Saturday, 1 July 2017

Outcomes After Out-of-Hospital Cardiac Arrest Treated by BLS vs. ALS: polishing a pig

There is a developing rationale that giving ALS care during out-of-hospital cardiac arrest (OHCA) might actually be harmful. The reasons often include potential harm by trying to establish an advanced airway, drugs have never been shown to improve meaningful outcomes, and the extra time it takes. This delay may distract from other beneficial interventions.

Thus far, the best quality data comes from Captain Ian Stiell’s OPALS study out of Canada. This was a before and after design and concluded no benefit to ALS over BLS with a focus on rapid defibrillation.

Obviously a properly done RCT with allocation concealment would be ideal to answer this research question. But there are questionable ethical hurdles and genuine issues of feasibility.

These authors sought to answer the question with another hypothesis raising observational study. 

Unfortunately, it has several fatal flaws and probably should not be read beyond the abstract.

They looked at patients with OHCA who had ALS or BLS dispatched in non-rural counties in the USA. They identified the variables by Medicare billing and coding data.

This study was not randomised and there could be very good reason why one type of dispatch was chosen over another. Could the ALS cohort have been sicker?

To try to correct for this confounding by indication, the authors tried the usual propensity matching based on all kinds of variables that may or may not have been measured correctly.

In short, this study was based on a multitude of assumptions and dubious statistical analysis of poor quality billing data. There is no doubt they tried hard and put in a lot of effort. But there is only so much one can do to polish a pig. In the end, it’s still swine.


Covering:

Sanghavi P, Jena A, Newhouse J, et al. Outcomes After Out-of Hospital Cardiac Arrest Treated by Basic vs. Advanced Life Support. JAMA Intern Med. doi:10.1001/jamainternmed.2014.5420




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