Perioperative oxygen and surgical site infection

In November 2016 the WHO produced guidelines on the prevention of surgical site infection. Along with some very sensible recommendations about when to give antibiotics and whether patients should have a bath before surgery there was a section on how much oxygen we anaesthetists should administer to patients during and immediately after an operation. (Section 4.12 in the guidelines below).

http://www.who.int/gpsc/global-guidelines-web.pdf?ua=1

The guidelines state that the group looked at the evidence and then performed their own meta-analysis, and a further subgroup analysis. Some of you may already know that meta-analyses are one of my personal hobby horses. Every trial has its own biases and then we bunch a load of them together in order to concentrate and distill these biases, then do a subgroup analysis to focus on the areas where those biases may have taken the trial results to statistical significance. I can name you many subjects where a meta-analysis has changed our practice only to be disproven a few years later by a well conducted trial. 

I sent these guidelines out to my consultant colleagues and not one supported it. In fact one of my colleagues who is also a medical statistician produced an excellent piece of work summarised here:

They answered the wrong question, looking only at infection rates and ignoring overall benefit or harm to the patient. In a Cochrane analysis Here the chance of high oxygen concentrations reducing surgical site infection was described as low, and in addition there could be a 20% increase in mortality for those patients with high oxygen concentrations. 

So essentially high oxygen concentration may reduce SSIs a little, or it might cause a 20% increase in mortality. Or neither. In any case the evidence is far too flimsy to put this into international guidelines, and there is a chance they may actually cause harm to the patients we’re treating. I won’t be changing my practice based on these guidelines, it’s a shame it’s been included at all as it reduces the impact of the rest of the document.