Pacing; Roadside to Resus
Highlights
- Asystylae in the Setting of Cardiac Arrest
Summary:
The Recess Council UK gives the indications for pacing as we talked about before. Life threatening compromise of Braddockardia, which is not responsive to Atropine and non-compromised Braddockardian but with the risk of asystylae. So patients with recent asyStylae's should be considered for trans-venous pacing. As a bridge, you can use drugs, so Atropine, Isopronulin, Adrenaline or you can go on to transcutaneous pacing.
Transcript:
Speaker 2
So to recap, which of the sorts of patients that we're talking about when we're thinking about considering the need for emergency pacing? Well, the Recess Council UK gives the indications for pacing as we talked about before as life threatening compromise of Braddockardia, which is not responsive to Atropine and non-compromised Braddockardia, but with the risk of asystylae. So patients with recent asystylae's, maybe it's type 2 blocks and complete heart blocks with wide QRS complexes or ventricular pauses of greater than 3 seconds. Now both of these groups should be considered for trans-venous pacing. And as a bridge, you can use drugs, so Atropine, Isopronulin, Adrenaline, as we covered in that previous episode, or you can go on to transcutaneous pacing. Now finally, the RC UK state that in the setting of cardiac arrest, the presence of P-waves makes obtaining an output more likely, but pacing is rarely successful in asystylae in the absence of P-waves and should not be attempted routinely in this situation. So in other words, you can attempt to bridge the gap in some patients with P-wave asystylae, but if there's absolute asystylae, there is no point considering those patients. Okay, so we're picking this up when we've assessed the patient, identified all the reversible factors that we can do, and have treated those appropriately. (Time 0:01:25)
- Bradycardic Percussion Pacing
Summary:
Pacing is a technique that doesn't require any additional equipment. In the UK, generally this only lies within the scope of practice of specialist or critical care paramedics. And so if addrapins failed and you've got a really critically compromised patient in front of you, what do you do? I don't see why you shouldn't try it.
Transcript:
Speaker 1
Well, that's a very good question, actually, Simon. I'm glad you asked. It's an interesting question, isn't it? Because there was definitely a few questions on Twitter around, you know, what can we do pre-hospitality if pacing doesn't lie within our scope of practice? And certainly in the UK, I think I'm right in saying that generally this only lies within the scope of practice of sort of specialist or critical care paramedics and generally the sort of degree level paramedics working on the ambulances don't have transcutaneous pacing within their skill set. And so if addrapins failed and you've got a really critically compromised patient in front of you, you know, what do you do? And I think this is probably one of the only options available to you other than sort of calling for additional assistance from, you know, enhanced or critical care teams. And I don't really see any reason why you shouldn't try it. I mean, I think we'll go on to describe what it is and maybe how it works in a second. But this is a technique that doesn't require any additional equipment and doesn't really have any side effects other than maybe a little bit of discomfort for the patient, but then so do all of these kind of pacing mechanisms. So, you know, I don't see why you shouldn't try it. I probably wouldn't apply this to every single bradycardic patient. I'd sort of reserve this for the patients who are super compromised and, you know, heading towards unconsciousness because they really need some sort of intervention. And you know, certainly this is pretty much supported by the RC UK. They state that actually percussion pacing can be attempted whilst waiting for pacing equipment, you know, and if it's not available to you and you're waiting for it on your arrival at ED, that seems to me to fit within the guidance. So I think it's definitely something to consider. (Time 0:04:23)
- Percussion Pacing for Bradycardia
Summary:
Multiple case reports exist of successful percussion pacing for bradycardia. You use a close fist to deliver repeated firm thumps on the pre-cordium just to the side of the lower left stern ledge. Now, you do this by raising your hand about 20 centimeters above the chest before each thump. And then you look to see whether a QRS complex is generated by each thump that you're delivering.
