Transcript
Speaker: Welcome to Critical Matters, a sound podcast covering a broad range of topics related to the practice of intensive care medicine.
Speaker: Sound provides comprehensive critical care programs to hospitals across the country.
Speaker: To learn more about our programs and career opportunities, visit www.soundphysicians.com.
Speaker: And now your host, Dr. Sergio Zanotti.
Speaker: Temporary pacing is often required in the immediate post-operative period after cardiac surgery.
Speaker: Critically ill patients presenting to the ICU may also require temporary pacing for several medical conditions.
Speaker: Critical care clinicians at the bedside are more commonly managing patients requiring temporary pacemakers today.
Speaker: In today's episode of the podcast, we will discuss the practical aspects of temporary pacing in the ICU.
Speaker: Our guest is Dr. Christopher Null, a critical care attending at Cooper University Healthcare.
Speaker: Christopher Null is an assistant professor of medicine at Cooper Medical School of Bruin University.
Speaker: He's also the associate program director for the Critical Care Medicine Fellowship and the clerkship director for Critical Care Medicine Clerkship for Medical Students.
Speaker: He's an excellent clinician and clinical educator with a special interest in critical care echocardiography, extracorporeal support, stimulation training, and medical education.
Speaker: Chris, welcome to Critical Matters.
Speaker: Sergio, thanks for having me.
Speaker: I'm really excited to be here.
Speaker: Well, like I said, this is, I think, a very practical topic that I know that you spend a lot of time at the bedside taking care of patients, but also teaching fellows in the simulation lab and also at the bedside.
Speaker: And something that we were commenting before we started recording is that...
Speaker: Temporary transvenous pacemakers were usually a rare occurrence for most intensivists.
Speaker: Now they might occur more frequently with a growing number of cardiac patients, but the management of temporary pacemakers in patients who are post-op is becoming very, very common for intensivists at the bedside.
Speaker: So we figured this would be a great topic to discuss with you.
Speaker: So my first question is, why do you think it's important to discuss this for the bedside critical care clinician?
Speaker: Yeah, absolutely.
Speaker: I mean, I think you hit the nail on the head is that we are expected to manage them.
Speaker: So whether for whatever reason they're put in or whoever put them in, you know, we're the patient, we're the person at the bedside who's expected to come and figure out what the problem is in the middle of the night as much of everything else we do.
Speaker: And so I think it's important to have a basic understanding and framework for how to troubleshoot them.
Speaker: And in terms of, could you make some general comments on clinical situations when the bedside critical care clinician may interact with these temporary pacemakers?
Speaker: So maybe a little bit of a list of some of the indications that we see today in the ICU.
Speaker: Sure.
Speaker: So, you know, for patients,
Speaker: For a lot of situations, it may be just your high-degree AV block, so someone with symptomatic bradycardia is either a bridge to a permanent pacemaker or as a trial period while you're waiting for some medications to wash out.
Speaker: Maybe they're on a beta blocker or a calcium channel blocker.
Speaker: The other reason would be someone who is post-cardiac surgery.
Speaker: So they may need some pacemaker support coming up bypass, whether it be due to the effects of cardiopulmonary bypass and the loss of an adequately perfusing rhythm after that, or if it's secondary to inflammation or edema related to the actual surgery themselves.
Speaker: Or in some cases, though pretty rare, would be for overdrive pacing in the setting of recurrent ventricular arrhythmia.
Speaker: So whether it's a transvenous modality or, you know, through epicardial wires, as I'm sure we'll talk about, you know, it's they all work in a similar fashion.
Speaker: And, you know, being able to manage them through those periods is helpful.
Speaker: I think as we begin our discussion, Chris, maybe we can start with just an overview of the basic PACER modes.
Speaker: I think this is obviously very conventional nomenclature that all intensivists should be aware of.
Speaker: So could you tell us a little bit about the PCR code and what it means at the bedside?
Speaker: Yeah, so if you get into more complex PACER modalities, there's actually more codes that apply.
Speaker: But I think for the intensivists, the first three...
Speaker: letters of the code PSR are really what's important.
Speaker: And most of the pacers we're dealing with modes that we'll be dealing with are encompassed by that.
Speaker: So what does that mean?
Speaker: Is it every pacer mode is defined by the acronym PSR.
Speaker: So it's easy to remember, I think, because it's
Speaker: phonetically spells out pacer or i guess it could be pisser if you want it to be but psr so what that refers to is p is the first letter of the mode and that's going to indicate what what cardiac chamber is getting paced the the second letter is designated by s is what chamber is getting sensed so what are you looking at from the native heart
Speaker: Which chambers are you looking at?
Speaker: And then R, the third letter, is designated in what's the response to what you sense.
Speaker: So as an example for PSR, you might be pacing the ventricle.
Speaker: You might be sensing whether the patient has a native ventricular rhythm.
Speaker: And then your response may be to inhibit the pacer because there is a native rhythm that is faster than the pacing rhythm that you want to apply.
Speaker: So, you know, using the nomenclature, what the letters that you would use for that mode would be VVI.
Speaker: So P would be V for ventricle.
Speaker: S for sensing would be V for ventricle.
Speaker: And then the response I for inhibit.
Speaker: And so, you know, to give an example, if you had a patient who has a native rhythm, let's say they recover a native rhythm, their heart rate is 100 and it's now
Speaker: sinus.
Speaker: If you had set your pacer at 60 beats per minute on VVI, it's going to send, it's going to try to pace the ventricle, but say, you know what?
