All posts by The Trauma Pro

Impact Of Arm Position On Torso CT Scan

February 22, 2016 The Trauma Pro Leave a comment

CT scan is a valuable tool for initial screening and diagnosis of trauma patients. However, more attention is being paid to radiation exposure and dosing. Besides selecting patients carefully and striving for ALARA radiation dosing (as low as reasonably achievable) by adjusting technique, what else can be done? Obviously, shielding parts of the body that do not need imaging is simple and effective. But what about simply changing body position?

One simple item to consider is arm positioning in torso scanning. There are no consistent recommendations for use in trauma scanning. Patients with arm and shoulder injuries generally keep the affected upper extremity at their side. Radiologists prefer to have the arms up if possible to reduce scatter and provide clearer imaging.

A retrospective review of 710 patients used dose information computed by the CT software and displayed on the console. Radiation exposure was estimated using this data and was stratified by arm positioning. Even though there are some issues with study design, the results were impressive.

There was no difference in scanning time for any arm position. Here are the factoids for radiation dose:

Both arms up: 19 mSv (p<0.0000001)
Left arm up: 23 mSv
Right arm up: 24 mSv
Arms down: 25 mSv

Bottom line: Do everything you can to reduce radiation exposure:

Be selective with your imaging. Do you really need it?
Work with your radiologists and physicists to use techniques that reduce dose yet retain image quality
Shield everything that’s not being imaged.
Think hard about getting CT scans in children. They probably don’t need it!
Raise both arms up during torso scanning unless injuries preclude it.

There is a commercial product now available that helps position the arms without tape, paper clips, or other office supply items. It doubles as a pillow for the patient and is held in place by their weight

Courtesy of http://accessoryaccommodations.com/

Related posts:

Reference: Influence of arm positioning on radiation dose for whole body computed tomography in trauma patients. J Trauma 70(4):900-905, 2011.

General

Can Lead Poisoning Occur After A Gunshot?

February 19, 2016 The Trauma Pro Leave a comment

This is a fairly common question from victims of gunshots and their families. As you know, bullets are routinely left in place unless they are superficial. It may cause more damage to try to extract one, especially if it has come to rest in a deep location. But is there danger in leaving the bullet alone?

One of the classic papers on this topic was published in 1982 by Erwin Thal at Parkland Hospital in Dallas. The paper recounted a series of 16 patients who had developed signs and symptoms of lead poisoning (plumbism) after a gunshot or shotgun injury. The common thread in these cases was that the injury involved a joint or bursa near a joint. In some cases the missile passed through the joint/bursa but came to rest nearby, and a synovial pseudocyst formed which included the piece of lead. The joint fluid bathing the projectile caused lead to leach into the circulation.

The patients in the Parkland paper developed symptoms anywhere from 3 days to 40 years after injury. As is the case with plumbism, symptoms were variable and nonspecific. Patients presented with abdominal pain, anemia, cognitive problems, renal dysfunction and seizures to name a few.

Bottom line: Any patient with a bullet or lead shot that is located in or near a joint or bursa should have the missile(s) promptly and surgically removed. Any lead that has come to rest within the GI tract (particularly the stomach) must be removed as well. If a patient presents with odd symptoms and has a history of a retained bullet, obtain a toxicology consult and begin a workup for lead poisoning. If levels are elevated, the missile must be extracted. Chelation therapy should be started preop because manipulation of the site may further increase lead levels. The missile and any stained tissues or pseudocyst must be removed in their entirety.

Reference: Lead poisoning from retained bullets. Ann Surg 195(3):305-313, 1982.

Philosophy

How To Tell If Research Is Crap

February 16, 2016 The Trauma Pro Leave a comment

I recently read a very interesting article on research, and found it to be very pertinent to the state of academic research today. It was published on Manager Mint, a site that considers itself to be “the most valuable business resource.” (?) But the message is very applicable to trauma professionals, medical professionals, and probably anyone else who engages in research pursuits. The link to the full article is listed at the end of this post.

