Category Archives: General

Technology: More On Bioprinting Body Parts

I believe that bioprinting (using 3D printers to create organs, skin grafts and other stuff we need) will be the next big thing. Lots of people are working in the field now, and the printed products are getting much more sophisticated. 

Tracheas and bladders have already been done. But now, how about an ear? Loss of an ear is very disfiguring and, like other injuries to the head and face, can create a fair amount of psychological trauma. Bioengineers at Weill Cornell Medical College have now printed an ear that is nearly indistinguishable from the ones we are born with.

Bioprinter creating an ear encapsulated in hydrogel.

The technique used here is a little different than others I have described. In this case, a digitized image of the subject’s other ear is used to print a “negative”, actually a mold that can create the new ear. The mold is filled with a collagen mixture (from rat tails!), and then injected with cartilage cells (from cows!). The collagen serves as a structure over which the cartilage can grow. 

The whole process is fast. It takes half a day to model the mold, a day to print it, 30 minutes to inject the gel, and the ear is ready 15 minutes later. Obviously, it has no skin so must be implanted under a prepared skin area in the patient. Over a few months, the cartilage grows and replaces the collagen within the ear. 

The next step is to use human collagen and cell cultures. Ideally, if the patient can be the source, there should be no chance of future rejection. Expect more advances in this technology creating more ways to rebuild our patients.

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Reference: High-Fidelity Tissue Engineering of Patient-Specific Auricles for Reconstruction of Pediatric Microtia and Other Auricular Deformities, PLoS ONE, 2013, DOI: 10.1371/journal.pone.0056506.

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Why I Don’t Write About Animal Studies

If you’ve been reading these posts for any length of time, you may have realized that I regularly write about new (or sometimes not so new) research studies that I believe have some impact on trauma professionals. But if you look closely, you’ll see that the vast majority are human studies. I can only recall 1 or 2 animal studies that I’ve commented on in the past 3+ years.

Why is that? Well, there are several reasons.

First, many of those papers describe low-level biomedical research that is tough for the average person to follow. They use sophisticated measurement and analysis techniques to pick apart a specific biological pathway or process. It almost takes a PhD to understand them.

Next, most of these studies are performing work that only incrementally increases our understanding of what’s going on at that microscopic level. These little bits of progress may ultimately add up to a major advance. But if I find it difficult to provide the big picture view of the importance of one of these minor findings to the average trauma professional, I’m not going to write about it.

Finally, and most importantly, many of these published results will not have any significance to our field. Some interesting, positive finding in an animal model may have been discovered. But why should we believe this will translate to something relevant to humans?

Look at the model of inflammation that’s been used to develop all manner of potential human drugs to block it in critically ill patients. To date, there have been nearly 150 such drugs developed and tested, at great expense. How many have actually worked and been approved for human use? Zero. Why? It turns out that the inflammation model used in mice creates a response that looks the same as what happens to humans. But it’s not. It turns out that completely different, parallel pathways have been studied. So the thousands of papers that picked apart these pathways used to treat mouse inflammation do not really apply to human medicine. Only to veterinary medicine. And mice veterinarians only!

Reference: Genomic responses in mouse models poorly mimic human inflammatory diseases. Proc Nat Acad Sciences, ePub Feb 11, 2013.

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Grading Spleen Injures – Simplified

Spleen injury grading is not as complicated as people think! The grading system ranges from Grade I (very minor) to Grade V (shattered, devascularized). 

There is one nuance that people frequently don’t appreciate: multiple injuries can increase the grade. Technically, multiple injuries advance the maximum grade by one point, up to a maximum of Grade 3. So Grade 1 + Grade 1 = Grade 2, but Grades 2+2 = 3! Weird arithmetic!

The vast majority of injuries are Grades 1 to 3, and they are actually the easiest to grade. I use this simple rule: 1 and 3, 10 and 50.

The first set of numbers indicates the depth of a laceration in centimeters.

  • Grade 1 – < 1 cm laceration depth
  • Grade 2 – 1-3 cm laceration depth
  • Grade 3 – >3 cm laceration depth

The second set of numbers refers to size of a subcapsular hematoma in percent of the total surface area of the spleen. Hint: most of these low grades are determined by laceration depth. Very few actually have sizable subcapsular hematomas. So memorize the 1-3 rule first!