Speaker: The native heart rate is actually higher than my set rate of 60.
Speaker: It's actually a hundred.
Speaker: So as a response, I'm going to inhibit the pacer box and not actually fire that energy to try to pace the ventricle.
Speaker: So for, for the first, for the P and the S, you only basically have three options, right?
Speaker: It's either A, B or D, right?
Speaker: Which is both chambers.
Speaker: Yeah, correct.
Speaker: So A would be for your atria, B would be for your ventricle and then D would be for a dual.
Speaker: So both of the ventricles, maybe pacing.
Speaker: What are the options for the R for the response?
Speaker: Yeah.
Speaker: So for the response, there's essentially three letters, three main letters.
Speaker: So
Speaker: The first example we talked about was inhibit I for inhibit.
Speaker: So if it detects a native beat, then it's going to say to the pacer box not to fire and pace.
Speaker: The other option, this other simple option is a O or zero for essentially asynchronous pacing.
Speaker: So it's not going to try to sense, it's not going to respond in any way to whatever is being sensed.
Speaker: And it's just going to fire the pacer at the specified rate.
Speaker: So for the example we gave, a rate of 60, it's just going to fire at 60.
Speaker: It's not going to look at what's going on with the native conduction system.
Speaker: And then the third letter is D, and really that designates that we're responding to both what's happening with the atria and the ventricle.
Speaker: And so we may be inhibiting or we may be causing us to pace for one or both of those chambers.
Speaker: Perfect.
Speaker: And are there some modes that are more frequent in the ICU that we're more likely to encounter?
Speaker: I'd say the most common that I see and I think in general would be, I think the most common for emergency pacemakers, so thinking of your transvenous pacemaker, is going to be VVI.
Speaker: And it's really because we're putting in a single lead pacemaker in order to get electrical and mechanical capture by pacing the ventricle.
Speaker: So VVI.
Speaker: And then if you have someone who has postcardiotomy, they may have epicardial wires that are attached to both the atria and then also the ventricle.
Speaker: And so those patients may be on DDD.
Speaker: That allows for you to be pacing the atria if need be, pacing the ventricle if, you know, there's a conduction, AV conduction delay in order to respond to the native P wave, or it allows you to pace both the atria and the ventricle if neither are adequate.
Speaker: An additional mode that I know is very common in a lot of the Medtronic boxes, which are the most commonly utilized, I think, in most ICUs is the emergency mode, which I think is a DDO.
Speaker: Is that correct?
Speaker: Yeah, the DOO.
Speaker: So if your institution uses that particular box, and many other models, there's often a button on an emergency button.
Speaker: And if you push that, it's essentially going to pace
Speaker: at a rate that you set and it's not going to care what happens with the native rhythm and it's not going to, uh, and it's not going to inhibit anything.
Speaker: Um, so essentially you're going to pace at whatever the rate that you set.
Speaker: Perfect.
Speaker: So that's a D O O actually not a DDO.
Speaker: Like I said, okay, perfect.
Speaker: Chris, could we talk about capturing sensitivity?
Speaker: If you could just explain what the comp sets mean and how do they apply a clinically at the bedside?
Speaker: Sure.
Speaker: So,
Speaker: When you have a patient who is in probably the most important of those terms is our capture threshold or otherwise referred to as the pacing threshold.
Speaker: This refers to the current in milliamps that's required to obtain electrical and mechanical capture.
Speaker: The reason it's one of the most important is because if you have a patient who has an unstable bradycardia and need to get their heart rate faster, that's really what is going to allow you to do that.
Speaker: And so as it's referring to the milliamps, we're going to need a certain amount of milliamps in order to generate that pulse, generate that rhythm from the pacer.
Speaker: That's really what that's referring to.
Speaker: The other threshold is the sensing threshold.
Speaker: Some may also refer to as the sensitivity.
Speaker: And I'll explain.
Speaker: I think that's a little bit of a confusing term because it conflicts a little bit in the way that we think about sensitivity with respect to statistical analysis.
Speaker: But it's referring to the millivolts, basically the threshold at which the pacer detects a native cardiac conduction, either that be the P wave or the R wave.
Speaker: So this isn't my term, but I heard it and I think it's very helpful to think about to clarify what is otherwise a confusing term is rather than say sensitivity, we can talk about it as use the term fensitivity, because what it's saying is we're setting a fence
Speaker: in millivolts and if that's the top of the fence and you're if you're looking for a native beat, the native beat has to generate millivolts electrical voltage that's higher than that fence in order to be seen by the pacer box.
Speaker: So let's say we had the sensitivity at two millivolts
Speaker: it's not going to detect that there's native cardiac rhythm present if the native voltage is one millivolt.
Speaker: Well, if it's three millivolts, so above that two millivolt sensing threshold.
Speaker: Perfect.
Speaker: And we talked about the different types of leads a little bit at the beginning, but maybe we can jump into the lead discussion and start maybe by what are the different types of leads that we might encounter in the ICU?
Speaker: Sure.
Speaker: I think the most common that people are going to be familiar with is going to be the transvenous pacer lead.
Speaker: So this is a bipolar lead.
Speaker: We'll talk about what that means.
Speaker: But essentially it's a lead that's placed usually from an IJ or subclavian line, can be from the femoral but more difficult to place and often needs fluoroscopy, that you're essentially just trying to get epicardial capture of the ventricle.
