Comments Off on Interesting literature November 2008
Here’s the latest update of literature relevant to what we do. Don’t get stressed if you don’t get round to reading all the original articles – reading the regular summaries should soothe your conscience and remove any nagging worries that you might be missing something big out there.
Critical care and retrieval
We all assume obese patients do badly on intensive care, but body fat may confer a survival advantage in critical illness. A study and editorial in Intensive Care Medicine add to the ‘large body’ of literature showing the optimal BMI for surviving critical illness is probably much higher than normally assumed, as adipocytes perform a number of protective functions including an immunomodulatory role.
A meta-analysis of six RCTs tells us that prophylactic administration of steroids in multidose regimens before planned extubation reduces the incidence of laryngeal oedema after extubation and the consequent reintubation rate in adults, with few adverse events. The accompanying editorial suggests a prudent approach might be to limit use to those patients at greatest risk of post-extubation stridor. Risk factors include female sex, short stature, trauma, and prolonged intubation. Laryngeal oedema may be predicted by deflating the cuff and demonstrating a leak of <18%
Pre-hospital Care and Trauma
For those of you following the etomidate story, a small nonblinded RCT in trauma patients comparing etomidate with fentanyl/midazalom is the first study to couple adverse clinical endpoints with depressed adrenocortical function. Not an issue in Australia of course, but there are enough Americans and Brits for this to give the willies to. http://www.ncbi.nlm.nih.gov/pubmed/18784570
So you’re at a primary where a patient is trapped under a bus and just the legs are sticking out. Tempted to attach the Zoll to the lower limbs for Sats and BP? In normal subjects the mean NIBP at the calf or ankle is very similar to that at the arm, whereas the systolic will be a bit off. Now your obs chart needn’t look incomplete even if your patient does.
Ever been taught a simple way of predicting mortality from burns based on age and total body surface area burned (BSAB)? Examples include if age + BSAB > 75, there is a >50% probability of death. Well now there’s a complicated one but it has a catchy acronym: The FLAMES score (Fatality by Longevity, APACHE II score, Measured Extent of burn, and Sex) was derived and (retrospectively) validated. The authors argue that a new more accurate predictive tool is needed because burns mortality has improved over the last few decades as a result of better management of burn shock, use of more effective topical antimicrobials, better systemic antibiotics, organization of regional burn units, earlier excision, and alternative measures for wound closure. Clearly this is tool for hospital use, catches on remember you heard it here first.
More info this month on detection of intracranial hypertension by sonographic optic nerve sheath diameter measurement, this time in patients undergoing ICP monitoring. The take home messages: optic nerve sheath diameter correlates better than optic nerve diameter with ICP, and a small ONSD probably means ICP isn’t raised. I’m not selling this very well am I?
A nice example of an international collaborative pre-hospital research trial is VITRIS (Vasopressin In refractory TRaumatic HemorrhagIc Shock), being studied by a network of 40 EMS helicopters in Austria, Germany, Switzerland, The Netherlands. The rationale? To maintain coronary and cerebral perfusion pressures and minimise subdiaphragmatic bleeding in patients who would otherwise bleed out and arrest before getting to a hospital trauma team. This thinking is supported by successful animal studies, all further explained in the uploaded article.
Trial homepage: http://www.vitris.at/frameset.htm
Further data to support a liberal FFP and Platelet transfusion strategy in trauma is supplied by Vanderbilt University Medical Centre where they retrospectively evaluated their ‘Trauma Exsanguination Protocol’ (only in America… ). 30 day mortality was significantly better with FFP:RBC ratios > 2:3 and Plt:RBC ratios > 1:5. Nice to have civilian data to compare with the controversial and scarely achievable military 1:1:1 recommendations.
There’s another couple of papers to add to the pre-hospital intubation pile (thanks to Mark Newcombe for these). The first paper shows that air medical teams find it harder to effect advanced airway interventions inside the aircraft compared with on scene, and the second takes an interesting look at the effect of out of hospital intubation (OOH-ETI) on outcome when related to distance from hospital . At all distances OOH-ETI was associated with worse outcomes unless patients were transported by helicopter. Take home message? Intubation bad, helicopters good – or perhaps the RSI delivered by experienced helicopter teams provides a survival benefit in salvageable patients (as opposed to patients dead enough to be intubated without drugs). Take a look for yourself and see if you can make sense of it!
First paper: http://www.ncbi.nlm.nih.gov/pubmed/18924006
Second paper: http://www.ncbi.nlm.nih.gov/pubmed/18924009
You attend a motor vehicle collision and the driver’s airbag has deployed. Which part of the body is most likely to be injured by the airbag and its housing? The answer is the upper limbs , particularly forearm fractures. The risk is maximised when the forearm crosses the middle of the steering wheel, for example the left forearm when turning right. As pre-hospital specialists, you can sleep soundly at night smugly reassured that no-one else knows this sort of thing.
And on the horizon….
A supplement to November’s Critical Care Medicine contains a glimpse of what might be to come in the field of cardiopulmonary resuscitation: animal studies demonstrate the possible benefit of head cooling during CPR, infusion of bone marrow stem cells to facilitate neurological repair post-resuscitation, and replacing conventional chest compressions with electrical stimulation of thoracic cage musculature. Perhaps the most likely of the proposed interventions to reach clinical practice in the shorter term is the impedence threshold device, which appears to contribute to improved outcomes in both piglets and humans, although it has been around for a few years now without catching on.