Category: Trauma

Your Lungs Will Not Explode

Gas laws dictate the relationship between pressure and volume.  As pressure decreases, the volume of a gas increases.  If that volume of gas is a pneumothorax … the Aerospace Medical Association and the British Thoracic Society feel such hypobaric conditions, e.g., commercial air travel, are absolutely contraindicated.

But, does the small difference in atmospheric pressure – ~550mmHg versus 760mmHg – truly induce clinically important changes, such as tension physiology?

These clinicians in Salt Lake City enrolled patients with recently-treated traumatic or iatrogenic pneumothorax and subjected them to 2-hours of simulated air travel using a hyperbaric and hypobaric chamber.  Twenty patients were included, 14 of whom received tube thoracostomy for their pneumothorax, with 11 still having residual pneumothorax visible on chest x-ray.  Two types of simulated flights were performed – an initial 554mmHg phase intended to simulate aircraft cabin pressure, and a second phase using 471 mmHg, intended to compensate for the low baseline barometric pressure of 645 mmHg present in Murray, UT.

Did the volume of pneumothoracies increase as atmospheric pressure decreased?  Yes.  Did lungs explode?  No.  Did patients require emergency needle decompression?  No.  Did patients have any change in vital signs?  No.  And, all pneumothoracies returned to their baseline size following return to baseline atmospheric pressure.

Is this durable, generalizable, slam-dunk data regarding prospective guidance for air travel following small pneumothoracies?  No.  But, it’s a lovely bit of dogmalysis demonstrating an unnecessarily absolutist approach certainly is inappropriate, and doesn’t accurately describe the true individualized risks.

“Cleared for takeoff: The effects of hypobaric conditions on traumatic pneumothoraces”

Helmets Are Good Things

It seems intuitive helmets are beneficial – helmet vs. pavement or brain vs. pavement – yet the topic is somehow controversial.  The only question should not be “if”, but the magnitude of the protective effect.

This brief article is a simple survey of motorcycle and moped accidents in Hawaii, stratified by helmet use or non-use.  There are only small differences in admission to hospital and mortality in the overall cohort, however, those differences are magnified when further broken out into motorcycle or moped use.  The key data: 3.5% fatality rate in helmeted motorcycle crashes versus 8.7% fatality rate in unhelmeted.  The corresponding data for mopeds was 0.7% versus 1.1%.  The authors performed multivariate logistic regression to adjust for age, crash location, and gender with no substantial effect on overall results.

This is retrospective, billing database data, and there are biases and missing information associated with limiting the reporting of only patients for whom EMS was contacted.  This data also does not mention the cause of death – which would make for a much stronger association between fatality and helmet use if head injuries were implicated in the difference.

Regardless, most of the contextual evidence leans towards a protective effect for helmets, and the effect appears magnified as speed increases.  If surviving a motorcycle accident is preferable to the alternative, it seems helmets are the way to go.

“Helmet use among motorcycle and moped riders injured in Hawaii: Final medical dispositions from a linked database”
http://www.ncbi.nlm.nih.gov/pubmed/25494427

Merry Christmas!

If you truly must read literature on Christmas, then I direct you to thebmj, and a selection of articles from its Christmas issue:

“Televised medical talk shows—what they recommend and the evidence to support their recommendations: a prospective observational study”
http://www.bmj.com/content/349/bmj.g7346

“CARTOONS KILL: casualties in animated recreational theater in an objective observational new study of kids’ introduction to loss of life”
http://www.bmj.com/content/349/bmj.g7184

“When somebody loses weight, where does the fat go?”
http://www.bmj.com/content/349/bmj.g7257

“Are some diets “mass murder”?”
http://www.bmj.com/content/349/bmj.g7654

Should Children Receive Thoracotomy After Blunt Trauma?

Survival rates in the absence of signs of life following blunt trauma, as many have previously noted, are dismal – to be measured in the fractions of a percent.  As such, few advocate the use of the resuscitative thoracotomy, particularly outside centers with such surgical expertise as to definitively manage underlying injury.

But, children tend to exhibit remarkable healing powers compared to adults – are their outcomes any better?

Barely.

This National Trauma Data Bank review identified 3,115,597 individuals less than 18 years of age treated for blunt trauma.  Of these, 7,766 had no signs of life upon initial evaluation.  One quarter of these successfully regained signs of life prior to Emergency Department arrival – and ultimately 13.8% survived to discharge.  The remainder had no signs of life on Emergency Department arrival, and only 1.5% survived.  499 ED thoracotomies were performed – and survival was 1.3% in this cohort.