Speaker: So you're trying to pace someone out of a symptomatic bradycardia, high degree AV block, complete heart block.
Speaker: So that's one.
Speaker: The other common type of lead that you'll see is epicardial leads.
Speaker: So these are placed in the setting of a sternotomy from cardiac surgery.
Speaker: And so depending on the surgeon preference,
Speaker: They may place atrial epicardial leads.
Speaker: So in order to pace and sense the atrium, they may pace ventricular leads to pace and sense the ventricle, or they may place both.
Speaker: And these are basically implanted into the epicardium that can be used for that post-cardiotomy period to help to stabilize a patient until either their native rhythm recovers or they demonstrate that they need a permanent pacemaker implanted.
Speaker: And then one other type of lead that you may see or type of pacing or two other types of pacing would be esophageal.
Speaker: So there's some modalities to pace someone from an esophageal probe.
Speaker: This is more often done with atrial pacing.
Speaker: And I have not personally had any experience with this type.
Speaker: I think it's more used in
Speaker: in the setting of diagnostic purposes or in terms of the lab, but it's generally done for atrial pacing.
Speaker: And then the sure proof kind of catch all would be our transcutaneous pacing in the emergency with our typical pads that we use for ACLS and whatnot.
Speaker: Excellent.
Speaker: And obviously, as we were discussing, Chris, probably the one that most intensivist has been exposed to is the transcutaneous, like you said, as part of our ACLS training, but is also something that we can always use in a last resort.
Speaker: But the epicardial leads are the ones that are commonly seen in post-op cardiac patients.
Speaker: And I think that there might be a little bit more to talk about there just to clarify.
Speaker: So when should we expect to see EpiCardio leads?
Speaker: Is this for all cases or some cases are more likely than others?
Speaker: Yeah, it's...
Speaker: it, a lot of it depends on the surgeon preference, um, for patients who are coming out bypass.
Speaker: It's not an insignificant number of patients that will require a cardiac pacing after bypass surgery, at least for that, maybe that period or perhaps longer.
Speaker: Um, the highest risk patients are tend to be more your valvular surgeries.
Speaker: So tricuspid valve, aortic valve and mitral valve.
Speaker: Um, and, and some of that has to do with, you know, where the, uh, conduction system is, um, compared to those, uh, valvular apparatus.
Speaker: But, um,
Speaker: you know, that a lot of it comes down to certain preference.
Speaker: I would say that the majority of, um, majority of patients do get them placed in the, in the OR, um, and, and come out with those, um, that we're either on backup or being actively used when they come out of the operating room.
Speaker: And can you talk a little bit about the difference between a unit polar and a bipolar epicardial lead?
Speaker: Yeah.
Speaker: So,
Speaker: Clinically, the function is the same, but what it's referring to is that if you have a bi, kind of classically a unipolar lead, what that means is that someone, the surgeon has implanted the negative anode to the epicardium, and that is connected to the pulse generator for the pacer.
Speaker: And then they've implanted the cathode to a structure that's not the epicardium.
Speaker: So something lying further away.
Speaker: It may have to be sub-Q tissue.
Speaker: In some places I've even seen, they just put a needle through the skin and that's what's attached to the pacer, but it's a ground.
Speaker: And so when we talk about unipolar, it's, there's a larger distance between that epicardial lead and the ground.
Speaker: And so that energy has to travel a further distance, go through more tissue.
Speaker: And then when you're thinking about things like sensing your, you can sense more, more electrical activity kind of in that span between those two spaces.
Speaker: That's in con the unipolar is in contrast to the bipolar where on that one lead that they implant in the epicardium,
Speaker: there is insulation between the anode and the cathode.
Speaker: And so this is in some models, it's about several millimeters, like eight millimeters or so between the two leads.
Speaker: And so there's a much smaller distance and requires usually less energy to get from one lead to the other.
Speaker: And they're all encompassed within the same wire that then comes out, exits the skin, and splits off so that it can then be attached to the pulse generator.
Speaker: Go ahead.
Speaker: Sorry.
Speaker: I was going to say the, you know, the rationale for one versus the other can be surgeon preference, but some of the benefits that may be seen with bipolar is that there's often less, like you're thinking about the energy that you're using or the milliamps that you're using for your capture threshold, that is often less milliamps required.
Speaker: In studies that have looked at it, they've shown that there's less decay and less, like you don't have to go up on that amount of milliamps as much over time.
Speaker: They may last a little bit longer.
Speaker: And then the same token for when you're sensing through a bipolar lead, because we're talking about that smaller distance, it often has better ability to sense the native electrical activity versus the unipolar leads.
Speaker: So you can actually keep that sensitivity, that sensitivity threshold in millivolts higher than
Speaker: while still detecting the patient's native cardiac rhythm versus the unipolar, which can pick up electrical activity from other areas.
Speaker: So let's say you have ventricular unipolar wires.
Speaker: Well, because those two nodes are far apart, then you may pick up atrial activity when you're trying to sense the ventricle versus the bipolar, which is all encompassed right in the ventricle and has a little bit better ability to do that.
Speaker: Perfect.
Speaker: And is there a way of knowing which one it is or just something that just used by convention or we know they'll tell us this is what I put?
Speaker: I would honestly talk to your surgeon.
Speaker: There's some color differentiation between different models and depending on where they implant the unipolar lead, whether they surgically do it, you know, underneath the sternotomy wound.
Speaker: or if it's subcutaneous, that can be a clue.
Speaker: But what comes out and attaches to the pulse generator often looks the same.
