Foundations of Invasive Hemodynamics

Transcription

1 Foundations of Invasive Hemodynamics Contact Hours: 2.0 First Published: April 17, 2013 Course Expires: September 30, 2016 Copyright 2013 by RN.com All Rights Reserved Reproduction and distribution of these materials is prohibited without the express written authorization of RN.com

2 Acknowledgements RN.com acknowledges the valuable contributions of Juli Heitman, RN, MSN. Juli has thirteen years of nursing experience. For five years she worked at the bedside in medical-surgical and cardiovascular intensive care units. The last eight years have been in the nursing education role as a nursing adjunct instructor and a critical care hospital educator. She currently works as an Education Specialist for Mercy Regional Health Center, Manhattan, Kansas. She specializes in critical care, cardiovascular lab and radiology education and staff development. She received her Bachelor of Science in Nursing from the University of Nebraska Medical Center in 1999 and Masters of Science Degree in Nursing Education at University of Central Missouri in She is a member of the American Nurses Association, National Nurse Staff Development Organization, and American Association of Critical Care Nurses. Conflicts of Interest and Commercial Support RN.com strives to present content in a fair and unbiased manner at all times, and has a full and fair disclosure policy that requires course faculty to declare any real or apparent commercial affiliation related to the content of this presentation. Note: Conflict of Interest is defined by ANCC as a situation in which an individual has an opportunity to affect educational content about products or services of a commercial interest with which he/she has a financial relationship. The author of this course does not have any conflict of interest to declare. The planners of the educational activity have no conflicts of interest to disclose. There is no commercial support being used for this course.

3 Purpose The purpose of this course is to inform the healthcare provider about the function, maintenance, and complications associated with the pulmonary artery (PA) catheter, arterial line, and central venous pressure monitoring. Learning Objectives After successful completion of this course, you will be able to: 1. Describe the indications for invasive hemodynamic monitoring. 2. Review hemodynamic values. 3. Describe three steps to ensure waveform accuracy. 4. Discuss preload, afterload, and contractility. 5. Identify the nursing care of a patient with hemodynamic monitoring. 6. Explain SvO2 in its relevance to hemodynamic monitoring. 7. Apply hemodynamic monitoring concepts through case study.

4 Introduction The pulmonary artery catheter was developed and used by Dr. H.J. Swan and Dr. W. Ganz in It still has a presence in the intensive care units but has declined slowly over the years. Currently, it is used in patients who undergo cardiac, extensive non-cardiac surgeries and critically ill patients in a critical care setting. It is also used in evaluation of the right side cardiac pressures in the cardiac cath lab. In some instances, if a patient s condition is deteriorating and traditional therapies are not working, a PA catheter can assist the practitioners to see detailed information about the heart and lungs. Even though the PA catheter can provide useful information, it is an invasive procedure in which the catheter is cannulated through a large vein and inserted into the heart itself. It is floated into the right side of the heart and remains in the pulmonary artery until it is removed. Therefore the risks and benefits should be weighed and discussed before insertion. For the therapies to be successful, the PA catheter waveforms and values must be accurately interpreted. It is imperative to have a well trained physician and nursing staff who have a good understanding of cardiopulmonary hemodynamics, so they are able to ensure accuracy of the values and promptly care for the patient as their condition changes. Functions of a PA Catheter The PA catheter provides continuous, detailed hemodynamic information that cannot be obtained through traditional and non-invasive assessments. The PA catheters are able to directly measure core body temperature, cardiac output, cardiac index, right-sided intra-cardiac pressures, pulmonary artery pressures, and pulmonary artery wedge pressures. Additionally, based on those values the PA catheter can assist in determining estimates for pulmonary vascular resistance and systemic vascular resistance and other hemodynamic values that are based on body surface area. Depending on what type of PA catheter is used, mixed venous blood oxygenation (SvO2) and transcutaneous pacing can be done. It is also important to note depending on type of catheter used, that SvO2 and cardiac output can either be measured continuously or intermittently.

5 Review of Pulmonary Anatomy and Physiology A PA catheter may be considered with a patient who is experiencing cardiopulmonary difficulties when traditional medical and pharmacological methods are not working. The physician may be attempting to rule out pulmonary conditions which would be causing the patients decline. Pulmonary Anatomy and Physiology The right lung has three lobes while the left lobe has two. Lung expansion or inspiration is possible because the pressure in the pleural space is less than the atmospheric pressure. Expiration occurs passively as the intercostal muscles relax. The lungs are responsible for many things such as ventilation, diffusion, and perfusion (Hodges, Garrett, Chernecky & Schumacher, 2005). Pulmonary Circulation The right ventricle feeds unoxygenated blood into the pulmonary artery. The pulmonary artery divides in the right and left branches which brings unoxygenated blood to the alveolar capillaries. As the red blood cells pass through the alveolar capillaries, there is an exchange of carbon dioxide for oxygen. Pulmonary veins then return oxygenated blood to the left atrium to be finally distributed to the aorta via the left ventricle. Can Stock Photo

