The concept of cardiac arrest centres is not entirely new and is something we’ve been talking about in Virchester for some time. Indeed, there are several articles in the literature and a fairly reasonable patho-physiological argument for them1–3. We know that post resuscitation care is increasingly complex and also that new interventions such as ECMO are not going to be available everywhere. Like many other conditions such as major trauma there are logical arguments that can be made for centralisation.
As for the evidence? Well that’s still lacking and the world of medicine is full of great ideas that just don’t really work. We need evidence and so it was pleasing to see this trial published in Resuscitation4.
It’s a randomised controlled trial, which as we know is the best way of determining the effectiveness of an intervention. Importantly though, this is a ‘pilot trial’ and therefore it is not aimed to give a definitive answer. It has been designed and reported as a small trial to demonstrate feasibility of the concept of randomising patients, it doesn’t seek to give us a definitive answer but rather tells us whether a future trial might be able to answer the real question of whether cardiac arrest centres improve patient outcome.
What did they do?
Ths trial was based in London. They randomised patients to either the local hospital or to direct transfer to a cardiac arrest centre at St.Thomas’s in central London. Patients were randomised after 3 cycles of CPR using a sealed envelope system on a 1:1 basis. However, it’s unclear exactly what happened here. The authors state that randomisation occured after 3 cycles, but also that refractory VF/VT was defined as more than 3 cycles and yet later on they report that only 3 patients had refractory VF. These numbers don’t really add up or I’ve read it incorrectly. As written it appears that you only get randomised after 3 cycles – but what if you got ROSC after 1? It looks as though you would not have been included but is that really correct? I’m not sure what’s going on here but the numbers don’t really seem to add up as described.
CLARITY – Tiffany Patterson, the amazing lead author of the study has very kindly clarified this. Patients did not need to wait until after 3 cycles before randomisation and could be included if they got ROSC from 0,1, or 2 shocks. That makes a lot more sense from a pragmatic point of view and links in nicely to the subsequent trial which you can find described on the ISRCTN registry 5. The main trial aims to recruit 840 patients across London and with more cardiac arrest centres involved. (Ed – another example of #FOAMed and social media being able to clarify and discuss in real time).
Tell me about the patients.
They only looked at VF/VT patients without an obvious external cause and excluded those with ST elevation. They only included patients who had had a witnessed cardiac arrest. I suspect that ST elevation was excluded as those patients get sent to the same centre for PCI anyway (and thus they could not go into the control group). They screened 118 patients and randomised 40 although 63 were eligible, so there was a significant drop off in recruitment that will need to be considered carefully if this goes through to a full trial (Ed – although that’s not a bad percentage compared to many trials). Think though, if this is only VT/VF, witnessed and not ST elevation it’s likely to be a much smaller proportion of arrests than you might think. We don’t have data in this paper to determine what proportion it represents but the high survival rates point to this being a subset of patients.
What about the results?
Let’s be cautious here. It’s a pilot study and so the real result relates to the question of whether a future trial could answer the question of whether a larger RCT of cardiac arrest centres could take place. It seems that this study says yes, but there will be work and adjustments to be made on the back of the findings. As for the patients randomised the outcomes were very similar and non-significant. 30-day mortality was 50% in the intervention group and 40% in the control group. Similarly the cerebral performance score (cpc) was similar in both groups as were the number of major cardiac cardiac and cardiovascular outcomes. That may sound disspointing but remember that this study is in no way powered to give a definitive answer. On the plus side that data can be helpful when estimating the sample size for any future study.
Another part I still don’t understand is in the discussion. I think the authors state that they would exclude patients with refractory VF/VT from a future trial. If that’s the case then this sounds as if it will be a trial of ROSC patients rather than cardiac arrest patients. That’s a very different group and would thus change the options for treatment and outcomes. I may have misread this, but it’s a fundamental change in the original idea. The change is explained as the non ROSC patients would require mCPR which is not available in this system.
So if it’s non definitive, why are we talking about it?
Two reasons. Firstly, it’s a great piece of work to put this together and the authors should be congratulated in piloting a study that needs to be done. It’s clearly of interest and it reflects a pattern of specialisation for critical illness and injury. These sort of systems may well be our future of cardiac arrest care, but let’s wait for the evidence and be mindful that this is a subset of cardiac arrest patients. Secondly, we thought we’d pop this post out today as we’ve got a bit of space on the publication roster as we wait for a quite fabulous one tomorrow. Don’t miss tomorrows post though please don’t do so until you’ve opened and read all your valentine cards.
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