Speaker: So there's going to be two pegs that go into your pulse generator, one negative, one positive, and that can look the same.
Speaker: And I mentioned that one experience I've had, one surgeon, they would put the ground or the positive lead, they would put actually a needle through the sub-Q tissue in the skin.
Speaker: So you would just see it underneath the sternotomy site
Speaker: And that would be plugged right into the pulse generator.
Speaker: And so that's obviously an option.
Speaker: And that was a big clue that that was a unipolar lead.
Speaker: Perfect.
Speaker: In terms of identifying when people have two leads, where each lead is coming from, is there some convention in terms of relation to where the leads come out in the sternotomy in the chest?
Speaker: Yeah, it's a great question.
Speaker: So if you're looking at someone's sternotomy,
Speaker: On the patient's right, the convention is that the patient's right, that's the side from which the atrial wires will exit.
Speaker: And the patient's left is the side from which the ventricular wires will exit.
Speaker: And, you know, important when you're thinking about trying to pace or, you know, one or more ventricles to know which of those leads is attaching to your pacer box and the, you know, connection for A or V port.
Speaker: Excellent.
Speaker: Let's talk a little bit about just how we go about checking the pacer function and how we interact with the pacer box at the bedside.
Speaker: I know that you talk about a framework that you share with your trainees and you used to think at the bedside.
Speaker: Could you just share that with us in terms of what's your framework for approaching the pacers at the bedside?
Speaker: Sure.
Speaker: So one of the important things is to understand what the underlying rhythm is.
Speaker: This is particularly important in the post-cardiotomy patients to know, you know, what is my backup?
Speaker: Am I just using this pacer to eke out a little bit better hemodynamics until they recover post, you know, cardiopulmonary bypass?
Speaker: So let's say we're pacing at a rate of 80, an AV pacing, but they actually have a rhythm that's 60 underneath and they maintain a reasonable blood pressure.
Speaker: That's a patient I feel much more comfortable with
Speaker: if the pacer were somehow malfunctioned, that it's okay, that they'll be okay, versus someone who comes out of the operating room and they have zero rhythm underneath and they're asystolic.
Speaker: So how do we differentiate those?
Speaker: You will see people do a lot of things which are all recommended.
Speaker: The recommended way to look at what is the underlying rhythm is just to turn the rate on your pacer down.
Speaker: So turn it down if it's at 80%.
Speaker: Come to 70, see if there's a rhythm that then the native rhythm comes through because their rate is at 76.
Speaker: Turn it down to 60, turn it down to 50, turn it down to 40.
Speaker: Still not seeing a rhythm underneath.
Speaker: Their blood pressure is not tolerating it.
Speaker: I think we're done.
Speaker: You know, that's the approach that would be recommended for
Speaker: versus other things you may see people do which have the risk of losing capture completely and not being able to recover it.
Speaker: So that patient who's asymptotic underneath could be a catastrophic situation.
Speaker: Things that you'll see people do would be turning down that capture threshold until you lose capture.
Speaker: Not good because you could potentially lose it if someone has no underlying rhythm and is asymptotic underneath.
Speaker: turning off the pacemaker box, obviously that would be a not optimal way to check that.
Speaker: And then disconnecting your wires from the pacemaker box all would be not, not ideal ways to check for the underlying rhythm and would not recommend doing that.
Speaker: So just think about turning the rate down to see what starts coming through or what doesn't.
Speaker: And once you reach a heart rate that, you know, you should either you see hematomic effects or you should start seeing a rhythm, you're done.
Speaker: You can say there's no
Speaker: real perfusing rhythm underneath this pacer box yet um so that that's that's step number one is think about what so what's underlying my rhythm uh from where i'm pacing number two is looking at what's my capture threshold so for similar reasons we care whether our capture threshold is uh kind of do we have you know if we're if we're
Speaker: Do we have any wiggle room?
Speaker: If we're capturing at the highest amount of miliamps that the pacer box can generate, that's not a very stable situation if the patient doesn't have a very good rhythm or very good blood pressure with that rhythm underneath what we're doing with the pacer box.
Speaker: So trying to understand what we've seen is the capture threshold over time.
Speaker: for these temporary pacemakers which can get corroded can stop functioning as well over time it's important to know what that threshold is so how do we do that so number one is you want to only do this when you have some sort of underlying rhythm because as we mentioned if you have no underlying rhythm trying to figure this out could cause loss of capture so let's say we have an underlying rhythm
Speaker: How are we going to know what our capture threshold is?
Speaker: So what that milliamps is to get mechanical electrical capture?
Speaker: What we would do here is we're going to first turn if we're not pacing right now.
Speaker: So let's say we're in our pacer is set on a rate of 60, but our native rate is 80.
Speaker: We want to know that if the heart rate drops to 60, the pacer is going to kick in.
Speaker: So the way that we would do that is one, we would turn the pacer box heart rate
Speaker: up higher than our native rate, so that native rate of 80, we'd go to the pacer box to, let's say, 90.
Speaker: So then we start pacing the patient.
Speaker: And then once we do that, we're going to turn down the milliamps, turn down that capture, sequentially down maybe by 1.5 milliamps until we lose that electrical mechanical capture.
Speaker: our heart rate drops from the paste rate of 90 back down to the patient's native rate of 80.
Speaker: That value where we lose capture is our capture threshold.
