Hi there, thank you for this opportunity. My name is Ashish Khanna and today I'll be talking about the very familiar pulmonary artery catheter. Is my PAC leading me astray? These are some of my disclosures. So when we talk about the PAC or the pulmonary artery catheter, we have to talk about shock. Just to sort of describe the lay of the land, mortality from cardiogenic shock varies anywhere between 40 to 67%. And in our armamentorium to monitor hemodynamics in cardiogenic shock, the pulmonary artery catheter is often combined with an arterial line, an arterial line giving us clear indication of beat-to-beat hemodynamics. We also obviously look at biomarkers, we look at echocardiography, and all in all, it's a team approach. In fact, an actual shock team approach with various consultants has been shown to improve 30-day overall survival in this patient population from, you know, an overall about 40% to all the way up to the mid-70%. So why the pulmonary artery catheter? Well, simplistically speaking, it is a great tool to measure intracardiac pressures. With or without a CVP, it will tell you a CVP, it will tell you a PA pressure, it will tell you a pulmonary capillary wedge pressure when wedged appropriately and used in that methodology. It will also provide cardiac output with an intermittent thermodilution or one of the continuous methods of providing cardiac output. It will also give you an access port to measure mixed venous oxygenation, clearly an important tool to check oxygen content and delivery. And also, furthermore, it will calculate out various numbers that are important in the titration of therapeutics that not just includes cardiac output and cardiac index, but also things like CPO, CPI, and PAPI. Left and right heart performance, such as the stroke work index, can also be calculated through the PAC. So the important PAC-based decisions are both in terms of the SKY classification of cardiogenic shock are both sort of diagnostic and help in classification of patients. And thereby, as patients advance from being at risk or beginning stages of shock to being an extremist, we are able to monitor them better, we are able to intervene early, and hopefully that early intervention prevents or changes the overall course of the patient. So here is why PACs may be really, really important. I talked about the fact that they help us titrate our therapeutics and decide therapeutics. They also help us making decisions in vasopressors versus inotropes are a combination and or inclusion of mechanical circulatory support. Importantly, they are really critical in unmasking mixed shock and also look at normal tensive cardiogenic shock, which is an entity with poor flow and increased vascular tone. Now an example here is a recent analysis that we did and published where we did see that in patients with cardiogenic shock, when sepsis and septic shock was superimposed on cardiogenic shock with or without a STEMI, their overall adjusted in-hospital mortality did increase. Now, clearly meaning that patients who come in with cardiogenic shock, when they have septic shock to add to the mix, that is a problem and a good way of unmasking different types of shock is the pulmonary artery catheter. Now, if I go back in time, the earliest work with the PSC goes all the way back to the 1970s. So it's published in the New England Journal of Medicine, William Ganz and Jeremy Swan first catheterized the heart of a human with the use of a floor-directed balloon-tipped catheter and presented their work. And it would turn out to be, you know, obviously practice-changing, obviously 50 years later we use the PA catheter as a routine. But I just wanted you all to look at how it all started. And another look back into this beautiful piece of work shows the images of the early pulmonary artery catheters. And interestingly, if you look at the average passage times, they are in the 30 to 45 second ranges, which is amazing, but it's important to realize that they were using fluoroscopy to guide passage of these catheters. So how has evolution evolved over time? Well, actually, the use may be declining over the years. After an initial period of enthusiasm, there was overall decline of the pulmonary artery catheter, although in recent years that has stabilized. Importantly, there's been meta-analyses, but this Cochrane review is fairly recent and it looked at all types of mortality in general intensive care patients, in high-risk surgical patients, and whatever way the data was sliced and diced, there was no difference whatsoever in overall mortality, length of stay, cost, and so on and so forth, although studies have pointed in both directions. In fact, some recent studies have actually shown a cost-benefit. In the end, the use of APSC is still very much dependent on local practice culture in your ICU, in your cardiac operating rooms, or other operating rooms. And recommendations vary. And again, it's beyond the scope of this talk to go into all of the society recommendations for APSC, but I just wanted to show you an overview of the data. This is a nice piece of work that was published in the JAMA and says exactly what I just said, that overall trends in use of the pulmonary artery catheter have