Month: October 2015

Is NODESAT Overhyped?

In the last few years, we’ve had a little bit of a sea-change in oxygenation during intubation.  We’ve stopped relying solely on pre-oxygenation to bridge our patients through apnea, and started providing passive oxygenation during intubation.  Usually supplied by high-flow nasal cannula, this takes advantage of physiology and diffusion to distribute oxygen into circulation.

But, as these authors state, the evidence for this practice is spotty – mostly observational evidence from controlled intubation settings.  Our critically-ill patients hardly have the same physiology as those undergoing elective airway procedures, and are generally less responsive to oxygenation adjuncts.  So, this is the FELLOW trial, a pragmatic, open-label randomized trial comparing apneic oxygenation vs. “usual care” – which was none.

With 150 patients in their intention-to-treat analysis, this cartoon sums up the results sufficiently:

Not much difference!

Their two groups were relatively well-balanced in terms of physiology and airway comorbidities.  The intubating operators were reasonably experienced (median >50 intubations), and 2/3rds of the patients were intubated on the first attempt.  There were probably no important differences in pre-oxygenation or procedural factors.

But, it is quite a small trial.  There are small differences here favoring the apneic oxygenation arm that simply might not reach statistical significance.  The exclusion criteria included “if the treating clinicians felt a specific approach to intra-procedural oxygenation or a specific laryngoscopy device was mandated for the safe performance of the procedure”, which could have introduced a selection bias.  The open-label effects may or may not be confounding.  The ICU environment and exclusion criteria also affect generalizability to the Emergency Department.

In the end, the answer is: apneic oxygenation still probably helps, particularly considering the pre-study evidence favored the intervention, and this one study does not move the needle much.  However, the observation here of a clinically unimportant effect size is not unreasonable.  If the effect size is small, the cost of an intervention becomes important.  However, in this case, the cost is fairly minimal – a small addition to set-up time and procedural complexity.  Considering the low cost and the post-test odds still favoring the intervention, it would be erroneous to stop providing apneic oxygenation based on this trial, and further study is indicated.

“Randomized Trial of Apneic Oxygenation during Endotracheal Intubation of the Critically Ill”
http://www.ncbi.nlm.nih.gov/pubmed/26426458

When Peripheral Vertigo Isn’t

But, such misdiagnosis is rather rare.

These authors conduct a retrospective, administrative database study of patients discharged from an Ontario, Canada, Emergency Department between 2006 and 2011 with a diagnosis of peripheral vertigo.  They identify 41,794 patients with appropriate data and an explicit diagnosis of peripheral vertigo, and follow them for adverse outcomes.  Most importantly for this paper, looking at subsequent stroke diagnoses, they find 57 (0.14%) received a diagnosis of stroke within 7 days.  To these authors, this number represents a miss rate for actual cerebrovascular causes of vertigo on initial presentation.

It’s a little hard to put great confidence in this precise number, however, because there were actually 270,865 visits discharged with diagnoses of dizziness & vertigo.  The largest cohort of these, 71% of them, were discarded from analysis because their diagnosis was “Dizziness, giddiness, lightheadedness, vertigo NOS”, which was not specific enough for these authors’ purposes.  It would have been enlightening to have included this less-specific cohort in this analysis, at least as a parallel comparison group, for additional insight.

However, the authors do something I quite like in this paper, and something I think would improve the robustness of many other studies:  a propensity-matched analysis attempting to establish a baseline level of risk.  For these authors, they choose renal colic – a generally benign, yet frequent, condition, that ought confer no special additional risk of stroke.  These authors have no difficulty finding 34,872 of patients to pool into a cohort relatively well-matched on important risk factors.  These renal colic patients have very similar rates of falls and fractures in the short-term after discharge – but they have many fewer strokes.  Most of the difference between cohorts arises in the first 7 days, with 50 occurring in the vertigo cohort versus zero in renal colic.  Between day 7 and and 365, however, the rate difference narrows, with 74 strokes in the vertigo cohort and 49 in renal colic.

Despite the massive limitations of retrospective review and relying on diagnosis codes, I think the authors’ general observation is correct.  Dizziness can be a quite challenging diagnosis to evaluate in the Emergency Department, and clearly some patients are being erroneously given diagnoses of peripheral etiologies.  However, the rate of misdiagnosis in this cohort is likely somewhere better than 1 in 700, which I find generally clinically acceptable considering the impossibility of utilizing advanced imaging in such a vast population.

We can certainly endeavor to do better, but we have a lot of work cut out for ourselves in improving the specificity of our clinical evaluation first.

“Outcomes among patients discharged from the emergency department with a diagnosis of peripheral vertigo”

A Call to Retire Routine C-Spine Immobilization

Remember the heartwarming children’s tale of the young woman with the ribbon around her neck?  Once removed, the head falls from the body, and the unfortunate woman expires.  Thus, the inspiration and evidential basis for modern trauma care utilizing immobilization of the cervical spine.

This article asks a very simple question: is there evidence to support the notion of incidental cerebrospinal movement resulting in subsequent paralysis?  Their answer: probably not.

These authors review several thousand abstracts to extract twelve publications describing a mere 41 cases of patients who were not completely immobilized, and thence suffered subsequent neurologic deterioration.  The individual cases reported upon provide, generally, rather spotty detail regarding the circumstances.  Some patients had additional falls or trauma in the ED, others were intoxicated and combative, while many others seemed to have gradual worsening without a specific event.

These authors propose this gradual worsening represents the primary time scale of neurologic deterioration – and suggest the suspected precipitating events documented by these cases represent contextual red herrings.  Rather than becoming tetraplegic as a consequence of repositioning in the Emergency Department, it is more likely clinical manifestations result from ligamentous disruption, bleeding, and edema related to the primary injury, and immobilization would not have prevented their progression.

Of course, this paucity of documented examples cannot represent an exhaustive report of all known secondary deterioration after an initial, non-immobilized injury.  However, just as erroneous is the presumption that immobilization prevents such secondary deterioration – particularly when coupled with the known inconveniences and harms of mass immobilization during transport and evaluation.

It’s time for routine cervical spine immobilization to go!  However, such discontinuation need be undertaken in such a setting as capable of detecting any adverse events resulting from such.

“Early Secondary Neurologic Deterioration After Blunt Spinal Trauma: A Review of the Literature”
http://www.ncbi.nlm.nih.gov/pubmed/26394232