6 Indications for Use PA catheters are used when a patient s hemodynamic status requires detailed, continuous monitoring which cannot be accomplished through non-invasive means such as physical assessment and non-invasive vital signs. Specifically, it is used for patients who have a complicated myocardial infarction (MI) in which a patient develops cardiogenic shock or congestive heart failure; in the presence of respiratory failure to assist in improving oxygen delivery; in burns, multisystem organ failure, shock (cardiogenic, hypovolemic, septic) where vasoactive medications and fluid management are essential for positive outcomes. Because PA catheters offer continuous, real time patient data this assists the physician to order the appropriate pharmacological interventions in attempts to improve the patient s condition. Contraindications Before inserting the PA catheter it is imperative the physician and nurse identify if there are any contraindications. All are considered relative contraindications; therefore the risks and benefits must be identified for each one and discussed with the patient and/or patient s family. Relative contraindications are as follows: Presence of fever (>101ºF [38ºC]): If a patient has a fever prior to insertion, a PA catheter insertion should be carefully considered due to its invasive nature and possibility of introducing micro-organisms directly into the heart. Patients with existing left bundle-branch block are at increased risk for complete heart block, as the electrical impulses are already slowed or blocked as they travel through the conducting tissue in the ventricles. In complete heart block, none of the electrical impulses reach the ventricles. If the patient is in an anti-coagulated state or has received anti-thrombotic medications this has the potential to place the patient at high risk for blood loss. Mechanical tricuspid valve or presence of an endocardial pacemaker is contraindicated. If there is a history of heparin-induced thrombocytopenia (HIT), the catheters may be coated with heparin and therefore non-heparin-coated catheters should be used. (Wiegand, 2011)

7 Risks Due to the invasive nature of this procedure, the following are complications that could arise during the insertion or while the PA catheter is in place. The catheter could cause dysrhythmias if it comes in contact with the endocardium during insertion, while in place or while being removed. In the same manner, be aware of the patient s electrolyte imbalances and correct them if possible before insertion because electrolyte imbalances make the heart more susceptible to dysrhythmias. Infection can occur if the sterile field was jeopardized during insertion or during dressing changes. PA perforation can occur if the patient has feeble vessels due to pathology. The catheter could become entangled in the valves or chordae tendinae causing structural damage. If the balloon is in wedge greater than 15 seconds, this will cause pulmonary artery ischemia and possible pulmonary infarct. Rarely, the balloon at the tip of the catheter could rupture causing an air embolus. Pulmonary artery infarction is the most serious and fatal complication of PA catheter insertion. Test Yourself Which of the following risks of pulmonary artery catheters is the most life-threatening? A. Infection B. Dysrhythmias C. Pulmonary artery infarction The correct answers are C. Although infection and dysrhythmias are potential complications of a PA insertion, pulmonary artery infarction is the most serious and fatal complication of PA catherter insertion.

8 Types of PA Catheters There are various types of PA catheters available as most PA catheters seen in the ICU will have the capability to continuously monitor central venous pressure (CVP), pulmonary artery pressures (PAP), pulmonary artery wedge pressure (PCWP), and cardiac output either intermittently or continuously. Most of them can be inserted into a subclavian, jugular, or femoral vein. In the cardiac cath lab setting, a basic kind of PA catheter is typically used for right heart pressure monitoring and diagnostic studies in patients. During uncomplicated heart cath procedures, the catheters are removed when the procedure is over. The technology of PA catheters has improved over the years; some catheters have a port for temporary pacing. Specialized catheters can either be atrial and/or ventricular pace (A-V pacing) or just ventricular pace. Other catheters have ports that continually monitor mixed venous oxygen saturations (SvO2) as well as continuous right ventricular end diastolic volume (RVEDV), and right ventricular ejection fraction (RVEF) ( n.d.).

9 The PA Catheter There are different types of PA catheters that can be used to monitor the patient; however the most common type is a catheter that has four lumens. 1. The proximal port is for monitoring CVP/right atrial pressures (injectate port for cardiac output). 2. The PA distal port is used to monitor PA pressures (systolic, mean, and diastolic). 3. The balloon inflation port is used for inflating and deflating the balloon during insertion as well as when the PCWP is being measured. The balloon maximum inflation is 1.5 ml of air, though at times less air is needed to gain the desired result. ONLY use the syringe the manufacturer included in the kit and NEVER fill this balloon with fluids. 4. The thermistor connector is used for connecting it to the monitor cable for measurement of cardiac output/cardiac index and blood temperatures. It assists in measuring the change in blood temperature. 5. If other ports exist then these are used for additional monitoring, fluid infusion, or for inserting a pacemaker electrode.

10 Test Yourself The PA distal port is used for: A. Fluid administration B. ABG monitoring C. PA pressure monitoring The correct answer is C. The PA distal port should only be for monitoring and not infusion of fluids. Insertion The procedure for the insertion of the PA catheter will differ somewhat between hospitals. It is good nursing practice to refer to your hospital s own policy and procedure manual to ensure patient safety. Because this is an invasive procedure, an informed signed consent is obtained prior to the procedure. The physician should discuss the risks and benefits associated with this procedure to the patient and/or the patient s family. To reduce anxiety and before signing the informed consent, ensure there has been a proper explanation to the patient and/or family why the patient needs a PA catheter. During the procedure assist the patient in remaining still yet providing comfort as the patient will be asked to lay flat and a sterile sheet will be placed over them.

