1. Chapter 16 Assessment of Hemodynamic Pressures

2. Learning Objectives After reading this chapter you will be able to:
Describe the following regarding arterial cannulation:
Indications for placing an A line
Catheter; common insertion sites
Procedure for placement of the catheter
Interpretation of arterial pressure waveforms
Pressures measured and their interpretation
Potential complications

3. Learning Objectives
Describe the following regarding central venous pressure (CVP) monitoring:
Indications for placing a CVP catheter
Catheter; insertion sites
Procedure for placement of the catheter
Interpretation of the CVP waveform
Interpretation of pressures measured
Relationship of CVP to left and right ventricular function
Potential complications

4. Learning Objectives
Describe the following regarding pulmonary artery (PA) pressure monitoring:
Indications for placing a PA catheter
Catheter; insertion sites
Procedure for placement of the catheter
Interpretation of PA waveforms
Interpretation of pressures measured

5. Learning Objectives (cont’d)
Relationship between PA diastolic pressure and pulmonary capillary wedge pressure (PCWP)
How to obtain an accurate PCWP reading
Relationship between transmural pressure and PCWP
Effect of positive end-expiratory pressure on PCWP measurements
Complications of using the PA catheter

6. Introduction Hemodynamic monitoring is performed to:
Evaluate intravascular fluid volume
Evaluate cardiac function
Evaluate vascular function
Identify sudden changes in the patient’s hemodynamic status
Invasive monitoring is needed to obtain an accurate evaluation of hemodynamics

7. Arterial Pressure Monitoring
Indications
In patients with severe hypotension or hypertension
In patients who may need frequent arterial blood gas assessment
Patients in shock or respiratory failure are candidates for placement of an arterial line

8. Placement of the Arterial Line
Most often placed in the radial artery
This site is readily accessible and has collateral circulation
This site is easy to monitor for bleeding or other complications
The femoral artery is less affected by vasoconstriction but more difficult to monitor for bleeding

9. Arterial Pressure Waveforms
The arterial pressure wave should have a clear upstroke on the left
A dicrotic notch on the downstroke on the right
The dicrotic notch represents aortic valve closure

10. Arterial Pressure Waveforms (cont’d)

11. Arterial Pressure Waveforms (cont’d)

12. Interpretation of Arterial Pressures
Normal = 120/80 mm Hg
Hypertension = >160/90 mm Hg
Hypotension = <90/60 mm Hg
Arterial pressure is only a general sign of circulatory status
Hypotension is often a late sign of low cardiac output

13. Interpretation of Arterial Pressures (cont’d)
Hypotension is caused by:
Low blood volume
Poor cardiac function
Low vascular resistance
A low diastolic pressure can compromise coronary artery perfusion

14. Interpretation of Arterial Pressures (cont’d)
Hypertension is caused by:
Excessive contraction of the left ventricle
Vasoconstriction
Administration of vasopressors
Sympathetic stimulation (as occurs with fear and stress)

15. Interpretation of Arterial Pressures (cont’d)
Pulse pressure: difference between systolic and diastolic pressures
Normal is 30 to 40 mm Hg
A low pulse pressure is common when stroke volume is low
Mean arterial pressure (MAP) is normally 80 to 100 mm Hg
MAP <60 mm Hg compromises function of vital organs

16. Complications of Continuous Arterial Pressure Monitoring
Ischemia
Occurs with embolism, thrombus, or arterial spasm
Can result in tissue necrosis if not recognized rapidly
Hemorrhage
Occurs if line becomes disconnected
Infection

17. Monitoring CVP Indications
To assess circulating blood volume and filling pressures of the heart
To assess right ventricular function
Patients who have had major surgery or trauma need a CVP catheter
Patients with pulmonary edema often benefit from CVP monitoring

18. CVP Catheters and Insertion Sites
Most popular catheter is 7 French with a triple lumen
The triple lumen allows infusion of medications and a port from which to obtain blood samples
The internal jugular is a popular site for insertion of the catheter