Transcript:
Speaker 2
So we should really describe a little bit about what this is so that we can think about how we could apply it. Now, multiple case reports exist of successful percussion pacing for bradycardia and we've put the links to those in the show notes because I always thought this was a bit of a theoretical thing, but it does actually seem there's some evidence behind it. Now, whilst it's described in the literature, there is, as James has said, high risk that you're going to cause some pain and actually that you could cause some injury by repeatedly thumping the chest. And unless the patient was rob or James, it's not really one of those things that you'd really be queuing up to do. It does seem a bit brutal. But anyway, there are, as we've said, some rare occasions where this might need to happen. Okay. So what do you actually do? Well, the recess council described this and essentially you use a close fist to deliver repeated firm thumps on the pre-cordium just to the side of the lower left stern ledge. Now, you do this by raising your hand about 20 centimeters above the chest before each thump. Don't worry, don't have to measure it with a tape measure. And then you look to see- Roughly. ... On 2021. And then you look to see on the ECG whether a QRS complex is generated by each thump that you're delivering. (Time 0:06:00)
- Depolarization of the Myocardium
Summary:
We want to take over the pacemaker activity of the heart and regulate the contractility of the myocytes. And we do that through application of these external stimuli, either electrical or thumping. It could be a while. Well, it's nice to inform practice, isn't it? But let's step away from the history for a little bit and let's clarify what we're actually trying to achieve with pacing.
Transcript:
Speaker 1
It could be a while. Well, it's nice to inform practice, isn't it? But let's step away from the history for a little bit and let's clarify what we're actually trying to achieve with pacing. Because in these brady dysrhythmias that we're talking about, the normal physiological electrical impulses of the heart that we talked about at length that would travel from the sinoelectural node or through that beautiful kind of finely tuned electrical conduction system through to the ventricles becomes affected or interrupted. And that causes the heart rate to drop right off. And correspondingly, our cardiac output absolutely plummets. And therefore, we want to take over the pacemaker activity of the heart and regulate the contractility of the myocytes. And we do that through application of these external stimuli, either electrical or thumping. And that causes depolarization of the myocardium. Now I guess ideally we'd stimulate the atria, wouldn't we? And that would then follow the normal electrical pathway so that we get this lovely coordinated contraction of the heart. But actually, that is really, really difficult to achieve regardless of how amazing your pad placement is. And actually what we end up achieving with external pacing is activation of a focal point in the left ventricle. And then the wave of depolarization kind of spreads out from there across the myocardium at the heart from that focal point. And that obviously doesn't follow the normal electrical pathways. (Time 0:10:39)
- Pacing Pad Positioning
Summary:
There are things like excessive body hair, sweating and skin abrasions they can all increase both the discomfort associated with pacing and the energy required. So choose a spot away from these hazards or address them by shaving the body hair and wiping the skin. Always avoid putting pads over an implanted cardioverted device or a pacemaker.
Transcript:
Speaker 1
Great and you know what there's actually probably a few more things to think about actually when it comes to doing really effective pacing and when it comes to putting the pads onto the chest because as we say we really want to minimize the amount of electricity we're using because that's going to reduce the discomfort for the patient. So once you've picked your pad positioning either AP or AL there are some other factors that might help us to reduce the energy load and there are things like excessive body hair, sweating and skin abrasions they can all increase both the discomfort associated with pacing and the energy required. So choose a spot away from these hazards or address them by shaving the body hair and wiping the skin and obviously always avoid putting pads over an implanted cardioverted device or a pacemaker. So when we're thinking about wiping the skin we want to clean the area with an alcohol wipe that gets rid of some of the greases on the skin and then allow it to dry off that can also increase the adherence of the pad and therefore theoretically reduce the pacing threshold and the discomfort. And you know when we read around this poor pad placement is a really common cause of failure to capture a Simon was discussing. So we've got to ensure that the anterior electrode is placed over either the cardiac apex or the position of lead V3 and then the posterior electrode obviously this is if we're using AP should be placed inferior to the scapular so below it or between (Time 0:18:06)
- How to Properly Place the Anterior Electrode
Summary:
Poor pad placement is a really common cause of failure to capture a Simon was discussing. So we've got to ensure that the anterior electrode is placed over either the cardiac apex or the position of lead V3 and then the posterior electrode obviously this is if we're using AP should be placed inferior to the scapular. And something else to be aware of actually is to pay attention to the description on each pad because if we use the AP orientation then the posterior electrodes needs to be positive.
