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Hemodynamics

by Jill Beavers-Kirby
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    00:00 Hi, my name is Jill Beavers-Kirby and today we're going to be talking about Hemodynamics. So how do we monitor hemodynamics? This system was something a called a pulmonary arterial catheter, or you'll also hear it referred to as a PA catheter.

    00:19 This catheter is inserted under sterile technique by a physician. The brand name that most facilities use is by Swan-Ganz. It's a hyphenated name. The Swan-Ganz catheter has several ports that's used to monitor several different parameters of heart function and central circulation. The catheter is inserted into a large vein, such as the internal jugular, the subclavian, and it will terminate in the pulmonary artery. That's a very important thing to remember.

    00:53 So remember, the tip of the catheter ends in the pulmonary artery. That's why it's called a pulmonary arterial catheter. So one thing we can measure with a Swan-Ganz or PA catheter is the central venous pressure. This is the measure of the blood pressure in the right atrium and the vena cava and it's from the proximal lumen of the PA catheter. I'm not going to review with you all the normals of all these measurements, these are noted on the slides, but you should know them for your test.

    01:21 So why do we need to measure the central venous pressure or CVP? This can tell us how the right side of our heart is functioning. It can tell us systemic fluid status. We can also use central venous pressures to know if we need to give large amounts of fluid. And we can also use the central venous port to draw blood, to take blood tests on patients. So your central venous pressure can be elevated or higher than normal when you have too much fluid in your venous system. This increases your venous return. Or if you have heart failure, so in heart failure your heart muscle becomes kind of boggy and it's not a nice strong muscle. So if the heart muscle instead of pumping like this, it just kind of pumping like this, you can have higher pressures because it's requiring higher pressures to circulate all that venous return.

    02:18 You can also have pulmonary artery stenosis which can cause a higher than normal CVP. Or if your patient's on a ventilator and they've got positive pressure as the setting of their breathing, this can also cause your central venous pressure to be elevated. Pulmonary artery pressure. So if we remember that the pulmonary arterial catheter terminates in the pulmonary artery, pulmonary means lung, so this, the PAP pressure, is measuring the blood pressures in the pulmonary artery. So, like I said, I'm not going to review normals or means, but you should probably know them for your test.

    02:59 So elevated PA pressures. So if you think this is in the pulmonary artery that's going to the lungs, you're going to have elevated PA pressures pretty much with anything that affects the lungs. So COPD, chronic obstructive pulmonary disease or emphysema, or if you have pulmonary artery hypertension, there's certain medications that cause this, or if you have a pulmonary embolus, that would be a clot in one of the pulmonary arteries. Or if you have left ventricular heart failure. Now why is that? That's because the blood is returning from the lungs and it goes into the left ventricle. Or if you have pulmonary edema, that's fluid overload that is affecting the circulation in and around the lungs.

    03:45 Another thing that might cause high PA pressures, and this is a left to right cardiac shunt. This is rare but it does happen. This when if you have a small ventricular septal defect, so you have a little hole between the right ventricle and the left ventricle, and this can make your pulmonary artery pressures higher than normal. Another hemodynamic parameter that we monitor is the pulmonary arterial wedge pressure. You'll see this abbreviated as PAWP, and this measures your left ventricular end diastolic pressure. So remember that, we're going to talk about that again in a few minutes.

    04:24 So if your PAWP or wedge pressure is high, you can probably have left ventricular failure. If the PAWP or wedge pressure is low, you probably have hypovolemia.

    04:40 You've lost blood, you've lost fluid, so you need fluid resuscitation. So cardiac output and cardiac index are two other parameters you can measure with one of these Swan-Ganz catheters. The cardiac output measures the volume of blood that is pumped out of the heart in one minute, and varies with body size. Obviously if you have a small person, they're going to have a small total blood volume. You have a large person, they can have a larger blood volume. So it's not very sensitive, but it is something we kind of take note of. A more sensitive way to measure heart function is the cardiac index, because this is based on BSA, body size. So a low cardiac index you will usually see in cardiogenic shock. So if the heart instead of pumping like a good strong muscle, becomes acutely bogged down and isn't pumping very effectively, the cardiac index is going to be lower. So preload, afterload, stroke volume and Frank Starling mechanism. I remember when I was trying to learn these for the first time as a new registered nurse, and they drove me crazy. So I'm going to try and break this down for you.

    05:49 Preload is the end diastolic pressure. This is what stretches the ventricles, the bottom chambers of your heart. So in other words, it's the end diastolic volume, the amount of blood that occurs at the beginning of systole. Afterload is the ventricular pressure at the end of systole. So in other words, this is the resistance that the heart has to overcome with every beat. So your preload is the pressure at end diastole, afterload is what has to overcome at the end of systole. Stroke volume is simply the amount of blood that is pumped out of the heart with every beat.

    06:36 This is around 70 milliliters. And then Frank Starling mechanism. If you think of a rubber band, so the Frank Starling mechanism simply states that if I put more blood into my heart chambers, my ventricles have to stretch out further. If I keep doing that to my heart, just like a rubber band, it's eventually going to get overstretched and it's not going to be as stretchy as it once was, and it becomes very broken down. That's simply what the Frank Starling mechanism says. So what is systemic vascular resistance? It's the amount of resistance in the systemic circulation.

