Category Archives: Technology

Best Of AAST 2022 #10: REBOA For Pelvic Fractures

September 19, 2022 The Trauma Pro Leave a comment

Papers for Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) use in trauma patients have been accumulating for the past decade or so. There are three zones within the aorta, and the REBOA balloon can be inflated in either Zone II for abdominal vascular injuries or Zone III for pelvic bleeding. Here’s a nice diagram for reference:

The original studies focused on Zone II deployments, but over the past five years or so there has been growing focus on using REBOA in Zone III. Pelvic arterial bleeding can be quite problematic, and if the patient is hypotensive in the emergency department, it is not permitted to take them to interventional radiology for management. The only choice is a trip to OR for preperitoneal packing or some less effective procedure. With the use of Zone III REBOA, it became possible to stabilize vital signs and then allow transport to IR or hybrid OR for angioembolization.

After the initial rush of very positive research, more recent papers are a bit more tempered with results that are not as cut and dried. This abstract from Hartford Hospital attempts to add a bit more information about the use of Zone III REBOA in patients who required a hemorrhage control procedure. The authors performed a retrospective review of four years of TQIP data. They compared outcome data in hypotensive adult patients with pelvic fractures requiring some type hemorrhage control procedure. The authors divided patients into REBOA+ and REBOA- groups, and looked at mortality, blood utilization, lengths of stay, and REBOA complications.

Here are the factoids:

Of the 4,453 patients who met inclusion criteria, only 139 patients underwent Zone III REBOA
The REBOA+ patients had lower BP and GCS and ISS was higher prompting the use of propensity matching
In order to equalize comparisons patients were propensity matched the the variables listed above, yielding 121 pairs for study
In-hospital and 24-hour mortality were double in the REBOA+ group (50.5% vs 25% and 31% vs 14.3%, respectively)
Blood transfusion was also higher in the REBOA+ group (median 4L vs 1.75L)
AKI was higher in the REBOA+ group (16% vs 7%) but the amputation rates were the same (no numbers given)

The authors concluded that Zone III REBOA appears to have worse outcomes and suggest that more prospective studies are indicated.

Bottom line: I have been a REBOA skeptic for some time so I have to be careful not to feed my confirmation bias. Many of the previously published positive papers include authors who have a relationship with one of the major REBOA device manufacturers. Papers from centers without any conflicts of interest are generally less positive.

Despite my own bias I also have some major questions about this abstract. The biggest thing is that I can’t make the statistics work. Granted, the entire analysis is not in the abstract. But the mortality rates given in percentages don’t yield integers when multiplied by the 121 patients in each group.

This makes me worry that we are not seeing all the statistics and we are somehow getting relative risk rather than absolute risk. I’m also confused about why the SBP, ISS, and GCS matched groups would have a difference in AKI rates in addition to the mortality numbers. Are there other significant variables affecting morbidity and mortality that were not identified or controlled?

Here are my comments and questions for the authors / presenter:

Review the mortality calculations for us. How can you have a hospital mortality rate of 50.5% with 121 patients (= 61.105 people)? Provide the absolute mortality numbers so we can do the math.
Why are the transfusion numbers so much higher in the REBOA+ group? Isn’t this device supposed to reduce bleeding? It seems unlikely that REBOA is making them bleed more. Is there something else going on?
Similarly, why would AKI be higher in REBOA+ patients? The balloon is located below the kidneys and they should benefit from better perfusion.
Could there be other factors not analyzed that contributed to the poorer outcomes in the REBOA+ group? What might they be?

I suspect the snapshot that the TQIP data allows may not be enough to let us see the entire picture here. I am looking forward to additional information during the presentation to help clarify these issues.

Reference: DOES THE USE OF REBOA IMPROVE SURVIVAL IN PATIENTS WITH PELVIC FRACTURES REQUIRING HEMORRHAGE CONTROL INTERVENTION? AAST Plenary paper #46, AAST 2022.

Technology

First, There Was REBOA, And Now… GROA?!

June 21, 2022 The Trauma Pro Leave a comment

REBOA (Resuscitative Endovascular Balloon Occlusion of the Aorta) is a “newer” resuscitative technique that has actually been around since the Korean War. It was first used to treat two injured soldiers, and although they ultimately died, it spurred research into the technique and its applications.

Balloon occlusion techniques were then adopted by vascular surgeons and were found to be useful as an adjunct in managing ruptured abdominal aneurysms. A slow trickle of studies on human use in trauma began to surface. But when autopsy studies carried out during the Gulf War showed that uncontrolled torso hemorrhage was a major cause of death, research in the technique exploded.