Speaker: And so once we know that as a safety mechanism,
Speaker: see different recommendations but generally set the capture that value of the milliamps you want to set it at twice the threshold you just determined just to give a little bit of buffer in case the efficiency of those leads declines over time from the before the next time you check it so the third thing we're going to want to check with our pacer in addition to what the underlying rhythm is in our capture threshold is going to be our sensing threshold
Speaker: So this one I think is a little harder to conceptualize, but important to think about.
Speaker: So what this is, is we're going to only check the sensing threshold if there's an underlying rhythm that perfuses the patient.
Speaker: And hopefully that'll become clear as I explain the steps.
Speaker: So step one, and then just to back up, when we talk about our sensing thresholds,
Speaker: This, like I said before, is the fence, the level of the fence with which if you have a native cardiac electrical activity that the pacer box, if it's over that level, then the pacer box is going to see it.
Speaker: If it's below that level, the pacer box will not sense it.
Speaker: So we're trying to determine what's the level, what's the height of that fence that we can then see our actual electrical activity versus not.
Speaker: So in order to do this, we're going to one, make sure we have an underlying rhythm because otherwise we're not going to perform this check.
Speaker: Two is we're going to turn the milliamps.
Speaker: So turn capture value all the way down to the minimum.
Speaker: And why we do this is because when we're changing the sensitivity,
Speaker: We don't want to create a situation where the pacer box does not see the native rhythm and then we deliver a pacing impulse and create an RNT phenomenon.
Speaker: So the first step in doing this is we want to turn down the milliamps to the minimum value.
Speaker: Once we do that, then we're going to gradually raise that sensing threshold, raise the level of that fence in millivolts higher and higher.
Speaker: until on the pacer box we see that there's a light on the generator, the sensing light, see that it no longer lights up, meaning that the generator is no longer sensing our native cardiac electrical activity because that level of defense, that sensing threshold has been raised so high that it's above the native voltage.
Speaker: Once we have that level, that's our sensing threshold.
Speaker: We want to set it at half, about half of that value for safety.
Speaker: And so that's really, and so why do we check this?
Speaker: Why are we looking at this?
Speaker: Let's say we had the sensing threshold set too high.
Speaker: Well, like I said, we're not going to see the patient's, we're not going to sense the patient's native electrical activity.
Speaker: And so the pacer may inadvertently or may fire on to cause an RNT phenomenon and cause the patient to go into a ventricular arrhythmia.
Speaker: So we don't want the sensing threshold to be too high.
Speaker: We also don't want it to be too low because if we drop it too low,
Speaker: then we're going to see all sorts of electrical activity that may not be relevant.
Speaker: So if we only care if we're trying to ventricularly pace the patient who has a heart rate of, let's say, 35, if we also now see, because they have a high-degree AV block, that we put the sensing threshold so low that we're seeing the atrial impulses for the atrium, which is actually firing at an okay rate, it's going to incorrectly assume that that atrial impulse
Speaker: voltage is the ventricular voltage and then it's going to turn the pacer off say what we don't need to deliver a beat because we just sensed native electrical activity and so the pacer will inappropriately not fire in that setting so we want to balance between getting rid of the noise and also seeing what's truly our native electrical activity
Speaker: And I think, Chris, that important here is that every patient, because of where the lead is placed, the myocardial tissue will be different.
Speaker: So being very precise and optimizing both capture and sensitivity for the individual patient is going to be very important.
Speaker: Right.
Speaker: And over time, too.
Speaker: And those may change.
Speaker: So every shift, every day, these leads are not meant to be in forever.
Speaker: And over time, generally, the capture threshold will generally go up.
Speaker: And the sensitivity will generally go down, meaning you'll have to lower that fence more and more in order to just detect what's going on with the patient's native electrical activity because it's less efficient actually like seeing what's happening.
Speaker: Excellent.
Speaker: And that's why I think the analogy that you make with the fence is so useful because it's a bit counterintuitive in terms of how you set it and how we should be thinking about it.
Speaker: But now that I think of sensitivity, I think it's a lot easier to conceptualize.
Speaker: So I think that's a great, great analogy.
Speaker: Yeah, I think get rid of the term sensitivity because it's just say sensing threshold or sensitivity and you'll think about it in a lot better manner.
Speaker: Absolutely.
Speaker: Can you talk a little bit about rate and how you think about rate or how you frame that?
Speaker: Sure.
Speaker: So in general with pacers is only use them when you need to.
Speaker: So if you have a patient who has a perfusing native rhythm.
Speaker: but you're worried that, you know, they have risk for, or intermittently they go into a high degree AV block and they need to be paced.
Speaker: You really want the pacer as a backup.
Speaker: Um, for, for, for several reasons.
Speaker: One is you want to preserve those wires and the efficiency for as long as you can.
Speaker: Two is generally, um,
Speaker: generally patients native rhythm, if they're, you know, particularly if they're in sinus is going to end up giving them better perfusion, better cardiac output because it's more efficient with respect to atrial ventricular timing than we can do with the pacer.
Speaker: And the third reason is even though we're being very thoughtful and careful about our sensing, setting our sensing threshold about setting our capture is that
Speaker: Things can happen, things can change in between when we check it or just in general with the patient.
Speaker: And you don't want the pacer box heart rate to be competing with the patient's native beat, and then you end up with a RNT phenomena causing a ventricular arrhythmia when, you know, otherwise you could have avoided that.
Speaker: Excellent.
Speaker: Any comments on troubleshooting pacemakers when we get into trouble?
Speaker: I know that one of the things that people always are concerned is with loss of capture and failure to pace.
