Category Archives: Abstracts

Best Of AAST #2: REBOA And Unstable Pelvic Fractures

REBOA is the new kid on the block. Human papers first started appearing in the trauma resuscitation literature about six years ago. Since then, we’ve been refining the details: how to use it, who to use it in, as well as a lot of the technical tidbits.

The group at Denver Health Medical Center compared their experience with pelvic packing vs REBOA for patients with unstable pelvic fractures. They reviewed four years of experience to see if they could further clarify some of the benefits of this technique.

Here are the factoids:

  • A total of 652 patients presented with pelvic fractures, and 78 underwent pelvic packing for control of hemorrhage
  • Of these 78 patients, 31 also had a REBOA catheter placed and 47 did not
  • The ISS in the REBOA+ group was significantly higher at 49 vs 40
  • Although systolic blood pressure and heart rate were statistically more abnormal in the REBOA+ group, these values were not clinically different (SBP 65 vs 72, HR 129 vs 117)
  • The amount of transfused red cells and plasma was twice as high in the REBOA+ patients (RBC 16 vs 7, FFP 9 vs 4)
  • There was no difference in survival rate (REBOA 84% vs packing 87%)

The authors concluded that this study suggests REBOA plus pelvic packing provides life-saving hemorrhage control in otherwise devastating injuries.

Here are my comments:  So the authors inserted REBOA catheters in addition to pelvic packing in half of their patients that were more severely injured, gave them twice as much blood product, and had the same number of survivors. But the primary outcome was the same. It’s very difficult to tease out which factors are responsible when there are such significant differences between the groups with respect to factors that have a definite impact on survival.

Did the use of REBOA equalize survival in the more severely injured patients, or was it the additional blood products, both, or neither? It’s really not possible to say. REBOA may be a valuable adjunct to trauma resuscitation, but we still need more information so we can be sure we are using it in the right patients.

And some questions for the authors:

  • How did you select patients for REBOA? This could make a big difference and inject significant selection bias. Could your surgeons have been primed to use this in patients who looked sicker?
  • Have you considered matching subsets of your patient groups with similar ISS and transfusion volumes, and then comparing mortality? This could be revealing, but I suspect the numbers will be too small to have the statistical power to show any differences.

This will be a very interesting paper to listen to! I look forward to more details.

Reference: Inflate and pack! Pelvic packing combined with REBOA deployment prevents hemorrhage related deaths in unstable pelvic fractures. AAST 2020 Oral Abstract #4.

Print Friendly, PDF & Email

Best of AAST #1: What Has The MTP Bought Us?

Let’s kick off my reviews of AAST 2020 abstracts with a paper on the results of recent advances in hemorrhage control. Over the past 10+ years we have seen the following new (and old) tools move into more widespread use:

  • Massive transfusion protocol (MTP) with a goal of 1:1 ratios of red cells to plasma
  • Availability of liquid plasma for more rapid use in the MTP
  • Addition of tranexamic acid (TXA) to resuscitation
  • Resurgence of tourniquet use by prehospital providers
  • Adoption of REBOA and TEG
  • Transfusion with whole blood

The authors analyzed their experience after serially introducing these tools to their resuscitation strategies, and studied their impact on overall mortality.

They retrospectively reviewed the experience over a 12 year period at their large Level I trauma center. Here are the factoids:

  • The reviewed a total of 824 MTP events. To put this into perspective from a volume standpoint, this is a little over one MTP activation per week.
  • Patients were primarily young (median age 31), male (81%), with a penetrating mechanism (68%). Median ISS was 25
  • Prehospital times were significantly longer at the end of the study, but the authors state that there was no correlation with an increase in in-hospital mortality
  • During the entire study, overall mortality ranged from 38% to 57%, and logistic regression did not identify an effect from any of the interventions

The authors concluded that their mortality rates have not improved despite all of the advancements we have added over the past decade. They suggest that future efforts should attempt to move targeted hemorrhage control backwards in time, out of the ED and toward to injury scene.