The authors of this study are very clearly negative in their assessment of the value of ED thoracotomy in this population.  It is a reasonable stance, given the apparent low yield of intervention in such a population.  While it is imprudent to use the word “never” – depending on the resource utilization, costs, and risks associated with an individual resuscitation, unfortunately, it rather seems aggressive measures ought be undertaken only in exceptional circumstances.

“Survival of pediatric blunt trauma patients presenting with no signs of life in the field”
http://www.ncbi.nlm.nih.gov/pubmed/25159245

The Trauma Pan-Scan Saves Lives

… and redeems them for valuable prizes.

Such is the message of this systematic review and meta-analysis, evaluating the published literature comparing “whole body CT”, arbitrary complete scanning, with “selective imaging”, scanning as indicated by physical examination.

Identifying seven studies, comprising 23,172 patients, these authors found a 20% reduction in mortality – 20.3% versus 16.9% – associated with the use of WBCT, despite a higher mean Injury Severity Score in the WBCT cohort.  The implication: choosing a selective scanning strategy was harmful, even in the face of a less-injured cohort.  Thus, the authors conclude the mortality advantage far exceeds any risks from radiation, and WBCT should be considered the standard method of evaluation.

Except, all but 2,610 of the patients in these pooled studies are from retrospective cohorts fraught with selection bias.  There are many reasons why trauma patients with lower ISS might yet have higher mortality, and otherwise aggressive diagnostic evaluation not indicated.  And, when those retrospective patients are tossed out, the comparison is a wash in the prospectively studied cohort.

If you’re a fan of selective imaging, this study probably changes little in your mind.  If you’re a fan of WBCT, it’s another citation to add to your quiver.  The authors of this study are hoping REACT-2 gives us the definitive answer – but with only 1,000 patients, I doubt that will be the case, either.

“Whole-body computed tomographic scanning leads to better survival as opposed to selective scanning in trauma patients: A systematic review and meta-analysis”
http://www.ncbi.nlm.nih.gov/pubmed/25250591

Blood is Good for the Injured Brain – Or is it?

A guest post by Dr. Andrew Kirkpatrick (@AskEMdoc), an Emergency Medicine resident at the University of Texas Medical School at Houston.

Hypoxia, of course, is lethal to vulnerable cells.  Erythropoeitin, in many small trials, has been shown to be neuroprotective after injury.  So, given these apparently obvious beneficial and synergistic treatments, the authors of this study set out to answer the question: What happens when a patient with Traumatic Brain Injury (TBI) is given blood and erythropoietin?
This is a randomized control trial with a factorial (2×2) design that tested Erythropoietin (Epo) versus Placebo and Transfusion Threshold of 7.0g/dL versus 10g/dL to determine if either of the above interventions conferred the benefit of improved neurologic recovery in TBI.  A total of 200 individuals with TBI were randomized into one of four groups using a block randomization strategy, sorting individuals into groups with and without transfusion thresholds or Epo administration.  Both the treatment team and the follow up personnel were blinded to Epo administration, but only follow up personnel could be blinded to transfusion threshold group.  Then, to make this study even further convoluted, the Epo dose and frequency was changed mid-stream due to safety concerns, dividing the Epo arm into the Epo1 and Epo 2 groups.   They also changed the study from a superiority trial to futility, and unusually selected 0.15 as their one-tailed alpha – a choice severely restricting their ability to reject the null hypothesis.
Determination of primary outcome data was completed utilizing the Glasgow Outcome Scale (GOS) using a variety of strategies, including in person and phone follow up.   For all comparisons – both transfusion thresholds and Epo – no statistically significant difference was detected.  Given their small sample, they may simply have been unable to produce a difference – as Epo seemed to potentially have some beneficial effect, though transfusion certainly showed no such signal.  Risk of death, infection, ARDS, and Cardiovascular complications including VTE were evaluated for as well, and both Epo groups and the 10g/dL transfusion group had significant increased risk of adverse events.  And, regarding resource utilization, the transfusion threshold group obviously consumed more blood products.
The study had several limitations including change in Epo protocol with 1/3 of the patients already enrolled, inability to blind clinicians to transfusion threshold, the aforementioned statistical limitations, and generalizability limitations owing to its enrollment at only two trauma centers.  Overall the results were unable to demonstrate benefit to either strategy – but were able to demonstrate definite harms.  Until further evidence is presented, it is prudent to continue conserving blood products and abstaining from giving ineffective, expensive medication.
“Effect of Erythropoietin and Transfusion Threshold on Neurological Recovery After Traumatic Brain Injury A Randomized Clinical Trial”

http://www.ncbi.nlm.nih.gov/pubmed/25058216

The Most Dangerous Holiday!

Here in the United States, it is Labor Day – a Federal holiday established in 1886 by U.S. President Grover Cleveland.  We, apparently, have Canada to thank for this innovation.

