The use of cricoid pressure to prevent aspiration during
intubation was never based on high
quality evidence. Recently, it has been dying a slow death with many ED
doctors abandoning this practice. But there still is controversy, and our
anaesthetics counterparts are having trouble letting go.
Pulmonary aspiration during endotracheal intubation is exceedingly uncommon. The study of rare
events requires enrolment of lots of patients to have the statistical power to
come to an answer. As such it has not been
feasible to get high quality RCT’s to inform practice.
These authors tried… but we are still not totally clear.
This was a double
blind RCT non-inferiority trial conducted in 10 academic centres in France.
Patients undergoing RSI in the operating
theatre (not the ED) were randomised to proper cricoid vs. sham cricoid
(hand was put in place, but no pressure applied).
The primary endpoint
was aspiration and they also looked at several secondary outcomes.
They considered sham to be “non-inferior” if the incidence
of aspiration was not more than 50% higher (i.e. relative risk of 1.5).
Results?
After enrolling 3472
patients they only had 10 cases
of aspiration in the cricoid group
vs. 9 in the sham. This gives a relative risk of 0.9.
Sham wins!?!
Not officially…
With such tiny numbers of aspiration, it is no surprise that
the confidence intervals are rather wide.
The 95% confidence interval was 0.33-2.38. This is greater than the
non-inferiority margin of 1.5 and as such this is officially a negative study… i.e. they failed to demonstrate the
non-inferiority of the sham procedure in preventing pulmonary aspiration.
From a purist EBM standpoint this may be a negative study, but many interpret this as another nail in
the coffin for cricoid pressure. Outcomes were rare regardless. A look at
the secondary outcomes shows worse
laryngoscopic view and greater time to intubate with cricoid. There was
really nothing to suggest any benefit from cricoid pressure.
If someone happened to “invent” cricoid pressure today, we
would never take it up. But tradition, culture and "eminence-based" medicine is
hard to kill.
Unfortunately, this study has the possibility of being misleading. Years from now, I imagine
it will be casually mentioned as evidence in favour of cricoid pressure. This
is precisely why it is good to dissect these papers, take the pressure off (pun
intended) and to find the hidden truth.
Covering:
Birenbaum A, Hajage D, Roche S, et al. Effect of Cricoid
Pressure Compared with a Sham-Procedure in the Rapid Sequence Induction of
Anesthesia. The IRIS Randomized Clinical Trial. Jama Surg 2019;154:9-17. [link
to article]
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