Speaker: Yeah.
Speaker: So I think the biggest question is like any of our patients is are they stable or unstable?
Speaker: So somebody who's extremely unstable and they're not pacing and they need to pace.
Speaker: So
Speaker: You know, the example would be a post-cardiac surgery patient who is asystolic underneath the pacer and it's not working anymore.
Speaker: You can hit your emergency settings.
Speaker: So when you talk about emergency settings, either there's a button on the generator, like a little exclamation point or otherwise, depending on the model, which will set your rate at 100 and set your capture to the maximum milliamps that you have.
Speaker: And then it will also essentially turn off sensing.
Speaker: So turn it into the DOO mode so that you're not trying to look for a native rhythm.
Speaker: So it's essentially saying, you know what, I want you to give me electrical mechanical capture at all costs.
Speaker: Do everything you can to do that.
Speaker: And so if you have a patient who's not perfusing in any way, that's what you need to do.
Speaker: If you have a patient who's more stable, we have some time to figure out what's going on.
Speaker: And so the first question I would ask myself, if you're not having electrical mechanical capture, particularly if they're stable, is it actually that the pacer is working?
Speaker: Is it just that the native heart rate's higher than what the pacer was set at?
Speaker: And if that's the case, then the pacer box is actually appropriately sensing the native rhythm.
Speaker: and appropriately suppressing with the pacer generated electrical impulses.
Speaker: But if that's not the case, number two is, and this is particularly true for your transvenous pacers,
Speaker: as it happens quite a lot, is where is the lead?
Speaker: Is it malpositioned?
Speaker: Did it move off?
Speaker: Did the patient turn and the lead kind of floated around in the ventricle and is no longer in the appropriate position?
Speaker: Because that's a very common reason why if it was working, it stops working rather than some odds change in the settings.
Speaker: Number three, think about is just, as we said, these pacer wires can get less efficient over time, and you may require a higher milliamps to get your capture to that capture threshold.
Speaker: And so just turning up your milliamps may help you to regain capture when otherwise the pacer is working just fine.
Speaker: Four is think about your sensitivity.
Speaker: So is that sensing threshold, is that sensing threshold that fence too high?
Speaker: This is rarely the case, particularly if you use the default setting when you just turn on a pacer box.
Speaker: The sensing threshold, the fence is usually set quite low.
Speaker: But just something to think about.
Speaker: This would be a scenario where the pacer box is inappropriately saying that they're not sensing the patient's native rhythm.
Speaker: But just think about that and look at where your sensing threshold is set at.
Speaker: And then five is think about your pacemaker box and the cables.
Speaker: So it sounds like these things would not misfire, but you'd be surprised sometimes the cable and the connection is all that's needed.
Speaker: Either the cable's faulty, you need a new set of cables, so between the pacer wire leads and the generator box, or replace your generator box.
Speaker: Maybe that's not working.
Speaker: And then five,
Speaker: For epicardial wires, there's some particular troubleshooting steps which can help you if all the above things are not the problem.
Speaker: So for epicardial wires, it doesn't sound like it should make much of a difference, but sometimes the easiest thing to get things working again is actually just reverse the polarity.
Speaker: So when you look at your pacer, you have your pacer generator box, you have your wires leading into the connected with the leads.
Speaker: So just switch the leads from the negative to the positive terminal to flip them around.
Speaker: And that may get you get you capture back.
Speaker: If that doesn't work, there's some higher level of steps that you can do in an emergency to try to regain capture, all of which I'd say are you're doing these while also preparing for your backup pacing modality.
Speaker: We're already employing your backup pacing modality, which for epicardial wires would be either placing a transvenous pacer or externally pacing the patient, depending on the urgency of the situation.
Speaker: But regardless, for the epicardial wires, if you're having trouble capturing,
Speaker: is one is reverse the polarity, switch from the negative to the positive, positive to the negative.
Speaker: If that didn't work, then what you can do is actually replace the positive lead with a ground.
Speaker: So this either for both the unipolar or the bipolar that we spoke about,
Speaker: What you can do is very simply is take is you're essentially you're regrounding your unipolar or you're converting the bipolar into a unipolar system.
Speaker: And so what are you what you're going to do is you're going to take a needle.
Speaker: So let's say an 18 gauge needle, just stick it through the patient's skin so that it's it's sticking out on both ends.
Speaker: and then plug the needle into the positive terminal of the wires.
Speaker: And that will create a new ground at the skin.
Speaker: And by doing that, you may regain capture by regrounding your unipolar wire or creating a ground and converting your bipolar to unipolar.
Speaker: If all that fails, you've done that, is now you're going to reverse the polarity again.
Speaker: So take that needle, put it into the negative terminal, take the other lead that was in the negative terminal, put it in the positive terminal.
Speaker: And all that fails, you're really relying on your backup pacing modality, that TVP or the external pacer.
Speaker: Excellent.
Speaker: And obviously you did mention that as a backup modality, sometimes we might have to put a transvenous pacemaker.
Speaker: So I think this is maybe a good place to just talk a little bit about some general considerations on bedside placement of a transvenous temporary pacemaker by the intensivist.
Speaker: Maybe we can just start with how you would approach that and just give us some general comments and tips.
Speaker: Yeah.
Speaker: So, um, not so, so this,
Speaker: I think most intensivists are comfortable with placing central venous access.
Speaker: It's the nuances of when we place the wire, what are we setting the box at?
