1. Focus on Hemodynamic Monitoring and Circulatory Assist Devices
(Relates to Chapter 66, “Nursing Management: Critical Care,” in the textbook)
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2. Hemodynamic Monitoring
Measurement of pressure, flow, and oxygenation within the cardiovascular system
Includes invasive and noninvasive measurements
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3. Hemodynamic Monitoring
Invasive and noninvasive measurements
Systemic and pulmonary arterial pressures
Central venous pressure (CVP)
Pulmonary artery wedge pressure (PAWP)
Cardiac output (CO)/cardiac index (CI)
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4. Hemodynamic Monitoring
Invasive and noninvasive measurements (cont’d)
Stroke volume (SV)/stroke volume index (SVI)
O2 saturation of arterial blood (SaO2)
O2 saturation of mixed venous blood (SvO2)
From these measurements, the nurse will calculate several values, including resistance of the systemic and pulmonary arterial vasculature and O2 content, delivery, and consumption.
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5. Hemodynamic Monitoring General Principles
CO: volume of blood pumped by heart in 1 minute
CI: CO adjusted for body size
SV: volume ejected with each heartbeat
SVI: SV adjusted for body size
CI is a more precise measurement of the efficiency of the pumping action of the heart than CO.
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6. Hemodynamic Monitoring General Principles
Systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR)
Opposition to blood flow by systemic and pulmonary vasculature
Preload, afterload, and contractility determine SV.
Table 66-1 presents the formulas and normal values for common hemodynamic parameters.
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7. Hemodynamic Monitoring General Principles
Preload: volume of blood within ventricle at end of diastole
Afterload: forces opposing ventricular ejection
Systemic arterial pressure
Resistance offered by aortic valve
Mass and density of blood to be moved
Frank-Starling law explains the effects of preload and states that the more a myocardial fiber is stretched during filling, the more it shortens during systole and the greater the force of the contraction.
As preload increases, force generated in the subsequent contraction increases, thus SV and CO increase.
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8. Hemodynamic Monitoring General Principles
Contractility: strength of ventricular contraction
PAWP: measurement of pulmonary capillary pressure; reflects left ventricular end-diastolic pressure under normal conditions
Contractility is said to increase when preload is unchanged, yet the heart contracts more forcefully. Epinephrine, norepinephrine (Levophed), isoproterenol (Isuprel), dopamine (Intropin), dobutamine (Dobutrex), digitalis-like drugs, calcium, and milrinone increase or improve contractility. These agents are termed positive inotropes.
Contractility is reduced by negative inotropes. Examples include certain drugs (e.g., alcohol, calcium channel blockers, β-adrenergic blockers) and clinical conditions (e.g., acidosis). Increased contractility results in increased SV and increased myocardial O2 requirements.
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9. Hemodynamic Monitoring General Principles
CVP: right ventricular preload or right ventricular end-diastolic pressure under normal conditions, measured in right atrium or in vena cava close to heart
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10. Principles of Invasive Pressure Monitoring
Equipment must be referenced and zero-balanced to environment, and dynamic response characteristics optimized.
Referencing: positioning transducer so zero reference point is at level of atria of heart or phlebostatic axis
{See next slide for figure of components.}
The stopcock nearest the transducer is usually the zero reference for the transducer. To place this level with the atria, you use an external landmark, the phlebostatic axis.
{See slide 12 for technique to identify phlebostatic axis.}
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11. Components of Pressure Monitoring System
The cannula, shown entering the radial artery, is connected via pressure (nondistensible) tubing to the transducer. The transducer converts the pressure wave into an electronic signal. The transducer is wired to the electronic monitoring system, which amplifies, conditions, displays, and records the signal. Stopcocks are inserted into the line for specimen withdrawal and for referencing and zero-balancing procedures. A flush system, consisting of a pressurized bag of intravenous fluid, tubing, and a flush device, is inserted into the line. The flush system provides continuous slow (approximately 3 mL/hr) flushing and provides a mechanism for fast flushing of lines.