shown a decline, at least from the early 90s to the early 2000s. Now this is old data, and I will tell you that if we were to do something like this again today, there would probably be an overall stabilization of the use of the pulmonary artery catheter, definitely something to think about for an updated analysis. So what are the challenges with the pulmonary artery catheter? The challenges, number one, are complications, right? And we all understand, like any other central line, that this one going through an introducer, chances of a pneumothorax, hemothorax are as much as any other central cannulation, air embolism, pulmonary infarction when inappropriately placed, pulmonary artery perforations have been reported, pseudoaneurysm formations have been reported, and ruptures have been reported as well, thrombobolic phenomenons has been reported, atrial or ventricular arrhythmias, rare case valve rupture or cardiac wall perforations, and then very commonly, misplacement and looping of the pulmonary artery catheter within the RV or sometimes even within the pulmonary artery itself. Now again, some of these complications have actually, over a period of time, we've been able to deal with them. Most centers don't put the catheter in a wedged position all the time and only use intermittent wedging and so on and so forth. And we have sort of come to a point where we know how to balance the risk-benefit equation. But there are challenges with PAC numbers, importantly, placement and positioning. Don't place the catheter properly, don't position the patient properly, don't zero the transducer properly, don't level the transducer properly, PAC numbers will be inappropriate. An under-damped or over-damped pulmonary artery catheter is a big problem. And not many of us test this by doing a regular square wave test. We should be doing a regular square wave test all the time when we put a patient on a swan GANS. Unfortunately, not done as much as it should be done, but that's another problem that can lead to an under-damped or over-damped waveform. Continuous cardiac output swans versus intermittent thermal dilution is really, really important as recently continuous cardiac output swans have come into evolution and are being increasingly utilized. However, there are some fallacies with those that I'll talk about. Response times do vary, and there might be an element of drift and certain arrhythmias again that are common with a pulmonary artery. And those arrhythmias then interfere with the numbers that come from a pulmonary artery catheter, namely cardiac output. So I talked about continuous cardiac output swans. They have some sort of a thermistor and a heating circuit that warms up the blood in the RV as it flows through the RV into the pulmonary artery and then measures the change in temperature compared to an intermittent thermal dilution where there would be a bolus of something injected through the catheter itself, and then the change in temperature is measured, and that calculates out the cardiac output. So intermittent thermal dilution relying on usually three shots of that bolus injected and intermittently measured cardiac output versus a CCO doing it automatically. Now is there a difference? Nice little analysis in Critical Care recently published in 2021 saw pooled mean differences less than 0.1 liters per minute, 95% limits of agreement only being between 1.6 to 1.8 on either side of the axis, pooled percentage error of about 30%. So 30% is sort of that cutoff line for us when we compare devices. So the continuous pulmonary artery thermal dilution swan did pass the interchangeability criteria with intermittent pulmonary artery thermal dilution, although this criteria was just about barely met based on this analysis that was just published. Now what are some challenges with pulmonary artery catheter numbers? The first one is what is the best response time? So we do know that the continuous cardiac output swan averages out and responds differently in terms of cardiac output numbers compared to other measures of cardiac output. We have been doing some work where we have compared peripheral arterial waveform guided cardiac output measurements to a continuous cardiac output swan and here our analysis does show in the red a continuous thermal dilution swan versus in the blue a continuous arterial line measure and does show that the response times to cardiac output seem to vary in both of them with a little bit of a lag of the continuous cardiac output. Now whether this is significant clinically or not remains to be seen and what is an appropriate response time also remains to be seen, but there is a difference whatso, you know, nonetheless. And then misplacements with the pulmonary artery catheter are common. We have all seen horror stories, x-rays where catheters are placed all over. There is a real horror story where this one was placed intrathecally and clearly, you know, these kinds of misadventures obviously lead us to believe that the pulmonary artery catheter itself and its placement is not a benign procedure. So what else could replace a pulmonary artery catheter? Well, echocardiography and noninvasive estimation including continuous cardiac output and measures of