Transcript:
Speaker 1
So when we're thinking about wiping the skin we want to clean the area with an alcohol wipe that gets rid of some of the greases on the skin and then allow it to dry off that can also increase the adherence of the pad and therefore theoretically reduce the pacing threshold and the discomfort. And you know when we read around this poor pad placement is a really common cause of failure to capture a Simon was discussing. So we've got to ensure that the anterior electrode is placed over either the cardiac apex or the position of lead V3 and then the posterior electrode obviously this is if we're using AP should be placed inferior to the scapular so below it or between the right and the left scapular but avoiding the spine and it definitely shouldn't be placed over the scapular or the spine because that can increase the impedance that the electricity has to get through. And something else to be aware of that I didn't know about actually is to pay attention to the description on each pad because if we use the AP orientation then the posterior electrode needs to be positive. I like that that works for me posterior positive great and the anterior one therefore has to be negative and apparently if we reverse that orientation then it can lead to failure to capture. (Time 0:18:55)
- ECG - Is Demand Mode Working?
Summary:
In demand mode the pace maker generates electrical stimulus to pace the ventricles when the heart rate falls below the pacing rate. If there's loads of movement artifact for example then that means that demand mode won't work as well because it gets confused. One option to overcome that is to increase the gain on the ECG to get bigger complexes one option but if that doesn't work then we might need to switch to a fixed rate pacing mode and that stimulates the heart regardless of its own activity.
Transcript:
Speaker 1
So the first choice to make is demand or fixed rate pacing so in demand mode the pace maker generates electrical stimulus to pace the ventricles when the heart rate falls below the pacing rate and that is generally the options we're going to select because it avoids competition between the patients intrinsic electrical activity and our external source of stimulation and it also reduces the overall number of pacing pulses and so therefore reducing the patient's discomfort. But it's not always going to work for you in demand mode and if there's loads of movement artifact for example then that means that demand mode won't work as well because it gets confused it can't identify the R waves that it needs to spot to work out when it needs to pace and so one option to overcome that is to increase the gain on the ECG to get bigger complexes one option but if that doesn't work then we might need to switch to a fixed rate pacing mode and that stimulates the heart regardless of its own activity. And I guess another time this could be useful is in those profusely diaphoretic patients when you just can't get the ECG dots to stick which are obviously smaller than the big pads we're using for pacing and that's because fixed rate pacing doesn't need to sense the underlying rhythm because it just gets on with it it keeps firing off no matter what the heart is doing. (Time 0:20:31)
- I Think You're Absolutely Right About Pacing Thresholds
Summary:
I think we almost need to see these as two separate cohorts of patients don't we the compromised but conscious bradycardic patient or those who were pacing because of a concern over their deterioration. Then there's the unconscious compromised patients who are really in extremis and I think you're absolutely right. That second group of patients starting low and gradually working your way up just in case we hurt the patient a little bit is definitely not the right approach when they are absolutely peri arrest.
Transcript:
Speaker 2
So those patients change you describe quite nicely sort of starting off low and then cranking up the energy to get to a point of affected pacing but I guess going back to the beginning where we were thinking about the clinical context I mean some of these patients are absolutely clapped out aren't they and unconscious. So are you going to take the same approach with that or are you going to actually you know if you've got someone who is unconscious and really looks like they're going to arrest I presume you're actually going to start a bit higher than down the very bottom of the scale.
Speaker 1
I think you're absolutely right and I think we almost need to see these as two separate cohorts of patients don't we the compromised but conscious bradycardic patient or those who were pacing because of a concern over their deterioration and then there's the unconscious compromised patients who are really in extremis and I think you're absolutely right and that second group of patients starting low and gradually working your way up just in case we hurt the patient a little bit is definitely not the right approach when they are absolutely peri arrest and certainly the guidance would support that you go in high and actually go backwards down the amplitude until you lose capture and then go back above it again. (Time 0:25:24)
- I Think You're Absolutely Right About Pacing Thresholds
Summary:
I think we almost need to see these as two separate cohorts of patients don't we the compromised but conscious bradycardic patient or those who were pacing because of a concern over their deterioration. Then there's the unconscious compromised patients who are really in extremis and I think you're absolutely right. That second group of patients starting low and gradually working your way up just in case we hurt the patient a little bit is definitely not the right approach when they are absolutely peri arrest.
Transcript:
Speaker 2
So those patients change you describe quite nicely sort of starting off low and then cranking up the energy to get to a point of affected pacing but I guess going back to the beginning where we were thinking about the clinical context I mean some of these patients are absolutely clapped out aren't they and unconscious. So are you going to take the same approach with that or are you going to actually you know if you've got someone who is unconscious and really looks like they're going to arrest I presume you're actually going to start a bit higher than down the very bottom of the scale.
