All posts by TheTraumaPro

The CT Crystal Ball – Part 2

Yesterday, I wrote about a study that looked at a CT scan-derived index that promised to predict complications and mortality based on the waist-hip ratio. It was actually a very good one. But there is another abstract being presented at the American College of Surgeons Clinical Congress this week that promises miracles from the CT scanner as well.

This next abstract looks at muscle mass in trauma patients, as measured by CT scan. Specifically, the authors measured the density of the psoas muscle by determining its cross-sectional area and its density in Hounsfeld units. They then looked at the relationship between this and 90 day mortality, complications, and disposition location.

Really? Well, here are the factoids:

  • The study involved only 152 patients age 45+ from the year 2008
  • Median ISS was only 9
  • Patients with the lowest psoas cross-sectional area had an associated significantly higher death rate
  • Those with lowest psoas density had an associated increase in complications, dependency on discharge, and mortality
  • The authors suggest that these measurements could aid in patients who would benefit from aggressive nutritional support and physical therapy, and could aid in discharge planning

Bottom line: Very different from yesterday’s abstract. This one has no grounding in prior research. It appears to be one that was just dreamed up from nowhere. And it is truly an association study. No causality can or should be inferred.

There were only 152 patients studied. From 2008. Why? Why didn’t the authors use a more contemporary dataset? There is something weird going on behind the scenes. Is this an old study that was forgotten, and is just now being conveniently dusted off for analysis and submission? A power analysis to find out how many patients should be reviewed is not possible, so it is important to err on the high side. Not just 152 patients.

If you were to just read the abstract and especially the conclusions, you really might get the wrong idea. This is a study that will not see it’s day in any journal. Read and learn from it. But don’t duplicate it!

Related post:

Reference: Computed tomography-measured psoas density predicts complications, discharge location, and mortality in trauma patients. ACS Scientific Forum, trauma abstracts, 2016.

 

 

Using The CT Scan As A Crystal Ball For Trauma?

Two abstracts that are being presented at the American College of Surgeons Clinical Congress this week use CT scans to predict interesting things. They are things that you would not think a CT scanner should be able to do.

So can we use arcane measurements of things found on CT scan to make accurate predictions about our patients? Sure, if we see very low density bubbles (free air) in the abdomen, it’s pretty likely that some kind of abdominal catastrophe has occurred. Or if their is a large amount of high density fluid (blood) in the left chest after a stab wound, the patient will probably require a chest tube.

But what about other measurements that wouldn’t seem to be related to anything? Could we have found a magic crystal ball here, or is it just wishful thinking?

The first abstract evaluated the ability of the waist to hip ratio (WHR) to predict outcomes after trauma. Obviously, this is the width of the waist divided by the width of the body at the hips.

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Here are the factoids for this study:

  • 555 patients were analyzed retrospectively over 1 year at a Level I trauma center.
  • In-hospital complications and death were specifically analyzed
  • Using a receiver operating characteristic curve, the authors determined that a magic ratio of 1 was the best predictor
  • Complications were significantly higher in the group with WHR>1 (50% vs 19%) as was mortality (17% vs 7%)
  • Regression analysis showed that patients with WHR>1 were 4x more likely to have a complication and 3x more likely to die
  • WHR was only weakly correlated with BMI

Bottom line: WTF? How can this be, you ask? Just because your patient is a bit “fusiform” in shape, they have a rougher time after trauma? Well, in this case there may actually be some basis for the findings. There are thousands of articles in the literature that have identified that this shape actually is associated with higher complications and mortality in general. And there are already some published trauma papers that have confirmed this association. Interestingly, the BMI was less predictive that the WHR in this study, so this may be a better surrogate measure for obesity.

The number of patients enrolled is reasonable, and the statistics look sound (for just being an abstract). So there may be something here. However, before you start using the “measure tool” on your CT console on every trauma patient, wait for the confirmatory prospective studies to come along. 

Tomorrow, a look at a not-so-good study of this type, looking at an even more arcane metric on the CT scan.

Reference: Computed tomorgraphy-measured waist to hip ratio: a reliable predictor of outcomes after trauma. ACS Scientific Forum, trauma abstracts, 2016.

The Chance Fracture

Centers that take care of blunt trauma are familiar with the spectrum of injury that is directly attributable to seat belt use. Although proper restraint significantly decreases mortality and serious head injury, seat belts can cause visceral injury, especially to small bowel.