Fig Components of a pressure monitoring system. The cannula, shown entering the radial artery, is connected via
pressure (nondistensible) tubing to the transducer. The transducer converts the pressure wave into an electronic signal. The
transducer is wired to the electronic monitoring system, which amplifies, conditions, displays, and records the signal. Stopcocks
are inserted into the line for specimen withdrawal and for referencing and zero-balancing procedures. A flush system, consisting
of a pressurized bag of intravenous fluid, tubing, and a flush device, is inserted into the line. The flush system provides
continuous slow (approximately 3 mL/hr) flushing and provides a mechanism for fast flushing of lines.
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12. Identification of the Phlebostatic Axis
A, Phlebostatic axis is an external landmark used to identify the level of the atria in the supine patient. The phlebostatic axis is defined as the intersection of two imaginary lines: one drawn vertically through the fourth intercostal space at the sternum, and another drawn horizontally through the midchest, halfway between the outermost anterior and outermost posterior points of the chest.
B, As the backrest of the supine patient is elevated, the phlebostatic axis remains at the same anatomic location, becoming progressively elevated from the floor. The zero reference point must be repositioned with changes in backrest elevation, to keep it at the phlebostatic level.
Fig Identification of the phlebostatic axis. A, Phlebostatic axis is an external landmark used to identify the level of the
atria in the supine patient. The phlebostatic axis is defined as the intersection of two imaginary lines: one drawn vertically
through the fourth intercostal space at the sternum, and another drawn horizontally through the midchest, halfway between
the outermost anterior and outermost posterior points of the chest. B, As the backrest of the supine patient is elevated, the
phlebostatic axis remains at the same anatomic location, becoming progressively elevated from the floor. The zero reference
point must be repositioned with changes in backrest elevation, in order to keep it at the phlebostatic level.
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13. Principles of Invasive Pressure Monitoring
Zeroing: confirms that when pressure within system is zero, monitor reads zero
During initial setup of arterial line
Immediately after insertion of arterial line
To do this, open the reference stopcock to room air (off to the patient) and observe the monitor for a reading of zero. This allows the monitor to use the atmospheric pressure as a reference for zero.
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14. Principles of Invasive Pressure Monitoring
Zeroing (cont’d)
When transducer has been disconnected from pressure cable or pressure cable has been disconnected from monitor
When accuracy of values is questioned
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15. Principles of Invasive Pressure Monitoring
Optimizing dynamic response characteristics involves checking that equipment reproduces, without distortion, a signal that changes rapidly.
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16. Principles of Invasive Pressure Monitoring
Optimizing dynamic response (cont’d)
Perform dynamic response test (square wave test) every 8 to 12 hours and
When system is opened to air
When accuracy of values is questioned
{See next slide for figure.}
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17. Dynamic Response Test (Square Wave Test)
Dynamic response test (square wave test) using the fast flush system: normal response.
Fig Optimally damped system. Dynamic response test (square wave test) using the fast
flush system: normal response.
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18. Types of Invasive Pressure Monitoring
Continuous arterial pressure monitoring
Acute hypertension/hypotension
Respiratory failure
Shock
Neurologic shock
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19. Types of Invasive Pressure Monitoring
Continuous arterial pressure monitoring (cont’d)
Coronary interventional procedures
Continuous infusion of vasoactive drugs
Frequent ABG sampling
A 20-gauge, 2-inch (5.1 cm) nontapered Teflon catheter is typically used to cannulate a peripheral artery (e.g., radial, femoral) using a percutaneous approach. After insertion, the catheter is sutured in place.
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20. Arterial Pressure Monitoring
High- and low-pressure alarms based on patient’s status
Measure at end of expiration.
Risks/complications
Hemorrhage
Infection
Thrombus formation
Neurovascular impairment
Loss of limb
Dysrhythmias that significantly diminish arterial BP are more urgent than those that cause only a slight decrease in systolic amplitude.
Hemorrhage is most likely to occur when the catheter dislodges or the line disconnects. To avoid this serious complication, use Luer-Lok connections, always check the arterial waveform, and activate alarms.
{See next slide for figure.}
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21. Arterial Pressure Monitoring
A, Simultaneously recorded electrocardiogram (ECG) tracing.
B, Systemic arterial pressure tracing. Systolic pressure is the peak pressure. The dicrotic notch indicates aortic valve closure. Diastolic pressure is the lowest value before contraction. Mean pressure is the average pressure over time calculated by the monitoring equipment.