Speaker 1
I think you're absolutely right and I think we almost need to see these as two separate cohorts of patients don't we the compromised but conscious bradycardic patient or those who were pacing because of a concern over their deterioration and then there's the unconscious compromised patients who are really in extremis and I think you're absolutely right and that second group of patients starting low and gradually working your way up just in case we hurt the patient a little bit is definitely not the right approach when they are absolutely peri arrest and certainly the guidance would support that you go in high and actually go backwards down the amplitude until you lose capture and then go back above it again. So yeah absolutely great I think there's two different patient cohorts here and I think the final thing to say about sort of pacing thresholds is that we need to definitely be aware that actually they can increase with prolonged periods of pacing so don't set the pace and you (Time 0:25:24)
- Pulse Oximetry Waveform Can Be Incredibly Helpful
Summary:
The pulse is obviously the first thing we want to check but if you do a full patient reassessment you should hopefully at this stage be facing a really improving clinical picture. But like I said you know you need to be on your guard as there are definitely quite a few case reports of patients who initially get an electrical and a mechanical capture but their clinical picture deteriorates again over time. And most likely what we're talking about here is that increasing threshold that we're going to see over time so it's going to take more and more to essentially get that capture mechanically and electrically as James mentioned.
Transcript:
Speaker 3
Absolutely and you know there will be other things that come alongside that so the pulse is obviously the first thing we want to check but if you do a full patient reassessment you should hopefully at this stage be facing a really improving clinical picture so that's meaning that those adverse signs that we talked about in the other episode should hopefully be either improving or potentially they might have even gone and you might have a much more stable patient. But like I said you know you need to be on your guard as there are definitely quite a few case reports of patients who initially get an electrical and a mechanical capture but their clinical picture deteriorates again over time and only for clinicians to find that whilst the monitor still looks like we're getting what we want from this that crucial mechanical capture or that pulse has disappeared and most likely what we're talking about here is that increasing threshold that we're going to see over time so what we mean here is it's going to take more and more to essentially get that capture mechanically and electrically as James mentioned. Now thankfully you know we do have some tools that might make this a little easier to spot so firstly think of that pulse oximetry waveform and that can be incredibly helpful as of course it's like it's a visual representation of you know arterial flow to the peripheries and that is exactly what we're interested in isn't it so you know whilst we initially do that pulse check keeping an eye on pulse oximetry waveform can be super helpful. (Time 0:29:22)
- Capturing a Pulse
Summary:
electrical capture doesn't always equal mechanical capture or a pulse and those muscular contractions of those skeletal muscles might be really misleading. In the face of a deteriorating patient you need to ensure that you've got a way of making sure that you know that pulse is still present so I think for me what I'd say is unless you want to add anything in of course boys is that as a bare minimum I would suggest that the first thing you do is that manual palpation of that pulse and then you apply that pulse oximetry to give you that visual reference from that waveform.
Transcript:
Speaker 3
So I guess with regard to capture you know basically what I want to say is you just got to be a bit cautious as there are some potential errors you need to be aware of and that is predominantly that electrical capture doesn't always equal mechanical capture or a pulse and those muscular contractions of those skeletal muscles might be really misleading and in the face of a deteriorating patient you need to ensure that you've got a way of making sure that you know that pulse is still present so I think for me what I'd say is unless you want to add anything in of course boys is that as a bare minimum I would suggest that the first thing you do is that manual palpation of that pulse and then you apply that pulse oximetry to give you that visual reference from that waveform and then of course always be aware that what you see on that monitor needs to correlate with that clinical picture in front of you so if it doesn't match up you need to go back and make sure you do a thorough reassessment.
Speaker 2
Yeah that sounds good to me and I think what we're describing here is the situation where you do need to keep a really close eye on your patient with lots of monitoring that's going on and lots of awareness of what can go wrong but this can get quite difficult because it's really painful and it's frequently stated that most patients can't tolerate pacing at 50 milliamps or more so you need to be really prepared and anticipate that you're going to need either an analgesic or sedation strategy to help them cope with it. (Time 0:31:12)