Archive for August, 2010|Monthly archive page

Oxygen – too much of a good thing ?

We’ve known for sometime that high inspired oxygen fractions (>0.8) are associated with atelechasis (and decruitment / shunt) and lung injury and suspected that hyperoxia also leads to the generation of toxic oxygen free radicals, which may have deleterious effects in other pathologies. A recent paper adds to this story;

Association between arterial hypoxia following resuscitation from cardiac arrest and In Hopsital mortality. Hope, J et al. JAMA. 2010;303(21):2165-2171 (doi:10.1001/jama.2010.707).

This paper has been appraised by a colleague, Paul Townsley, and you can download his presentation from the blue box on the right. Although the methodology has some potential flaws (which is probably inevitable), the paper provides evidence of definite harm of hyperoxia in ischemic brain injury.

Of course, there is an alternative weight of evidence of the harm associated with even short periods of desaturation in traumatic brain injury (and presumably also brain injury from poor perfusion). How to square this circle? The devil as always is in the detail. Controlling hyperoxia is probably important, but whether the benefits of avoiding hyperoxia outweigh the additional risk of periods of desaturation, or how often those periods occur within patient populations, is unknown. There is sufficient evidence to warrant a carefully designed RCT in the post resuscitation phase, (and maybe also in ARDS while we’re at it).

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Post Publication Peer Review

First an apology, there’s been quite a gap since my last post. I will be trying my best to increase the frequency of appraisals on Critical Insight, especially since Schringer & Altman’s editorial in this week’s BMJ. They comment that the “lack of post-publication review of medical research is a sign of an unhealthy research environment in clinical medicine”, and that “we need a change in culture to value public discussion”, I couldn’t agree more.
The major journals have a vested interest in suppressing critical appraisal of published papers as this tends to undermine their pre-publication peer review, a process that has failed to prevent publication of flawed research and in any case adds little to clinicians ability to apply that research. Letters to the editor are limited, screened by the same process that published the original research and significantly delayed. Apart from the BMJ other major journals have not embraced post publication discussion, although there are other sites that are filling the gap, for instance F1000 (conflict of interest – I have also published appraisals for this site).

Critical Insight was started to help fill this post publication review gap, and your help in the form of comments and posts is always welcome. To that end I’ve removed the need to be signed in to comment, if you can see the site you should be able to post a comment.