Arterial Line Pressure Monitoring (Nursing)

00:01 Hi, my name is Corey and welcome to my class on Hemodynamics.

00:05 Hemodynamics is a very important aspect of critical care nursing and something that I am very passionate about.

00:12 If you're interested in becoming a critical care nurse, I'm going to teach you the most important things to know about hemodynamics.

00:18 Like how to read PA waveforms and titrate medications, and prepare you to answer key questions when you're communicating with physicians.

00:27 Let's get started.

00:28 The first thing we're going to cover in our invasive hemodynamic monitoring is arterial lines.

00:33 Typically, when we get blood pressure, we get static blood pressures from a blood pressure cuff, either on the arm or on the leg.

00:41 But sometimes patients are critical and we need to have a continuous blood pressure.

00:45 We do this by an arterial line that's placed directly into the artery.

00:51 Usually, we place it in the radial artery or the femoral artery.

00:56 The femoral artery is less desirable because it's dirty.

01:00 But sometimes we need quick access or the patient's anatomy doesn't allow us to put it in the radial artery.

01:06 Other places we can put it in are the ulnar artery, the brachial artery, or the dorsalis pedis artery.

01:14 Once we've gained access to the artery with our arterial catheter, we need to hook up a transducer and a pressure tubing to that catheter.

01:22 The goal of the transducer is to take the blood pressure and then transduce it into an electrical waveform and send it to the bedside monitor.

01:31 When you look up at the bedside monitor, you're going to see an arterial line waveform.

01:36 The first part of that arterial line waveform is the systolic upstroke.

01:41 This is the beginning of systole.

01:43 When that left ventricle contracts, it causes that waveform to go up.

01:47 At the very top of the waveform is called our systolic peak pressure.

01:52 This is where we get our systolic pressure from.

01:56 Then we have a decline in our waveform, and we get what's called the dicronic notch, that little blip in the arterial line waveform.

02:05 That dicrotic notch is the aortic valve slapping shut.

02:10 This indicates the beginning of diastolic pressure.

02:14 Following this, we have another cardiac cycle in which you'll see the upstroke in the beginning of systole.

02:21 When you look at the waveform and hole, you'll see a bunch of cardiac cycles.

02:25 And then over to the right, you'll have your blood pressure your systolic, your diastolic and in parentheses underneath that, you'll have your mean arterial pressure.

02:35 Okay.

02:36 Prior to accessing the radial artery, we need to make sure that there is blood flow through the ulnar artery.

02:42 Why is that important? Well, there is a risk when we access a radial artery, we may block blood flow to the hand through that artery.

02:51 Now, hopefully they'll have enough blood flow through the ulnar artery to perfuse the rest of the hand.

02:56 Now we check this with what's called the modified Allen's test.

03:00 In order to do this, we place our thumb on the radial artery and our other thumb on the ulnar artery, that we have the patient pump his hand four or five times until the hand becomes white.

03:11 This indicates there is no blood flow going to the hand, Then we release our thumb on the ulnar artery, and we should get blood flow back to the hand, we'll see color, come back to the skin, and we'll have good capillary refill.

03:26 This is an indication that the ulnar artery is patent, and you have blood flow through that.

03:32 Let's go into a complications of the arterial line.

03:36 Our first complication that we may have is pain.

03:39 Anytime we access an artery, we're going to cause pain to the patient.

03:43 Hopefully, we can do this in a controlled setting.

03:45 And we can give the patient some lidocaine so they don't they don't feel it.

03:49 What's important is to educate the patient on what's going on, that they'll feel pressure and that the procedure will be quick.

03:57 The next complication is infection.

04:00 This is more rare than a central line infection, but it is a complication.

04:04 We want to make sure that the dressing is clean and dry, or change it when it becomes saturated.

04:10 Make sure that this area is as sterile as possible.

04:14 The next complication of an arterial line is bleeding and hematoma.

04:18 If your patient is on a heparin drip, or is at risk for bleeding already, they are probably going to bleed a little bit around that catheter site which is okay, you're just going to have to change the dressing more often.

04:28 But we want to be aware that bleeding could become more profuse or we could have a hematoma forming.

04:34 If you see swelling around the area and a lot of swelling around the area that indicates a possible hematoma.