11 Test Yourself To reduce patient anxiety, what would be most helpful to the patient who is not intubated? A. Get the procedure over as soon as possible, ignoring sterile and aspetic techniques. B. Allowing them to see how the PA catheter is inserted, even though they have a productive cough. C. Explain the procedure to them as it happening. Speak with a calm and reassuring voice. The correct answer is C. Calmly explaining the procedure as it happens gives the patient reassurance.

12 Insertion Step One: Gather Supplies No matter which type of PA catheter is selected for insertion, there are specific types of supplies which are needed. PA Catheter: The physician selects the PA catheter appropriate to the patient s condition. Percutaneous Sheath: Introducer kit with sterile catheter sleeve. Flush Solution: Flush solution as recommended by your hospital s standards. This will allow a small continuous flush of 3-5 ml/hour for patency and flushing when needed. Pressure Bag: Remember to use the appropriate size pressure bag. The bag should always be inflated to 300 mm/hg. Pressure Tubing: This tubing is non-compliant tubing. Prior to insertion, the tubing should be flushed completely and all air bubbles eliminated. This fluid-filled tubing transmits the signal from the patient to the transducer, which then is translated to waveforms and values on the monitor. Pressure Transducer/Manifold: This is where the stopcock will be placed. Stopcocks: Stopcocks are part of the pressure tubing. Place non-vented caps on the stopcocks as this will prevent air from entering the system. Since the pressure waveforms/values are measured relative to atmospheric pressure (the air pressure around us), then the transducer, using the stopcock, must be zeroed. IV Pole: To hold the transducer. Cables: Cables are plugged into the transducer as well as the module connected to the monitor. Module: Parts of the monitor that will need to be assigned to which hemodynamic value the nurse is monitoring. Monitor: Where all the values and waveforms are seen. Zeroing is also achieved at the monitor. Emergency Equipment/Crash Cart: In preparation for dysrhythmias or worsening condition of patient.

13 Insertion Indelible Marker: Used to mark the phlebostatic access. Sterile Dressing Supplies: Place over PA catheter insertion site. Level: To ensure transducer/stopcock are placed accurately in relation to the phlebostatic axis. This is the time where the nurse calibrates the equipment and zero s the monitor. Insertion Safety Ensure you complete a time out and have TWO patient identifiers for SAFETY and there is an appropriate number of head coverings, fluid-shield masks, sterile gowns and gloves, and nonsterile gloves for those involved in the procedure. Click here to watch the Swan-Ganz Catheter Placement video.

14 Set Up for the PA Catheter Step Two: Set-up the pressure transducer system. This will include the pressure tubing, flush solution, transducer, and IV pole. In an aseptic technique, spike and prime the pressure tubing until all air is eliminated. Hang the solution on the IV pole and flush all the pressure tubing, take special care to flush out all the air in the tubing and stopcocks. Be sure to replace the ends of the stopcocks with non-vented caps. Label the transducer as well as the tubing with the appropriate colors. Typically, the blue label is used for the CVP line, the yellow label is used for the PA port and the red label is used for the arterial line (which is not part of the PA catheter set-up). Image courtesy of Federal Drug Administration, 2013.

15 Insertion: Step Three While preparing the patient for the procedure, take one more look and make sure you have all the supplies needed for the procedure in the room. Anti-anxiety medication may be prescribed if the patient is anxious. The physician may request to put a small rolled up towel between the shoulder blades to assist in obtaining the desirable position for PA catheter insertion. The whole bed is raised and some of the side rails are put down to meet the needs of the physician/practitioner. If the patient can tolerate, the head of bed is usually flat. In some cases the Trendelenburg position is used to increase the blood flow to the veins. Insertion: Step Four The cardiac monitor needs to be in a position where both the physician and nurse can see the ECG and waveforms. In addition, the RN is responsible for reporting dysrhythmias to the physician as they occur. After the physician connects the PA catheter to the pressure tubing, all the lumens shall be flushed. Then connect it to the pressure system and zero the transducer. The PA catheter is 110 cm in length and the thin dark hash marks on the catheter reflect 10 cm, while the thick hash marks reflect 50 cm.

16 Insertion: Step Five Sterile technique must be used to decrease the risk of patient acquiring a central line catheter infection. After the site is cleaned (usually jugular or subclavian) sterile drapes are applied over the patient. The physician/practitioner complies with sterile technique by wearing the appropriate personal protective equipment. Waveforms When the PA catheter is inserted, the physician and the nurse should know how to read the waveforms. Right atrial (RA) waveform or CVP is the first waveform seen and the physician will ask for the balloon to be inflated. This facilitates the catheters movement through the heart. During the insertion, the physician may direct the nurse to inflate and deflate the balloon as needed to float the PA catheter through the heart. Right ventricular (RV) waveform is seen when the catheter arrives in the RV. Pulmonary artery pressures waveforms are different than the RV wave forms and the physician will instruct the balloon to inflate until it is wedged in the pulmonary artery. When the balloon is released, then PAP s will appear again. The PA catheter remains in the PA until it is removed. It is important to know the differences between the RV and PA waveforms in case it migrates back to the RV. The physician will continue to advance the catheter in the pulmonary artery until the tip (with the balloon inflated) is properly in the wedge position. Once the PCWP is noted the balloon is deflated. The catheter remains in the pulmonary artery.