Lap belt use has been associated with Chance fracture (flexion distraction injury to the lumbar spine) since 1982. The association between seat belts and intra-abdominal injury, especially with an obvious “seat belt sign” was first described in 1987.

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Chance fracture. The vertebra appears to split in half from posterior to anterior.

Twenty years ago, orthopedic surgeons in Manitoba finally put two and two together and reported a series of 7 cases of Chance fractures. They noted that 6 of the fractures were associated with restraint use. Seat belt sign was also present in 5 of the 6 patients with fractures and three of the six had bowel injuries.

The authors noted that many provinces were mandating seatbelt use at the time, and they predicted that the number of Chance fractures, seat belt signs and hollow viscus injuries would increase. On the positive side, the number of deaths and serious head injuries would be expected to decline.

Although this was a small series, it finally cemented the unusual Chance fracture, seat belt sign, and bowel injury after motor vehicle trauma.

Thankfully, three point restraints (lap belt + shoulder harness) has been required in the seats next to doors for a long time. And since 2007, they have been mandated in the middle seat as well. Thus, these injuries seldom occur in any but the oldest (beater) cars on the road. They are seen more frequently now with sports and extreme sports injuries.

Chance fractures are frequently unstable, involving all three columns of the spine. The anterior column fails under compression, and the middle and posterior columns fail from the distraction mechanism. Usually, this fracture pattern requires operative fixation. However, if the posterior column is intact, a TLSO brace can be tried. This fracture is at risk for non-union and development of kyphosis or a flat back, which can lead to chronic pain and an abnormal posture.

Reference: Pediatric Chance Fractures: Association with Intra-abdominal Injuries and Seatbelt Use. Reid et al. J Trauma 30(4) 384-91, 1990.

 

Submental Intubation – The Video!

Yesterday, I described a technique for providing a secure yet short-term airway tailored to patients who can’t have a tube in their mouth or nose. Patients undergoing multiple facial fracture repair are probably the best candidates for this procedure.

A picture may be worth a thousand words, but a video is even better. Please note that it is explicit and shows the blow by blow surgical procedure. Of note, it is a quick and relatively simple advanced airway technique.

Related post:

By Request: Submental Intubation

I’ve had a number of recent requests regarding this technique, so I’m updating and reposting today and tomorrow.

Here’s one of the weirder procedures I’ve seen in some time. Imagine that you need a definitive airway, but you can’t use the face for some reason (mouth or nose). The usual choice would be a tracheostomy, right? But what if you only need it for a few days? Typically, once placed, trachs must be kept for a few weeks before decannulation is safe.

Enter submental intubation. This technique involves passing an endotracheal tube through the anterior floor of the mouth, and then down the airway. This leaves the facial bones, mandible, and skull base untouched.

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The technique is straightforward:

  • After initially intubating the patient  orotracheally, a 1.5cm incision is created just off the midline in the submental area under the chin.
  • Using a hemostat, all layers are penetrated, entering the oropharynx just lateral to the tongue.
  • A 1.5cm incision is then made at the puncture site, parallel to the gum line of the lower teeth.
  • The ET tube is removed from the ventilator circuit, and the connector at the proximal end of the tube is removed.
  • The hemostat is placed through the chin incision again. The proximal end of the ET tube is curled into the oropharynx and grasped with the hemostat, then pulled out through the skin under the chin, leaving the distal (balloon) end in the trachea.
  • The connector is reinserted, and the tube is then hooked up to the anesthesia circuit again.
  • The tube is then secured using a stitch under the chin.

After a final position check, the surgical procedure can commence. Cool!

 

There are a number of variations on this technique, so you may encounter slightly different descriptions. The tube can be pulled at the end of the procedure, or left for a few days to ensure safe extubation, if needed.

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A small series of 10 patients undergoing this technique was reviewed, and there were no short or long term problems. Scarring under the chin was acceptable, and was probably less noticeable than a trach scar.

Bottom line: This is a unique and creative method for intubating patients with very short-term airway needs while their facial fractures are being fixed. Brilliant idea!

Tomorrow: Submental intubation – the video!

Reference: Submental intubation in patients with panfacial fractures: a prospective study. Indian J Anaesth 55(3):299-304, 2011.

Photo source: internet