Not cool man, not cool.

Just when I thought I knew what I was doing…along comes a study to prove me wrong.

This time, it’s therapeutic hypothermia (TH) in the post-arrest patient.  Published today is another paper from The Alfred ICU on TH post Out Of Hospital Cardiac Arrest (OHCA), designed primarily to confuse me (and many others I suspect).

The article is in Resuscitation and is behind a paywall at the moment:

Changing target temperature from 33°C to 36°C in the ICU management of out-of-hospital cardiac arrest: A before and after study.

As you all know, TH was the intervention du jour for OHCA for some time.  At least until the TTM trial was published it was.  TTM changed things, as it found that the ‘dose’ of hypothermia didn’t matter too much – there was no difference between cooling a post arrest patient to 33°C versus 36°C.  As a result, most institutions opted to cool to 36°C, as this was likely to be easier to get too, and provide the same benefit (this is still cooling, just to a different end point, as fever is common and bad after cardiac arrest)

However…  It turns out that cooling to 36°C may not be quite as easy as we thought.  This is before and after study, looking at outcomes from post VF arrest patients admitted to The Alfred ICU during the 33°C cooling period, and post changing to 36°C cooling.  The demographics of patients, and the interventions performed remained the same between the two groups (except for the temperature of course), however the outcomes were different.

After the change to 36°C, fewer patients reached the target temperature, and more patients had fever.  Worse than that though, patients in the post-TTM group did worse clinically: fewer were discharged alive, fewer who were discharged alive were discharged home, and there was a decrease in favourable neurological outcome…



(However, one interesting tidbit from the trial is that more patients in the 36° group had bystander CPR performed – 18 vs 48 {86% vs 92%}, so something is going well out there!)

This is not an indictment on The Alfred ICU.  I know many of the intensivists who work there, and it is truly a centre of excellence.  Given this, I strongly suspect that similar experiences would be found in other ICUs.

This was a small study (76 patients) and the badness did not reach statistical significance as a result.  However I am sure that most of us would nonetheless consider the outcomes clinically significant regardless of the p value.

So what does this mean for me, a Paramedic?

Possibly not much.  It is relatively uncommon to find pyrexia in our post-arrest patients (excepting environmental causes of course), so it is not likely that we necessarily need to start cooling again.

However, we do need to remember that we have not abandoned TH, merely adjusted the dose.  Whilst in our role of primary response it is unusual to find fever as part of post-cardiac arrest syndrome, we may potentially come across it when carrying out retrieval.

If we do come across pyrexia in the post-arrest patient, this study reminds us that we cannot be laissez-faire about our management.  We still need to be aggressive in ensuring that fever does not rear it’s ugly head, and diligent in monitoring for the same.

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