Here are my comments: This is an interesting and simple-appearing study. Overall, the authors didn’t really show that any of our “modern” resuscitation interventions did much for their patients at all.  There was a suggestion that tourniquet implementation and use of whole blood tended toward improving things.

But don’t be fooled by simplicity. There are many, many factors that enter into whether an individual patient lives or dies. When you fail to see a significant result in a study, first look at the methods and tools used for measurement. Are they powerful enough to discern changes? Do they cover enough of the factors that promote survival, not just our resuscitative advances? Or is the tool looking at the wrong things?

One big difference at this center is the sheer volume of penetrating trauma. This could have a major impact on survival, and may be very different from the experience of most centers that have predominantly blunt injury mechanisms.

And some questions for the authors:

  • What exactly is your definition of mortality? Made it out of the ED? Lived twenty four hours? Thirty days? This makes a big difference in how you look at the results.
  • Since you have only about one MTP event per week, do you think your numbers are large enough to actually detect a mortality difference? 
  • Did you consider looking at your unexpected survivors to see if there were any common threads in their care that might have made the difference? Maybe some of our resuscitative advances do make a difference, but only in specific subsets of patients.
  • Can you speculate about the reasons for longer prehospital times, and the impact on mortality?
  • How would you recommend pushing hemorrhage control back toward the scene? New tools for prehospital providers? More advanced providers in the rigs? This is an intriguing concept and it would be interesting to hear your thoughts.

This is a thought provoking paper that questions our assumptions about our time-honored resuscitation tools. I look forward to hearing it live next month!

Reference: After 800 MTP events, mortality due to hemorrhagic shock remains higha nd unchanged despite several hemorrhage control advancements; is it time to move the pendulum? AAST 2020 Oral Abstract #1.

Print Friendly, PDF & Email

The Best Of The AAST 2020

The 79th Annual Meeting of the American Association for the Surgery of Trauma starts in just three weeks! As usual, I will select a number interesting abstracts from the bunch to review. I’ll go over the findings of the research, critique it, and then provide a series of questions for the presenter to consider. These questions are ones that members of the audience may very well ask (hint, hint).

And FYI, I always send a heads-up to the presenters with a link to the post so they can study up beforehand!

I’ll begin posting my commentary on the best abstracts on a daily basis, starting tomorrow. And if you see things in them that you think I have missed the mark on, please feel free to comment!

Print Friendly, PDF & Email

Best Of EAST #10: MTP With Whole Blood

Here’s one last abstract to consider before the EAST meeting kicks off this afternoon. Every trauma center must have a massive transfusion protocol (MTP). But not every one has access to whole blood. And whole blood is all the rage now for transfusion in the trauma world.

Believe it or not, we must still ask the question “is using whole blood safe?” More than 50 years ago, all we had was whole blood. But we didn’t use it in trauma the way we do today. And we didn’t have the tools then to determine whether there were any adverse effects from its use. Now we do, and we are slowly rediscovering the nuances of using it. Some work has shown that small volumes of whole blood appear to be safe. But there is little information on the safety of using large volumes in MTP.

The group at Oregon Health Sciences University in Portland attempted to do this with a quick shot paper to be presented tomorrow morning. They reviewed their experience over a two year period. For the first 18 months, they used standard component therapy (PRBC + plasma + platelets) in their MTP. For the final six months, they used cold-stored uncrossmatched, low-titer group O blood. Any patient who had MTP activated and received even a single unit of blood was included in the study. 

Here are the factoids:

  • 83 patients received component therapy and 42 received whole blood; demographics were the same
  • The component therapy patients received an average of 6 PRBC, 5 plasma, and 0 platelets; the whole blood group received 6.5 units (4 PRBC, 4 plasma, and 1 platelets based on the usual composition of a unit)
  • Plasma:RBC ratio was 0.8:1 for the component group and 0.94:1 in the whole blood group (statistically significant, but not clinically significant, see below)
  • The authors described a component-equivalent unit of product which is not defined. It was 12 for component therapy and 27 for whole blood.
  • There were no differences in 24-hour or 30-day mortality, and no transfusion reactions

The authors concluded that MTP using whole blood is feasible, and that it appeared to be safe and effective. They also commented that it may lead to more balanced resuscitation.