Fig A, Simultaneously recorded electrocardiogram (ECG) tracing and B, systemic arterial pressure
tracing. Systolic pressure is the peak pressure. The dicrotic notch indicates aortic valve closure. Diastolic
pressure is the lowest value before contraction. Mean pressure is the average pressure over time
calculated by the monitoring equipment.
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22. Arterial Pressure Monitoring
Continuous flush irrigation system
Delivers 3 to 6 mL of heparinized saline per hour
Maintains line patency
Limits thrombus formation
Assess neurovascular status distal to arterial insertion site hourly.
The limb with compromised arterial flow will be cool and pale, with capillary refill >3 seconds.
Symptoms of neurologic impairment (e.g., paresthesia, pain, paralysis) may be noted. Neurovascular impairment can result in loss of a limb and is an emergency.
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23. Pulmonary Artery Pressure Monitoring
Guides management of patients with complicated cardiac, pulmonary, and intravascular volume problems.
PA diastolic (PAD) pressure and PAWP: indicators of cardiac function and fluid volume status
Monitoring PA pressures allows therapeutic manipulation of preload.
PAD and PAWP decrease with volume depletion. Fluid therapy based on PA pressure can restore fluid balance while avoiding overcorrection or undercorrection of the problem.
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24. Pulmonary Artery Pressure Monitoring
PA flow-directed catheter
Distal lumen port in PA
Samples mixed venous blood
Thermistor lumen port near distal tip
Monitors core temperature
Thermodilution method measuring CO
Example of PA flow-directed catheter is Swan-Ganz.
The standard PA catheter is number 7.5-French, 43 inches (110 cm) long, with four or five lumina.
{See next slide for figure.}
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PA Catheter
A, Illustrated catheter has five lumina. When properly positioned, the distal lumen exit port is in the PA and the proximal lumen ports are in the right atrium and right ventricle. The distal and one of the proximal ports are used to measure PA and central venous pressures, respectively. A balloon surrounds the catheter near the distal end. The balloon inflation valve is used to inflate the balloon with air to allow reading of the pulmonary artery wedge pressure. A thermistor located near the distal tip senses PA temperature and is used to measure thermodilution cardiac output when solution cooler than body temperature is injected into a proximal port.
B, Photo of an actual catheter.
Fig Pulmonary artery (PA) catheter. A, Illustrated catheter has five lumens. When properly positioned,
the distal lumen exit port is in the PA and the proximal lumen ports are in the right atrium and right ventricle.
The distal and one of the proximal ports are used to measure PA and central venous pressures, respectively.
A balloon surrounds the catheter near the distal end. The balloon inflation valve is used to inflate the balloon
with air to allow reading of the pulmonary artery wedge pressure. A thermistor located near the distal tip
senses PA temperature and is used to measure thermodilution cardiac output when solution cooler than
body temperature is injected into a proximal port. B, Photo of an actual catheter.
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26. Pulmonary Artery Pressure Monitoring
Additional lumina
Right atrium or right atrium and right ventricle
Right atrium port
Measurement of CVP
Injection of fluid for CO measurement
Blood sampling
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27. Pulmonary Artery Pressure Monitoring
Additional lumina (cont’d)
Second proximal port
Infusion of fluids and drugs
Blood sampling
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28. Pulmonary Artery Pressure Monitoring
When measurements are obtained
PA: at end expiration
PAWP: by inflating balloon with only enough air until PA waveform changes to a PAWP waveform
Balloon should be inflated slowly and for no more than four respiratory cycles or 8 to 15 seconds.
{See next slide for figure.}
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29. PA Waveforms During Insertion
Change in pulmonary artery pressure (PAP) waveform to pulmonary artery wedge pressure (PAWP) waveform with balloon inflation. The balloon is inflated while the bedside monitor is observed for changes in the waveform. Balloon inflation (arrow) in patient with a normal PAWP.
Fig Change in pulmonary artery pressure (PAP) waveform to pulmonary artery wedge pressure
(PAWP) waveform with balloon inflation. The balloon is inflated while observing the bedside monitor for
change in the waveform. Balloon inflation (arrow) in patient with a normal PAWP.
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30. Effect of Overinflated Balloon
Balloon inflation (arrow) in patient with elevated wedge pressure. Overwedging of balloon (balloon has been overinflated). The danger of overinflating the balloon is that the pulmonary artery (PA) vessel may rupture from the pressure of the balloon.