17 Monitoring and Securing the PA Catheter After the PA catheter is inserted and the sterile dressing is applied, then a chest x-ray should be ordered and completed promptly to ensure proper placement. In addition, while the PA catheter is in place, daily chest x-rays should be ordered to ensure the catheter has remained in the pulmonary artery. Once the PA catheter is confirmed to be in the proper place, secure the catheter as well as the pressure tubing and cables coming in from it.

18 Hemodynamic Accuracy There are three steps to hemodynamic accuracy. These are, leveling, zeroing, and the square wave test. These three methods should be used for hemodynamic monitoring such as arterial lines, CVP lines as well as PA catheters. Leveling The phlebostatic axis is what the nurse should LEVEL to the stopcock. The phlebostatic axis is located at the 4 th intercostal space, mid-axilalary line. This is the location of the right atrium. Best practice is to always use a leveling device. DO NOT eye-ball the phlebostatic axis when leveling. If the head of the bed is increased or decreased this will change the location of the phlebostatic axis, so re-level and zero for accuracy (Lippincott, Williams & Wilkins, 2007). Zeroing Zeroing is the second step, which can be also known as zeroing the transducer. After leveling the transducer to the phlebostatic axis, then turn the stop-cock off to the patient and remove the cap. Be certain not to contaminate the cap. Press the zero button on the monitor and wait for the number 0 to appear. Replace the cap and return the stop-cock to its original position. Why do we do this? We want to remove the atmospheric pressure by creating a neutral pressure of 0 mm Hg, from which hemodynamic values can be accurately measured. This ensures the pressure values we see on the monitor are only those values which are reflected in the vessel or heart (Lippincott, Williams & Wilkins, 2007).

19 Hemodynamic Accuracy Square Wave Testing The third step in ensuring accuracy is called the square wave test. This is done by fast-flushing the system for 1-2 seconds and noting the waveform or the square wave and the oscillations that precede it in correspondence to the fast flush. There are three types of square waves; optimally damped system, over-dampened system, and under-dampened system: 1. Optimally dampened system correlates with a properly working system and does not require any interventions. 2. Over-dampened waveform is the most common and this may be caused from not enough pressure in the pressure bag, flush bag is empty, blood clots or air bubbles in the non-compliant tubing. 3. Under-dampened waveform may be caused by air bubbles in the system. Image provided courtesy of Smith Medical. 2010

20 Performing a Wedge Pressure Depending on the condition of the patient a wedge pressure is performed every 2-4 hours. Slowly inflate the balloon with air. Although the maximum amount of air is 1.5 ml, not every wedge will require the full amount. Once slight resistance is felt, look up at the monitor to see if the PAP waveform now resembles a PCWP waveform. Record the pulmonary pressures going into wedge as well as coming out of wedge. Do not keep the balloon inflated more than 15 seconds. In addition, when the air is released and pulmonary artery pressures are noted on the monitor, close the stopcock and remove all air out of the syringe so it will not be accidently inflated.

21 Cardiac Output/Index Depending on what kind of set-up you have, you may either have intermittent bolus thermodilution (TDCO) or continuous cardiac output (CCO). If you are working with continuous output, then the rule of thumb is to get three consistent and accurate waveforms. If completing TDCO, then the injectate must be the intravenous solution of 500 ml of D5W. The injectate syringe must be connected to the proximal port and it is very important that there is not any IV fluids or solutions infusion at the time you are completing CO. If tolerated, the patient head of bed should be between 0-20 degrees. Draw up the D5W solution into the 10 ml syringe included in the CO monitoring kit. Inject the solution within four seconds and at endexpiration allowing 60 seconds between each CO measurement. Repeat up to five times with room-temperature injectate (three times for cold injectate) and calculate three values that are within 10% of each other (Wiegand, 2010). One benefit of CCO eliminates the fluid boluses as used in the TDCO. The CO readings on the monitor are updated every seconds. However, the nurse should be cautioned when treating a hemodynamically unstable patient, because the CO is not real time data, but instead reflects the values prior 3-6 minutes of information in regards to CO (Wiegand, 2010).

22 Hemodynamic Concepts: HR The building blocks of hemodynamics start with the heart rate (HR). As you know the heart rate is measured by how many beats per minute (bpm) the heart is contracting. If a patient is in sinus rhythm, the normal heart rate is between bpm. Hemodynamics will be altered if their rhythm is too slow or too fast and the impulse does not originate from the SA node. For example, if a patient is in atrial fibrillation, there is a loss of atrial kick and heart rate variability that needs to be taken into consideration. Hemodynamic Concepts: SV and CO The next building block is stroke volume (SV). SV is the amount of blood pumped out of the ventricle with each contraction. A normal stroke volume is between ml/beat. Another hemodynamic value can be calculated is called SVI. It is calculated by taking SV BSA (body surface area) (Wiegand, 2011).. The third building block is cardiac output (CO). CO is the amount of blood that is pumped out of the ventricles in one minute. A normal CO is between 4-8 L/min. Therefore, HR x SV = CO. Blood Volume: Think About It The next time you are at the grocery store picking up some milk, think about your heart. Every minute your heart is pumping 1-2 gallons of blood, which correlates to gallons of milk every hour. Now that s a lot of milk, I mean blood!

23 Hemodynamic Concepts: CO and CI Cardiac index (CI) is a hemodynamic measure that relates the cardiac output (CO) to body surface area (BSA). This relates heart performance go the size of the individual. The cardiac index (CI) is usually calculated using the following formula: CCCC = CCCCCCCCCCCCCC OOOOOOOOOOOO (CCCC) BBBBBBBB SSSSSSSSSSSSSS AAAAAAAA (BBBBBB) = SSSSSSSSSSSS VVVVVVVVVVVV (SSSS) HHHHHHHHHH RRRRRRRR (HHHH) BBBBBBBB SSSSSSSSSSSSSS AAAAAAAA (BBBBBB) The unit of measurement is liters per minute per square meter (L/min/m2). The normal range of cardiac index (CI) at rest is L/min per square meter. Note! If the CI falls below 1.8 L/min/m2, the patient may be in cardiogenic shock. Test Yourself What is normal CO/CI? A. 2-6 L/min; L/min/m2 B. 4-8 L/min; L/min/m2 C L/min; L/min/m2 The correct answer is B. Normal CO/CI is 4-8 L/min; L/min/m2.

24 Determinants of Cardiac Output Cardiac output = Heart rate stroke volume Three factors directly influence stroke volume: 1. Preload 2. Afterload 3. Contractility Hemodynamic Concepts: Preload Preload is the STRETCH of the cardiac muscle fibers in the ventricle. It stretches to accommodate the fluid in the chambers. Preload can also be considered volume or filling pressures. It is the filling pressure of the ventricles at end-diastole. It is like asking how much pressure is in the ventricles right before the blood is squeezed out. Since there are no obstructing valves between the vena cava and right atrium, it is possible to measure the right atria filling pressures by central venous pressure (CVP) monitoring.

25 Hemodynamic Concepts: Measuring CVP CVP can be either measured by a central line catheter, peripherally inserted intravenous catheter (PICC) or a PA catheter. With the PA catheter, the nurse can indirectly measure the left atrial filling pressure by the pulmonary capillary wedge pressure (PCWP) monitoring. It also called wedge or wedge pressure. PCWP is also referred to as the pulmonary artery occlusive pressure (POAP). Even though we are measuring the right and left atria pressures we associate those pressures as venous filling pressures from systemic (vena cava) and pulmonary (pulmonary veins). Frank-Staling Law The Frank-Starling Law states, The greater the stretch, the greater force of the next contraction (Hodges, 2005). To better understand the Frank Starling Law, let s use the example of the rubber band being the heart s muscle. The less the rubber band is stretched the less it will propel in the air. The further the rubber band is stretched the greater the force and it will propel in the air further. As this relates to preload, if there is too little preload (stretch) as in hypovolemia, the heart will not have enough stretch to propel the blood (cardiac output) through the body. If volume increases, the more preload (stretch) the heart will have and will contract with more force. In the same manner if the rubber band is continually, excessively stretched over time it will lose it elasticity. The heart muscle will wear out and lead to heart failure.

26 Hemodynamic Concepts: CVP and PCWP Preload is measured through the hemodynamic values called CVP and PCWP. CVP is the measurement of the preload/stretch on the right side of the heart. Normal values for CVP is 2-6 mm/hg. PCWP is the measurement of the preload/stretch on the left side of the heart. Normal values for PCWP are 4-12 mm/hg. In general what increases preload (both CVP and PCWP)? Increased intravascular fluid volume Vasoconstriction In general what decreases preload (both CVP and PCWP)? Decreased intravascular fluid volume Vasodilation Volume displacement- 3 rd spacing Dysrhythmias in which there is a loss of atrial kick and/or atrial filling Increased intrathoracic pressure Right Ventricular Preload Measured By: CVP Left Ventricular Preload Measured By: PAWP Afterload is the RESISTANCE or pressure the ventricular heart muscle must overcome to eject its own volume. Afterload is measured through the systemic pressure and is clinically measured by the blood pressure. For example if the patient has a blood pressure of 180/84, the left ventricle must reach a pressure greater of 180mm/Hg to open the aortic valve. OR you can also look as it as there is a 179 pounds of pressure or RESITANCE on top of the aortic valve and until the left ventricle reaches 180 mm/hg it will not open.