19. CVP Waveforms Reflects the pressures in the right atrium
Normal waveforms have three waves: “a”, “c”, and “v”
“a” wave occurs with atrial contraction
“c” wave occurs with movement of AV valve back toward the atrium during systole
“v” occurs with atrial filling during systole

20. CVP Waveforms (cont’d)

21. Respiratory Influence on CVP Waveforms
Spontaneous inspiratory efforts cause CVP to decrease and are seen on the waveform
Positive pressure breaths cause the CVP to increase
CVP monitoring during mechanical ventilation requires brief disconnection of the ventilator unless PEEP is being applied

22. Methods of Measuring CVP
Transducer system
CVP reported in mm Hg
More accurate and provides a waveform
Water monometer
Reported in cm H2O
Inexpensive
Easy to use

23. Interpretation of CVP Causes of increased CVP Fluid overload
Right/left heart failure
Pulmonary hypertension
Tricuspid valve stenosis
Pulmonary embolism
Increased venous return

24. Interpretation of CVP (cont’d)
Causes of decreased CVP
Reduced circulating blood volume
Vasodilation (reduced venous return)
Leaks in the pressure system
Spontaneous inspiration

25. Complications of CVP Monitoring
During placement
Bleeding
Pneumothorax
Over time
Infection (main potential problem)
Embolus
Air embolus

26. Pulmonary Artery Pressure Monitoring
Developed to allow better evaluation of left ventricular function
Allows assessment of:
Left ventricular filling pressure
Pulmonary vascular resistance
Arteriovenous oxygen difference
Mixed venous oxygen levels

27. Indications for PA Pressure Monitoring
Indications not well defined
Research shows many complications and may be of limited benefit
Today PA catheter is placed on a case-by-case basis taking into consideration patient’s condition and staff qualifications

28. Indications for PA Pressure Monitoring (cont’d)
Conditions for using the catheter
Severe cardiogenic pulmonary edema
Patients with ARDS who are hemodynamically unstable
In patients who have had major thoracic surgery
Patients with septic or severe cardiogenic shock

29. Catheters and Insertion Sites

30. Catheters and Insertion Sites (cont’d)
The PA catheter has multiple lumens and is balloon tipped
The balloon is used to float the catheter in place and to measure left ventricular filling pressures
Most common sites for insertion include the subclavian and internal jugular veins

31. Insertion of the Catheter
Catheter is floated through the right side of the heart and into the pulmonary artery
Once it wedges into place, balloon is deflated
Distinctive waveforms seen as catheter passes through the right atrium, right ventricle, pulmonary artery, and into the wedge position

32. PA Pressure Waveforms

33. Interpretation PA systolic pressure (20-30 mm Hg)
Increases with high pulmonary vascular resistance
Decreases with poor right heart function and pulmonary vasodilation
PA diastolic pressure (8-15 mm Hg)
Normally reflects left heart filling pressures
Does not reflect left heart filling pressures when pulmonary vascular resistance elevated

34. Interpretation (cont’d)
Wedge pressure
Normally 4 to 12 mm Hg
Must be interpreted in light of the patient’s medical history (history of MI will cause a stiff left ventricle and lead to higher pressures)
Elevates with left heart failure or mitral stenosis
Decreases with hypovolemia

35. Obtaining an Accurate Wedge Pressure
Requires careful calibration of equipment
Measure at end exhalation
Catheter tip must be in West zone III where blood flow is continuous
Low blood volume and high alveolar pressures can cause wedge pressure readings to be inaccurate

36. Complications of PA Monitoring
During cannulation hemothorax, pneumothorax, and damage to blood vessels are possible
Dysrhythmias can occur as catheter passes through the heart and during monitoring
Catheter source of infection, thrombus, embolism, bleeding, and hematoma
Pulmonary infarction possible

37. Summary
Hemodynamic monitoring common in the ICU to identify cardiovascular problems and to measure the effects of therapies
Continuous monitoring of arterial pressure, CVP, and PA pressures available
Placement of catheter and its continuous use have potentially serious complications
A risk/reward assessment must be done