This is suspected when the waveform looks “wedged” spontaneously, when <1 mL is needed to wedge the tracing, or when an “overwedge” tracing is obtained.
Fig Balloon inflation (arrow) in patient with elevated wedge pressure. Overwedging of balloon
(balloon has been overinflated). The danger of overinflating the balloon is that the pulmonary artery (PA)
vessel may rupture from the pressure of the balloon. PAP, Pulmonary artery pressure.
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31. Central Venous Pressure Monitoring
Measurement of right ventricular preload
Obtained from
PA catheter using one of the proximal lumina
Central venous catheter placed in internal jugular or subclavian vein
{See next slide for figure.}
Although PA diastolic pressure and PAWP are more sensitive indicators of fluid volume status, CVP also reflects fluid volume problems.
Elevated CVP indicates right ventricular failure or volume overload. Low CVP indicates hypovolemia.
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32. Central Venous Pressure Waveforms
Cardiac events that produce the central venous pressure (CVP) waveform with a, c, and v waves. The a wave represents atrial contraction. The x descent represents atrial relaxation. The c wave represents bulging of the closed tricuspid valve into the right atrium during ventricular systole. The v wave represents atrial filling. The y descent represents opening of the tricuspid valve and filling of the ventricle.
Fig Cardiac events that produce the central venous pressure (CVP) waveform with a, c, and v waves.
The a wave represents atrial contraction. The x descent represents atrial relaxation. The c wave represents
the bulging of the closed tricuspid valve into the right atrium during ventricular systole. The v wave represents
atrial filling. The y descent represents opening of the tricuspid valve and filling of the ventricle.
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33. Measuring Cardiac Output
Intermittent bolus thermodilution method
Continuous cardiac output method
With the TDCO method, a fixed volume (5 to 10 mL) of room temperature (18º to 25º C [64.4º to 77º F] or cold (0º to 12º C [32º to 53.6º F]) solution of normal saline or 5% dextrose in water is injected rapidly (≤4 seconds) and smoothly into the proximal lumen port of the PA catheter
Repeat this procedure 3 times, with measurements 1 to 2 minutes apart.
The CCO method uses a heat-exchange CO catheter.
{See next slide for figure.}
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34. Measuring Cardiac Output
Normal cardiac output curve. Cardiac output is calculated from the temperature change in the pulmonary artery when a fixed volume at known temperature of a solution is injected into the proximal port in the right atrium. The nurse should observe the curve during injection to make sure that it is smooth.
Fig Normal cardiac output curve. Cardiac output is calculated from the temperature change in the
pulmonary artery when a fixed volume and known temperature of a solution is injected into the proximal port
in the right atrium. The nurse should observe the curve during injection to make sure that it is smooth.
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35. Measuring Cardiac Output
SVR, SVRI, SV, and SVI can be calculated when CO is measured.
↑ SVR
Vasoconstriction from shock
Hypertension
↑ release or administration of epinephrine or other vasoactive inotropes
Left ventricular failure
High SV is seen with bradycardia and exercise, and with the use of positive inotropes (e.g., dopamine).
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36. Measuring Cardiac Output
SVR, SVRI, SV, and SVI calculated (cont’d)
↓ SVR
Vasodilation
Shock states and drugs that ↓ afterload
Changes in SV are becoming more important indicators of pumping status of heart than other parameters.
Low SV is seen with tachydysrhythmias, extreme vasodilation, and cardiac tamponade.
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37. Noninvasive Hemodynamic Monitoring
Impedance cardiography (ICG)
Continuous or intermittent, noninvasive method of obtaining CO and assessing thoracic fluid status
Impedance-based hemodynamic parameters (e.g., CO, SV, SVR) are calculated from Zo, dZ/dt, MAP, CVP, and ECG.
Based on the concepts of impedance (resistance to flow of electrical current [Ω]), ICG uses four sets of external electrodes to deliver a high-frequency, low-amplitude current that is similar to that used in apnea monitors.
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38. Noninvasive Hemodynamic Monitoring
Major indications
Early signs and symptoms of pulmonary or cardiac dysfunction
Differentiation of cardiac or pulmonary cause of shortness of breath
Evaluation of causes and management of hypotension
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39. Noninvasive Hemodynamic Monitoring
Major indications (cont’d)
Monitoring after discontinuing a PA catheter or justification for inserting a PA catheter
Evaluation of pharmacotherapy
Diagnosis of rejection following cardiac transplantation
ICG is not recommended in patients who have generalized edema or third spacing because the excess volume interferes with accurate signals.