    07:21 Increased systematic vascular resistance can be due to vasoconstriction, so instead of your blood vessels being opened like this, they're clamped down like this.

    07:31 That's going to increase the pressure. You kind of think like a garden hose. You have a big hose, this big, the water pressure's going to come out very slowly. If you have a smaller hose, the water pressure is going to come out normal.

    07:43 If you get a teeny tiny hose, the water pressure is going to be increased.

    07:48 So an increased systemic vascular resistance or SVR can be due the vasoconstriction, shock or decreased circulating volume. The opposite of that is a decreased SVR. This will be due to anything that vasodilates those blood vessels. So something like morphine, nitrates, nitroglycerine, or any other type of vasodilator. So nursing actions when it comes to the Swan-Ganz catheter or the PA catheter. Often times we'll be called in to help assist putting this in, because these are done in ICUs and they're frequently done at the bedside. Sometimes they're done in the pre-op holding area when a patient's getting ready to go in for surgery. So what you're going to want to do, you're going to want to gather all the equipment, all the tubing and all those sterile gowns and gloves that are needed. You want to make sure you maintain sterile procedure. You'll usually put the patient in Trendelenburg position, this is when the head is lower than the feet, or strictly supine.

    08:52 Most physicians prefer the Trendelenburg position because it causes the blood flow to go up towards the veins that they need to access. Sometimes patients will need a little bit of sedation or pain medicine prior to putting this in.

    09:05 Additional nursing actions when it comes to inserting a PA catheter or a Swan-Ganz catheter, includes levelling the transducer. The transducer is a square thing on the Swan-Ganz catheter that has to be levelled with the center of the heart in order to help measure the pressures inside the heart. So this has to be levelled with the patient's surrounding atmospheric pressure. So in order to do this, you level the transducer at the phlebostatic axis, this is at the 4th intercostal space, mid-axillary line. So you can literally raise somebody's arm and count down four rib spaces, and the transducers are usually attached to a pole at the bedside. You'll level the transducer at that fourth intercostal space, and that also coincides with the middle of the person's heart. This will give you the most accurate readings. After you've done that, you also have to get a chest x-ray to verify placement of these catheters before you instill any type of fluids into them. You can get some preliminary hemodynamic parameters before the chest x-ray is done, but before you put any type of fluid into that line you have to get a chest x-ray for placement. So after chest x-ray, you'd want to attain the initial hemodynamic readings, record them, let the physician know. And you'd also want to monitor your patient's response to the therapies that you're giving based on these numbers. So what are potential complications of inserting a PA catheter? Any time you break the skin, one of the potential complications is infection.

    10:48 Well this catheter is going directly into the central circulation, so you can also cause sepsis. This is when bacteria gets into the central circulation such as your blood stream. You'll usually see infection or sepsis occur when the catheter is inserted, or it can be from a dressing change that has not been done under sterile technique. Another potential complication is an embolus.

    11:13 This is when a blood clot or a plaque becomes dislodged in the catheter and can float through the circulation once again. Another potential complication, this is a short acting complication, you'll see irritation of the ventricle when they are putting in the catheter. So you have to remember the catheter is going into the subclavian, it goes down the vena cava, into the right atrium, right ventricle, left ventricle and finally up into the pulmonary artery.

    11:43 Usually when the catheter is passing through the right ventricle, on the cardiac monitor you'll see a little this, this is very short lasting, lasts less than a second. Once you're through the right ventricle you usually don't see that anymore. However, if you do see additional ectopy, you need to let the physician know because the catheter has been mispositioned. Another potential complication, and this is rare, is perforation of the pulmonary artery.

    12:10 When you're getting a wedge pressure reading, this is done by inflating the balloon on the end of the catheter, if you over inflate the balloon you can rupture that artery. Pneumothorax is simply air that is leaked into the pleural space.

    12:26 This can be caused during insertion from the physician when they can accidentally nick the lining of the lung and caused air to enter that pleural cavity. A thrombus.

    12:38 Your lines have to be heparinized, this means they have to have a little bit of heparin in them so that the lines don't clot off. So if you don't use a heparinized solution when you're initially priming these lines, you can get blood that clogs off that catheter somewhere throughout heart.

    12:56 Thrombus and infection are the two most common types of complications you'll see with these PA catheters. You might see that in the future on your test. Thank you.

    13:08 This has been Jill Beavers-Kirby discussing hemodynamics.


    About the Lecture

    The lecture Hemodynamics by Jill Beavers-Kirby is from the course Physiological Integrity. It contains the following chapters:

    • Hemodynamics
    • Central Venous Pressure (CVP)
    • Pulmonary Artery Pressure (PAP)
    • Systemic Vascular Resistance (SVR)
    • Nursing Actions
    • Possible Complications

    Included Quiz Questions

    1. Pulmonary artery
    2. Right Atrium
    3. Right Ventricle
    4. Left Atrium
    1. To assess electrolyte status
    2. Measure right ventricular function
    3. Measure systemic fluid status
    4. Rapid infusion of fluid

    Author of lecture Hemodynamics

     Jill Beavers-Kirby

    Jill Beavers-Kirby


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