First, there were a rash of pig studies evaluating the feasibility of using a percutaneously placed occlusion device in the early 2010s. This transitioned to human studies around 2014, and after that we were off to the races. Over 100 papers on REBOA are now published each year.

REBOA has been shown to have some advantage in patients with abdominal or pelvic sources of bleeding. The catheter is inserted in the groin and the balloon inflated in one of two zones, depending on the location of the hemorrhage (see diagram below). For abdominal bleeding, it is inserted just above the diaphragm in Zone I. For pelvic bleeding, it is inserted below the takeoff of the visceral arteries and above the aortic bifurcation, in Zone III.

In the US, REBOA catheters are only inserted upon arrival to the hospital. There are a few random reports of field placement where a physician is part of the prehospital team. By definition, this technique is generally not available in austere environments, only upon arrival in the emergency department.

Researchers at the University of Michigan began looking for an alternative technique that could be applied in the field by non-physicians. They noted the close anatomic relationship of the distal esophagus, proximal stomach, aorta, and thoracic vertebrae, and designed a device to compress the aorta against the spine in this area.

They developed a prototype device which they named GROA (gastro-esophageal resuscitative occlusion of the aorta). It consists of a gastro-esophageal tube with an ovoid balloon, an air pump with pressure measurement device, and an external compression device. Here is a picture of the device:

And here’s a diagram of what it looks like when inserted:

The tube is inserted and the balloon inflated. The external compression device is then placed around the patient, with the top plate located over the epigastrium and the bottom plate under the patient. It is designed to apply anterior pressure over the balloon, but to avoid circumferential constriction of the abdomen.

Bottom line: This device is an interesting development in the balloon occlusion space. As with early studies of REBOA, GROA is currently being investigated using a pig model. If it appears to be beneficial, it will still be several years before it makes the jump to human subjects. If effective, this concept would allow prehospital providers to apply some degree of hemorrhage control when it originates in the abdominal cavity.

There are currently exactly three papers on this new technique, and I have included the references below if you are interested in reading them. I’m sure there are many more to come and it may eventually be competing with REBOA for journal space.

There is one consideration to be aware of when reading these papers that is similar to much of the research on REBOA. Two of the authors have a financial interest in the company that licenses the GROA technology. And in the most recent study, another one of the authors is an advisory board member for one of the manufacturers of REBOA catheters. For these reasons, it is less likely that they will publish papers that are not favorable to the product. So read critically!

References:

Gastroesophageal resuscitative occlusion of the aorta: Physiologic tolerance in a swine model of hemorrhagic shock, Journal of Trauma and Acute Care Surgery: December 2020 – Volume 89 – Issue 6 – p 1114-1123 doi: 10.1097/TA.0000000000002867
Gastroesophageal resuscitative occlusion of the aorta prolongs survival in a lethal liver laceration model, Journal of Trauma and Acute Care Surgery: May 2022 – Volume 92 – Issue 5 – p 880-889 doi: 10.1097/TA.0000000000003444
Tandem use of Gastroesophageal Resuscitative Occlusion of the Aorta followed by REBOA in a Lethal Liver Laceration Model, Journal of Trauma and Acute Care Surgery: June 10, 2022 – doi: 10.1097/TA.0000000000003719

Abstracts, Technology

Best Of AAST #10: The Hybrid ER Room?

September 2, 2020 The Trauma Pro Leave a comment

The next abstract is an interesting demonstration of the use of technology is trauma resuscitation. Pretty much all technology imaginable. It details the use of a “hybrid ER” room, which combines resuscitation space with all sorts of imaging and even interventional angiographic procedures. Here’s an image of the room when it was first written about in 2012.

A = CT scanner B = CT exam table C = movable C-arm D = monitor screen E = ultrasound F = ventilator

This setup was installed at Osaka General Medical Center in Japan nearly 10 years ago. The authors have written occasional papers about it, and have now performed a study on its impact on trauma patient survival. They studied major trauma patients during two time periods. The first was pre-installation (2007-2011), and the second started immediately after installation (2011-2020). They specifically looked at 28-day mortality, and tried to tease out the relation to injury severity.

Here are the factoids:

About a thousand patients were studied, 348 in the pre (conventional) group and 702 in the post (hybrid) group
28-day mortality was significantly lower in the hybrid group
Using a fancy statistical test (cubic spline analysis), they showed that 28-day mortality sharply decreased 200 days after installation of the hybrid ER
Mortality decreased disproportionately more in the hybrid ER as the injury severity score (ISS) increased

The authors concluded that the hybrid ER may have improved survival, especially in the more severely injured patients.

Here are my comments: Hmm. This is an association study that only looks at one variable, the new hybrid ER room. How many other variables may have a potential impact on survival? And how have those variables changed over the past 11 years? I worry that the study premise is too simplistic, but it certainly makes this unique resource look good.