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40. Venous Oxygen Saturation
PA and CVP catheters can measure oxygen saturation of hemoglobin in venous blood–mixed venous oxygen saturation.
SvO2, ScvO2
O2 saturation of blood from the PA catheter is termed mixed venous oxygen saturation (SvO2).
Similarly, O2 saturation of venous blood from the CVP catheter is termed central venous oxygen saturation (ScvO2).
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41. Venous Oxygen Saturation
SvO2/ScvO2 reflects balance between oxygenation of arterial blood, tissue perfusion, and tissue oxygen consumption (VO2).
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42. Venous Oxygen Saturation
Normal SvO2/ScvO2 at rest is 60% to 80%.
↓ in SvO2/ScvO2
↓ arterial oxygenation
Low CO
Low hemoglobin level
↑ oxygen consumption or extraction
Observe for changes in arterial oxygenation (e.g., monitor pulse oximetry or ABGs), and indirectly assess CO and tissue perfusion. This is done by noting any changes in mental status, strength and quality of peripheral pulses, capillary refill, urine output, and skin color and temperature.
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43. Venous Oxygen Saturation
↑ in SvO2/ScvO2
May indicate clinical improvement (e.g., improved arterial oxygen saturation)
Worsening clinical condition (e.g., sepsis)
In sepsis, O2 is not extracted properly at the tissue level, resulting in increased SvO2/ScvO2 .
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44. Complications With PA Catheters
Infection and sepsis
Asepsis for insertion and maintenance of catheter and tubing mandatory
Change flush bag, pressure tubing, transducer, and stopcock every 96 hours.
Air embolus (e.g., disconnection)
Careful surgical asepsis for insertion and maintenance of the catheter and attached tubing is essential to prevent infection. Cleanse the skin according to institution policy, usually with a chlorhexidine preparation. Cover the insertion site with a sterile occlusive dressing.
Always check the catheter for balloon integrity before insertion, and discard any defective catheters. After insertion, balloon rupture or injection of air into any of the lumina, including the lumen of a ruptured balloon, can cause an air embolus.
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45. Complications With PA Catheters
Ventricular dysrhythmias
During PA catheter insertion or removal
If tip migrates back from PA to right ventricle
PA catheter cannot be wedged.
May need repositioning
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46. Complications With PA Catheters
Pulmonary infarction or PA rupture
Balloon rupture (e.g., overinflation)
Prolonged inflation
Spontaneous wedging
Thrombus/embolus formation
To reduce these risks, never inflate the balloon beyond the balloon’s capacity (usually 1 to 1.5 mL of air).
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47. Preventing PA Rupture and Pulmonary Infarction
Check PA pressure waveforms often for signs of catheter occlusion, dislocation, or spontaneous wedging.
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48. Preventing PA Rupture and Pulmonary Infarction
Continually flush system with a slow infusion of heparinized saline solution.
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49. Noninvasive Arterial Oxygenation Monitoring
Pulse oximetry
Continuous method of determining arterial oxygenation: SpO2
Monitoring SpO2 may ↓ frequency of ABG sampling
Normally 95% to 100%
SpO2 is normally 95% to 100%.
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50. Noninvasive Arterial Oxygenation Monitoring
Pulse oximetry
Monitoring SpO2 may ↓ frequency of ABG sampling (cont’d)
Measurements may be difficult if patients are hypothermic, receiving IV vasopressors, or experiencing hypoperfusion.
Alternate locations for placement of probe: forehead, earlobe
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Nursing Management
Obtain baseline data.
General appearance
Level of consciousness
Skin color/temperature
Vital signs
Peripheral pulses
Urine output
Does the patient appear tired, weak, exhausted?
Cardiac reserve may be insufficient to sustain even minimum activity.
Pallor, cool skin, and diminished pulses may indicate decreased CO.
Changes in mental clarity may reflect problems with cerebral perfusion or oxygenation.
Monitoring urine output reflects the adequacy of perfusion to the kidneys.