1. Research is not good because it is true, but because it is interesting.

Interesting research doesn’t just restate what is already known. It creates or explores new territory. Don’t just read and believe existing dogma.

Critique it.

Question it. Then devise a way to see if it’s really true.

2. Good research is innovative.

Some of the best ideas come from combining ideas from various disciplines.

Some of the best research ideas are derived from applying concepts from totally unrelated fields to your own.

That’s why I read so many journals, blogs, and newsfeeds from many different fields. And even if you are not doing the research, a broad background can help you sort out and gain perspective as you read the works of others.

3. Good research is useful.

Yes, basic bench level research can potentially be helpful in understanding all the nuances of a particular biochemical or disease process.But a lot of the time, it just demonstrates relatively unimportant chemical or biological reactions. And only a very small number actually contribute to the big picture. For most of us working at a macro level, research that could actually change our practice or policies is really what we need.

4. The best research should be empirically derived.

It shouldn’t rely on complicated statistical models. If it does, it means that the effect being measured is very subtle, and potentially not clinically significant. There is a big difference between statistical and clinical relevance.

Reference: If You Can’t Answer “Yes” To These 5 Questions, Your Research Is Rubbish. Garrett Stone. Click here to view on Manager Mint.

General

Misleading Abstract Alert: Injuries Identified By Chest CT

February 12, 2016 The Trauma Pro Leave a comment

Here is another one of those papers that have this nicely done abstract that arrives at what seems to be a reasonable conclusion. But then you sit back and think about it. And it’s no longer so reasonable.

This study seems like it should be a good one! It’s a multi-center trial involving data from ten level I trauma centers. The research infrastructure used to collect the data and the statistical analyses for this retrospective review were sound.

Here are the factoids:

Of nearly 15,000 patients with blunt chest trauma, about 6,000 (40%) underwent both chest x-ray and CT
25% (1,454) of these patient had new injuries discovered by the CT
954 were truly occult, only being found on the CT; the remaining 500 scans found more injuries than seen on chest x-ray
202 patients had major interventions (chest tube, ventilator, surgery)
343 had minor interventions (admission, extended observation)
Chest x-ray was not very good at detecting aortic or diaphragm injury (surprise)
76% of the major interventions were chest tube insertions
32% of of patients with new fractures seen were hospitalized for pain control
None of the odds ratios reported were statistically significant

Bottom line: What could possibly go wrong? Ten trauma centers. Six thousand patients. Lots of data points. There are two major issues. First, the primary outcome was a major intervention based on the chest CT. The problem with having so many participating centers is that it is hard to figure out why they performed the interventions. Are they saying that a pneumothorax or hemothorax that was invisible on chest x-ray required a chest tube? Based on whose judgment? Unfortunately, that is a big variable. The authors admit that they did not know whether “interventions based on chest CT were truly necessary or beneficial because we did not study patient outcomes” and that the decisions for intervention “were largely made by residents (usually) or fellows.”

And the secondary outcome was admission or extended observation based on the chest CT. Yet these admissions were primarily for pain management in patients with fractures. Did the patients develop additional pain due to irradiation, or was it there all along?

So adding a chest CT greatly increases the likelihood of doing additional procedures. And it is difficult to tell (from this study) if those procedures were truly necessary. But we know that they can certainly be dangerous. If you back out all of the potentially unnecessary chest tubes and the admissions for pain that should have been admitted anyway, this study demonstrates very little additional value from CT.

A well-crafted imaging guideline will help determine which patients really need CT to identify patients with those occult injuries that are dangerous enough that they can’t be missed. The authors even conclude that “a validated decision instrument to support clinical judgment is needed.”

Related posts:

Reference: Prevalence and clinical import of thoracic injury identified by chest computed tomography but not chesty radiography in blunt trauma: multicenter prospective cohort study. Annals Emerg Med 66(6):589-600, 2015.

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