  • Grade 1 – <10% subcapsular hematoma
  • Grade 2 – 10-50% subcapsular hematoma
  • Grade 3 – >50% subcapsular hematoma

Grades 4 and 5 use other criteria, but in general if it looks completely pulped it’s a 5, and if it’s a little less pulped, it’s a 4.

  • Grade 4 – hilar injury with >25% devascularization OR contrast blush (active bleeding)
  • Grade 5 – shattered spleen, or nearly complete devascularization

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The Societal Cost of ED Thoracotomy

ED thoracotomy can be a dramatic, life-saving procedure. From the patient’s perspective, there is only an upside to performing it; without it there is 100% mortality. But to trauma professionals, there is considerable downside risk, including accidental injury, disease transmission and wasted resources. What is the societal risk/cost if ED thoracotomy is performed for weak indications?

The trauma group at Sunnybrook in Toronto looked at this question by retrospectively reviewing 121 patients who underwent the procedure over a 17 year period. They looked at appropriateness, resource use and the safety of the trauma professionals involved. They used the following criteria to determine appropriateness:

  • Blunt trauma with an ED arrival time < 5 minutes
  • Penetrating torso injury with an ED arrival time < 15 minutes with signs of life

Most of the patients were young men (avg age 30) with 78% penetrating injury and 22% blunt. About half (51%) underwent thoracotomy for inappropriate indications. The vast majority of inappropriate cases were for penetrating injuries with long transport times. Only 3 of the inappropriate thoracotomies were for blunt trauma, yet 24 of the “appropriate” procedures were done in the face of blunt trauma.

Resource use in the 63 inappropriate cases included 433 lab tests, 14 plain images and 9 CT scans (!!!?), 6 cases in the OR, 244 units of packed red cells and 41 units of plasma. Accidental needlestick injuries occurred in 6% of the inappropriate thoracotomies. None of the patients receiving inappropriate thoracotomy survived.

Bottom line: ED thoracotomy remains a very dangerous procedure. I’ve previously written about guidelines to determine which ones are appropriate (see link below). In this study, many of the procedures were performed on patients with blunt trauma. That means that the number of inappropriate thoracotomies would have been much higher if today’s standards had been applied. So use the guidelines and save your own health, safety and hospital resources. Is it really worth it if you know the patient will not survive?

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Reference: Societal costs of inappropriate emergency department thoracotomy. J Amer Col Surg 214(1):18-26, 2012.

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How To: Deal With Fence Impalement (Part 3)

The patient impaled himself in the thigh while climbing over a wrought iron fence. A section of the fence (including him) has been carefully been separated, and it’s been secured while he is loaded into the ambulance. He’s just been dropped at your emergency department. What to do?

Trauma team activation? Yes! This should have been called in advance so the team could assemble prior to the patient’s arrival. This will definitely require a team, and the surgeon will be essential in planning further care.

Sedation? Definitely! If the embedded object is unwieldy or causes much discomfort, even consider electively sedating and intubating the patient for ease of management without causing more pain.

OR activation? Yes! Even before the patient arrives, the surgeon should call the OR to ready a room, since this will almost certainly require surgical attention.

ATLS guidelines? Yes! This case presents a perfect example of the Dang! factor (see below). Don’t let the team focus attention on the dramatic problem while ignoring his impending airway obstruction or some other major problem. A good physical exam of the involved part is essential to detect any subtle neurovascular symptoms that may give clues to deeper injuries.

Imaging? Maybe. Only if it will provide information that would help guide the extraction process. Just remember, it’s iron. Most radiographs and any MRI will be significantly degraded by so much metal.

The top left bar was in the groin crease, the middle left bar pierced the back of the thigh. There were no vessels or nerves involved.

Extraction in OR? Almost always! Only the smallest object embedded in the most benign areas can be removed in any place other than the OR. Depending on how close the foreign body is to any vital structure, the surgeon needs to decide whether to cut down on the object vs sliding it out and watching for the consequences (bleeding). Tourniquets may be used in more distal areas (not this case, though, due to how proximal it is).

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