Category Archives: General

Best Of AAST #6: Timing Of Venous Thromboembolism Prophylaxis

Venous thromboembolism (VTE) and pulmonary embolism (PE) have caused major problems for trauma professionals for at least 50 years. Interestingly, despite advances in chemical and mechanical prophylaxis, the mortality rates for both have remained about the same.

The group at St. Joseph Mercy Hospital in Ann Arbor looked at the timing of start of VTE chemoprophylaxis. They were curious as to whether the start time made a difference in mortality. They reviewed a collaborative database with 12 years of data, tallying information for all trauma patients who were admitted for at least 48 hours.

Here are the factoids:

  • Over 89,000 patients were analyzed; 1.8% developed VTE and 1.9% died (?)
  • Delay in starting chemoprophylaxis increased the risk of VTE (see figure)
  • Delaying chemoprophylaxis beyond 48 hours was associated with increased mortality and increased incidence of VTE

The authors concluded that early initiation of chemoprophylaxis reduces mortality and thrombotic complications.

Here are my comments: Unfortunately, I’m not entirely clear about the details of the abstract. This frequently happens because the authors have to strain to fit all of their ideas in a finite amount of space.

First, it’s a large database study, so it’s difficult to ensure that all the factors you want to study have been included in it. Somebody else designed it years ago, so you get what you get.

I’m a little confused about the incidence of complications and death. They are both about the same number (1.8%). Typically, VTE incidence is a few percent and death from PE is less than 1%. The death number seems high, unless it includes some other type of death.

The VTE incidence vs time graph is very interesting, although the goodness of fit looks a little off toward the right side. It looks like it could easily be a little lower.

Finally, segregating time periods into two 24-hour periods (0-24 hours, 24-48 hours)and one 72-hour plus one (48-120+ hours) seems like it might bias your data. The longer that last period, the greater chance that each patient will develop VTE or die.

Overall, the numbers in Table 1 are noted to be statistically significant, but clinically they appear to be very similar.

Here are some questions for the presenter:

  • Please explain the mortality numbers (1.9%). What did these patients die of? A pulmonary embolism? Something unrelated? This number seems high, since it is equal to your VTE incidence.
  • Tell us about the risk adjustment you used to calculate mortality rates. What patient factors were available to you? Are there others that might have been helpful to have in the database?
  • What tool did you use to fit the curve in Figure 1? The right side looks considerably higher than the data bars would suggest. Please be sure to explain all of the statistical techniques you used, as they were not fully covered in the abstract.
  • What was the impact of cramming 3 days of data into your last cohort? Wouldn’t this be expected to yield higher incidences of VTE and death?

I agree that VTE prophylaxis is best started early, but I need a wee bit more information. I’m intrigued by the paper, but I think you will have to spend some time explaining how you designed the analysis so we can all understand.

Reference: Association of timing of initiation of pharmacologic venous thromboembolism prophylaxis with outcomes in trauma patients. AAST 2020, Oral Abstract #14.

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Announcing My New Trauma PI Website!

For my audience members who have an interest in trauma performance improvement (PI), I have a special announcement. I’ve officially unveiled by new website dedicated exclusively to that topic.

You can find it at There, you will find a growing collection of instructional videos, courses, PI blog posts, and downloadable materials. I am migrating the entire library of my trauma newsletters to the site as well.

My intent is to provide performance improvement information that you want to know about. To that end, I encourage you to sign up on the site and let me know what topics really interest you.

And if performance improvement is just not your thing, keep reading this blog!

I just released an 8-minute video detailing “When The Trauma PI Clock Starts Ticking.” Click the link or picture below to head over to the site and view it.

And please follow the new site on Facebook and Twitter, and use those platforms to send me topics to include in future content.



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What? Still Using MRI For Cervical Spine Clearance?

Cervical spine clearance as evolved considerably over the years. First, there were five views of the spine using plain radiography. Then there were three. Then we moved to CT scan with clinical clearance. And currently, many institutions are relying only on CT.