04:41 We want to take the catheter out and hold pressure and then call the physician.

04:47 Our next complication is an arterial embolus.

04:51 This means either we've had air go through the arterial catheter or a foreign object.

04:57 This is an issue because it may block blood flow to the hand.

05:01 If the hand becomes discolored, or we see a large amount of air going through the catheter, we need to call the physician so that they can intervene quickly.

05:10 The last complication I wanted to discuss here is misinterpretation of the data.

05:14 This means that the blood pressure you're seeing on the monitor, the systolic, the diastolic and the mean arterial pressure are incorrect.

05:22 This can happen when the tubing is kinked.

05:24 When there's air in the tubing, when there's a clot at the catheter tip, or when the transducer is not at the level of phlebostatic axis.

05:32 This may cause you to perform an intervention that is not appropriate for that patient and may cause patient harm.

05:38 So make sure that the data that you're seeing is correct.

05:44 So we talked about the misinterpretation of data, probably the most common cause of that is your transducer.

05:51 That transducer which has a stopcock on, it needs to be in line with the phlebostatic axis.

05:57 The phlebostatic axis is also the right atrium of the heart.

06:01 It's the fourth intercostal space in the axillary line.

06:06 So when you're measuring that transducer, you're gonna get it right in line with that phlebostatic axis of the heart, and that is giving you the most accurate blood pressure.

06:16 If that transducer is below the phlebostatic axis, you're going to have an artificially high blood pressure.

06:22 And if that transducer is above the phlebostatic axis, you're going to have an artificially low blood pressure.

06:29 Now, with patients, we can get the transducer to be incorrect when we're moving patients around, when we're bringing the head up or down, when we're turning the patient.

06:39 Every time we do something with a patient, we need to double check that transducer and make sure that it is in line with the phlebostatic axis.

06:47 Also, we need to be zeroing the system to make sure that we have an accurate blood pressure as well.

06:53 So after we make sure that the phlebostatic axis is in line, we need to turn the stopcock up which is off to the patient and open to air.

07:03 And then we go to our monitor and we zero it out.

07:06 Depending on your monitor and maybe a different ways of doing this, but basically this is zeroing the system so that we're getting an accurate blood pressure.

07:15 And then again, we're always checking with a manual blood pressure if we think our arterial line is not working correctly, if we think our arterial line is dampened.

07:24 Always check with a manual blood pressure cuff to see if they are accurate or close within one another.

07:31 If they're not, then usually you're going to trust the manual blood pressure cuff over the arterial line pressure.

07:37 Our last assessment on our arterial line waveform is our square wave test or also called our snap test.

07:46 In order to do this, we have to pull the flush tab fully until the waveform becomes flat and up to 300 millimeters of mercury.

07:54 Once that happens, we released the flush tab and caused an audible snap to to occur.

08:01 After that happens, we look up at our arterial line waveform and we assess for oscillations.

08:07 An optimally damped system or optimally damped waveform is 1-2 oscillations.

08:14 If you have under 1 oscillation, you have an overdamped waveform.

08:17 And if you have greater than 2 oscillations, you have an under damped waveform.

08:23 The most common alteration in our arterial line is an overdamped waveform.

08:27 This is a dampening of the signal from the catheter to the transducer.

08:31 This causes our arterial line to be less crisp, and we may lose our dicrotic notch.

08:38 Causes of an overdamped waveform are air or bubbles in the tubing, clots at the catheter tip, catheter tip against the vessel wall, the stopcock could be partially closed, deflated pressure bag, tubing is kinked, or an extension pressure tubing is used but it's not the correct diameter or size.

08:56 I would say the most common cause of an overdamped waveform would be error bubbles in the tubing system.

09:02 The other alteration that we have in arterial lines are an under damping waveform.

09:07 This is an artificially enhanced signal from the catheter to the transducer.

09:11 This will lead to an overestimation of systolic blood pressure and an underestimation of diastolic blood pressure.

09:18 But our map should be accurate.

09:21 Causes of this could be tachycardia, more of our atrial tachycardia than our ventricular tachycardias or we have extra stopcocks added to the system.

09:31 Or if we also have a very high cardiac output, we could have an under damped waveform and we get a bounding arterial line.