Should I Cool the Cardiac Arrest Patient?

One of the most useful things for me in the past two years has been using FOAMed to change my practice. As a rural doctor, my expertise intersects spheres of primary care, emergency medicine, resuscitation, obstetrics and anaesthesia. I don’t hold out to be an expert in any of these per se – indeed, the expertise of a rural doctor is in dealing with ambiguity across the board and having relevant skills for his or her community.

Casey Parker summarised this well at SMACC2013 in his talk ‘The MacGyver Dilemma‘. FOAMed helps us to shorten that ‘knowledge translation’ gap and apply relevant techniques to the population who need it.

Perhaps the most dramatic presentation in medicine is that of cardiac arrest. We drill as medical students and junior doctors in the Advanced Cardiac Life Support algorithms. Some of us go on to attend or instruct on ALS courses. The nursing staff in rural hospitals have mandatory ALS training; rural doctors are required to do the same as part of our triennial CPD requirements via various ‘merit badge’ courses.

What they don’t teach us is finesse – concepts such as teamwork and human factors (‘making things happen’), resuscitation room management, the ongoing debate over anti-arrhythmics and inotropes etc. Hell, some are still advocating hyperoxia. My gut feel is that O2 is GOOD for you early in the post-arrest phase – for a short while (as hypoxia seems to be bad for most)…but longer term hyperoxia in the process of retrieval and post-arrest ICU management is bad.

In 2011 I was the registrar in a 14 bed ICU in regional NSW; yet during that tenure I never heard of “therapeutic hypothermia” (TH) – despite the fact that many places were doing this and it was in established guidelines!

Barriers of course included the invariable differences in management by the lead intensivist for each week. If Dr X was on for the week, all patients were sedated on fentanyl/midazolam and gor noradrenaline as inotrope of choice; at handover on Monday Dr Y came on and inotropes were switched to dopamine, sedation to dexemetomidine. Now such variation in management probably reflects wither equipoise (as good as each other) or voodoo (neither works terribly well). In fact, Dr Z hit the nail on the head “intensive care is more about doing the simple things well, than the nuances”. Better to have a FAST HUG in bed than to obsess over USCOM vs Swann-Ganz vs IVC collapsibility vs passive leg raise for assessment of filling etc. I left ICU in late 2011 and took up in rural practice again.

Cooling in the bush

But I digress. Cooling post cardiac arrest was the topic.

We don’t get many cardiac arrests out bush (highlighting the difficulty of relative infrequency of critical illness leading to skills atrophy and complacency).

Again, the ‘knowledge translation’ gap between cutting edge medicine and rural was shortened by use of FOAMed. The guidelines do advocate cooling – but the application of that knowledge didn’t percolate down to isolated rural practitioners and certainly wasn’t taught on any courses I attended recently.

I was pleased to say that I’ve achieved therapeutic hypothermia to 32-34 degrees in the cases I have managed in pas two years – despite the fact that TH as a concept was alien to the rural hospital and no formal protocol existed within the CHSALHN body to make TH happen.

Job well done, high fives all around. After all, TH seems biologically plausible.

There’s a good lay summary in ‘The Lazarus Effect’ by Dr Sam Parnia and more detail for doctors in the Australian Resus Guidelines. In 2013 I went along to SMACC2013. Having streamed sessions meant I couldn’t attend all the talks – indeed I was presenting in some sessions. Thankfully the SMACC organisers saw fit to release all talks as podcasts or vodcasts – a great way to review content during the year when jogging, cycling or commuting. You can access them across the Intensive Care Network and affiliated sites. Macken gave a good talk on targetted temperature management – I didn’t realise until  heard this talk that the basis for TH was on 352 patients only. He alluded to the TTM trial, results due later this year.

Well – the results are now out. Two papers, one in NEJM and one in JAMA mean that we should perhaps review the basis for TH. It may be more about preventing cerebral hyperthermia than cooling to 32-34 degrees.