pulmonary artery systolic pressures and SVR could. Here is a review by Bernd Sogl and colleagues just published in Anesthesiology that divides cardiac output monitoring into the traditional invasive with the swan GANs in the middle, minimally invasive with pulse wave analysis from an arterial catheter, I just showed you some of that, with an esophageal Doppler and a probe and then totally noninvasive with a finger cuff or applanation tonometry sensor or with a pulse wave transit time using an EKG and a pulse oximeter or a bioimpedance through the chest wall and bioreactants using thoracic electrodes. So there's a full spectrum going from totally invasive measures to measure a cardiac output and then minimally invasive and totally noninvasive. It's beyond the scope of this talk but I did want to present this slide for those who are interested. This is a great review, it goes over all the technology that is currently available that will measure cardiac output and is alternative to a traditional swan GANs measuring cardiac output. And there's been lots and lots of studies that have compared and cross-validated technology. Here is one that compares the LITCO-PICO flow track and pulmonary artery catheters and all of this work is being done again and again as new technology comes out. This one, the most important thing I liked about the conclusion of this study was that utility and validation studies using only one cardiac output device may potentially not be extrapolated to equivalency of using another similar device. So difficult to say that one device is the same as the other device just based on validation studies. It has to be more patient-specific. Here are some studies that we are doing at our own institution. For example, we are looking at pulse decomposition analyses as a tool to measure cardiac output in ICU patients. Now normally arterial waveform based analyses look at left ventricular ejection time based derivations of the A-line. We are using in this technique something called exponential decay estimates that effectively estimate peripheral arterial resistance and give an improved value for a systolic area. And potentially they're more accurate than just systolic pulse area estimates. Here is some initial data. We're still waiting on a full analysis of the correlation and validation data set. However, more to follow. The initial data looks fairly encouraging. We have also done recently analysis of something called the long-time interval arterial blood pressure waveform. This is the latter half of the single beat response of an A-line waveform that is not distorted by reflection caused by peripheral vascular resistance. What we have seen in the long-time interval based arterial waveform analyses is a fairly robust correlation with continuous cardiac output measured Swann-Ganz thermodilution in both a regular correlation analysis and a Bland-Altman analysis with a fairly tight across the means variance and fairly good accuracy and precision. We also did this analysis on a subset of patient population that had arrhythmias. Arrhythmias, you know, are fairly common after cardiac surgery. Our correlation of the LTI and continuous cardiac output Swann was fairly strong, as you can see here, both on a regular correlation plot and a Bland-Altman analysis. There are a lot of different method comparison studies for cardiac output monitors where the reference standard is a pulmonary artery catheter. That is number one on this infographic. Number two, it's important to see whether the authors a priori stated what would be an acceptable level of correlation or agreement that would be clinically relevant and acceptable and not just statistically significant. Number three, did they present a scatter plot of the two methods that they used? Are they mathematically correlated across a range of values? Number four, does their Bland-Altman analysis include allowances for repeated measures because these would be repeated measures, as well as confidence intervals around the limits? And number five, a trending analysis wherever possible using a four-quadrant technique should be done unless a reference standard is not known. And finally, is the pulmonary artery catheter still alive? And a very nice review, again, by Daniel DeBacker and Jean-Louis Vincent has a really nice table that goes over the different types of monitoring and a comparison of pulse wave analysis guided cardiac output of transpulmonary thermodilution and a pulmonary artery catheter. And clearly, the pulmonary artery catheter is very much still alive. It has excellent reliability of measurements. It can give you additional measurements such as a PA pressure, a pulmonary artery occlusion pressure, mixed venous oxygen saturation, and will be and should be exclusively used in a severely ill patient with marked left or right cardiac dysfunction. So bottom line, right patient, right use with improved training, teaching, and awareness, the pulmonary artery catheter, even though it has its nuances and possible fallacies, it is still very much alive in clinical practice. Thank you so much for your time, and I'm open for questions.

pulmonary artery catheter

monitoring

cardiogenic shock

intracardiac pressures

cardiac output