Tag Archives: CT

Best of AAST #5: Pneumothorax – How Big Is Too Big?

Deciding when to place a chest tube can be challenging. Sometimes, it’s obvious: there is a large hemo- or pneumothorax staring you in the face on the chest x-ray. But sometimes, it’s there but “not that big.” The real question is, how big is too big.

That’s a question that’s been very difficult to quantify. The authors of this abstract, from the Medical College of Wisconsin, conducted a six-year retrospective review of every patient with an isolated pneumothorax at their Level I trauma center. Based on their previous research, a 35mm threshold was used to stratify patients into two groups. This measurement was obtained from axial images of a CT scan. Statistical analysis was performed to identify the predictive value in determining whether the patient could be managed without a chest tube.

Here are the factoids:

  • A total of 1767 patients had a pneumothorax during the 6-year period, and about half met inclusion criteria for the study
  • Of the 385 with pneumothorax alone, 92% were managed without a chest tube
  • Of those 353, 95% had a maximum chest wall to lung distance (335)
  • The 35mm measurement was statistically shown to be an independent predictor of successful management without a tube for both blunt and penetrating trauma

Bottom line: Not so fast! Although this looks like a slam dunk abstract, it’s really not. First, many (or most?) pneumothoraces are initially diagnosed using a plain old chest x-ray. A 35mm measurement is meaningless here because there can be significant changes in position of the pneumothorax on the image. Sometimes, the air is located anteriorly with little or no lateral component.  Does this mean we should CT every patient with a known or suspected pneumothorax? I think not.

And the second issue is the subjectivity surrounding the definition of a failure. What criteria were used when the tube was actually placed in this series. If every patient had to become symptomatic first, then I might agree. But I suspect the tubes were placed when followup imaging showed that the air was just “too big.” You can’t statistic away this kind of potential bias from subjectivity.

So what’s the answer? Unfortunately, there still isn’t one. The need for a chest tube must still be based on subjective size on a chest x-ray, physiologic status, and the patient’s ability to tolerate a given amount of lost lung function. It continues to boil down to the  assessments of each trauma professional as to “how big is too big.”

Reference: Observing pneumothoraces: the 35mm rule is safe for both blunt and penetrating chest trauma. Session XVA Paper 28, AAST 2018.

Torso Trauma CT (Nearly) ALWAYS Requires Contrast

Most stable patients with blunt trauma undergo CT scanning these days. Hopefully, it’s done thoughtfully to optimize the risk/benefit ratio using a well-designed imaging protocol. The majority of these torso imaging protocols call for the use of IV contrast. But as I’ve written before, this can pose risks, especially to the elderly and others who have some degree of renal impairment.

Unfortunately, I occasionally encounter scans done at other hospitals that omit the use of contrast. This usually hinders diagnosis significantly. And it’s usually not clear why this happened, so let’s think about it a bit.

The use of contrast in CT is designed to show blood, or things that are filled with lots of blood. Specifically, a great deal of detail about the blood vessels and solid organs is displayed.

Let’s break it down by type of scan:

  • Chest – we are really only interested in the aorta. The only way to reliably demonstrate an aortic injury is by using contrast. And this is one of those injuries that, if you miss it, the patient is very likely to die from it. Therefore, if you are ordering a chest CT properly, you must add contrast.
  • Abdomen/pelvis – generally, we are looking for solid organ injury, potential mesenteric injuries, and extravasation of blood from organs or soft tissue. Once again, the only way to really see any of these is with contrast enhancement.
  • Vascular – CT is replacing conventional angiography for the investigation of vascular injury in many cases. Obviously, this study is worthless without the contrast.

Bottom line: Pretty much any CT of the chest, blood vessels, or abdomen/pelvis must have IV contrast injected for accurate diagnosis. But what if your patient is old, or is known to have some degree of renal impairment? First, decide if you can wait until a point of care or standard creatinine measurement is done. If you can, use the result to do your own risk/benefit calculation. Is the injury you are worried about potentially life-threatening AND reasonably likely? Are there other less harmful ways to detect it? Then use them. And if you really do need the study in a patient with renal dysfunction, give the contrast, monitor the serum creatinine regularly, and do what you can to optimize and protect their renal function over the next several days.

Radiographic Image Sharing Systems

There are generally three ways to share radiographic images with your upstream trauma center:

  • Hard copy. These days, that usually means a CD. Nearly all PACS systems (picture archiving and communications systems) can write CDs that can accompany your patient. Advantage: super cheap. Possible downsides: the CD may be corrupted and not openable, the software on the disk cannot be installed or will not run at the receiving hospital, and finally it can just be forgotten in the rush to get the patient out of the ED.
  • PACS system connections. These are software links that enable one hospital’s PACS software to communicate with another’s. They must be established in advance, and generally require some expertise from the hospitals’ IT departments. Images can be pushed from one system to another. Advantages: once set up, it is very inexpensive to maintain, and images can be viewed prior to patient arrival at the receiving hospital. Possible downside: Al-though the interchange format is standardized, every once in a while the systems just can’t communicate.
  • Web-based image sharing system. This consists of a web server-based software application available via the internet that allows subscribing hospitals to sign on and share images. Referring hospitals can upload images from their PACS systems for free, and the receiving hospital can view the images and/or download into their own system. Advantage: these products are simple to set up, and easy to use after just a little training. Compatibility is very high, and the services are continually working to ensure it. Downside: expensive. Depending on specifics, the annual subscription may be up to $100K per year, and is generally footed by the receiving trauma center.

