Tag Archives: abstract

Best Of EAST 2023 #12: VTE Prophylaxis In Severe TBI

Time for another abstract on venous thromboembolic disease (VTE) prophylaxis, but this time in patients with severe head injury. VTE is a significant problem for trauma patients. Those with a potential source of bleeding from their injuries cause us to hesitate and consider the timing of chemical prophylaxis closely. Do we really want to cause more bleeding?

This is particularly problematic with intracranial hemorrhage, as the treatment is major brain surgery. Over recent years, the literature has been leaning toward earlier prophylaxis as soon as the intracranial blood has stopped evolving.

The EAST Multicenter Trials Group performed a seven-year retrospective review at 24 Level I and II trauma centers to assess the safety and efficacy of VTE chemoprophylaxis.  They divided patients into three groups: no prophylaxis, early prophylaxis (within 24 hours), and late prophylaxis (after 24 hours).

The authors assessed two endpoints: VTE occurrence and expansion of intracranial hemorrhage (ICH). They used several regression models to check their hypotheses.

Here are the factoids:

  • A total of 2,659 patients met the inclusion criteria. This averages out to 15 eligible patients per month per center. This is probably reasonable when combining a few high-volume centers with more lower volume centers.
  • Compared to early prophylaxis, patients who received late prophylaxis were twice as likely to develop VTE, although this was not statistically significant (p = 0.059)
  • Compared to early prophylaxis, patients who received no prophylaxis were a third less likely to develop VTE, although this, too, was not statistically significant (p = 0.39
  • About 25% of patients who received either early or late prophylaxis suffered an extension of their ICH, but only 17% of the no-prophylaxis group did
  • The regression model showed that the no prophylaxis group was 36% less likely to develop ICH extension compared to either early or late prophylaxis groups.

The workgroup concluded that the development of VTE was not dependent on the timing of the start of prophylaxis. Furthermore, patients who did not receive any prophylaxis had significantly decreased odds of ICH extension. The group recommended larger randomized studies to extend this work.

Bottom line: Shocker! This multicenter study suggests that the no prophylaxis and early prophylaxis groups had fewer VTE events than the late group, although these results were not statistically significant. This means that there wasn’t an advantage to giving the shot.

And the other major conclusion was that both early and late prophylaxis was associated with a significantly higher incidence of ICH extension. 

Roll these together, and you will find that neither early nor late prophylaxis help prevent VTE, yet they are both associated with additional bleeding in and around the brain! 

Heresy! I am trying to figure out what to make of these results. Perhaps the retrospective nature of the study and the wildcards this introduces influenced the results. It could be a study power problem, except the numbers were approaching significance that was unfavorable for prophylaxis.

I will be very interested to hear how the authors explain these findings. And yes, a well-powered randomized study would be great, but I don’t think many institutional review boards will be keen on a no-treatment group given our current fear of VTE. So don’t count on any real answers soon.

Reference: EARLY VTE PROPHYLAXIS IN SEVERE TRAUMATIC BRAIN INJURY: A PROPENSITY SCORE WEIGHTED EAST MULTICENTER TRIAL. EAST 2023 Podium paper #38.

Best Of EAST 2023 #11: Prehospital Use Of TXA

More stuff on TXA! I published two posts back in December on TXA hesitancy. This Friday, the trauma group at Wake Forest is presenting an abstract on TXA use by prehospital trauma professionals.

It is very likely that EMS carries tranexamic acid (TXA) in your area. Each agency has its own policy on when to administer, but the primary indication is hemorrhagic shock. A few ALS services may infuse for serious head injury as well.

The Wake Forest group was concerned that TXA administration might be occurring outside of the primary indication, hemorrhagic shock. They reviewed their experience using a six-year retrospective analysis of their trauma registry. The patients’ physiologic state before and after arrival at the hospital was assessed, as were the interventions performed in both settings.

Here are the factoids:

  • Of 1,089 patients delivered by 20 EMS agencies, one-third (406) had TXA initiated by EMS
  • Only 58% of patients who received prehospital TXA required transfusion after arrival
  • TXA administration based on BP criteria were as follows:
  • Similar compliance was noted when examining only high-volume EMS services

The authors concluded that TXA use is common in the prehospital setting but is being used outside of literature-driven indications.

Bottom line: This is an interesting snapshot of TXA use surrounding a single Level I trauma center. As such, it can’t be automatically applied to all. However, my own observations suggest that this drug is being used more liberally nationwide.

Clearly, the prehospital providers are starting TXA on patients who do not fit the category of severe hemorrhagic shock. Only 30% of patients receiving it had SBP < 90. Is this a bad thing? Referring back to my conversation on TXA hesitancy, I think not. But do keep in mind that giving any drug when not indicated adds no benefit and can certainly increase risk. The good news is that TXA is very benign when it comes to side effects.

However, policies are designed for a reason: safety. And if the EMS agency policy says to give TXA only for SBP < x, then that’s when it should be given. The prehospital PI process (or the trauma center’s) should identify variances and work to correct them. If EMS is “overusing” TXA in your area, your trauma center should add this as a new prehospital PI filter and let them know when it happens.

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

  • Is using the need for transfusion a valid measure of the need for TXA? You found that half of the patients receiving TXA were not transfused. The decision to transfuse depends on surgeon preference, and they don’t always use objective criteria. And hey! Maybe the TXA worked, obviating the need for blood!