27 PVR Pulmonary vascular resistance (PVR) is the resistance of blood flow through the pulmonary circulation (Lippincott, Williams & Wilkins, 2007). A normal PVR is dynes/sec/cm Increases PVR Hypervolemia Vasoconstrictors Decreases PVR Early septic shock Arterial vasodilators Right Ventricular Preload Measured By: CVP Left Ventricular Preload Measured By: PAWP SVR Systemic vascular resistance (SVR) is the resistance against which the left ventricle must pump in order to move blood through the systemic circulation. Left ventricular afterload is increased by atherosclerosis, valve stenosis and vasoconstrictors. A normal SVR is dynes/sec/cm Increases SVR Hypervolemia Vasoconstrictors Right Ventricular Preload Measured By: CVP Decreases SVR Early septic shock Arterial vasodilators Left Ventricular Preload Measured By: PAWP

28 PVR/SVRI SVR and PVR can be further broken down by body surface area. Those values are referred to as systemic vascular resistance index (SVRI) and pulmonary vascular resistance index (PVRI). In general, if the values are high this indicates vasoconstriction, while lower values would show vasodilation. Contractility Another determinant of stroke volume is contractility. Contractility is defined as the degree of ventricular squeeze independent of preload or afterload. The contractility is primarily affected by the sympathetic nervous system (Orlando Health, 2010). If the patient is anxious or has pain, the heart will squeeze harder. As you remember the Frank-Starling law states the greater the stretch the greater the contraction. However, increased preload in a compromised cardiac patient does not necessarily equal great contraction, the cardiac muscle might not stretch at all because of overuse/failure. Contractility cannot be measured directly. However, ventricular stroke work index (VSWI) is used to measure myocardial contractility. (The equation for VSWI is: MAP-PCWP x SVI x ) (Hodges, Garrett, Chernecky & Schumacher, 2005).

29 Contractility Medications Electrolytes Increases (SQEEZE) Contractility Positive inotropes (Ex. Digoxin, dopamine, dobutamin) Hypercalcemia (calcium stimulates the heart to contract) Decreases (RELAX) Contractility Negative inortopes (Ex. Betablockers, calcium channel blockers Decreases magnesium, sodium, calcium, increases potassium O2 & CO2 Hypoxemia, acidosis, hypercapania Myocardial infarction Stunned heart, scar tissue HR & Rhythm Increased HR Tachy for too long, them decompensates Autonomic nervous system Sympathetic Parasympathetic Hemodynamics

30 SvO2 Another benefit of continuous cardiac monitoring is that they also monitor mixed venous oxygen saturation (SVO2). SvO2 can be monitored via a fiberoptic thermodilution PA catheter. It is the assessment of the balance of oxygen delivery and oxygen consumption (Wiegand, 2011). Oxygen demand is the amount of oxygen the cells and tissues require for their own metabolism. There are conditions like suctioning, turning and shivering which increase the oxygen demand. To better understand Svo2, let s trace a red blood cell, called Ruby. As Ruby leaves the body through the left ventricle, it goes into the aorta with an oxygen saturation of %. She branches out with her other red blood cell family into other arteries where they deliver oxygen to the tissues and cells who need it. Then it continues to travel to the arterioles, capillaries, then venules and veins. It finally ends back up into the vena cava, right atrium, right ventricle, and then the pulmonary artery, where before it goes into pulmonary circulation we can take a continuous reading of how much oxygen the arteries used. The normal values of Svo2 are between 60-80%. Increases SvO2 (decreases body s demand for oxygen) Anesthesia Chemical paralysis Increased oxygen saturations Hypothermia Increased cardiac output Increased hemoglobin Sedation Decreases SvO2 (increases body s demand for oxygen) Cardiogenic shock Septic shock Decreased cardiac output Decreased hemoglobin Fever Seizures Shivering (Lippincott, Williams & Wilkins, 2007)

31 Case Study: Introduction A 76 year-old was admitted to the medical floor with two days of nausea and vomiting. He has a history of diabetes, myocardial infarction five years ago with a drug-eluting stent placed in his right coronary artery (RCA). At that time he had an ejection fraction (EF) of 40%. You noted he has amputated 4th and 5th digits on right hand. Case Study: Patient s Vital Signs On admission is vital signs were: Day BP 100/60 HR 124 RR 22 SaO2 93% Physician ordered 0.9% NS to infuse at 125 ml/hour x 12 hours, then a maintenance infusion at 75 ml/hour Labs were drawn and CXR was completed Cardiac telemetry shows sinus tachycardia All home blood pressure medications were held Ondansteron (Zofran) 4mg IV every six hours was ordered Patient remains NPO No supplemental oxygen is ordered

32 Case Study: Lab Values With two doses of ondansteron (Zofran) the patient was able to rest without nausea or vomiting. His labs returned with abnormal white blood count (WBC) at 14,000 without a shift to the left. His potassium was 5.2 with his BUN/creatinine 22/2.0. At 0200 note the patient s vital signs. Patient was alert and oriented, but sleepy. Case Study: Fluid Assessment What other assessment(s) would be helpful in determining if the patient is getting enough fluid? ü Urine output The patient s urine output was recorded as 50 ml in the last 12 hours. His 12- hour intake/output was 1500mL/50mL. You asked him to void again before calling the physician. He was unable to void. He denied feeling like his bladder was full. To ensure there was not retention, you also palpated his bladder and it was not full or distended. Day BP 88/52 HR 130 RR 28 SaO2 92%

33 Case Study: Bolus In addition to noting a decrease urinary output, you notice a persistent tachycardia (HR of 140 bpm) and hypotension (BP 90/40). You immediately call the physician orders a 500 ml 0.9% NS bolus to be given over 30 minutes and to continue the fluids at 125 ml/hour after the bolus is completed. The bolus infuses without incident and you place the maintenance fluids at 125 ml/hour. The patient denies pain and you re-take his vital signs at Case Study: Second Bolus An hour after the bolus was infused the patient s vital signs have not improved. You notify the physician and he ordered another 500mL 0.9% NS bolus. The bolus is infused and at 0500 his vital signs are as follows: Day BP 90/48 120/82 HR RR SaO2 92% 90%

34 Case Study: Central Line Insertion The physician makes his rounds at 0630 and notices his blood pressure is improved. However his tachycardia should have resolved with his blood pressure increasing. The patient starts to complain of shortness of breath. On auscultation, the physician hears crackles bilaterally. Due to a history of a prior MI and an EF of 40%, the patient was transferred to the cardiac stepdown unit for CVP monitoring. In addition, 12-Lead ECG, ECHO and cardiac enzymes were ordered. A central line was placed in the right internal jugular (IJ). The pressure tubing and manifold was set up. The stop-cock was leveled to the fourth intercostal space, mid-axillary line (phlebostatic axis). The brown (proximal) port was used to measure CVP. The initial readings of the CVP were at end-expiration. His blood pressure is 110/70. Case Study: Elevated CVP What would cause his CVP to be elevated? Right ventricular heart failure, with the left starting to fail. ECHO showed an EF of 20%, the 12- Lead showed some ischemia in the anterior leads, which correlates to the coronary arteries which supply blood to the left ventricle. The physician ordered furosemide 40 mg IV x 1, keep NPO, and decrease the IV fluids to 25 ml/hour.

35 Case Study: Day Two It is now 1400 on day two of his hospitalization. The 40 mg of furosemide was administered at 0800 and the patient voided 400 ml. His vital signs at 1200 are noted. Day BP 100/52 HR 120 RR 26 SaO2 88% The physician decided to place an arterial line in the right radial artery to monitor his blood pressure continually as well as start to draw frequent arterial blood gases (ABGs). Case Study: Patient Plan of Care The physician suspects this patient is having cardiac ischemia because of this continued tachycardia. Ischemia is noted in the 12-Lead ECG and low urine output. Even though the patient s cardiac enzymes are negative, we will continue to monitor them and consult a cardiologist. Because of the patient s blood pressure and tachycardia with dropping saturations, he inserted an arterial line because this patient is slowly becoming more unstable especially noting his drop in oxygen saturations.

36 Case Study: Patient Monitoring We will start monitoring ABGs every four hours as well as arterial line pressures every 15 minutes. He would like to be called if the mean arterial pressure (MAP) falls below 70 mmhg. Normal MAP is (Ferns, T., et al, 2010). Due to the condition of this patient he is going to transfer the patient to intensive care unit. The cardiologist has been called and after he is finished with a procedure in the cardiac cath lab he will see the patient. In the meantime, the patient is closely monitored and his plan of care, which includes placing an arterial line, frequent lab draws, cardiologist consult and transfer to the ICU is discussed with the patient and his family that are at the bedside. Case Study: Radial Artery The radial artery is the most common place for arterial line placement. However, it can be inserted in other arteries such as the brachial, axillary, or femoral depending on patient condition and physician's preference. The arterial line is set similar to the PA catheter in which a pressurized fluid system is required, transducer, monitoring cable, monitor, and level. If inserting a radial arterial line, an Allen s Test should be performed to ensure there is blood supply to the hand if the arterial line becomes occluded.

37 Allen s Test Procedure 1. Raise the patient s hand and ask them to make a fist. Occlude both of the radial and ulnar arteries by applying pressure with your fingers. 2. Instruct the patient to clench their fist a few times and take note of blanching or paleness that will occur. 3. Release pressure from the ulnar artery, while maintaining pressure on the radial artery. If the ulnar artery is patent, you will see the hand color return (then release pressure from the radial artery). 4. If it takes more than 5-10 seconds for color to return after you have released pressure from the ulnar artery, the Allen s Test is considered negative and that radial artery should not be used. (Hodges, Garrett, Chernecky & Schumacher, 2005)

38 Case Study: Cardiologist Examination The patient was seen by the cardiologist and because of his ischemia and history of an MI and stent placement five years ago he will take the patient to the cardiac cath lab for a right and left heart catheterization. The cardiologist explained to the patient and his family the procedure as well as the risks and benefits of associated with the cardiac catheterization. Informed consent was obtained and patient was prepped from the procedure which was scheduled for The patient was admitted to the cardiac cath lab. A right and left heart cath was performed. It was noted he had severe multi-vessel disease and needed coronary artery bypass graft (CABG) surgery. The patient was taken to operating room and he had four-vessels bypassed. The patient was returned to the cardio-thoracic ICU. Due to the nature of his surgery, the patient had a PA catheter inserted intraoperatively for additional monitoring. Let s continue to learn about the hemodynamics to better interpret what the numbers mean clinically. Day CO 3.4 CI 1.7 CVP 10 PCWP 16 PVR 93 SVR 1500 HR 80