Is a web-based solution worth it? MetroHealth in Cleveland looked at this over five years ago, and published their results in 2015. They looked at their experience pre- and post-implementation and found the following:

  • Three years of transfer data prior to the web system implementation was compared to one year of experience after
  • CT imaging decreased at both referring and receiving hospitals across the study period
  • Repeat scan rate decreased from 38% to 28%. Repeat head scans were the major driver at 21%.
  • Cost of reimaging dropped from about $1000 per patient to $600

Bottom line: As a referring hospital, it is your responsibility to ensure that the (hopefully) few images you obtain make it to the upstream trauma center. Although hard copy (CD) is the cheapest, it is also the least reliable. Work with your radiology and IT departments to determine which electronic solution is best for you. Some states and regional trauma systems help subsidize or provide a web-based solution for their member hospitals.

Reference: Implementation of an image sharing system significantly reduced repeat computed tomographic imaging in a regional trauma system. J Trauma 80(1):51-56, 2016.

Natural History of the Splenic Blush

In my last post, I described the two types of solid organ “blushes.” I also described my thoughts on the natural history of these findings. Now, a multicenter study on the natural progression of the splenic “blush” has just been published. I found this paper very interesting, because it challenged some of my own existing beliefs. But once I read it, my enthusiasm faded.

The Western Trauma Association sponsored a multicenter (17 Level I and II centers) review of data collected prospectively over an unspecified period of time. Patients were excluded if their injury was older than 24 hours, if they had a previous splenic injury, and if they had any number of diseases or hereditary conditions that might affect the spleen. Strict definitions of nonbleeding and actively bleeding injuries were applied, and detailed information on intervention and outcomes was collected.

Here are the factoids:

  • 200 patients were enrolled from 17 centers, but the paper does not state how long that took
  • 20% were low grade (1 or 2) and 80 % high grade (3-5)
  • 29% had a pseudoaneurysm, and 83% showed extravasation, which means that several patients had both
  • 15% underwent early splenectomy, 59% underwent angiography, and 26% were observed
  • For those with initial angiography, 6% had repeat angio and 7% eventually underwent splenectomy
  • Of those were were initially observed, 9% had delayed angio and 8% underwent splenectomy
  • Based on a read by an expert radiologist, an actively bleeding injury was associated with a 41% splenectomy rate
  • The authors conclude that the majority of patients with spleen injury with pseudoaneurysm or extravasation are managed with angio and embolization and that splenectomy remains a rare event (??)

Bottom line: This paper just doesn’t do it for me. The biggest problem is that it is what I call a “we do it the way we do it” study. It examines how 17 different centers evaluate and treat patients with significant splenic injury. There was no guidance or guideline on how to treat, so they each did it their way. And the number of patients was small.

They don’t tell us anything about the use or effectiveness of angio by grade. Or whether the specific hospitals routinely rely on angio rather than just going to the OR for high grade injuries (typically if angio response times are long).

Unfortunately, this paper gives the appearance of containing a lot of interesting stuff. But a 15% initial splenectomy rate is not a “rare event” in my book. Everything published here is at odds with what I’ve observed over the years for centers with well developed management guidelines and easy access to angio (< 5% splenectomy rate in hemodynamically stable patients with nonoperative management).

My recommendation is to send all stable patients with pseudoaneursym and/or extravasation to angio immediately! Yes, some will have nothing found by the time they get to angio, and you’ll have to come up with a plan at that point. But most have something wrong, and it won’t stop until it’s been plugged up (or your patient bleeds to death, whichever comes first)!

This article has all the right buzzwords: multicenter, prospective data, etc. But it’s already been moved to my recycle bin. 

Related post:

Reference: Natural history of splenic vascular abnormalities after blunt injury: A Western Trauma Association multicenter trial. J Trauma 83(6):999-1005, 2017.

Chest CT vs Chest X-Ray After Chest Tube Insertion

Two days ago, I discussed getting the traditional chest x-ray routinely after chest tube insertion. The answer was yes, it is important even if it appears to be functioning correctly. But yesterday, I also showed you how the chest x-ray can lie.

Remember this image?

Looks perfect! But it’s a 2-D view and you don’t know where the tube is in the anterior-posterior axis. It turns out to be in the patient’s subcutaneous tissues of his back, near his scapula!

So what if this is a trauma activation patient and you are getting ready to send your patient for a chest CT shortly? Should you follow the usual dogma and still get a conventional chest x-ray prior to leaving the trauma bay?

The answer is no! Typically, your trauma activation patient should have rapid access to the CT scanner, so you won’t have to wait very long. And the additional 3-D information is very helpful in making sure the tube is placed exactly where you want it.

Bottom line: If you are planning on obtaining a chest CT anyway in your trauma patient, don’t bother with a conventional chest x-ray first to check chest tube position. But DON’T order a chest CT for this reason alone! Remember, the chest CT is only for detecting aortic injury in blunt trauma. It should not be used for diagnosing fractures, hemothorax, or pneumothorax. Or chest tube position!

Related posts: