Maybe.
Despite advanced life support protocols, there is little
evidence that drugs do very much to improve meaningful outcomes after cardiac
arrest.
Along with this comes a tremendous effort and trial published
in the New England Journal of Medicine. Unfortunately it may not help us too much
but, it does provide us with some interesting data to ponder.
This was a randomized,
double blind placebo controlled trial in adults with shock refractory VF or
VT that took place in 10 sites in the
USA and Canada. (Ian Stiell is one of the authors of course. One cannot conduct
a large trial in Canada without his approval.)
The primary outcome
was survival to hospital discharge. It was powered to find a 6.3% absolute
difference. This was done by a per-protocol analysis rather than intention-to-treat
which was fine in this case. They also looked at more important secondary
outcomes. You could probably guess what they are…
Results? 37,889
patients were screened for eligibility (holy smokes) and about 3000 patients
ultimately randomized to amiodarone, lidocaine or placebo. 70% of the arrests
were witnessed and the time to EMS arrival was just over five minutes.
Between the groups, there was no difference in the primary outcome. The absolute difference between
amiodarone and placebo was 3.2% (95% CI 0.4 to 7.0.) p=0.08. Nevertheless, this
is quite an eyebrow raising trend.
In the pre-specified subgroup of witnessed arrest, the drugs
seem to work. At least it was statistically significant with a 5% increase in
survival to hospital discharge.
As expected, the conclusion as printed in the NEJM is very
measured and reported as a negative trial. However, I’m sure this study will be
interpreted in many different ways.
We know that the best predictors of successful outcomes in
out-of-hospital cardiac arrest are; witnessed arrest, bystander CPR, and an initial
shockable rhythm. It makes sense that an intervention will be more successful
in this particular group. So perhaps we should be aggressive.
I don’t think we should be throwing away our drugs quite
yet. In fact, I interpret this trial as supporting the existing protocols and
use of amiodarone in selected patients. The press release from the NIH seems to
agree. However, we could ultimately be proven wrong.
Enjoy,
Covering:
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