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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.

Related posts:

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.

Head

Is Decompressive Craniectomy Any Better Than Craniotomy?

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Severe TBI consists of a primary injury to the brain, followed by swelling, vascular, and ischemic problems which may cause a secondary injury. Much of the critical care management of this injury involves avoiding or ameliorating secondary injury. This is typically accomplished via medical means first, and through surgical procedures when medical management is insufficient.

Two types of surgical decompression are currently practiced: craniotomy and evacuation of blood/clot, and decompressive craniectomy with removal of a bone flap. The latter can be performed prophylactically before severe swelling occurs, or therapeutically as a damage control procedure when ICP is refractory to all other measures.

There has been a decades-old debate as to whether craniectomy, which is a major undertaking with months of skull/bone flap management, is actually worthwhile. Most studies have examined the utility of damage control craniectomy for refractory ICP. The results have not really been convincing one way or the other.

But what about prophylactic decompressive craniectomy (DC) to avoid future ICP problems while the patient is in the ICU? The surgical group at the University of Arizona at Tucson performed a five year retrospective review of their experience. Using propensity score matching, they identified 99 severe TBI patients who underwent DC (33) or craniotomy only (CO, 66). A power analysis showed that this sample size should be sufficient to demonstrate a significant difference.

Here are the factoids:

  • Both groups were similar with respect to age, GCS, ISS, AIS-head, and type of bleed
  • 26% died and 63% were discharged to rehab or skilled nursing facility
  • When comparing DC to CO groups, there were no differences in mortality, discharge to skilled nursing facility, discharge GCS or Glasgow Outcome Scale
  • There were more complications in the DC group, including shunt insertion for hydrocephalus (9% vs 0%), and reoperation (12% vs 2%)
  • Rates of wound infection and ventriculitis were the same for both groups (0-3%)

Bottom line: Although the study is small, it supposedly had enough patients for identification of significant differences. And basically, it didn’t show a positive difference for prophylactic decompressive craniectomy. There is certainly some opportunity for selection bias by the neurosurgeons that cannot be controlled for by this retrospective design. But it is yet another piece of the decompressive craniectomy puzzle. 

Overall, the literature support for either prophylactic or damage control craniectomy is not very strong. If it were, we would have identified some real benefits by now. What we don’t know is if there are specific subgroups of severe TBI patients who might benefit from it. So if your center is not involved in a project to study this, you should probably ask your neurosurgeons to base their practice only on what we know about this procedure to date. 

Performance Improvement

When Is It Not An “Unplanned ICU Admission?”

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All US trauma centers verified by the American College of Surgeons (ACS) must now subscribe to the ACS Trauma Quality Improvement Program (TQIP). This program allows each center to benchmark themselves against other trauma centers that are just like them (level, volume, acuity, etc).  Every quarter, TQIP members receive a report that details their performance in a number of key categories. The report slices and dices a large number of data points, and shows how they compare to those other trauma centers.

One of the more interesting portions of the TQIP report deals with risk-adjusted complications. The one I wrote about yesterday, the “ICU bounce back,” is officially called an “unplanned ICU admission.”

I’ve had several trauma centers ask me what constitutes an unplanned ICU admission. Is it any bounce back? What about patients who were never in the ICU?

This questions is particularly important to me because my own center’s TQIP report shows that we have a significant number of unplanned ICU admissions. But I know for a fact that they are not surprises. We have an inpatient trauma unit, with capabilities somewhere between the usual ward bed and an ICU bed. Patients can get telemetry, continuous oximetry, vital signs every 2 hours, and more. It functions as a kind of step-down unit, so we frequently admit patients who may require ICU admission at other hospitals.

Every once in a while, a patient who is receiving care in the trauma unit shows signs that they are going to need a true ICU level of care. In that case, we promptly move them to the ICU before they decompensate any further.

Is that situation an “unplanned ICU admission?” In my opinion, no. The patient received the highest level of care while outside the ICU, and ultimately a considered decision was made to move them. In my mind, this is a “planned ICU admission.”

Bottom line: There are two issues at play if your “unplanned ICU admissions” get flagged on your TQIP report. The first is determining if it was truly unplanned. If the Rapid Response Team (RRT) was called, then it was almost certainly unplanned. But if the patient was being monitored properly, showed signs that they would need an ICU level of care, and was preemptively transferred there, it was not. Similarly, if one of your surgical specialists wants the patient transferred (e.g. MAP goals), then that is also a planned admission.

The second factor is figuring out why the admissions are getting reported to TQIP as unplanned. This is usually a trauma registrar issue. They may be looking for any ward to ICU transfer, and classifying it as unplanned. Educate all your registrars on the nuances of what is planned and what isn’t.

If you are on the receiving end of a TQIP variance on unplanned ICU admissions, use the drill-down tool to identify the exact patient records involved. Review the involved medical records, paying close attention to vital signs, monitoring, and all decision making leading up to the time of the ICU transfer. If it isn’t truly unplanned, educate your registrars. But if it is, make sure that it was properly dealt with by your trauma performance improvement program.