But MRI has been used as an adjunct for quite some time. Initially, it was the tie breaker in patients who had equivocal CT findings, and for a while it was used for clearance in obtunded patients. And thanks to conflicting literature and disparate studies, the occasional usage became more frequent.

The group at Cedars-Sinai Medical Center in Los Angeles  noted that the percentage of patients undergoing MRI for cervical spine evaluation at their center slowly slowly crept up from 0.9% to 5.6% over a 10 year period. They designed a study to analyze the utility of this practice and inform their future practice.

Here are the factoids:

  • Over 9,000 patients had cervical spine CT during the 10-year study period; 513 (5.6%) were positive
  • Of the 513 CT-positive patients, 290 (56%) underwent an MRI. This showed:
    • Confirmation of the major injury in 250
    • Minor injury in 40
    • Clinically significant injury was seen in only 2 which was no surprise since they both had neurologic deficits
  • Of the 8,588 CT-negative patients, only 9 had clinically significant findings and 8 of them had neurologic deficits

Bottom line: So what have we learned here? First, MRI usage at Cedars-Sinai increased over time but was really not that useful. The main use was for imaging obtunded patients or those with an obvious neurologic deficit.

More than half of patients with positive CT scans also underwent MRI. If a major injury was seen on CT, MRI confirmed it. But if the CT findings were minor, none of the MRIs added any clinically significant findings in the absence of a neurologic deficit.

And what about MRI after negative CT? In the absence of a deficit, only one had a clinically significant finding (which only required a brace).

This study shows the wisdom of monitoring “how we do it.” There is sometimes some creepage away from what the literature shows is the best practice. The best way to remedy this is to do a good study, just like the authors did. They saw a slow change in practice, investigated it, and found that there was no good clinical reason for it. This gives the trauma program the ammunition to squelch the unwelcome behavior and return the clinicians to best practices.

Reference: Is MRI becoming the new CT for cervical spine clearance? Trends in MRI utilization at a Level I trauma center. J Tra publish ahead of print, DOI: 10.1097/TA.0000000000002752, 2020.

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Trauma Activation Patients Staying Too Long In Your ED?

One of the long-held beliefs in trauma care relates to the so-called “golden hour.” Patients who receive definitive care promptly do better, we are told. In most trauma centers, the bulk of this early care takes place in the emergency department. However, for a variety of reasons, throughput in the ED can be slow. Could extended periods of time spent in the ED after patient arrival have an impact on survival?

Wake Forest looked at their experience with nearly 4,000 trauma activation patients who were not taken to the OR immediately and who stayed in the ED for up to 5 hours. They looked at the impact of ED dwell time on in-hospital mortality, length of stay and ventilator days.

Overall mortality was 7%, and the average time in the ED was 3 hours and 15 minutes. The investigators set a reasonable but arbitrary threshold of 2 hours to try to get trauma activation patients out of the ED. When they looked at their numbers, they found that mortality increased (7.8% vs 4.3%) and that hospital and ICU lengths of stay were longer in the longer ED stay group. Hospital mortality increased with each hour spent in the ED, and 8.3% of patients staying between 4 and 5 hours dying. ED length of stay was an independent predictor for mortality even after correcting for ISS, RTS and age. The most common cause of death was late complications from infection.

Why is this happening? Patients staying longer in the ED between 2 and 5 hours were more badly injured but not more physiologically abnormal. This suggests that diagnostic studies or consultations were being performed. The authors speculated that the knowledge, experience and protocols used in the inpatient trauma unit were not in place in the ED, contributing to this effect.

Bottom line: This is an interesting retrospective study. It reflects the experience of only one hospital and the results could reflect specific issues found only at Wake Forest. However, shorter ED times are generally better for other reasons as well (throughput, patient satisfaction, etc). I would encourage all trauma centers to examine the flow and delivery of care for major trauma patients in the ED and to attempt to streamline those processes so the patients can move on to the inpatient trauma areas or ICU as efficiently as possible.

Reference: Emergency department length of stay is an independent predictor of hospital mortality in trauma activation patients. J Trauma 70(6):1317-1325, 2011.

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