Prior observational studies have challenged the widely held belief that IO access is just as good as IV. This paper further explored the association between IO access and poor outcomes compared to IV.
The authors performed a secondary analysis of a large trial of patients with out-of-hospital cardiac arrest. They were able to identify patients that got IV vs. IO as their means of access.
They excluded patients who had any failed attempts at either route of vascular access or who had both performed.
The primary outcome was favourable neurologic outcome on hospital discharge (mRS <3 i.e. patients could at least walk without assistance).
13,155 were included in the analysis. 5% had IO access and 95% had IV (obviously patients were not randomised to this intervention)
For all outcomes, the IV access was far superior. 7.6% of patients with IV access had favourable neurologic outcome vs. 1.5% with IO.
This is astounding! A huge difference… let’s throw away the IO’s!!!
But there is no way this is true.
No amount of fancy statistics can make up for systematic bias and residual confounding that is present in this cohort study. There is clearly a reason why paramedics went directly to IO rather than IV. The IO group was obviously a “sicker” cohort to start with and had worse outcomes.
Not all cardiac arrest is the same. We know those with witnessed arrest, bystander CPR and shockable rhythms do better. There are also many other factors that influence outcomes.
Capturing all potential confounders in a resuscitation is problematic. When under duress, data is hard to measure accurately. In addition, there are always the unknown confounders that go unmeasured and unadjusted. No statistics can truly fix bad or absent data.
Futhermore, what was the magic medicine they used to account for this five fold increase in favorable outcomes? No drugs have really been shown to work in ALS.
In the same context of “fake news” sometimes bad evidence is worse that no evidence at all. This study has the very unfortunate possibility to mislead and cause harm. At best, it is hypothesis generating for future prospective study.
For now, reject the fake news and keep drilling your IO’s.
Paper critiqued at Emergency Tasmania 2018. Special thanks to Dr Mark Reeves, FANZCA and audience for feedback.
Kawano T, Grunau B, Scheuemeyer FX, et al. Intraosseous Vascular Access is Associated with Lower Survival and Neurologic Recover Among Patients with Out-of-Hospital Cardiac Arrest. Ann Emerg Med. 2018;71:588-596.