Tag Archives: aorta

General

Trauma 20 Years Ago: Blunt Aortic Injury in Children

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We always worry about the aorta after high-energy blunt trauma in adults. Should we be doing the same in kids? After all, they are very elastic and for the most part they are tough to break.

A 13 year review was undertaken by the CV surgeons at Harborview twenty years ago which tried to answer this question. They looked at medical examiner records of all pediatric deaths (16 or younger) and identified the ones with traumatic aortic injury. They found only 12 deaths (2.1%), and somehow they also tracked one survivor (from ME data???). The age range was 3-15, with a mean of 12 (which means that the majority were in the older age group).

Six children were pedestrian struck, 5 were involved in car crashes, and two were on motorized bikes or ATVs. None of the children in car crashes were restrained and two were ejected. Four of the five were traveling > 55mph. All had other serious injuries, including abdominal and orthopedic.

It’s tough to draw any meaningful conclusions from this paper due to the small numbers, the retrospective design, and the lack of a denominator. The only thing it does tell us is that aortic injury is bad, and that kids should not get hit by cars and should wear their seat belts. The mean age suggests that it involves primarily older children. But we kind of knew all that already.

What it does not help with is figuring out at what age we need to start thinking about imaging the aorta with CT scan. I’ll be digging into that a little more this week.

Reference: Eddy et al. The epidemiology of traumatic rupture of the aorta in children: a 13 year review. J Trauma 30(8): 989-992, 1990.

General

Mechanisms for Blunt Aortic Injury

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What kinds of mechanisms can actually cause a thoracic aortic injury? Most physicians are aware that it involves sudden deceleration. This includes falls from a height and head-on car crashes. However, other mechanisms are associated with this injury as well.

Sudden acceleration can also tear the aorta. This can occur from a rear-end type car crash where one car is stopped and the other is traveling at a high rate of speed. It can also occur when pedestrians are struck by a car.

T-bone crashes also have a significant association with aortic injury. Twenty years ago, this was not really recognized, but now we know better.

One very interesting mechanism that I’ve seen about 5 times is the torso crush. This can occur when heavy objects tip over onto someone’s chest. I’ve seen this injury when multiple sheets of plywood have fallen on someone, and when a ditch caved in and the patient was crushed by dirt.

So when should you be concerned about the aorta enough to image it? In all cases, there must be a significant mechanism (see above). Falling over or being bumped at low speed just can’t do it. It’s also very rare in children under 10. I use the following guidelines:

  • Significant mechanism plus any one chest x-ray finding (see last 2 days of discussion)
  • Extreme mechanism alone. I define this as a closing velocity > 60mph, although you probably won’t know exactly how fast they were really going. You’ll need to estimate based on the usual speed on that particular road in the case of a car crash. Err on the side of predicting a higher speed. Extreme mechanism also includes pedestrian struck at moderate speed or better and torso crush.
  • Physical signs or symptoms consistent with aortic injury. These include tearing chest pain, especially between the shoulder blades, and pulse discrepancy (right radial pressure higher than left radial)

The gold standard screening test is now the helical chest CT. If the results are indeterminate, then a good old-fashioned aortogram may be needed.

General

What Is A Wide Mediastinum Anyway?

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Trauma professionals are always on the lookout for injuries that can kill you. Thoracic aortic injury from blunt trauma is one of those injuries. Thankfully, it is uncommon, but it can certainly be deadly.

One of the screening tests used to detect aortic injury is the old-fashioned chest xray. This test is said to be about 50% sensitive, with a negative predictive value of about 80%. However, the sensitivity is probably decreasing and the negative predictive value increasing due to the rapidly increasing number of obese patients that we see.

A wide mediastinum is defined as being > 8cm in width. In this day and age of digital imaging, you will need to use the measurement tool on your workstation to figure this out.

Unfortunately, it seems like most chest xrays show wide mediastinum these days. What are the most common causes for this?

  • Technique. The standard xray technique used to reduce magnification of the anterior mediastinum (where the aortic arch lives) is a tube distance of 72 inches from the patient, shot back to front. We can’t do this for trauma patients because we can’t stand them up and are reluctant to prone them. The standard trauma room technique is 36 inches from the patient shot front to back. This serves to magnify the mediastinal image and make it look wide.
  • Obesity. The more fat in the mediastinum, the wider it looks. The more fat on the back, the further the mediastinum is from the xray plate and the greater the magnification.
  • Other mediastinal blood. Major blunt trauma to the chest can cause bleeding from small veins in the mediastinum, making it look wide.
  • Thymus. Only in kids, though.
  • Aortic injury. Last but not least. Only a few percent of people with wide mediastinum will actually have the injury.

If you encounter a wide mediastinum on chest xray in a patient with a significant mechanism for aortic injury, then they should be screened using helical CT.

Tomorrow, I’ll talk about other xray findings that can clue you in to the presence of a thoracic aortic injury. Friday, I’ll finish by discussing what the significant mechanisms are for this injury.

General

Thoracic Aortic Injury in Very Young Children

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Trauma professionals routinely worry about the thoracic aorta when evaluating adults after major blunt trauma. The question is, how much do we have to worry about blunt thoracic aortic injury in children?

Younger children are more elastic, and their organs tend to withstand more punishment than adults. After reviewing the literature, I’ve come to the conclusion that this injury is very rare in children in the single digit age range. It’s difficult to find a good paper that addresses this question. The majority include kids up to age 16 or 18, which really skews the results. These patients are most commonly involved in motor vehicle crashes, although a significant number are also pedestrians struck by cars. 

The National Trauma Data Bank (NTDB) was queried for all children <18 years old sustaining blunt injury with at least 1 diagnosis code. There were nearly 27,000 records matching these criteria. Of these, only 34 had an injury to the thoracic aorta. And in the age range under 10, there were only 2! Both of these children were in very high energy car crashes.

The bottom line: Injury to the thoracic aorta practically never happens in children in the single digit age range. As they get closer to adolescence, they behave more like adults and become more susceptible. The diagnosis should be only be entertained in small children who are involved in very high-energy car crashes. Falls from the usual heights (2-3 stories) are probably not significant enough to cause it. A chest xray may show a full mediastinum, but this will most likely be due to a normal thymus. If investigation is warranted, the standard is to obtain a helical CT of the chest. This study would most likely be obtained anyway to evaluate the torso in a high-energy mechanism. Aortorgraphy is no longer used.

Reference: Trooskin, et al. Risk factors for blunt thoracic injury in children. J Pediatric Surg 40(1):98, 2005.