows the assessment of the filling pressures of the left side of the heart.

126. What is PAOP in Hemodynamic Monitoring?
PAOP stands for pulmonary artery occlusion pressure. It is also frequently referred to as pulmonary capillary wedge pressure (PCWP). PAOP provides an indirect measurement of left atrial pressure. 

127. What is the balloon at the tip of the catheter used for?
To float the catheter into position (into the right side of the heart and into the pulmonary artery) and obtain wedge pressure measurements.

128. What can resistance to pulmonary flow (increased PVR) be caused by?
Constriction, obstruction, or compression of the pulmonary vasculature or backpressure from the left heart.

129. What conditions cause increased pulmonary vascular resistance?
Pulmonary emboli, acute/chronic lung disease, cardiac tamponade, and left heart failure.

130. What should be immediately available at both the insertion and removal of a pulmonary artery catheter?
Lidocaine and emergency resuscitation equipment.

131. What should be optimized to decrease the risk of dysrhythmias?
Blood gases and serum electrolytes.

132. What is abnormal, and is an indication for obtaining a chest x-ray to assess the cause?
Catheter resistance

133. What are the factors that control blood pressure?
The heart, blood/fluid levels, and vessels.

134. The amount of blood pumped out of the left ventricle in a minute is known as what?
Cardiac output

135. What is the formula for systemic vascular resistance?
SVR = (MAP – CVP) x (80 / Cardiac Output)

136. What is the formula for pulmonary vascular resistance?
PVR = (MPAP – PCWP) x (80 / Cardiac Output)

137. What is the formula for cardiac output?
CO = Heart Rate x Stroke Volume

138. What is the formula for cardiac index?
CI = Cardiac Output / Body Surface Area

139. What is the volume or amount of blood ejected with each beat known as?
Stroke Volume

140. What is the formula for stroke volume?
SV = CO / HR

141. The right ventricle pumps against what?
Pulmonary vascular resistance

142. The left ventricle pumps against what?
Systemic Vascular Resistance

143. What happens when blood pressure is too low?
The tissues in the body won’t receive adequate oxygen.

144. What happens when blood pressure is too high?
It causes a strain on the heart and will eventually cause failure.

145. What is the respiratory therapist’s job when assisting the physician with inserting a pulmonary artery catheter?
Set up the bag, check the ports, inflate the balloon, and deflate the balloon.

146. The central venous pressure measures what three things?
Intravascular volume, venous return, and right ventricle preload.

146. What causes an increased central venous pressure?
Fluid overload, right ventricle failure, right-sided valve disorders, cardiac tamponade, and obstructive RA tumor.

148. What causes a decreased central venous pressure?
Hypovolemia and shock.

149. What causes an increased PCWP?
Left heart failure, intravascular volume overload, cardiac tamponade/effusion, and obstructive LA tumor.

150. What is the normal value range for PVR?
150-300 dynes/sec/cm

151. What is the normal value range for SVR?
900-1,400 dynes/sec/cm

152. How many lumens do PAC catheters have?
4-6

153. Which part of the PAC rests in the right atrium for the CVP measurement?
The proximal lumen.

154. Where does the distal lumen rest?
In the pulmonary artery.

155. Which lumen measures the PAP, PCWP, and obtains mixed venous samples?
The distal lumen because it is in the pulmonary artery.

156. When inserting a PAC, how do you know if it’s in the right atrium?
The pressure should read 2-6 mmHg.

157. How does negative pressure affect the heart?
It increases venous return and preload.

158. What can cause an increased PCWP?
Left ventricular failure, hypervolemia, mitral valve stenosis, and technical causes.

159. What would be seen on a chest x-ray with a PCWP greater than 18 mmHg?
The onset of pulmonary vascular congestion.

160. What would be seen on a chest x-ray with a PCWP greater than 25 mmHg?
Obvious pulmonary edema.

Final Thoughts

Hemodynamic monitoring is a pivotal tool in critical care that provides clinicians with a detailed view of a patient’s cardiovascular function.

By understanding and interpreting these metrics, healthcare professionals can make more informed therapeutic decisions, optimizing outcomes and ensuring patient safety.

Therefore, it remains imperative for practitioners to be well-versed in these hemodynamic monitoring techniques, ensuring the highest standard of care in cardiovascular management.