What the papers say

No difference in survival or neurological outcome after cardiac arrest between target temperatures of 33°C and 36°C. So controlling temperature after cardiac arrest is still important, but cooling down to the recommended range of 32-34°C is not.

No benefit to prehospital cooling for either OOHCA or survivors of non-VF arrest. But no worse.


Not sure what to do with all that ice in the resus room? I have an idea...
Not sure what to do with all that ice in the resus room? I have an idea…

Of course, the likelihood is that hypothermia and temperature management as a modality, whilst biologically plausible, may only benefit certain subgroups. At the moment we simply do not know who will benefit from hypothermia and who won’t – but we need to be clear that TTM avoiding cerebral hyperthermia is essential. Whether it applies to ROSC post VF vs post-non-VF arrests is uncertain. Whether we should induce hypothermia as part of a TTM protocol to 33 vs 36 degrees? Who knows?

As for prognostication post-arrest – this remains difficult. For me, I think it is sensible to cool to at least 36 degrees and to avoid cerebral hyperthermia. It also makes sense to use cold crystalloid to dilute pro-inflammatory mediators that may worsen neuronal apoptosis, but to be mindful that rapid administration of large volumes to a ‘knackered’ heart may cause increased rates of re-arrest and pulmonary oedema.

As Rittenberger & Callaway say in their NEJM editorial :

“The exceptional rates of good outcomes in both the 33°C and 36°C groups in the present trial may reflect the active prevention of hyperthermia. Whatever the mechanisms, it seems clear that we should not regress to a pre-2002 style of care that does not manage temperature at all.

“Perhaps the most important message to take from this trial is that modern, aggressive care that includes attention to temperature works, making survival more likely than death when a patient is hospitalized after CPR. In contrast to a decade ago, one half instead of one third of patients with return of spontaneous circulation after CPR can expect to survive hospitalization. Few medical situations have enjoyed such absolute improvement over the same time period. Future studies can continue to refine protocols, define subgroups that benefit from individual therapies, and clarify how to best adjust temperature or other interventions to each patient’s illness.”

You can also listen to Weingart and Rittenberger discuss this :

..or read Simon Carley’s analysis of the stats and more importantly the comments thereafter :

Cliff Reid (who I am increasingly convinced just pisses brilliance) distils it all down into a few lines – read his synopsis here :

Ken Milne from Sceptics Guide to EM weighs in with some NNT vs NNH data :

Robbie Simpson of AmboFOAM (never afraid of being ‘not cool anymore’) maintains that the prehospital cooling will continue in Victoria, Australia at least – as part of the intra-arrest RINSE trial :

Even EM Nerd weighs in :

If you have any interest in fever on ICU, you should watch this. My kind of medicine….



If there are any retrievalists out there – if it’s OK with you, I;m going to continue to cool any OOHCA survivors with ROSC to 36 degrees…for now. And I am going to rigorously avoid hyperthermia and hyperoxia which biologically seem to cause worsening neuronal damage and hence outcomes.

Making prognostic decisions early in the resus is difficult. I have a LOW threshold to abandon resuscitation where it is clearly futile or against best interests or the wishes of my patient. But when we simply do not know the patient’s wishes or distraught family ask for ‘everything to be done’, it is kind of hard to extubate in the rural ED.

Sensible doctors have these conversations and set treatment ceilings early – preferably in the primary care consulting room when managing chronic disease.

Rob Simpson from AMBO-FOAMed has done a good podcast on some of this. Worth a listen as a podcast for the commute home


ADDENDUM 20-11-13

NB : Since posting, there have been a flurry of conversations across social media – blogs, google +, twitter etc on the topic of TTM (targetted temperature management). Mike Cadogan summaries them here on the useful site. Like him, I am fascinated about the way in which FOAMed and SoMe work to enable conversations across boundaries – emergency physicians, intensivists, statisticians, rural doctors, retrievalists and ambulance – all discussing TTM in real time.

FOAMed – it’s heady stuff!


2 thoughts on “Should I Cool the Cardiac Arrest Patient?”

  1. Pingback: All in a lather over TTM - LITFL

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