Category Archives: Imaging

ACS Trauma Abstract #6: Scanning Unstable Trauma Patients???

If you’ve read my stuff for very long, you know I frown on sending unstable patients anywhere but to the OR. Instability tends to get worse, and that always happens at inopportune locations like hallways, elevators, and CT scanners. Imagine my surprise when I noticed an abstract being presented at the Clinical Congress of the American College of Surgeons this week suggesting that it was okay to scan hemodynamically unstable patients before “definitive therapy.”

Here’s the title:

“Computed tomography in hemodynamically abnormal thoracoabdominal trauma safely enhances surgical triage”

The devil is in the details and the language. This group from USC included all patients who were hemodynamically abnormal on arrival to the trauma bay but who normalized to SBP > 90 during the resuscitation were included.  A total of 253 of these patients were reviewed over a 9 year period, and the usual variables were analyzed (mortality, complications, hospital, ICU, and vent days, etc).

Here are the factoids:

  • Of the 253 patients studied, 45 went to straight to OR and 208 were taken to CT
  • Injury severity was identical for the two groups
  • Lengths of stay and mortality were not different, but only p values were given
  • Patients taken to CT cleared their lactic acidosis faster (12 vs 5 hours), and used a bit less plasma and significantly less blood transfusions
  • The OR group underwent more procedures (31% vs 13%), although what these were and when they were performed is not listed

Bottom line: The title of this abstract is misleading, and may fool those who don’t read the rest of the abstract. It should read:

“Computed tomography in previously hemodynamically abnormal thoracoabdominal trauma safely enhances surgical triage”

Someone who just skims through this issue of the journal may get the idea that it’s okay to scan an unstable patient. The authors are not saying this at all. If you read the conclusion carefully, you can see that the patients had to be resuscitated to a SBP > 90 before they considered taking to scan. And they did that for the majority of these patients.

The real question is, why do the scanned patients clear their lactic acidosis faster, need less blood, and undergo fewer procedures? It appears that there is some bias or selection process in play. Otherwise, why not use the magic CT scanner to make them all better?

Reference: Computed tomography in hemodynamically abnormal thoracoabdominal trauma safely enhances surgical triage. JACS 225(4S2):e175-176, 2017.

Print Friendly, PDF & Email

If A Tree Falls In A Forest…

After yesterday’s analysis of a not-so-good pan-scan vs selective-scan abstract, it’s time for a little philosophy today. There seem to be two camps in the world of initial diagnostic testing for trauma: selective scanning vs scan everything. I admit that I am one of the former. Yes, the more tests you do, the more things you will find. Some will be red herrings. Some may be true positives, but are they important? Here’s the key question:

“If a tree falls in a forest and no one is around, does it make a sound?”

There is a clinical corollary to this question in the field of trauma:

“If an injury exists but no one diagnoses it, does it make a difference (if there would be no change in treatment)?”

Here’s an example. On occasion, my colleagues want to order diagnostic studies that won’t make any clinical difference, in my opinion. A prime example is getting a chest CT after a simple blunt assault. A plain chest xray is routine, and if injuries are seen or the physical exam points to certain diagnoses, appropriate interventions should be taken. But adding a chest CT does not help. Nothing more than the usual pain management, pulmonary toilet, and an occasional chest tube will be needed, and those can be determined without the CT.

Trauma professionals need to realize that we don’t need to know absolutely every diagnosis that a patient has. Ones that need no treatment are of academic interest only, and can lead to accidental injury if we look for them too hard (radiation exposure, contrast reaction, extravasation into soft tissues to name a few). This is how we get started on the path to “defensive medicine.”

Bottom line: Think hard about every test you order. Consider what you are looking for, what you might find, and if it will change your management in any way. If it could, go ahead. But always consider the benefits versus the potential risks, or what I call the “juice to squeeze ratio.”

References:

  • George Berkeley, A Treatise Concerning the Principles of Human Knowledge, 1734, section 45.
  • paraphrased by William Fossett, Natural States, 1754.
Print Friendly, PDF & Email

ACS Trauma Abstracts #5: Pan-scan vs Selective CT For Pediatric Patients

In major adult blunt trauma, there are still two factions: those who pan-scan for diagnosis, and those who use CT selectively. The pan-scan proponents argue that they find everything, including things that would have been missed with selective scanning. The selective scanners argue that those things are typically not clinically significant, and radiation exposure is reduced.

Who is right? We’re still not sure. But when it comes to children, most believe that less radiation is always better. The group at USC decided to look at their experience with pan-scan vs selective imaging in blunt pediatric trauma patients, defined as those < 16 years of age. They reviewed their experience over a three year period, excluding those who had low blood pressure (<90). A total of 648 children met these criteria, and an array of variables were analyzed to try to determine “superiority.”

Here are the factoids:

  • 88% of these patients had low injury severity (ISS < 15), 567 patients
  • The low severity group who were selectively scanned had a half-day decrease in length of stay*, a quarter-day decrease in ventilator days, lower morbidity (15% vs 24%)*, and radiation exposure (8 vs 18 mSv)*, with the asterisked variables being “statistically significant”
  • The high severity also showed positive differences in decreased ICU length of stay, ventilator days, morbidity*, and radiation exposure*
  • For both pan- and selective-scanning, additional imaging led to no additional interventions in 95% of cases

Bottom line: Ugh! This is not a good abstract. It shows association, but not causation with anything but the radiation exposure calculations. Yes, if you scan less in the selective arm, there better be less exposure. But the other variables are either not clinically significant, or not defined well (i.e. morbidity).

The authors conclude that selective scanning is the way to go based on this (extremely weak) data. This is why I always recommend that you read the whole paper, not just the abstract, or in this case the whole abstract and not just the conclusion. The data, as presented in this abstract, do not support this at all.

The authors don’t say how many of these patients were very young, and how many of them actually received pan-scans. But any pediatric trauma surgeon would cringe if they read this  article. Although you may be a big believer in pan-scanning, reserve it for adults only until we have some better data. Don’t irradiate kids unnecessarily!

Reference: Selective CT imaging is superior to liberal CT imaging in the hemodynamically normal pediatric blunt trauma patient. JACS 225(4S1):562, 2017.

Print Friendly, PDF & Email

Are You Overusing Chest CT In Kids?

Many centers have developed guidelines for ordering various imaging studies, mostly in adults. These frequently dictate indications for head, cervical spine, and abdominal CT. The use of chest CT guidelines are far less common. And for the most part, such guidelines are significantly lacking for pediatric trauma evaluation.

Oregon Health Sciences University published a study detailing the use and utility of chest CT in pediatric patients, which they defined as age less than or equal to 18. They also looked at the impact of implementation of imaging guidelines for chest CT. They pooled data on blunt injuries from two Portland children’s hospitals. They collected a historical cohort over 8 years ending in 2015. One hospital had implemented region-specific imaging guidelines in 2010, and the impact of this was observed. They pooled data from both centers to identify mechanisms predictive of significant thoracic injury.

Here are the factoids:

  • Nearly 3000 patients were reviewed for thoracic CT use across the study period.
  • 1451 had chest x-ray only, 933 had chest CT only, and 567 had both
  • Although CT use in other body regions significantly declined across the study period, thoracic CT did not.
  • Chest CT changed management on only 17 of 1500 patients (1%).  There were 2 operations, 1 stent placement, 1 medical management, and 13 changes I consider rather weak (chest tube insertion, negative workup)
  • All clinically significant findings were predicted by an abnormal chest x-ray and motor vehicle mechanism

Bottom line: Chest CT continues to be overused in pediatric blunt trauma (and adults too!). This is especially unsettling due to it’s low yield and the unclear future danger of high dose radiation received during childhood. The major issue with this study is that it mixes adults and children and calls them all children. Specifically, most patients age 13-14 or above act anatomically and physiologically more like adults. It would have been nice to separate out the lower age group, but this typically results in very low numbers for analysis. In this case, it should have been possible because the median age was 13.

I recommend that all centers adopt some kind of blunt imaging guidelines to reduce clinician variability and unneeded radiation exposure. This is particularly true for children, since they are more sensitive to it and will live long enough to potentially experience the adverse effects from it. 

For both children and adults, chest CT should be reserved for evaluation of potential aortic injury, and nothing else. Rib fractures, hemothorax, and pneumothorax are best evaluated by traditional chest x-ray, and therapeutic decisions based on this alone. Abnormal chest x-ray findings, coupled with a high-energy mechanism (MVC, crush, pedestrian struck, and fall from a real height (3+ storys) should drive the decision to obtain a chest CT.

Related posts:

Reference: Limiting thoracic CT: a rule for use during initial pediatric trauma evaluation. J Ped Surg, In press, Aug 28, 2017.

Print Friendly, PDF & Email

Chest X-Ray After Chest Tube Insertion: Why Do We Do It?

More dogma, or is it actually useful? Any time a chest tube (tube thoracostomy) is inserted, we automatically order a chest x-ray. Even the ATLS course recommends obtaining an image after placement. But anything we do “automatically” is grounds for critical analysis to see if there is a valid reason for doing it.

A South African group looked at the utility of this practice retrospectively in 1004 of their patients. They place 1042 tubes. Here are the factoids:

  • Patients were included if they had at least one chest x-ray obtained after insertion
  • Patients were grouped as follows: Group A (10%) had the tube inserted on clinical grounds with no pre-insertion x-ray (e.g. tension pneumothorax). Group B (19%) had a chest x-ray before and had ongoing clinical concerns after insertion. Group C (71%) had a chest-xray before and no ongoing concerns.
  • 75% of injuries were penetrating (75% stab, 25% GSW), 25% were blunt
  • Group A (insertion with pre-x-ray): 9% had post-insertion findings that prompted a management change (kinked, not inserted far enough)
  • Group B (ongoing clinical concerns): 58% required a management change based on the post-x-ray. 33% were subcutaneous or not inserted far enough (!!)
  • Group C (no ongoing clinical concerns): 32 of 710 (5%) required a management change, usually because the tube was too deep

The authors concluded that if there are no clinical concerns (tube functioning, no clinical symptoms) after insertion, then a chest x-ray is not necessary.

Bottom line: But I disagree with the authors! Even with no obvious clinical concerns, the tube may not be functioning for a variety of reasons. Hopefully, this fact would then be discovered the next day when another x-ray is obtained. But this delays the usual progression toward removing the tube promptly by at least one day. It increases hospital stay, as well as the likelihood of infection or other hospital-associated complication. A chest x-ray is cheap compared to a day in the hospital, which would potentially happen in 5% of these patients. I recommend that we continue to obtain a simple one-view chest x-ray after tube insertion.

Related posts:

Reference: What is the yield of routine chest radiography following tube thoracostomy for trauma?  Injury 46(1):45-48, 2015.

Print Friendly, PDF & Email