But, what was actually news to me – Labor Day is actually the highest-volume holiday for pediatric trauma, outpacing all other holidays.  I’d have thought 4th of July – with it’s various explosive devices – would be the most popular pediatric trauma holiday, but, between 1997 and 2006, Labor Day takes the lead, followed by Memorial Day, and 4th of July as a close third.  Halloween, Easter, Thanksgiving, New Year’s and Christmas round out the list, in that order.

Most common documented products associated with injuries on Labor Day included:  Football, bicycles, stairs/ramps, playgrounds, and beds.  Contrast with Christmas:  Stairs, beds, skiing, tables, knives, and sofas.  And the article provides lists of appropriately seasonal injury mechanisms for each other holiday.

So – beware Labor Day!  The most dangerous holiday of the year!

“Epidemiology of Pediatric Holiday-Related Injuries Presenting to US Emergency Departments”
http://www.ncbi.nlm.nih.gov/pubmed/20368316

The BATiC Score for Pediatric Trauma – Promising, But Not Prime-Time

Excluding significant intra-abdominal trauma on the basis of clinical evaluation is a lost art in the realm of zero-miss.  Nowhere is this more important than in a pediatric population, considering the small, but real, potential from harms due to exposure to ionizing radiation from CT.

This is the Blunt Abdominal Trauma in Children (BATiC) score, derived in 2009 by a Swiss group.  This rule promotes use of clinical exam, ultrasonographic findings, and laboratory results to determine need for CT.  In this study, authors from the Netherlands retrospectively applied the rule to 216 pediatric trauma patients presenting in a four-year span between 2006 and 2010.  All told, this cohort contained 18 patients for whom intra-abdominal injury were identified, and a BATiC score cut-off of 6 would have a sensitivity of 100% and specificity of 87%, with an AUC of 0.98.  So, this all sounds splendid.

But, only 34 of these patients even received a CT scan as part of their evaluation – and, with the standard outcome definition being injuries diagnosed on CT or as part of hospitalization, there is potential for a fair number of missed diagnoses.  A reasonable case may be made whether any missed injuries were clinically significant, given lack of observed morbidity, but it would be difficult to have confidence based on such as small sample.  Furthermore, just as a simple cultural issue, trauma surgeons in the U.S. tend to feel any injury is clinically significant.

Then, 18.5% of observations used to validate this rule were missing from the retrospective data collection and required imputation.  The extent of this missing data further degrades the reliability of the observed diagnostic characteristics.  No confidence intervals are presented along with their results – but, rest assured, they are quite wide.  Ultimately, this decision-instrument may indeed be valid – but requires specific prospective evaluation.

As an interesting Costs of Care side note, the additional charge for a such a trauma encounter including a CT scan in the Netherlands?  A mere 148 euros.

“External validation of the Blunt Abdominal Trauma in Children (BATiC) score: Ruling out significant abdominal injury in children”
http://www.ncbi.nlm.nih.gov/pubmed/24747461

Get to the Choppa! Or … Maybe Not?

Helicopter transport is entrenched in our systematic management of trauma.  It is glamorized on television, and retrospective National Trauma Data Bank studies seem to suggest survival improvement – and those with head injury seem to benefit most.

But, these NTDB studies encompass heterogenous populations and are challenged in creating truly equivalent control groups.  This study, on the other hand, is a single-center experience, allowing greater consistency across divided cohorts.  In a novel approach, these authors collected all HEMS trauma transfer requests to their facility across their 30-county catchement area – and specifically looked at occasions when weather precluded HEMS.  This therefore created two cohorts of patients eligible for HEMS, with a subset that was transported by ALS due to chance events.  The paramedic crews manning the HEMS and ALS transfers were staffed by the same company, and therefore had roughly equivalent training.

This created a cohort of 2,190 HEMS transports and 223 ground transports.  Across ISS, GCS, initial transfusion requirements, and vital signs, the two groups had generally minor differences.  However, there was some potentially important variability of initial operative intervention upon arrival at the Level 1 trauma center – 27.4% of HEMS underwent craniotomy, compared with 15.4% of ALS transfers.  Based on multivariable logistic regression, type of transport did not enter into a best fit model of survival – and, thus, there was no difference (9.0% vs 8.1% mortality) between HEMS or ALS transport of trauma patients, despite the additional hour added from call time to arrival at the Level 1 trauma center.

Unfortunately, there are potentially critical flaws in their methods for patient selection.  They report 3,901 patients had a request for trauma transfer – but the number of patients transferred by HEMS or ALS only sums to 2,398.  An additional 49 were transported by BLS.  Then, another 208 died while awaiting transfer.  How many of these 208 died during weather delays awaiting ALS?  Are those deaths, in some fashion, related to the paucity of craniotomies performed on ALS transports?  And, what of the other 965 patients?

I tend to agree with their conclusion – HEMS is expensive and far over-utilized for patients who receive no particular benefit from the time savings.  However, I’m not sure this analysis includes all the data needed to be reliable evidence.

“When birds can’t fly: An analysis of interfacility ground transport using advanced life support when helicopter emergency medical service is unavailable”
http://www.ncbi.nlm.nih.gov/pubmed/25058262

A Moratorium on Steroids for TBI

A guest post by Rory Spiegel (@EMNerd_) who blogs on nihilism and the art of doing nothing at emnerd.com.

In 2004 the CRASH trial examining the efficacy of steroids for acute traumatic brain injury (TBI) was published in The Lancet.  This massive trial included over 10,000 patients was stopped prematurely because of an increased mortality in the patients who received corticosteroids. This should have definitively closed the book on such a therapy.  Despite this damning evidence, it appears all one has to do to make this question relevant again is to devise a disease-oriented endpoint with plausible clinical relevance and test it using a sample size too small to differentiate these harms from the surrounding noise of statistical chance.

Authors of the recently published Corti-TC trial did just this. Asehnoune et al examined the effect of the combination of hydrocortisone and fludrocortisone for the prevention of hopsital-acquired pneumonia (HAP) in patients with severe TBI. This is not the authors first foray into the efficacy of steroids for TBI. Their original trial was published in JAMA in 2011 and examined the effects of hydrocortisone to prevent HAP in patients having experienced poly-trauma. In this initial trial, about half the 149 patients randomized to either hydrocortisone or placebo suffered a severe TBI. The authors found that 35.6% of the patients in the active treatment arm developed HAP compared to 51.3% in the placebo group. This difference was seen exclusively in the subgroup of patients with TBI.  Thus the authors set out to validate these findings by solely examining patients suffering from acute TBI. As a harbinger of things to come, the authors justified the 3% increase in mortality as statistical chance, since it failed to reach statistical significance due to the small sample size.

In what essentially is a validation cohort the Corti-TC  trial was devised. Patients were randomized to either a 10 day course of both hydrocortisone and fludrocortisone or equivalent placebos. Cortisol levels were drawn before treatment was initiated, and in those found to be adrenally competent treatment was stopped. Once again the authors’ primary endpoint was the 28-day incidence of HAP as defined by a new infiltrate on chest x-ray with at least two of the following criteria; a temperature >38°C, leucocytosis >12 000 cells per mL, leucopenia <4000 cells per mL, or purulent pulmonary secretions.

Corti-TC demonstrated a similar difference in rates of HAP in patients given steroids vs those who received the placebo. Specifically 45% of the patients in the steroid group compared to 53% in the control group developed HAP over the first 28-days.  Although this difference did not reach statistical significance due to a lower than anticipated overall incidence of HAP, a relevant divergence between the active and control groups is evident. This difference remained consistent whether or not patients were found to have adrenal deficiency, indicating that cortisol levels do not predict a subset of patients who will benefit from steroids. Of concern is the 2% absolute increase in mortality of patients treated with steroids. This difference was observed primarily in the subset of patients later found to be adrenally intact. The authors once again justify this increased mortality by its failure to reach statistical significance (p-value of 0.32). That this exact trend was demonstrated in their original study goes unmentioned.  In fact, the same magnitude of harm caused the authors of the CRASH trial to halt their study prematurely. Given the collective consistency with which this mortality detriment has been demonstrated across trials it should not be written off as fluctuations of random chance. Interpreting this literature in its totality, it becomes obvious that these recent examinations of steroids in head trauma are vastly underpowered to detect the true harms involved with the utilization of such an intervention.

In the discussion section of both their trials, the authors question why their patients fared better than those in the CRASH cohort. They hypothesize that the overall higher acuity of their patients may be responsible for this difference in outcomes. The authors recommend further studies be performed to elucidate this uncertainty. I would argue that their cohorts fared no better than the CRASH patients. In fact, the absolute increase in mortality was identical to that of the CRASH trial. It is only because these authors defined success with a disease oriented outcome of little clinical significance(HAP), that their cohorts appear to fare better than the far more robustly powered CRASH cohort. At this point it seems clear steroids in acute TBI are harmful. Further studies to clarify the magnitude of benefit of irrelevant outcomes seem unwarranted.

“Hydrocortisone and fludrocortisone for prevention of hospital-acquired pneumonia in patients with severe traumatic brain injury (Corti-TC): a double-blind, multicentre phase 3, randomised placebo-controlled trial”
http://www.thelancet.com/journals/lanres/article/PIIS2213-2600(14)70144-4/fulltext