My comment: Alright, this is the last time I’ll mention study power (for a while). If a study does not have the statistical power to show a difference between groups, then seeing no difference means nothing. The absence of a difference does not mean that the two groups are equivalent. And this study of 125 patients is small potatoes for showing any difference in a crude outcome like mortality.

Besides having a small number of subjects, the average number of units given was low for an MTP. For most trauma centers, this was just over one cooler of products. Although ISS was 29, the patients don’t sound like they had huge blood replacement requirements, so it’s no wonder that mortality was the same between the two groups.

And finally, the statement about more balanced resuscitation is open to debate. The difference between 0.8 units of plasma and 0.94 units is 35cc per unit of red cells given, a little over 1 tablespoon. It’s hard to believe that this would ever make a difference clinically.

To those who read only the title or the conclusion of an abstract (or paper for that matter), beware. The devil is in the details. This study is a good start toward addressing the question posed, but needs several hundred more subjects (and a lot more blood products given) to close in on an answer.

Reference: Massive transfusion with whole blood is safe compared to component therapy. EAST Annual Assembly Quick Shot #8, 2020.

Print Friendly, PDF & Email

Best Of EAST #9: Is TXA Associated With VTE?

Most trauma programs can be divided into two types: those that believe in tranexamic acid (TXA) and those that don’t. I won’t get into the details of the CRASH-2 study here. But those centers that don’t believe usually give one of two reasons: they don’t think it works or they think the risk of venous thromboembolism (VTE) is too high.

EAST put together a multi-institutional trial to see if there was an association between TXA administration and subsequent VTE. The results are being reported as one of the paper presentations at the meeting this week. A retrospective study of the experience of 15 trauma centers was organized. A power analysis was preformed in advance, which showed that at least 830 patients were needed to detect a positive result.

Adult patients who received more than 5 units of blood during the first 24 hours were included. There were a lot of exclusionary criteria. They included death within 24 hours, pregnancy, pre-injury use of anticoagulants, interhospital transfer, TXA administration after 3 hours, and asymptomatic patients that had duplex VTE surveillance (huh?). The primary outcome studied was incidence of VTE, and secondary outcomes were MI, stroke, length of stay, and death.

Here are the factoids:

  • There were 1,333 eligible patients identified, and 887 (67%) received TXA
  • Females were significantly (over 2x) more likely to receive TXA (46% vs 19%)
  • 80% of patients given TXA received VTE prophylaxis, whereas only 60% of those who did not receive TXA got prophylaxis (also significant)
  • TXA patients had a statistically significantly higher ISS (27) compared to non-TXA patients (25) but this is not clinically significant
  • Mortality in the TXA group was significantly lower (17% vs 34%)
  • The number of units of blood, plasma, and platelets transfused were significantly lower in the TXA group
  • VTE rate appeared lower in the TXA group, but once multivariate analysis was applied, there was no difference

The group concluded that there was no association between TXA and VTE, but that it was linked to decreased mortality and transfusion need.

My comment: This was a study done the way they are supposed to be! Know your objectives and study outcomes up front. Figure out how many patients are needed to tease out any differences. And use understandable statistics to do so.

But, of course, it’s not perfect. No retrospective study is. Nor is any multi-institutional trial. There are lots of little variations and biases that can creep in. But the larger than required sample size helps with reducing the noise from these issues.

Basically, we have a decent study that shows that the clinical end points that we usually strive for are significantly improved in patients who have TXA administered. We don’t know why, we just know that it’s a pretty good association.

This study shows that the usual reasons given for not using TXA don’t appear to hold true. So hopefully it will convert a few of the TXA non-believers out there. I’m excited to hear more details during the presentation at the meeting.

Reference: Association of TXA with venous thromboembolism in bleeding trauma patients: an EAST multicenter study. EAST Annual Assembly, Paper #13, 2020.

Print Friendly, PDF & Email