focus on hemodynamic monitoring and circulatory assist devices (relates to chapter 66, “nursing...

Focus on Hemodynamic Monitoring and Circulatory Assist Devices

(Relates to Chapter 66, “Nursing Management: Critical Care,” in the textbook)

Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.

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Hemodynamic Monitoring

Measurement of pressure, flow, and oxygenation within the cardiovascular system

Includes invasive and noninvasive measurements


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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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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)


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Hemodynamic MonitoringGeneral 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


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Systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR) Opposition to blood flow by

systemic and pulmonary vasculature

Preload, afterload, and contractility determine SV.


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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

movedCopyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.

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Contractility: strength of ventricular contraction

PAWP: measurement of pulmonary capillary pressure; reflects left ventricular end-diastolic pressure under normal conditions


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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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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


Components of Pressure Monitoring System

Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 11

Fig. 66-3. 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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Identification of the Phlebostatic Axis


Fig. 66-4. Identification of the phlebostatic axis. A, Phlebostatic axis is an external landmark used to identify the level of theatria 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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Zeroing: confirms that when pressure within system is zero, monitor reads zero During initial setup of

arterial line Immediately after insertion

of arterial line


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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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Optimizing dynamic response characteristics involves checking that equipment reproduces, without distortion, a signal that changes rapidly.


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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


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Dynamic Response Test (Square Wave Test)


Fig. 66-5. Optimally damped system. Dynamic response test (square wave test) using the fast flush system: normal response.

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Types of Invasive Pressure Monitoring Continuous arterial

pressure monitoring Acute

hypertension/hypotension Respiratory failure Shock Neurologic shock


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Types of Invasive Pressure Monitoring Continuous arterial

pressure monitoring (cont’d) Coronary interventional

procedures Continuous infusion of

vasoactive drugs Frequent ABG sampling


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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


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Arterial Pressure Monitoring


Fig. 66-6. A, Simultaneously recorded electrocardiogram (ECG) tracing and B, systemic arterial pressuretracing. Systolic pressure is the peak pressure. The dicrotic notch indicates aortic valve closure. Diastolicpressure is the lowest value before contraction. Mean pressure is the average pressure over timecalculated by the monitoring equipment.

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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.


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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.


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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


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PA Catheter


Fig. 66-7. 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 balloonwith air to allow reading of the pulmonary artery wedge pressure. A thermistor located near the distal tipsenses PA temperature and is used to measure thermodilution cardiac output when solution cooler thanbody temperature is injected into a proximal port. B, Photo of an actual catheter.

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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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Pulmonary Artery Pressure Monitoring Additional lumina (cont’d)

Second proximal port Infusion of fluids and drugs Blood sampling


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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.


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PA Waveforms During Insertion


Fig. 66-9. 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 forchange in the waveform. Balloon inflation (arrow) in patient with a normal PAWP.

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Effect of Overinflated Balloon


Fig. 66-10. 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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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


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Central Venous Pressure Waveforms


Fig. 66-11. 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 representsatrial filling. The y descent represents opening of the tricuspid valve and filling of the ventricle.

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Measuring Cardiac Output

Intermittent bolus thermodilution method

Continuous cardiac output method


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Fig. 66-12. 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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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


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SVR, SVRI, SV, and SVI calculated (cont’d) ↓ SVR

VasodilationShock states and drugs that ↓ afterload

Changes in SV are becoming more important indicators of pumping status of heart than other parameters.


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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.


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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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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


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Venous Oxygen Saturation PA and CVP catheters can

measure oxygen saturation of hemoglobin in venous blood–mixed venous oxygen saturation. SvO2, ScvO2


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Venous Oxygen Saturation SvO2/ScvO2 reflects

balance between oxygenation of arterial blood, tissue perfusion, and tissue oxygen consumption (VO2).


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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

extractionCopyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.

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Venous Oxygen Saturation ↑ in SvO2/ScvO2

May indicate clinical improvement (e.g., improved arterial oxygen saturation)

Worsening clinical condition (e.g., sepsis)


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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)


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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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Complications With PA Catheters Pulmonary infarction or PA

rupture Balloon rupture (e.g.,

overinflation) Prolonged inflation Spontaneous wedging Thrombus/embolus formation


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Preventing PA Rupture and Pulmonary Infarction

Check PA pressure waveforms often for signs of catheter occlusion, dislocation, or spontaneous wedging.


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Preventing PA Rupture and Pulmonary Infarction

Continually flush system with a slow infusion of heparinized saline solution.


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Noninvasive Arterial Oxygenation Monitoring

Pulse oximetry Continuous method of

determining arterial oxygenation: SpO2

Monitoring SpO2 may ↓ frequency of ABG sampling

Normally 95% to 100%


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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


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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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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)


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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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Intraaortic Balloon Pump (IABP) Provides temporary

circulatory assistance ↓ afterload Augments aortic diastolic

pressure Outcomes

Improved coronary blood flow Improved perfusion of vital

organs


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IABP Machine


Fig. 66-13. Intraaortic balloon pump machine.

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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


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IABP


Fig. 66-14. Intraaortic balloon pump. A, During systole the balloon is deflated, which facilitates ejection of theblood into the periphery. B, In early diastole, the balloon begins to inflate. C, In late diastole, the balloon istotally inflated, which augments aortic pressure and increases the coronary perfusion pressure with the endresult of increased coronary and cerebral blood flow.

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Intraaortic Balloon Pump (IABP) Referred to as

counterpulsation Timing of balloon inflation

is opposite to ventricular contraction.


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Intraaortic Balloon Pump (IABP) Complications of IABP

therapy Vascular injury

Dislodging of plaque Aortic dissection Compromised distal circulation

Thrombus and embolus formation


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Intraaortic Balloon Pump (IABP) Complications of IABP

(cont’d) Mechanical complications

Improper timing of balloon inflation

↑ afterload ↓ CO Myocardial ischemia ↑ myocardial oxygen demand


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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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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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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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Ventricular Assist Devices (VADs) VADs can

Be implanted (e.g., peritoneum) or positioned externally

Provide biventricular support


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Schematic Diagram of Biventricular Assist Device


Fig. 66-15. Schematic diagram of a biventricular assist device.

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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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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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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.


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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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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.

Audience Response Question


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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

1.Why is it important to keep the transducer at the level of the phlebostatic axis?

2.How can you determine if the blood pressure is accurate?


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3. Why would you monitor the mean arterial pressure?

4.What measurements would be abnormal in someone with acute decompensated heart failure?


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5. If the PA/PAWP is elevated, what could this indicate?

6.What should the nurse do if the PA waveform looks wedged?

7.What purpose does thermodilution serve?


focus on hemodynamic monitoring and circulatory assist devices (relates to chapter 66, “nursing...

Documents

affiliate of elsevier

volume of blood

hemodynamic monitoringinvasive

phlebostatic axis copyright

blood flow

ventricular preload

density of blood

pulmonary vasculature