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52. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
Nursing Management
Correlate baseline data with data obtained from biotechnology (e.g., ECG; arterial, CVP, PA, and PAWP pressures; SvO2/ScvO2).
Single hemodynamic values are rarely significant.
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Nursing Management
Monitor trends and evaluate whole clinical picture.
Goals
Recognize early clues.
Intervene before problems develop or escalate.
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54. Circulatory Assist Devices (CADs)
Decrease cardiac work and improve organ perfusion when drug therapy fails.
Provide interim support when
Left, right, or both ventricles require support while recovering from injury (e.g., myocardial infarction)
Examples include intraaortic balloon pump (IABP) and left or right ventricular assist device (VAD). The most commonly used CAD is the IABP.
All CADs decrease ventricular workload, increase myocardial perfusion, and augment circulation.
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55. Circulatory Assist Devices (CADs)
Provide interim support when (cont’d)
Heart requires surgical repair and patient must be stabilized (e.g., ruptured septum)
Heart has failed and patient needs cardiac transplantation
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56. Intraaortic Balloon Pump (IABP)
Provides temporary circulatory assistance
↓ afterload
Augments aortic diastolic pressure
Outcomes
Improved coronary blood flow
Improved perfusion of vital organs
Table 66-5 lists clinical indications for an IABP.
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IABP Machine
Fig Intraaortic balloon pump machine.
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58. Intraaortic Balloon Pump (IABP)
Consists of
Sausage-shaped balloon
Pump that inflates and deflates balloon
Control panel for synchronizing balloon inflation with cardiac cycle
Fail-safe features
The balloon is inserted percutaneously or surgically into the femoral artery. It is advanced toward the heart and is positioned in the descending thoracic aorta just below the left subclavian artery and above the renal arteries.
{See next slide for figure.}
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59. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
IABP
Fig Intraaortic balloon pump. A, During systole the balloon is deflated, which facilitates ejection of the
blood into the periphery. B, In early diastole, the balloon begins to inflate. C, In late diastole, the balloon is
totally inflated, which augments aortic pressure and increases the coronary perfusion pressure with the end
result of increased coronary and cerebral blood flow.
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60. Intraaortic Balloon Pump (IABP)
Referred to as counterpulsation
Timing of balloon inflation is opposite to ventricular contraction.
The IAPB assist ratio is 1:1 in the acute phase of treatment. This means that there is one IABP cycle of inflation and deflation for every heartbeat.
Table 66-6 summarizes the hemodynamic effects of IABP therapy.
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61. Intraaortic Balloon Pump (IABP)
Complications of IABP therapy
Vascular injury
Dislodging of plaque
Aortic dissection
Compromised distal circulation
Thrombus and embolus formation
The action of the balloon pump can also cause physical destruction of platelets and thrombocytopenia.
Peripheral nerve damage can occur, particularly when a cutdown is performed for insertion.
Patients receiving IABP therapy are prone to infection.
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62. Intraaortic Balloon Pump (IABP)
Complications of IABP (cont’d)
Mechanical complications
Improper timing of balloon inflation
↑ afterload
↓ CO
Myocardial ischemia
↑ myocardial oxygen demand
Mechanical complications are rare but may occur.
If the balloon develops a leak, the pump will automatically stop. Signs of a leak include less effective augmentation, repeated alarms for gas loss, and blood backing up into the catheter.
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63. Intraaortic Balloon Pump (IABP)
To decrease risks of IABP therapy,
Obtain cardiovascular, neurovascular, and hemodynamic assessments every 15 to 60 minutes, based on patient’s status
Keep patient immobile and limited to side-lying or supine position with HOB <45 degrees
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64. Intraaortic Balloon Pump (IABP)
Decreasing risks of IABP (cont’d)
Leg with IABP catheter must not be flexed at hip to avoid kinking or dislodgement of catheter.
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65. Ventricular Assist Devices (VADs)
Provide short and longer-term support for failing heart
Allow greater mobility than IABP
Inserted into path of flowing blood to augment or replace action of ventricle
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66. Ventricular Assist Devices (VADs)
VADs can
Be implanted (e.g., peritoneum) or positioned externally
Provide biventricular support
A typical VAD shunts blood from the left atrium or ventricle to the device and then to the aorta.
{See next slide for figure.}
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67. Schematic Diagram of Biventricular Assist Device
Fig Schematic diagram of a biventricular assist device.
