Tag Archives: ct scan

Imaging

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

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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

When Can You Take A Hypotensive Patient To CT?

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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:

  1. 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.
  2. 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!

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Imaging

Can I Take A Hypotensive Patient to CT? Part 2

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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.

Philosophy, Resuscitation

Don’t Just Read The Abstract: CT Scanning The Unstable Patient

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I’ve said it many times before: “don’t just read the abstract.” They can be misleading, and doing so makes it impossible to see the shortcomings of the research model and the veracity of the conclusions. Yet good trauma professionals do it all the time.

So I’ve selected a recent poster child to demonstrate this tenet. Let’s go over the study details:

This paper is a retrospective, registry review from Japan. The authors point out that one of the long-held rules is to avoid scanning unstable trauma patients in the “tunnel of death.” The authors cite a prior study that did not show an increase in mortality from this practice. So they decided to repeat/confirm it using 11 years of national registry data.

They included all patients who arrived at the trauma center with blood pressure < 90. Interestingly, they excluded patients in frank or near arrest. And finally, patients with critical data points missing were excluded. They used a regression method to control for covariates such as age, ISS, and vitals upon arrival.

Here are the factoids:

  • Out of nearly 200,000 patients, about 7,000 were initially eligible. About 1,000 were excluded by the criteria above or because they were treated at a low volume facility. Only 5,809 were included in the study and another 500 were excluded because of missing covariates.
  • The authors found that there were significantly fewer deaths in the group of unstable patients taken to CT (20 fewer per 100 patients) (!!!?)
  • However, when corrected for confounders, this significant difference went away completely
  • But the authors conclusion in the abstract was: “We suggest physicians should consider CT as one of the diagnostic options even when patients are unstable.”

Bottom line: What? The study went from showing that taking an unstable patient to CT was amazing for decreasing mortality, to no different after applying more statistical methods. And since there was no difference, why not just go?

Here’s why. In-hospital and 24 hour mortality are not good indicators of anything because there are so many patient and hospital factors involved. And because it was a registry study, there was no way of knowing if the patient was hypotensive at the time they were taken to CT. They could have had a low blood pressure and responded well to resuscitation. Or they could have been normotensive on arrival and became hypotensive before CT scan. There is no way to cleanly identify the correct study group without a prospective study, or a very painstaking retrospective one.

One of the most important aspects of this study is some background info that is not stated in the paper. Surgeon involvement in initial resuscitation in Japan is not nearly as integrated as it is in the US. So if the resuscitating physicians can’t do anything about the bleeding in the ED, why not just scan them while awaiting arrival of the surgeon? If the patient crashes, was it due to the scan, or a delay in getting to the OR?

So don’t just read the abstract. If it seems to be too good to be true, it is. Or at least self-serving. Read the nitty gritty details and decide for yourself!

Next week: more on unstable patients and the CT scanner

Reference: Computed tomography during initial management and mortality among hemodynamically unstable blunt trauma patients: a nationwide retrospective cohort study. Scand J Trauma 25(1):74, 2017.

Imaging

The Pan-Scan For Trauma

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Diagnostic imaging is a mainstay in diagnosing injuries in major trauma patients. But the big questions are, how much is enough and how much is too much? X-radiation is invisible but not innocuous. Trauma professionals tend to pay little attention to radiation that they can’t see in order to diagnose things they can’t otherwise see. And which may not even be there.

There are two major camps working in emergency departments: scan selectively vs scan everything. It all boils down to a balance between irradiating enough to be satisfied that nothing has been missed, and irradiating too much and causing harm later.

A very enlightening study was published last year from the group at the University of New South Wales. They prospectively looked at their experience while moving from selective scanning to pan-scanning.They studied over 600 patients in each cohort, looking at radiation exposure, missed injuries, and patient injury and discharge disposition variables.

Here are the factoids:

  • Absolute risk of receiving a higher radiation dose increased with pan-scanning from 12% to 20%. This translates to 1 extra person of every 13 evaluated receiving a higher dose.
  • The incidence of receiving >20 mSv radiation dose nearly doubled after pan-scanning. This is the threshold at which we believe that cancer risk changes from low (<1:1000) to moderate (>1:1000).
  • The risk of receiving >20 mSv was lower in less severely injured patients (sigh of relief)
  • There were 6 missed injuries with selective scanning and 4 with pan-scanning (not significant). All were relatively minor.

Bottom line: Granted, the study groups are relatively small, and the science behind radiation risk is not very exact. But this study is very provocative because it shows that radiation dose increases significantly when pan-scan is used, but there was no benefit in terms of decreased missed injury. If we look at the likelihood of being helped vs harmed, patients are 26 times more likely to be harmed in the long term as they are to be helped in the short term. The defensive medicine naysayers will always argue about “that one catastrophic case” that will be missed, but I’m concerned that we’re creating some problems for our patients in the distant future that we are not worrying enough about right now.

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Reference: Comparison of radiation exposure of trauma patients from diagnostic radiology procedures before and after the introduction of a panscan protocol. Emerg Med Australasia 24(1):43-51, 2012.