Here are some questions for the presenter and authors:

How did you select your patients? You describe about 1,000 patients over 11 years, which is only about 100 per year. What about all the others?
What is it about the hybrid room that you think confers such a survival benefit to your patients? It seems to work for all patients, blunt or penetrating, badly hurt or not. What’s the magic?
Do you see the same effect for patients who were treated at other hospitals first and then transferred? The extra time that passed could decrease survival in severely injured patients.
Please explain cubic spline analysis clearly. I always worry when super-fancy statistical tests are needed to detect a difference. Why was it needed in this case?
Why did it take 200 days to see an effect from the installation of the hybrid ER? What happened at that point in time?
Please explain how the actual survival is so much better than predicted for ISS=75 patients. Your graph shows an actual survival of about 22%, as opposed to the 3% in your conventional ER. That is a massive improvement! How do you do it?

As you can see, I’m a bit uncertain about how this works and how the lessons can be applied to other centers. This is a unique resource, and the rest of the world needs to know a lot more about it before deciding to try it out themselves.

Technology

The Newest Flavor Of 3D Printing

February 6, 2019 The Trauma Pro Leave a comment

I’m fascinated with 3D printing, and have written a number of posts on the topic. There are numerous applications in medicine, and particularly in trauma care. We are currently able to print substitutes for bone, cartilage (trachea), bladder, skin, and more. To date, all of these use the same 2D technology found in ink-jet printers. But instead of 2D splashes of ink, three dimensional bits of plastic or metal are stacked on top of each other one layer at a time and fused by a laser.

UC Berkeley and Lawrence Livermore National Laboratory have developed a new 3D printing technology that coalesces an entire object at once using 3D information projected by shining light fro a standard LED projector into a column containing a special resin. The device has been renamed the “replicator” since it functions like the device seen in various Star Trek series. Here’s a brief video:

Bottom line: This is new technology, so it’s still a bit glitchy. The surface definition is lower than conventional 3D printing, which will limit its usefulness in some medical applications. And currently, the size limit is only four inches. But it will allow printing over existing objects, which may give it some real advantages. I’m sure there’s more to come with this promising new technology.

Related posts:

Technology

Best of AAST #7: What’s New With Reboa

September 19, 2018 The Trauma Pro Leave a comment

Despite all you read about it these days, REBOA is still very new. The first papers describing use in humans are barely 5 years old! A few select centers have been early adopters and are publishing a regular flow of research on their experience.

But we need more numbers! Many trauma centers have considered, or actually adopted the use of REBOA already. However, we are still working out a lot of the nuts and bolts of this very invasive procedure. The group at University of Arizona – Tucson reviewed the national experience over a two year period by massaging the data in the Trauma Quality Improvement Program (TQIP) database. All Level I-III trauma centers in the US are required to report their experience to this large, detailed collection of trauma data.

They performed a retrospective review of REBOA vs non-REBOA patients matched for demographics, prehospital and emergency department vital signs, mechanism of injury, degree of pelvic disruption in pelvic fracture patients, solid organ injuries, and lower extremity fractures and vascular injuries. The studied outcomes were complications and mortality.

Here are the factoids:

Nearly 600,000 records were scanned for the two year period, and only 140 REBOA patients were identified (!)
These 140 REBOA patients were matched with 280 similar non-REBOA patients
Average age was 44 and average ISS was 29, 74% were males and 92% were blunt trauma
Overall complication rate was 7.4% and mortality was 25%
There was no difference in 4-hour or 24-hour numbers of blood, plasma, or platelets transfused
ICU and hospital length of stay were identical
24-hour mortality in the REBOA group was significantly higher (36% vs 19%)
REBOA patients were significantly more likely to require amputation (5% vs 1%)

Bottom line: These are not great numbers for REBOA! What gives? There are a number of possibilities:

It’s a database study, so some key information might be missing
The numbers remain small, only 140 patients out of half a million records in two years!
There is no way to know how the patients were selected for REBOA
The experience and skill level at the hospital performing the procedure is not known
The interplay of other injuries and comorbidities is unclear
And many more…

BUT, the numbers are concerning. The early adopter centers have better outcomes, and this has prompted many centers with fewer eligible patients to jump on the bandwagon. We all need to remember that this is a brand new procedure and we are still learning the nuances. It is extremely important that every center performing REBOA contribute their results to a national registry. We still need to figure out which patients will benefit from it, how it should be used, and how we can minimize complications and maximize survival in our patients.

Reference: Nationwide analysis of resuscitative endovascular balloon occlusion of the aorta (REBOA) in civilian trauma. Session I Paper 5, AAST 2018.

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