Tuesday, August 30, 2005

Buckle Up, Part II

The images I will show in this post are ones that are going to be seen very rarely --- because they indicate a fatal process, and the patient usually will not survive the accident or trip to the hospital. However, they illustrate very well the importance of, you guessed it, seatbelts.

This accident occurred some time ago; this was an older lady who was an unbelted driver of a vehicle involved in a head-on collision. On arrival to the ED, she had obvious chest trauma, with rib fractures and a widened mediastinum seen on chest x-ray. In blunt chest trauma, this sign is worrisome for aortic trauma. She was taken to the CT scanner, where we saw this on the upper thoracic cuts:

There is blood around the aorta and a breech in the posterolateral wall of the aorta. This is where the dissection has started and there is free flow of blood outside the vessel. This is also where the flap of the dissection starts -- where a portion of the wall of the vessel has torn, blocking off normal flow through the lumen of the aorta, which worsens on lower cuts.

In this cut, the aorta can be seen behind the heart with with contrast filling only the anterior half of the vessel -- the dissection is larger here. As well, there is contrast material in the heart (as expected) but also outside the heart in the pericardium (definitely not expected). This once again is due to the aortic disruption causing blood to extravasate, here progressing back along the aorta and into the sac surrounding the heart. This will very rapidly cause the heart to become so constricted that it cannot allow blood to return from the vena cava and pump it back out again --pericardial tamponade.

This is a cut from the area of the diaphragmatic hiatus. The full effects of the dissection can be seen, with very little contrast seen in the lumen of the aorta. The right lobe of the liver is affected, with complete absence of blood flow seen; the left lobe is being perfused by a tiny branch off the nearly occluded celiac artery.

This lady was basically expiring in the CT scanner; it is extremely unusual that she survived to make it to the hospital, as the majority of these patients are dead at the scene. It may have been the case that she had a delayed progression of her dissection initially. At this stage, this is a non-survivable, non-treatable injury unless the patient is extremely stable -- which she was not. By the time the few minutes had passed to get these scans, she was in extremis.

Traumatic aortic rupture can occur with both frontal (head-on) and lateral (T-bone) auto crashes. There are some patients who suffer aortic tears who do not have such a catastrophic outcome, however; their ruptures are contained, and the dissection does not cause occlusion of the major intraabdominal vessels. In the past, they were treated with emergent operation, but complications were frequent as they generally had a variety of associated injuries. Today, in general, a delayed repair is recommended.