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68. Ventricular Assist Devices (VADs)
Indications for VAD therapy
Extension of cardiopulmonary bypass
Failure to wean
Postcardiotomy cardiogenic shock
Bridge to recovery or cardiac transplantation
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69. Ventricular Assist Devices (VADs)
Indications for VAD therapy (cont’d)
Patients with New York Heart Association Classification IV who have failed medical therapy
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70. Nursing Management Circulatory Assist Devices
Similar to care for patient with an IABP
Observe patient for bleeding, cardiac tamponade, ventricular failure, infection, dysrhythmias, renal failure, hemolysis, and thromboembolism.
Patient may be mobile and will require an activity plan.
Preparation for discharge is complex and requires in-depth teaching about the device and support equipment (e.g., battery chargers). Patients must have a competent caregiver present at all times.
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71. Nursing Management Circulatory Assist Devices
Goal
Recovery through ventricular improvement
Heart transplantation
Artificial heart implantation
Many patients will die or choose to terminate device, causing death.
Psychologic support for patient and caregiver is essential.
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Audience Response Question
The pulmonary artery waveform of a patient with a pulmonary artery catheter is blunted. The nurse notifies the health care provider, recognizing that:
1. The balloon is overinflated.
2. The catheter may be occluded by a thrombus.
3. The catheter is wedged in a pulmonary capillary.
4. The catheter has migrated from the pulmonary artery to the right ventricle.
Answer: 2
Rationale: The pressure tracing will be blunted if the catheter starts to be occluded. The pressure tracing will appear wedged if the PA catheter advances and becomes spontaneously wedged. Ventricular dysrhythmias can occur during PA catheter insertion or removal, or if the tip moves from the PA to the right ventricle and irritates the ventricular wall. In this case, you will note that the PA catheter cannot be wedged.
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Case Study
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Case Study
78-year-old man is admitted to ICU in acute decompensated heart failure.
Pulmonary artery catheter and arterial lines inserted
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Discussion Questions
Why is it important to keep the transducer at the level of the phlebostatic axis?
How can you determine if the blood pressure is accurate?
1. Pressure monitoring equipment is referenced and zero-balanced to the environment, and dynamic response characteristics optimized for accuracy. Referencing means positioning the transducer so that the zero reference point is at the level of the atria of the heart. The stopcock nearest the transducer is usually the zero reference for the transducer. To place this level with the atria, you use an external landmark, the phlebostatic axis.
2. Table 66-2 outlines the steps to be followed in obtaining BP measurements with an invasive line. Obtain measurements from both digital and printed analog outputs. Readings from a printed pressure tracing at the end of expiration (to limit the effect of the respiratory cycle on arterial BP) are most accurate.
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Discussion Questions
3. Why would you monitor the mean arterial pressure?
What measurements would be abnormal in someone with acute decompensated heart failure?
3. Mean arterial pressure (MAP) refers to the average pressure within the arterial system that is felt by organs in the body. In patients with invasive BP monitoring, this value is automatically calculated and takes the patient’s HR into consideration. A MAP greater than 60 mm Hg is needed to adequately perfuse and sustain the vital organs of an average person under most conditions. If the MAP falls significantly below this number for an appreciable time, vitals organs will be underperfused and will become ischemic.
4. Decreased CO/CI; increased PA pressures, PAWP.
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Discussion Questions
5. If the PA/PAWP is elevated, what could this indicate?
What should the nurse do if the PA waveform looks wedged?
What purpose does thermodilution serve?
5. Heart failure and volume overload
6. There is danger of rupture of the PA if the catheter moves distally into a smaller vessel, or if the balloon is overinflated. This is suspected when the waveform looks “wedged” spontaneously.
7. With the thermodilution CO method, a fixed volume (5 to 10 mL) of room temperature (18º to 25º C [64.4º to 77º F] or cold (0º to 12º C [32º to 53.6º F]) solution of normal saline or 5% dextrose in water is injected rapidly (≤4 seconds) and smoothly into the proximal lumen port of the PA catheter. The thermistor sensor detects the differences in blood temperature. The computer calculates the CO from the area under the temperature curve. The larger the area under the curve, the lower the CO, and, conversely, the smaller the area under the curve, the higher the CO.
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