New Tech: Augmented Reality In The OR?

Virtual reality headsets have been all the rage for some time. They immerse the wearer in a complete virtual world, and are typically used for gaming. Augmented reality, on the other hand, overlays virtual items on the real world so both are visible at the same time. Think the notorious Pokemon Go app:

What if this technology could be used for medical purposes? You could overlay diagnostic or anatomic information on your patient to help guide therapy, surgery, etc.

A group at the University of Alberta in Canada have been playing with this technology. ProjectDR takes any kind of image-related information and projects it directly on a patient.The patient is first scanned using surface markers like they do when making movies:

Obviously, no fancy suit or huge number of markers is needed. Once this is accomplished, the diagnostic information can be projected onto the patient. The patient can move, and the projector will compensate and keep the projection anatomically correct.

Here is a short video that demonstrates the system:

So is this useful? Unfortunately, not yet. It may eventually be good for office-based trauma professionals, but it needs further refinement. This version uses an actual digital projector, which means it will be subject to shadows which will interfere with viewing, especially if a surgeon gets his or her big head in the way.

Here’s how it will really have to work: The system could function quite well in surgical procedures. Imagine the surgeon being able to don a VR headset (lightweight, please!) and see the surgical field with key information overlaid on the display. Or even easier, incorporate it in the DaVinci robotic system display. Add vital signs in the upper corner and details of anatomic structures that have not been surgically exposed yet. It could help show anatomic anomalies in great detail, such as vascular variants. And heck, why not throw in some on-demand magnification as well?

As with most new and exciting tech that hits the general media, a version that is actually usable by clinicians is several years away. But it should be fun when it finally gets here!

Reference: University of Alberta ProjectDR system

Pop Quiz: What’s The Diagnosis? The Answer

Okay, time for the answer. This 12 year old crashed his moped, taking handlebar to the mid-epigastrium. Over the next 3 days, he felt progressively worse and finally couldn’t keep food down.

Mom brought him to the ED. The child appeared ill, and had a WBC count of 18,000. The abdomen was firm, with involuntary guarding throughout and a hint of peritonitis. The diagnosis was made on the single abdominal xray shown yesterday. Here is a close-up of the good stuff?

Emergency docs, your differential diagnosis list with this history is a pancreatic vs a duodenal injury based on the mechanism.

Classic findings for duodenal injury:

  • Scoliosis with the concavity to the right. This is caused by psoas muscle irritation and spasm from retroperitoneal soiling by the duodenal leak.
  • Loss of the psoas shadow on the right. Hard to see on this xray, but the left psoas shadow is visible, the right is not. This is due to fluid and inflammation along this plane.
  • Air in the retroperitoneum. In this closeup, you can actually see tiny bubbles of leaked air outlining the right kidney. There are also bubbles along the duodenum and a few along the right psoas.

We fluid resuscitated first (important! dehydration is common and can lead to hemodynamic issues upon induction of anesthesia) and performed a laparotomy. There was a  blowout in the classic position, at the junction of 1st and 2nd portions of the duodenum. The hole was repaired in layers and a pyloric exclusion was performed, with 2 closed drains placed in the area of the leak.

The child did well, and went home after 5 days with the drains out. Feel free to common or leave questions!

Best of: Blunt Duodenal Injury In Children

Blunt injury to hollow organs is rare in adults, but a little more common in children. This is due to their smaller muscle mass and the lack of protection by their more flexible skeleton. Duodenal injury is very rare, and most trauma professionals don’t see any during their career. As with many pediatric injuries, there has been a move toward nonoperative management in selected cases, and duodenal injury is no exception.

What we really need to know is, which child needs prompt operative treatment, and which ones can be treated without it? Children’s Hospital of Boston did a multicenter study of pediatric patients who underwent operation for their injury to try to tease out some answers about who needs surgery and what the consequences were.

A total of 16 children’s hospitals participated in this 4 ½ year study. Only 54 children had a duodenal injury, proven either by operation or autopsy. Some key points identified were:

  • The injury was very uncommon, with one child per hospital per year at best
  • 90% had tenderness or marks of some sort on their abdomen (seatbelt sign, handlebar mark, other contusions).
  • Free air was not universal. Plain abdominal xray showed free air in 36% of cases, while CT showed it only 50% of the time. Free fluid was seen on CT in 100% of cases.
  • Contrast extravasation was uncommon, seen in 18% of patients.
  • Solid organ injuries were relatively common
  • Amylase was frequently elevated

Although laparoscopic exploration was attempted in about 12% of patients, it was universally converted to an open procedure when the injury was confirmed. TPN was used commonly in the postop period. Postop ileus was very common, but serious complications were rare (wound infection <10%, abscess 3%, fistula 4%). There were 2 deaths: one child presented in extremis, the other deteriorated one day after delayed recognition of the injury.

Bottom line: Be alert for this rare injury in children. Marks on the abdomen, particularly the epigastrium, should raise suspicion of a duodenal injury. The best imaging technique is the abdominal CT scan. Contrast is generally not helpful and not tolerated well by children. Duodenal hematoma can be managed nonoperatively. But any evidence of perforation (free fluid, air bubbles in the retroperitoneum, duodenal wall thickening, elevated serum amylase) should send the child to the OR. And laparotomy, not laparoscopy, is the way to go.

Reference: Operative blunt duodenal injury in children: a multi-institutional review. J Ped Surg 47(10):1833-1836, 2012.

Best Of: Finding Rib Fractures On Chest X-Ray

A lot of people have been viewing and requesting this post recently.

Here’s a neat trick for finding hard to see rib fractures on standard chest xrays.

First, this is not for use with CT scans. Although chest CT is the “gold standard” for finding every possible rib fracture present, it should never be used for this. Rib fractures are generally diagnosed clinically, and they are managed clinically. There is little difference in the management principles of 1 vs 7 rib fractures. Pain management and pulmonary toilet are the mainstays, and having an exact count doesn’t matter. That’s why we don’t get rib detail xrays any more. We really don’t care. Would you deny these treatments in someone with focal chest wall pain and tenderness with no fractures seen on imaging studies? No. It’s still a fracture, even if you can’t see it.

So most rib fractures are identified using plain old chest xray. Sometimes they are obvious, as in the image of a flail chest below.

But sometimes, there are only a few and they are hard to distinguish, especially if the are located laterally. Have a look at this image:

There are rib fractures on the left side side on the posterolateral aspects of the 4th and 5th ribs. Unfortunately, these can get lost with all the other ribs, scapula, lung markings, etc.

Here’s the trick. Our eyes follow arches (think McDonald’s) better than all these crazy lines and curves on the standard chest xray. So tip the xray on its side and make those curves into nice arches, then let your eyes follow them naturally:

Much more obvious! In the old days, we could just manually flip the film to either side. Now you have to use the rotate buttons to properly position the digital image.

Final exam: click here to view a large digital image of a nearly normal chest xray. There is one subtle rib fracture. See if you can pick it out with this trick. You’ll have to save it so you can manipulate it with your own jpg viewer. 

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