All posts by TheTraumaPro

Best Of: What Percent Pneumothorax Is It?

Frequently, radiologists and trauma professionals are coerced into describing the size of a pneumothorax seen on chest xray in percentage terms. They may something like “the patient has a 30% pneumothorax.”

The truth is that one cannot estimate a 3D volume based on a 2D study like a conventional chest xray. Everyone has seen the patient who has no or a minimal pneumothorax on a supine chest xray, only to discover one of significant size with CT scan.

Very few centers have the software that can determine the percentage of chest volume taken up with air. There are only two percentages that can be determined by viewing a regular chest xray: 0% and 100%. Obviously, 0% means no visible pneumothorax, and 100% means complete collapse. Even 100% doesn’t really look like 100% because the completely collapsed lung takes up some space. See the xray at the top for a 100% pneumothorax.

If you line up 10 trauma professionals and show them a chest xray with a pneumothorax, you will get 10 different estimates of their size. And there aren’t any guidelines as to what size demands chest tube insertion and what size can be watched.

The solution is to be as quantitative as possible. Describe the pneumothorax in terms of the maximum distance the edge of the lung is from the inside of the chest wall, and which intercostal space the pneumothorax extends to. So instead of saying “the patient has a 25% pneumo,” say “the pneumothorax is 1 cm wide and extends from the apex to the fifth intercostal space on an upright film.”

Best Of: Spine Immobilization in Penetrating Trauma: More Harm Than Good?

The EMS standard of care for blunt trauma patients has been to fully immobilize the spine before transporting to an emergency department. This is such a common practice that it is frequently applied to victims of penetrating trauma prior to transport.

A recent study in the Journal of Trauma calls this practice in question, and suggests that it may increase mortality! The authors reviewed data in the National Trauma Data Bank, looking at information on penetrating trauma patients. They found that approximately 4% of these patients underwent spine immobilization.

Review of mortality statistics found that the mortality in non-immobilized (7%) doubled to 14% in the immobilized group!

The authors also found that medics would have to fail to immobilize over 1000 patients to harm one who really needed it, but to fully immobilize 66 patients who didn’t need it to contribute to 1 death.

Although this type of study can’t definitely show why immobilization in these patients is bad, it can be teased out by looking at related research. Even the relatively short delays caused by applying collars and back boards can lead to enough of a delay to definitive care in penetrating trauma patients that it could be deadly. The assumption in all of these patients is that they are bleeding to death until proven otherwise.

A number of studies have suggested that a “limited scene intervention” to prehospital care is best. The assumption is that the most effective treatment can only be delivered at a trauma center, so rapid transport with attention to airway, breathing and circulation is the best practice.

While interesting, some real-life common sense should be applied by all medics who treat these types of patients. The reality is that it is nearly impossible to destabilize the spine with a knife, so all stab victims can be transported without a thought to spine immobilization. Gunshots can damage the spine and spinal cord, so if there is any doubt that the bullet passed nearby, at least simple precautions should be taken to minimize spine movement.

Reference: Spine Immobilization in Penetrating Trauma: More Harm Than Good? Haut et al, Johns Hopkins. J Trauma 68(1): 115-121, 2010.

Taking A Few Days Off?

Yes, I’m traveling today through the end of next week. Of course, I’ll be keeping my eyes open for interesting trauma stuff. If I don’t find anything really interesting, I’ll be running some “best of” columns that highlight good stuff from the past.

I’ll be attending EAST after that, and I’ll be tweeting from the meeting like a madman.

I will be checking in regularly through Twitter via FourSquare, so if you’re interested, you can track what I’m up to. 

Thanks for reading!
Michael 

Hypothermia and Massive Transfusion

Tuesday, I talked about a new notion of using profound hypothermia to save critically injured trauma patients. Since this concept is not yet ready for prime time, we still have to treat hypothermia as our enemy. Most trauma centers have established massive transfusion protocols that detail the use and ratios of specific blood components to avoid fatal anemia and coagulopathy. But do we pay enough attention to hypothermia?

A multicenter study was carried out that will be reported at the upcoming EAST meeting in January. They looked at patients who received massive transfusion (>= 10u PRBC in 24 hours) and looked at their lowest temperature during that 24 hour period. 

They found that as temperature decreased, shock parameters, coagulopathy, injury severity and transfusion requirements increased significantly. Specifically, if a temperature of <34C doubled mortality risk, and this effect was most pronounced in patients who received relatively less plasma.

Bottom line: Temperature is still very important, and hypothermia must be avoided at all costs. This is true in the ED and the OR. Allowing temperature to drop below 34C significantly increases mortality and is at least as important as giving enough FFP to correct coagulopathy from dilution.

Related post:

Reference: Hypothermia in massive transfusion: are we not paying enough attention to it? Poster 2, EAST 25th Annual Assembly, Jan 2012.

Induced Hypothermic Arrest In Patients Bleeding To Death?

Here’s an interesting note out of the University of Pittsburgh. They are preparing to engage in a study to look at the role of hypothermic arrest as a way to salvage trauma patients who are bleeding to death. Sometimes we encounter catastrophic injuries that are exceeding difficult to stop the bleeding. Some vascular injuries within the abdomen come to mind, particularly retrohepatic vena cava injuries.

So what would happen if you rapidly reinfused the patient with cold preservative instead of more blood? The idea is to stop the heart and induce profound hypothermia that would essentially put the brain and other key organs into suspended animation. This might provide a period of time to do the needed repairs, but not worry about the imminent danger of brain death.

Sam Tisherman, the principal investigator, terms this scenario EPR or “emergency preservation and resuscitation” instead of CPR. The desired temperature after cardiac arrest is 50 degrees F, or 10 degrees centigrade. Animal trials have shown promise.

Bottom line: It will be interesting to see how this goes. We’ve tried hypothermia for heart attacks, head injury, and a number of other clinical problems. Unfortunately after initial enthusiasm, they’ve generally not lived up to their billing. It seems counterintuitive to use a maneuver guaranteed to produce coagulopathy to save somebody who is bleeding. But sometimes this type of bold thinking results in life-saving breakthroughs.