Speaker: How do we troubleshoot when it's not working?
Speaker: So we can talk some about that.
Speaker: Most pacemaker kits are nice in that they have a sheath.
Speaker: They come with a wire.
Speaker: If you have one of those at your institution, two things is one, use it.
Speaker: Two is when you're using it, make sure that you're using one with a balloon-tipped wire lead because if you get something from an emergency from the cath lab, sometimes they may carry ones that are just the
Speaker: pacer wire without a balloon tip and if we're doing these at the bedside really needs to be that balloon tip like we would for a pa catheter to allow it to float into the correct position but also safety as the the stiffer ones generally are or the non-balloon ones are generally quite stiff and designed to be placed under fluoro but if you have one of these kits most are often built around a six french six french introducer sheath or similar size
Speaker: and a five French or similar single lead wire.
Speaker: And so when placing these, either most commonly the IJ or the subclavian will be the easiest approach for you to float, then float the wire.
Speaker: Once you have the sheath in, take your wire, place it through the sheath, and insert it just as we would for a PA catheter, you know,
Speaker: Generally, I go somewhere around 15 centimeters in before I blow up the balloon, 10, 15 centimeters in from the edge of the sheath before I blow up the balloon.
Speaker: And then I want my pacer box set up, so I generally give that to...
Speaker: Either if there's the nurse there or if you are in a place with two providers, a provider, whoever's the most comfortable.
Speaker: And you're going to have them.
Speaker: What I'd like to do with the pacer box is you want to set the pacer box so that you're most likely to get captured when the wire's in the right place.
Speaker: So what are those settings?
Speaker: One is you want to make sure that the pacer rate that you set is higher than the native heart rate.
Speaker: This can be true like if you have a patient who's intermittently going bradycardic into the 30s, but then their rhythm recovers.
Speaker: You may not think, well, when you're floating it, their rhythm may be recovered.
Speaker: You need to make sure that you've set the pacer box high enough so that actually you can start generating, you can get electrical mechanical capture when it's in the right place.
Speaker: So their rates at 80, we want to set our pacer box, our rate of 100.
Speaker: So we'll set it there.
Speaker: And then with respect to our capture, so our milliamps,
Speaker: You'll hear different approaches on this, and I think it depends on the severity of the situation.
Speaker: So one approach is to maximize the milliamps, put it at the highest setting.
Speaker: And this may be pertinent to somebody who has essentially a very hypotensive, like almost non-perfusing rhythm, and you just need to get capture right away.
Speaker: That may be a scenario where you maximize the milliamps.
Speaker: I like to set it lower.
Speaker: I generally put it at around five milliamps when I'm floating these.
Speaker: And the reason I do that is because you can fool yourself that you're in the right place by getting electrical and mechanical capture when the positioning is not actually optimized if you use a really high milliamp value.
Speaker: Because you'll get capture, but it won't be optimized position, and then you find that it's very finicky after that.
Speaker: So I like to set it around five milliamps.
Speaker: So, already faster than the native beat, about 5 milliamps.
Speaker: And then I keep the sensitivity, the sensing threshold value, or the sensing value at the default of the generator when I turn it on, just for floating it.
Speaker: Because it's usually adequate for most scenarios, and obviously you're going to want to look, you can look at it afterwards once you get electrical and mechanical capture.
Speaker: um so those things heart rate faster than native rate uh low generally low milliamps around five or so uh and then keep the uh this the sensing number at the same level as what the the default for the pacer box so once you do that place the wire in once you get to about 15 centimeters or so inflate the balloon and then just progress by
Speaker: you know, just gradually floated in and you're going to be watching your monitor.
Speaker: You want to see both electrical and then also mechanical correlation of capture with that.
Speaker: If you're getting to somewhere around 50 centimeters and you have not 50, if you're getting somewhere around like
Speaker: 35 or so centimeters and you have not gotten any capture, you're probably, you've done one of a couple things is you may not have crossed the tricuspid valve, either looping in the atrium, you may be looping in the ventricle, it's not making contact with the wall, the ventricular wall, or sometimes I've seen where you actually go from your superior vena cava all the way passing into the inferior vena cava.
Speaker: So if you're reaching that setting, I would deflate your balloon and then retract back to that 15 centimeters and then restart.
Speaker: And then once you're happy with your, once you get electrical mechanical capture, now is when you want to lock the position at the introducer.
Speaker: And then also, this is the time when you can figure out what your capture threshold is, because that will help you.
Speaker: You don't want to keep it higher than you need to.
Speaker: So once I get electrical mechanical capture, I already knew what the underlying rhythm was because I just floated the pacer.
Speaker: And so now this is when I'm going to gradually turn that milliamps down until I lose electrical and mechanical capture.
Speaker: And then that's my capture threshold.
Speaker: And I'm going to set it twice of what that value is.
Speaker: And then obviously get your x-ray and go from there.
Speaker: Stupid question, but just to clarify for our listeners, what do you do with the balloon?
Speaker: Ah, good question.
Speaker: So once you've placed your catheter, once you've got electrical mechanical capture, you want to deflate your balloon.
Speaker: It doesn't need to be inflated and want to deflate it whenever you're retracting the catheter, inflated whenever you're advancing it.
Speaker: But once you have it in the right position, deflate that balloon.
Speaker: It's no longer needed at that time.
Speaker: And one of the things that you mentioned when we were talking about troubleshooting is that if you have a transvenous pacer, it is possible that the reason why you lose capture is because the catheter has moved.
