Podcast – ECMO in Trauma with Chris Bishop at Tactical Trauma 24

 Welcome to the St Emlyn’s podcast. I’m Iain Beardsell

 And I’m Liz Crowe.

And you join us again at Tactical Trauma 24 in the glorious Sundsvall in Sweden and it’s a true delight to have Chris Bishop with us. Chris, tell our listeners a little bit about yourself.

I’m Chris Bishop, I’m currently a clinical research fellow at the Centre for Trauma Sciences, part of Queen Mary University of London, where I’m doing my PhD looking at veno arterial ECMO support for cardiogenic shock that happens after major trauma hemorrhage.

By way of background, I’m a lead clinical perfusionist working in cardiothoracic surgery and,over the course of, many years of my career, I developed an interest, and a sort of an expertise and a real passion for mechanical circulatory support. And particularly, with ECMO and I’m truly excited to be doing this, work currently at, C4TS.

Now ECMO is a word we often hear bandied around but for many of us doesn’t form part of our day to day practice. Could you just remind our listeners what you mean when you say VA ECMO?

ECMO stands for Extracorporeal Membrane Oxygenation. It’s a, form of, life support therapy, which involves, essentially taking blood out of a patient, passing it through an extracorporeal circuit, which has an artificial lung, a membrane oxygenator, where oxygen is added and carbon dioxide is removed, and that blood is, returned.

So, in order for that to happen, the patient has to have two large cannulae inserted, into a femoral vein, so where we drain the blood, out of the right heart system and pump it through the oxygenator, as I’ve just described. And we can support, the failing heart with VA ECMO, so we’re taking blood from the vein and returning to the artery, or we can support, damaged and diseased lungs, VV ECMO, so where we would essentially return, the blood back into the venous system and essentially provide pre pulmonary oxygenation.

And this is the system where you’re really taking over the function of the heart and the lungs. And as part of this conference, obviously, we’re focusing on trauma. And the big thing for this discussion is the use of ECMO in the trauma patient. Can you just highlight when it is that you’re thinking about the ECMO might be useful?

Because I’m imagining some of our listeners might imagine this is pre hospital, but that’s not the case for this, is it?

So we’re interested in a particular subgroup of critically injured trauma patients who we’ve achieved damage control surgery on. So there’s been a surgical target which has been corrected either by an open operation or interventional radiology to stop the bleeding. But then these patients who go on to develop a cardiovascular failure associated with bleeding.

 We think we understand it’s multifactorial. so commonly, that could happen. due to the big hypoxic, ischemic, reperfusion hit of trauma. In London particularly, HEMS clinicians are placing zone one re boa as a hemorrhage control and cardiac, temporising tool. So when the balloon comes down, the patient can have, an ischemic hit from that.

We also see with these, massively, particularly polytraumatically injured patients, they have a big metabolic storm of trauma. So we often see things like they’re very acidotic and have high lactate, high potassium and low serum calciums. And this can often be refractory to, medical therapy to correct the electrolyte and acid base balance, all factors that, contribute to cardiovascular dysfunction. We have another small group of patients as well who, develop a sort of a cardiomyopathy, related to, high concentrations of,exogenous, adrenaline and, noradrenaline and can, cause a sort of form of cardiac failure.

a bit like, Takotsubo, cardiomyopathy that our cardiologists are very used to seeing so multifactorial. I think convincing the world, it exists is a bit of an uphill battle, but I think we’re getting there.

Why has there been such a strong resistance? I come from the world of paediatrics. At any given time, we might have, two to three babies in any PICU around the world, on ECMO. less for trauma, but not excluding trauma, but as a kind of rescue or a bridging method to something else.

Why has there been such a lag, in the adult world to trial this in trauma.

 I think it’s twofold. One, the worldwide experience with using VA cardiac support in trauma, there’s only been about 230 cases published worldwide. So it’s a relatively evidence poor zone that we’re operating in and with ECMO often as you’re taking the blood out of the patient, passing it through an extra corporeal circuit, we need to anticoagulate the patient. So that often means, putting heparin into the, the prime fluid, which we whiz around the ECMO circuit to get it ready. And also, the doctors having to administer a systemic heparin, to prevent clotting. And then you. put that into the mix with a traumatically injured patient who’s had massive bleeding,this doesn’t marry together and a lot of the reticence has been around,the worry of worsening coagulopathy, worsening bleeding and potentially, having, rebleeds.

So Chris, I know that you’re working with Karim Brohi and others in London about this. Can you just tell us a little bit about how this might work? So when is the patient going on to ECMO? How do you choose who’s going on to ECMO? And a little bit more about the, I know you have to have extensive conversations both within your trust and with other people to make that happen.

That’s a really, super interesting and really important question. As I said, it’s a bit of an evidence free zone that we’re operating in, but on the flip side of that, we do recognize that there are patients that could potentially benefit from cardiac support with ECMO, rest those heart and lungs, optimize systemic perfusion and organ function.

So we’ve essentially developed a trauma shock call, which is a multidisciplinary teleconference which can be convened very rapidly to discuss bleeding code red patients we think might benefit from ECMO and our kind of, go criteria. a patient with trauma who’s had, penetrating chest trauma or blunt trauma, we see much more, blunt trauma than we do penetrating, but nonetheless in our institution, we do see a lot of penetrating trauma. Patients that would have had, REBOA or been resuscitated to return a spontaneous circulation following a traumatic cardiac arrest. Those low flow patients I’ve described to you, with, those,metabolic, issues, secondary to their trauma.

We’ve controlled the bleeding, but they have evidence of cardiogenic shock. So that’s either clinical. So they have a high lactates, very, cool peripheries. They’ve got a base excess. If they’ve had echocardiography, we canvisualize, poor cardiac function. And some more extreme cases, we’re placing pulmonary artery catheters to measure the cardiac output, cardiac index, and other,invasive haemodynamic variables which, help us to diagnose cardiac dysfunction in these trauma patients.

And so this isn’t happening immediately. These patients have been stabilized. You’ve got hemorrhagic control. The bleeding has been to all intents and purposes stopped. You may have had to use other really advanced modalities to do that, but this is beyond this.

Really tackling the metabolic insult of the ischemia that’s been created from whatever trauma that’s going on.

 So we think there are two patient populations likely to benefit from ECMO.

So the crash and burn salvage that I’ve described, but also there’s a group of patients who declare themselves a little later on the ICU. These are ones that make it off the operating table. They look pretty good. But then a couple of days in, we see a sort of a tailing off of their cardiac function.

So typically, these patients, are having fluid boluses to improve their cardiac output. That’s not working. Then we’re adding some inoppressor vasoactive agents to, optimise their systemic perfusion. And we think in a small proportion of patients, we essentially max them out on, medical therapy. And they sort of in a sort of a spiral of cardiovascular decline. We know from previous work we’ve done at C4TS, actually patients with cardiovascular dysfunction, this drives their multiple organ dysfunction syndrome and the risk of death is significantly higher in these ICU trauma patients who develop cardiac failure versus the ones that don’t.

So from a longitudinal point of view,is it part of your PhD to look at, what are the neurological outcomes or what the quality of life looks like for patients post ECMO?

This is probably one of the most important things, and on the flip side, poorly understood aspects of ECMO care. The idea of ECMO is it’s a supportive intensive care modality to all intents and purposes, and what we’re hoping for is we can liberate the patient off VA ECMO relatively quickly within a few days of their trauma, typically three to seven, and that’s also born out in the literature that looked at VA ECMO for cardiac support for other things, like cardiac drug toxicity where the patient’s gone into shock, patients with, rapidly developing myocarditis and indeed following acute myocardial infarction with cardiogenic shock. But yes, neurological and functional outcome is very important.

So we’ve placed four patients on ECMO. Two of them have had penetrating chest trauma. Two of them have had poly trauma from a blunt mechanism of injury.

Both, hit and run incidents. So that we’ve had two survivors, so our survivors have been in the, in the blunt cohort. And, they’ve had their bleeding controlled, but developed, cardiogenic shock.

So there is some optimism to be had here, and it’s always amazing to hear about these subjects that are going on.

I know for me as a jobbing, dare I say, emergency physician, knowing that people like you, Chris, are pushing the frontiers of what we understand about physiology and the technology we can use. Even though it may not happen in my lifetime, knowing that the people like you doing the work I have to think we’re very appreciative of.

You must be excited about where this is going

I’m really excited and the VA ECMO in adults started about 50 years ago. So it’s a relatively young technology and indeed the first patient we did it on was a trauma patient. A young guy in Santa Barbara, California, knocked off his motorcycle, horrendous polytrauma, broke many bones in his body, he transected his, descending thoracic aorta and developed, severe, refractory respiratory failure.

He was placed on, a ECMO kind of MacGyvered, together from a cupboard, but nonetheless he survived after, short, run on ECMO for about three days and did very well. And it’s,in our ECMO circles we often say that this guy survived,in spite of the ECMO, but not because of it.

But what’s really exciting, we’re not doing, stuff that’s super new and novel, but we’re taking technology and techniques from cardiothoracic surgery chiefly and just applying them in new ways. What’s really exciting in the next couple of years is other sort of endovascular extracorporeal strategies that we have to manage patients with traumatic injury and shock.

So a couple of those. One taking Reboa, so resuscitative endovascular balloon occlusion of the aorta a step further, with a technique called selective aortic arch perfusion. So you have a balloon blown up in the aorta, but we’re also, able to connect the patient to a perfusion circuit where we can preferentially, perfuse the patient’s brain and coronary circulation as a bridge to ROSC in somebody that’s had traumatic cardiac arrest or as a bridging, intervention to, cardiac rescue in somebody with, severe cardiogenic shock and even more extreme, we have a technique called emergency preservation and resuscitation. So this is using, essentially cold preservation as a kind of cryostasis buying time. So we know from, combat casualties and civilian trauma victims, that patients will often have potentially survivable injuries, but because of the long transport times, involved on scene. the patient to definitive care inevitably leads to global hypoxic ischemic injury, which, leads to death, but we can potentially stop the clock doing this EPR techniques and emergency preservation resuscitation.

So we essentially can cool the patient down by infusing,rapidly, cold saline into the patient’s,aorta and targeting a brain temperature around 10 degrees and cooling the whole body. So essentially we’re stopping the clock on that massive,metabolic going off, if you like, which buys an operating surgeon and team up to two hours to repair the injuries.

And then standard, cardiac surgery cannulas are placed to put the patient on standard, operating room cardiopulmonary bypass to rewarm the patient up and restore the physiology. So it’s really exciting. I really look forward to what the next few years in trauma resuscitation have. The future is now.

Chris, thank you so much for sharing your passion with us on the St Emlyn’s podcast. It’s been a real delight talking to you and a joy to meet you. Thanks again and keep up that amazing work.