Modernising ED sedation practice with evidence

I think some EDs still have an overcautious ‘ASA 1 or 2 only’ criterion for procedural sedation, which makes no sense whatsoever when one considers the spectrum of cases in which emergent procedural sedation may be required.

Fortunately, the assumption that a higher ASA grade would be associated with increased complications has now been debunked by Edinburgh’s Emergency Medicine Research Group.

For more procedural sedation-related dogmalysis (such as pre-procedural fasting) check out EMCrit’s Practical Evidence Podcast that discusses the recently updated ACEP Policy.

Dawson, N., Dewar, A., Gray, A., Leal, A., on behalf of the Emergency Medicine Research Group, Edinburgh. (2014).
Association between ASA grade and complication rate in patients receiving procedural sedation for relocation of dislocated hip prostheses in a UK emergency department.
Emergency Medicine Journal 31(3), 207–209

OBJECTIVE: To determine the association between the American Society of Anesthiologists (ASA) grade and the complication rate of patients receiving procedural sedation for relocation of hip prosthesis in an adult emergency department (ED) in the UK.

DESIGN: Retrospective study of registry data from a large UK teaching hospital ED. Consecutive adult patients (aged 16 years and over) in whom ASA grade could be calculated, with an isolated dislocation of a hip prosthesis between 8 September 2006 and 16 April 2010 were included for analyses (n=303). The primary outcome measure was association between ASA and complication rate (any of desaturation <90%; apnoea; vomiting; aspiration; hypotension <90 mm Hg; cardiac arrest). Secondary outcome measures were relationship between ASA grade and procedural success, choice of sedative agent and sedation depth, and complications and choice of sedative agent, arrival time and sedation depth.

RESULTS: There was no significant difference between ASA grade and the risk of complication (p=0.800). Moreover, there was no significant difference between ASA grade and procedural success (p=0.284), ASA and choice of sedative agent (p=0.243), or ASA and sedation depth (p=0.48). There was no association between complications and sedative agent (p=0.18), or complications and arrival time (p=0.12). There was a significant difference between sedative depth and complications (p<0.001).

CONCLUSIONS: There is no clear association between a patient’s physical status (ASA grade) and the risk of complications, chance of procedural success or choice of sedative agent in relocation of hip prostheses. There is a higher rate of complications with higher levels of sedation (p<0.001).

The ‘Magic Eye®’ method of rhythm assessment

Are you someone who tries to determine whether an ECG trace is ‘irregularly irregular’ by drawing little dots on a piece of paper level with the R waves to see if they are evenly spaced? I’d done that for years until I read this fantastic suggestion, which I’ve been following for over a year now.

In the 1990s there was a popular series of posters and books called ‘Magic Eye‘. These contained a ‘random dot autostereogram‘ which appeared as a mish-mash of coloured dots, but when you stared at it for a while the illusion of a 3D image would emerge. They looked a bit like this (although this one won’t work at such reduced resolution):

Image Credit: Wikimedia Commons
Image Credit: Wikimedia Commons

Dr Broughton and colleagues from Cambridge, UK, discovered that this technique, which involves forcing a divergent gaze to get repeating patterns to appear to overlap, can be applied to an ECG trace.

Stereoviewing an ECG trace causes successive QRS complexes to visually overlap and produce a new image. As Broughton and colleagues point out:

When achieved, this will lead to one of three outcomes. Entirely regular rhythms will ‘click’ into place as a new image at fixed depth. Rhythms with only mild irregularity may be stereoviewable, and if so, will appear to show successive QRS complexes at subtly varying depths. Rhythms with marked irregularity will not be stereoviewable, instead (in our experience) merely giving the viewer sore eyes after several failed viewing attempts.”

The authors assert that this can be applied to continuous ECG monitors, although unless you are really good at stereoviewing while moving your head/eyes horizontally, you should really freeze the trace on the screen first.

The ‘Magic Eye®’ method of rhythm assessment
Anaesthesia. 2012 Oct;67(10):1170-1