Speaker: And in which case, after you troubleshoot the box, you might want to inflate that balloon in advance and retract first, inflate the balloon in advance and try to regain capture, correct?
Speaker: Exactly.
Speaker: And I think for, in my experience, that's been the most common reason why we lose capture is the position changes.
Speaker: And that's important to keep in mind because you can think about this in a very structured way and be like, oh, look at the rhythm.
Speaker: The pacer is not, it's not firing.
Speaker: It's not firing at all.
Speaker: Either that's maybe my milliamps are too low for my, you know, I need to have a higher milliamps to get capture.
Speaker: Or you could say, you know what, I'm really savvy and I think that it's not sensing when it's not sensing when it should be.
Speaker: So that's why my pacer is not firing.
Speaker: But the most common thing is just the wire has moved and it's not making contact.
Speaker: So always keep that in mind, I think, is the first thing with these transvenous pacers.
Speaker: They can be very finicky in that regard.
Speaker: Perfect.
Speaker: As we close Chris's discussion, are there any pearls and pitfalls you want to share in general with our audience?
Speaker: Yeah, I think, um, I think, uh, you know, as we do for other emergency scenarios is, um,
Speaker: you know, think about what pacers and always think about where we are and what's my, what's my backup to where we are.
Speaker: So with epicardial wires or transvenous, you know, we, so we think about our transcutaneously pacing if we need to.
Speaker: Um, cause as we've talked about, these can all, one, they lose efficiency over time.
Speaker: They're not meant to be in there and they all have their own pitfalls and, and, um, uh, can, can become dislodged or not work for whatever reason.
Speaker: um two is think about as i just mentioned with the transvenous think about your position first where's my position did it move um and then three is is think through these things know your equipment what you have available to you um these aren't depending on where you what environment you work in this isn't
Speaker: always that very common occurrence.
Speaker: And so knowing that equipment, just like anything else, is always helpful to be familiar with.
Speaker: As you may be the most, even though it may not be something we do that often, you may be the one who has to coach the nursing staff through how you're going to set the pacer box and whatnot, because it may not be something they're familiar with.
Speaker: Excellent.
Speaker: And thanks again for, for such a comprehensive and practical review of something that, like you said, most intensivists these days are expected to deal with.
Speaker: And I think it's a, it's a great refresher for our listeners.
Speaker: Chris, we have a, in the podcast, we usually close with a couple of questions that are unrelated to the clinical topic.
Speaker: Would that be okay?
Speaker: Yes.
Speaker: So the first question relates to books.
Speaker: Is there a book or books that have influenced you significantly or a book that you have gifted often to other people?
Speaker: That's a great question.
Speaker: I think my realm of books right now is primarily consisting of children's stories with my two young kids.
Speaker: But, you know, I do enjoy a good book from now and then.
Speaker: I'd say, you know, in terms of a
Speaker: informative and thoughtful approach to some tools.
Speaker: I'm sure other people may have mentioned this and Sergio, I know you're familiar with this book, but crucial conversations is I think a really powerful one to, to help inform, you know, situations that otherwise can, can seem frustrating or scary.
Speaker: I think it's helpful to navigate those.
Speaker: But I also think,
Speaker: I generally like to read.
Speaker: I like some historical novels, and the one I'm reading right now is The Mutiny on the Bounty, which by Peter Fitzsimmons, which is just a phenomenal rendering of the very...
Speaker: amazing and fascinating, um, uh, story in history.
Speaker: So highly recommend that, um, to, to anybody who's looking for, for a book right now.
Speaker: Excellent.
Speaker: And I would include a link to these books in the show notes.
Speaker: The second question is if you could share with us, Chris, something you changed your mind about over the last couple of few years.
Speaker: Yeah, I think oddly enough, um,
Speaker: you know, I've, I've always enjoyed podcasts, but I never thought I might be on a podcast.
Speaker: And, uh, and here I am, uh, you know, sitting in the, in the studio and talking about this.
Speaker: So there, there's a mind change.
Speaker: Perfect.
Speaker: And we obviously appreciate the opportunity to talk with you and learn from you.
Speaker: So to finish, is there a parting thought that you want all our intensivists who are listening to know could be a quote, a fact, or just a thought?
Speaker: I think, um,
Speaker: what I'd say is I think we're all, maybe it goes without saying, but I think we're all educators.
Speaker: And I think a key part of our job is, is to teach whether we're in the, in the, uh, academic environment, we have, you know, true designated learners or not.
Speaker: It's just such a critical part of our, uh, what we do.
Speaker: And, um, I, I think we should all as intensivists, uh, you know, and, um,
Speaker: Other physicians is really pride ourselves in that, whether it's educating our patients or other staff.
Speaker: As educators, we're always learning ourselves.
Speaker: I think it's one of the challenges of our job and also the most rewarding parts of it, too.
Speaker: I agree.
Speaker: And I think this is a perfect place to stop.
Speaker: Chris, thank you again for sharing your expertise and your time with us.
Speaker: Definitely look forward to having you back on the podcast to talk about other very important and practical topics for critical care.
Speaker: Thank you.
Speaker: Thank you so much for having me.
Speaker: Thank you for listening to Critical Matters, a sound podcast.
Speaker: Make sure to subscribe to Critical Matters on Apple or Google Podcasts and share with your network.
Speaker: Sound's transforming the way critical care is provided in hospitals across the country.
Speaker: To learn more, visit www.soundphysicians.com.