39 Test Yourself Day CO 3.4 CI 1.7 CVP 16 PCWP 16 PVR 93 SVR 1800 HR 80 Using the reference table above, why would the SVR & PCWP still be high and CO/CI low? a. Effects of cardiogenic shock b. Hypothermia c. Blood loss from CABG The correct answer is A. Signs of cardiac shock include an elevated SCR and PCWP with a low CO/CI.

40 Case Study: Dobutamine and Nitroglycerin Drips The cardiac surgeon orders a dobutamine drip as well as a nitroglycerin drip. What is his rationale? The dobutamine drip will increase the CO/CI and the nitroglycerin drip will decrease the SVR and PCWP (afterload) of the left ventricle. Some effects of the dobutamine drip are increased oxygen consumption and potential for dysrhythmias. Nitroglycerin drip may decrease the blood pressure, so slow titration is warranted. Look at the hemodynamics two hours after the start of the dobutamine and nitroglycerine drips. BEFORE AFTER Day Day CO 3.4 CO 5.2 CI 1.7 CI 2.6 CVP 16 CVP 10 PCWP 16 PCWP 12 PVR 285 PVR 185 SVR 1800 SVR 1000 HR 80 HR 84 As you can see the dobutamine increased the cardiac output/index and the nitroglycerine decreased the PCWP and CVP to normal values. The patient continued to progress through the night and was extubated the next day. The dobutamine and nitroglycerine drips were weaned off and the PA catheter was discontinued. Let s see how a PA catheter is discontinued. Day CO 5.2 CI 2.6 CVP 10 PCWP 8 PVR 128 SVR 1000 HR 84

41 Removal of PA Catheter According to the AACN Procedure Manual for Critical Care (2010) the following steps should be followed when discontinuing the PA catheter. The nurse washed hands and donned gloves. All IV and flush solutions were discontinued. The patient laid flat, but could not tolerate the Trendelenburg position. Trendelenburg is helpful if it is not contraindicated and they turn their head to the opposite side of the insertion site. The PA waveform was noted and it was not in wedge. The old dressing was removed and the sheath from the introducer was loosened. As AACN recommends, the gloves were changed, hands washed, and sterile gloves were applied. Sutures were present and removed without incident. Then, to prevent an air emboli, the patient was instructed to hold his breath and the PA catheter was removed with a constant, steady motion. Once the catheter is removed, the patient was instructed to exhale. The nurse placed her sterile-gloved finger over where the PA catheter was pulled out, until a sterile cap was placed over it to prevent air emboli. Due to poor IV access, the introducer remained in place, and meticulous site care was performed. The patient was soon transferred to the cardiac step-down unit and six days later returned home.

42 Future of Hemodynamic Monitoring Due to the invasiveness and risks associated with the PA catheter, a Pulmonary Artery Consensus Conference was held in 1997 in which it was debated if the use of the PA catheter was less beneficial and more risky to patients. The consensus was not to eliminate the PA catheter, but the need for standardized practice and education for both physicians and nurses was imperative (Smartt, 2005). Technology has assisted in the development of examining more detailed hemodynamic monitoring such as right ejection fraction (REF), right ventricular end-diastolic volume (RVEDV), and SvO2. Non-invasive monitoring devices, such as those listed below, are providing accurate values in clinical situations. However, they have yet to completely replace the PA catheter. (Smartt, 2005) Non-Invasive Monitoring Devices Esophageal Doppler Monitoring Central Venous Fiberoptic Technology Pulse Contour Cardiac Output Lithium Electrical Impendence Ultrasound Cardiac Output Measurement

43 References Edwards Lifesciences, n.d. Swan-Ganz Catheters retrieved from Ferns, T. et al. (2010). Mean arterial blood pressure and the assessment of acutely ill patients. Nursing Standard, 25(12), Hodges, Garrett, Chernecky & Schumacher (2005). Hemodynamic Monitoring. Philadelphia, PA: Elsevier-Saunders. Lippincott, Williams & Wilkins (2007). Hemodynamic Monitoring Made Incredibly Visual. Philadelphia, PA: Lippincott, Williams & Wilkins. Orlando Health (2010). Advanced Hemodynamics. Orlando Health, Education and Development. Retrieved from Scales, K. (2010). Central venous pressure monitoring in clinical practice. Nursing Standard, 24(29), Smartt, S. (2005). The pulomonary artery catheter: Gold standard or redundant relic. Journal of PeriAnesthesia Nursing, 20(6), Wiegand, D. (2011). AACN Procedure Manual for Critical Care. (6 th Ed.). Ambler, PA: Lippincott, Williams & Wilkins.

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