Category Archives: Imaging

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

October 19, 2017 The Trauma Pro Leave a comment

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.

Imaging

Are You Overusing Chest CT In Kids?

September 27, 2017 The Trauma Pro Leave a comment

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.

Imaging

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

September 14, 2017 The Trauma Pro Leave a comment

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.

Imaging

When Can You Take A Hypotensive Patient To CT?

August 1, 2017 The Trauma Pro Leave a comment

The last two posts, I went on a rant about taking hypotensive patients to CT. The bottom line is that this is a generally bad idea, even if bad papers say it’s okay. However, we all know that there are no absolutes, especially in trauma.

So yes, there are two cases where one could justify taking a hypotensive patient to CT scan. Here they are:

You believe that your patient has a catastrophic brain injury which is responsible for the hypotension. You would like CT confirmation so you can begin to withdraw support and terminate any other interventions.
Your patient has sustained a cervical spinal cord injury and has neurogenic shock. You have started fluid resuscitation and are considering a pressor to normalize blood pressure, but would like to continue your diagnostic routine.

But before you can even consider leaving your resuscitation room, you must ensure that there is no other source of hypotension. This means getting chest and pelvic xrays to look for hemothorax or fractures. It means getting a good FAST exam to make sure there is no significant hemoperitoneum. It also means making sure that any fractures are properly splinted and there is no uncontrolled external bleeding.

You can only go to CT scan once all of these other potential bleeding sources have been ruled out. If in doubt, you must proceed to OR to either stop the bleeding or prove that it does not exist.

Are there any other reasons to take one of these patients to CT that you can think of? If so, leave comments or tweet!

Related post:

Can I take a hypotensive patient to CT?

Imaging

Can I Take A Hypotensive Patient to CT? Part 2

July 31, 2017 The Trauma Pro 2 Comments

In my last post, I commented on a paper that tried to claim that there is no reason not to take a patient to CT if they are hypotensive. It had issues, as you saw. Today, I want to share another paper from a few years ago that tried to do the same. Again, read the abstract!

I’ve said it before: hypotension and CT scanners don’t play together well. For years I’ve cautioned against this, having seen a number of patients crash and burn in this area early in my career. But it’s a common error, and may jeopardize your patient’s safety. A paper that is now in press looked at this practice in a trauma hospital in Taiwan.

Patients who had blunt abdominal trauma were retrospectively reviewed. Those who remained hypotensive (SBP<90) after 2L of crystalloid were scruitnized. The CT scanner was described as being located in the same area as the ED resuscitation rooms. Furthermore, several physicians and nurses were present during scans, and a full selection of resuscitation equipment was available in the scan area.

Here are the factoids:

909 patients were entered into the study
Only 91 patients remained hypotensive after initial resuscitation, and only 58 of these were scanned before definitive management
As expected, patients who were hypotensive after initial resuscitation had more serious injuries (ISS 22 vs 12), required more blood transfusions (938 vs 202 cc), and had a higher mortality (10% vs 1%).
There were no significant differences in comparing hypotensive patients who went to CT scan vs those who did not if they underwent some sort of hemostatic procedure (laparotomy, angioembolization)
In the hypotensive patients, time to OR in the CT scan group was 58 minutes vs 62 minutes for those who skipped the scan.
In the same patients, time to angio in the CT scan group was 147 minutes vs 140 minutes without a scan first.

The authors conclude that “hypotension does not always make performing a CT scan unfeasible.” (weak!)

Read this paper closely and don’t get fooled! It is very retrospective and very small. And if you look at the times carefully, you will see some funny business. How can time to OR or angio be virtually identical regardless of whether CT is used? Is it the world’s closest, fastest scanner? Probably not.

The authors showed that hypotensive patients have a ten-fold increase in mortality. They also recognized that definitive control of hemorrhage is the key to saving the patients. Unfortunately, there are factors in this retrospective study, such as various biases and some undocumented factors that make their two patient groups look artificially alike. This gives the appearance that the CT scan makes no difference.

In reality, the fact that there is no difference in times ensures that there is no clinical difference in outcome. To really answer this question, this kind of study must be done prospectively, and must have an adequate population size.

Bottom line: Don’t even consider going to CT with hypotensive patients. Even if you have the fastest, closest scanner in the world. Shock time still kills, and most CT scan rooms are very poor resuscitation rooms. If your patient is unstable in the ED, do your ABCs, get a quick exam, then transport to the area where you can get control of the bleeding. This will nearly always be your OR.

Reference: Hypotension does not always make computed tomography scans unfeasible in the management of blunt trauma patients. Injury, 46(1):29-34, 2015.

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