Podcast – Impact Brain Apnoea with Gareth Davies (LTC 2014)

Welcome to the St. Emlyn’s podcast. I’m Iain Beardsell, and I’m privileged to be at the London Trauma Conference and delighted to have with me one of the UK’s, if not the world’s leading lights in trauma care and pre-hospital emergency medicine. Gareth Davis has very kindly agreed to come and talk to us following a really interesting talk about impact brain apnea. Many of you will know Gareth as the Director of London’s Air Ambulance, but also as a consultant in emergency medicine and pre-hospital emergency medicine at the Royal London Hospital. Thanks very much for joining us, Gareth. I wondered if you could maybe just take our listeners through one or two of the main learning points you had from your lecture this morning.

Well, the lecture this morning is essentially about primary brain apnea or impact brain apnea, which is something I suppose many people have never heard of before, but actually has been around as a concept for quite a long time. It’s certainly something that’s been haunting us for many years now that we felt that treating patients at the scene, there was something that didn’t add up—why one patient could cause a bull’s eye in a windscreen and do very badly, and another patient would be barely injured by it. We couldn’t quite understand it because we’d see the same crash at the same road, and we couldn’t work out what was causing this difference. With time and understanding human tolerance to injury, we began to work out what was happening and quite literally stumbled across the concept in the literature some time ago and have been trying to understand it ever since.

So, I suppose the first point about the lecture is that this concept really exists. We’re always trying to make things as simple as we can as an ambulance. What we’re really saying is that if you get a blow on the head, something happens in the brain stem that stops you from breathing. That may be the major injury that the patient has. If we can get them breathing again, they may recover. Simply put, it is that an impact to the brain does cause apnea, and unless we address that apnea and any airway problems associated with it, the patients do badly. But if we get on the case and sort out the patient’s breathing, what might at the outset look like a severe injury can actually become quite mild.

You were saying in your lecture that there’s a frightening lack of research into this area. I guess it’s hard to prove unless you’ve got that on-scene experience. And I’m presuming with your service and with your vast experience, you’ve seen this actually in patients by the roadside.

Yes, I mean, even for clinicians who practice pre-hospital medicine, it is quite rare to see it because we don’t get to the patients in the first minute, two minutes, three minutes, four minutes after the accident. With a dedicated dispatch policy like we have in London, we get there 12, 13, 14 minutes after. Of course, for many patients in apnea, that would be way too long. So actually, the only clinicians that really get to see this are the ones that stumble across it as part of their civilian life, so to speak. Those that partake in motorsport or other sports where patients get head-injured are the group that have seen it. But many people will often say, well, if we don’t have the evidence, it doesn’t exist. So how can you convince us that this actually is a real thing that exists?

Yeah, it is very difficult because the vast majority of clinicians are never going to see it and have to believe in something. More to the point, how are we ever going to demonstrate it because people aren’t hit by cars with ICP bolts in their heads? So I think a lot of it is about understanding and interpreting the literature. The animal work is unanimous that apnea exists as a part of head injury; it doesn’t matter which animal, which model of head injury, or which country—they all produce apnea. So I think the first part of that is understanding it, and the second one is taking good histories off bystanders. Also, I suppose the third one is looking for echoes. It’s a bit like the Higgs boson thing, where you don’t actually see the particle, you see an echo of it. One of the echoes of impact brain apnea is the result of the catecholamine surge, and that’s the cardiovascular collapse that people are seeing. When people are faced with that cardiovascular collapse, they’re duty-bound to explain it.

We can look at some physiology. You went through some really interesting ideas in the lecture about the way in which apnea causes one physiological response, but actually brain injury causes another physiological response and how those combine together.

Yes. There are two elements to the impact brain apnea research. One of them is quite simply that the impact to the medulla of the brain produces apnea, which produces hypoxia and hypercarbia. The other element of it is the huge catecholamine surge, which is well demonstrated in humans and persists for many hours, if not days, after head injury. But no one has ever really thought about that catecholamine surge in the first three or four minutes after an accident and its impact on a heart that may be hypoxic because of apnea. So it’s those things coming together that are so deleterious for patients, and we have to work on both elements of it. We’re saying that actually it’s the heart that’s struggling from the primary head injury; it’s getting this physiological disturbance from acidosis and hypoxia, but then you add in a whole load of catecholamines, and the heart just simply can’t cope and may cause what we would then see as traumatic cardiac arrest.

Yes, traumatic cardiac arrest. Or these are the patients that you see in your resus room that have had a head injury. They don’t appear to have blood in their chest, belly, or pelvis, but they are persistently hypotensive. Terms like central shock have been appended to this sort of phenomenon. I think because historically we have shied away from head injury causing hypotension, we’ll have just let it rest. But I think most clinicians that are listening to this podcast will have seen a head injury patient that is unresponsive to fluids and just drips down into cardiac arrest in their resus room or goes up to the ITU on masses of inotropes that are failing to produce systolics beyond 60 or 70. That’s the echo of the events that happened on scene.

You had a really interesting question from the floor after your lecture today where somebody pointed out that with traumatic cardiac arrest, we’re throwing blood products into patients now and concentrating on volume loading. But there is going to be this small cohort of patients, or maybe it’s not as small as we think, where their cardiac arrest is this centrally mediated system. Are you still advocating that patients we see following trauma who are in cardiac arrest we should treat aggressively with volume? How do you decide who gets those blood products and who doesn’t?

It’s really difficult, and you’ve got to be very clear on your examination that the patient isn’t hypovolemic or has a potential source for hypovolemia. I think the advice in the first instance is to presume hypovolemia, but there comes a point where you can’t find any injuries, and you’re piling blood and blood products into a patient that actually you should probably stop and think of an alternative.

So we have this potentially very straightforward disease with a potentially very straightforward solution, which is opening somebody’s airway and giving them ventilatory rescue breaths if you like in a near-patient style. Have we made trauma a bit too technical? Do we need to bring it back to the beginning, where we’ve got people responding quickly and early and doing the simple things well?

I think it’s really important for diseases such as this that the education of the public is correct, that people can address A, B, and C. Also, there is a responsibility on ambulance services. They need to be sure of what type of patient they’re dealing with and give the right instructions. There is a trend not just in the UK but all over the world for pre-arrival instructions for collapsed cardiac arrest to negate A and B and concentrate on C. But unfortunately for this group of patients, and we don’t know how big the group is, actually going back to A and B is the lifesaver. For these traumatic injuries, our key is always going to be airway and breathing, and actually, in traumatic cardiac arrest, that may be our most important intervention.

We’ve got this thought of this new disease really that we’re all not that familiar with. There isn’t much to read about it. How can we go about—podcasts are one way of educating the public and our colleagues that these things exist. Is there anything we can do about it, apart from having a trained responder on every street corner and every motorway?

Well, I think it is important that medicine and we as a group try and understand it and spread the word to our colleagues in the hospital. Is there anything that we can do about it? Well, yes, there is a move here in London and in other cities around the world for apps such as the GoodSAM app, which is about bringing people together who have the ability to deal with an airway, deal with some breathing and some circulation problems. Actually, the future might be about how those apps can help these patients long before the statutory ambulance service gets there.

We’ve featured the GoodSAM app on St. Emlyn’s before, but I know you’ve been involved with it. I think many people think it’s all about primary cardiac arrest, but I understand that it actually came from this idea of getting there and getting an airway and ventilation for this impact brain apnea.

The inspiration or one of the inspirations for that was a bottle of wine and amusing over all of these patients about how something could be done differently to treat this group of patients. Yes, it wasn’t born out of the cardiac group of patients. The inspiration behind it, believe it or not, was the primary brain apnea.

Garreth, that’s a really good fly-through of your lecture for those people who weren’t lucky enough to hear it in person. Are there any particular take-home points that you’d like listeners to remember when thinking about impact brain apnea?

Well, I think what I’d like people to remember is to try and believe in the concept and actually think about it and do some reading around it. The second thing is that there are two elements if you do identify it: there is the airway problem and the breathing problem, and then there is this circulation problem. I think if you can A) go looking for it and B) recognize those two issues, we might go some way to helping a lot of these patients.

Garreth, thank you so much for joining us on this St. Emlyn’s podcast here from the London Trauma Conference. As you can hear probably on the podcast, it’s lunchtime here, so I’ll let Garret go off and raid the sandwich table and just say thank you again, not just for this but also for setting up this conference itself and for everything he’s done for leading trauma care in the UK.

Thanks, Gareth. It’s been a pleasure having you on.

Cheers, Iain. Appreciate it.