Pulmonary Artery Catheters: Measuring Hemodynamics at the Bedside

Sometimes, I look around my patient’s room and wonder what I have entered into with all the machines beeping, the monitors giving me a random assortment of numbers, and a patient in a bed surrounded by all this technology. Despite the uneasy feeling it creates for most patients and families, it is where I feel most in my element. The thought of writing this blog about something that I eat, sleep and breathe should be easy in theory. Much easier than walking into that room, day after day, caring for patients, who are strangers really, and then going back to my normal, regularly scheduled life, but it’s not.

This blog is dedicated to the Swan-Ganz catheter (SGC), also known as the pulmonary artery (PA) catheter, which is enough to scare even the most seasoned intensive care (ICU) nurse. Technology has come a long way since Drs. Swan and Ganz developed this catheter, which is inserted at the bedside and gives continuous information about the patient’s hemodynamic profile through a balloon-tipped thermodilution catheter. Before the PA catheter, patients would go to the cath lab for a snapshot of their cardiac output and index. Now we have this technology at our fingertips to make lifesaving decisions each and every day. Additionally, we have advanced cardiac output information that can be simply obtained by an arterial line, and let’s not forget urine output, which is our sneak peek into end-stage organ damage.

What is a Swan Ganz Catheter?

Many intricacies seem to make this catheter overwhelming when you start learning how to use it. Especially when it comes to troubleshooting waveforms, most importantly the daunting and dreaded “wedge.” The PA catheter has many uses, but I find it is primarily used for patients with heart failure/heart transplant/mechanical support in my Cardiac Intensive Care Unit (CVICU). Clinicians love the information it provides about the right and left sides of the patient’s heart after placement. As the catheter is inserted into the right internal jugular and passes through the right atrium, you will see the central venous pressure (CVP) with an expected value between 0-8 mm Hg. You will also see the A, C and V waves. “A” stands for atrial contraction and will be aligned with the PR interval.

At this time, the catheter should be inserted about 15 cm, and the physician or advanced practitioner will instruct you to blow up the balloon to help “float” the catheter through the heart. This is where we usually start to sweat, but we do it and lock it into place. As the catheter passes through the tricuspid valve, there is mixed pressure and the waveform appears as ventricular tachycardia. We sometimes hold our breath as we watch this catheter float through the chamber, tickling the heart as it goes. Since the right ventricle has a higher systolic pressure than the right atrium, the expected values are the systolic of the PA and the diastolic of the right atrium with numeric values of 25/8. As the catheter continues to float through the right ventricle into the PA, the dicrotic notch of the pulmonic valve closure comes into view on the screen.

I teach everyone the easiest way to remember the normal values of the PA pressures are quarters over dimes (25-30/10-15). The catheter will be advanced into the right ventricle and “floated” into the pulmonary artery, where it will eventually be “wedged” into a small vessel against the wall of the artery, giving it the name of wedge or occlusive pressure. At this point, you will be asked to deflate the balloon on the catheter to prevent rupture.

There are many different names for wedge pressure. It can be referred to as pulmonary artery wedge pressure (PAWP), pulmonary artery occlusive pressure (PAOP) or left ventricle end diastolic pressure (LVEDP). As I was teaching the staff about PA catheters, the many names for wedge pressure became frustrating for them. Since it can be confusing to call the same thing many names, find out what your team prefers, so you are aware.

Do No Harm, Protect Yourself With Physician Orders

One of our biggest struggles, as nurses, is what we see in textbooks when we learn about waveforms. Our patients’ waveforms usually do not look like the pictures, making this procedure challenging to learn. It is very likely that patients with heart failure will have atrial fibrillation (A Fib), frequent ectopy and/or a paced rhythm. As you may know, our patients can have all three, in addition to a right or left bundle branch block; thus making the wedge procedure the most erroneously named procedure in our practice. Our unit does not allow this procedure to be done without a physician’s order because of the potential harm to patients. The balloon can become permanently wedged and occlude the artery, acting as a clot-obstructing blood flow mechanism.

So, we started with an unrecognizable waveform and now we get to magically align the A wave, end expiratory, with the QRS complex. I don’t know about monitors at your facility, but our monitors do not display an easy-to-read respiratory waveform. I place my hand on the patient’s chest to determine the end expiratory of respiration phase. The reason for this alignment is to take intrathoracic pressure out of play while you measure the mean of the A wave. As discussed earlier, the A wave is an atrial contraction, so that is the time when the mitral valve will be open, giving us an indirect look into the left ventricle. How fascinating to think about a completely venous system with the opportunity to see the left side of the heart! As antiquated as the PA catheter seems, it provides so much information to guide care for the critically ill patients who have compensated for so long and are at risk for multiorgan system failure. As nurses we have the opportunity to help our patients feel better with goal-directed therapies.

From the patient and family’s point of view, it appears that we are picking up radio frequencies from another planet. To them, it is just a bunch of squiggly lines running across the screen that often beep and alarm. Naturally, that sound is terrifying, not to mention annoying, but even more so if you don’t know what it means or how to interpret it. I try to take the time to educate patients and families with the truth … It’s data, and a lot of it! As ICU nurses, we use every bit of detail, data and assessment findings to provide the best and most comprehensive care possible. While the care may sometimes look frightening to patients and families, it’s very helpful to nurses.

Dynamics Keep Me at the Bedside

During peer interviews, I’m often asked why I have been at the bedside so long and what I like about being a bedside nurse. I enjoy the ICU, because I love seeing our work make a difference in patients’ lives. I especially love the cardiac ICU, because I love implementing a vasopressor or a vasodilator and know that, as critical care nurses, we hold so much knowledge. We understand and even anticipate what will happen as we work with these medications. A friend once told me that it’s hemoDYNAMICS for a reason; it’s always a dynamic change. We are constantly adapting our practice minute by minute to achieve patient stability.

I remember the day I first felt like a critical care nurse, even after being in the unit for a couple of years. I had a patient who was on every possible drip to keep their body responding to our interventions, and I probably had 13 or 14 pumps running. Back then we didn’t have four channels per main-brain infusion pump to reduce clutter in patient rooms. Can you imagine how that would look these days with various other pieces of equipment also in there? We wouldn’t be able to get to the patient. I was feeling pleased with her blood pressure and rhythm, so I weaned down the diltiazem infusion. About 45 minutes later, she went into rapid AFib and her blood pressure tanked as well. I knew I had to titrate up on the diltiazem. I was crazy for even thinking about titrating this drip off, knowing that it would also drop her blood pressure. I had to get her rhythm back under control in order to create hemostasis and save her life. Within 10-15 minutes of titrating up on her infusion, her rhythm had returned to sinus and her pressure improved as well. This story helps illustrate the dynamic world of hemostasis we strive to achieve among all the other duties we perform at the bedside.

Remember Your End Goals

Remember, however, it’s not just about data and numbers. Managing hemodynamics at the bedside is enhanced by all the technology, from the arterial line all the way to the PA catheter, to support our patient assessments. Having this data and patient assessment information helps us determine what type of shock our patient is in. From there we can begin to anticipate which vasopressors will benefit our patients and return them to hemostasis, which is our goal.

To Learn More About PA Catheters:

• Article: “Pulmonary Artery Catheterization”
• NTI Session: “Art of Hemodynamics Waveform Analysis and Assessment”
• Webinar: “Applying Functional Hemodynamics: A Goal-Directed Strategy”
• Practice Alert: “Pulmonary Artery/Central Venous Pressure Monitoring in Adults”