This is a straightforward and intriguing paper. I’m excited to hear more details on how you sliced and diced this data.

Reference: ARE DATA DRIVING OUR AMBULANCES? LIBERAL USE OF TRANEXAMIC ACID IN THE PREHOSPITAL SETTING. EAST 2023 Podium paper #34.

Best Of EAST 2023 #10: Early VTE Prophylaxis In Adolescents With Solid Organ Injury

Chemoprophylaxis against venous thromboembolism (VTE) is routine in trauma care. In most cases, it can be initiated shortly after admission in most trauma patients. However, there are a few major exceptions, including eye injuries and brain injuries with intracranial hemorrhage.

Solid organ injury used to be cause for concern when considering prophylaxis, but most trauma centers are now comfortable beginning within 24 to 48 hours after injury. Having said that, those numbers are for adult patients. What about the younger ones?

The University of California Irvine group queried the TQIP database (3 recent years) to examine outcomes for adolescent patients (12-17 years old) given VTE prophylaxis after injury to liver, spleen, and/or kidney. They excluded patients who had TBI, anticoagulation or coagulopathy, immediate laparotomy, transfers in, and patients who died or were discharged within 48 hours. They matched patients for age, comorbidities, grade of injury, overall severity of injury, and hypotension/need for transfusion.

Eligible patients who received chemoprophylaxis early  (within 48 hours) vs. late were reviewed to identify any differences in complications, length of stay, failed non-op management, and mortality.

Here are the factoids:

  • A total of 1,022 cases were isolated from the TQIP database, and 417 adolescent cases were matched to adults
  • VTE rate was statistically the same, 0.6% in the early group vs. 1.7% in the delayed group
  • Failed non-op management was identical at 5.9% vs. 5.6%
  • There was one death in the delayed group and none in the early group (not significant)
  • ICU LOS was the same at 3-4 days
  • One item not mentioned in the body of the abstract: hospital length of stay was significantly longer in the early group: 9 days vs. 6 days

The authors concluded that early VTE prophylaxis in adolescent trauma patients did not increase failure of nonoperative management, nor did it decrease the incidence of VTE.

Bottom line: This is a study that needed to be done. Due to IRB restrictions, it is typically more challenging to perform actual studies on children and adolescents. Retrospective use of databases helps overcome this problem, although it always introduces a few unwanted wrinkles.

We frequently assume that adolescents behave physiologically like adults. Although often true, you can’t always count on it. Those of us who take care of children and young adults know that they tend to do better than adults by most measures. But again, this is an assumption and needed to be studied.

This database study was limited to three years of data and only produced 417 matched cases for study. This is a small number, and I always worry about statistical power. If the results of such a study are negative, one is left wondering if a proper power analysis was done.

One puzzling result left me wondering about the power question. Patients who received early prophylaxis had exactly the same rate of VTE as those who received it late. Adult data indicates that early use should decrease this complication. Is this another indication of a statistical power problem? Would the inclusion of more patients have shown a real difference?

The other result that struck me (and was not commented upon in the body of the abstract) was the statistically significant 50% increase in hospital length of stay for the early prophylaxis group. Is there some unknown variable that was not matched that caused it? This is one of the known pitfalls of these retrospective database studies.

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

  • Broken record question: Did you have enough cases to provide adequate statistical power? This study showed a negative result. Did you have enough matched cases to actually be able to detect a difference if there was one? Why not add a few more years of data and recalculate?
  • How do you explain the failure of early VTE prophylaxis to protect these patients from DVT or PE? Is this also a statistical power problem?
  • Why is the hospital length of stay significantly longer in the early prophylaxis group?

This intriguing paper follows my bias toward treating these patients exactly the same as adults with early chemoprophylaxis. I just need a few of the loose ends tied up.

Reference: SIMILAR RATE OF VENOUS THROMBOEMBOLISM AND FAILURE OF NON-OPERATIVE MANAGEMENT FOR EARLY VERSUS DELAYED VTE CHEMOPROPHYLAXIS IN ADOLESCENT BLUNT SOLID ORGAN INJURIES: A PROPENSITY-MATCHED ANALYSIS. EAST 2023 Podium paper #27.

Best Of EAST 2023 #9: CT Of The Lumbar Spine

It is becoming clearer and clearer that patients with suspicion for fractures of the thoracic (T) and lumbar (L) spine should be imaged only with CT scan. Conventional imaging just doesn’t have enough sensitivity, even in younger patients with healthy bones. But when we obtain CT of the T&L spines there is a choice: just look at the axial / helical slices, or have the computer reconstruct additional images in the sagittal and coronal planes. The belief is that this multiplanar imaging will assist in finding subtle fractures that might not be seen on axial views.

The group at Rutgers in New Jersey tried to determine if adding the reconstructions amounted to overkill. They performed a retrospective review of patients at their Level I center over a six-year period. They focused on studies performed in patients who had T and/or L fractures who also had both CT of the chest, abdomen, and pelvis (CAP) and thoracic and lumbar reconstructions. Additional data were obtained from a review of the medical record and trauma registry.

Here are the factoids:

  • A total of 494 patients had both CAP and reconstructions
  • There were 1254 fractures seen on CAP, and an additional 129 fractures seen with recons (total of 1394)
  • The majority of additional injuries not detected on CT CAP were transverse process fractures
  • The number of other fracture patterns not seen on CT CAP were statistically “not significant”
  • However, these numerically “not significant” fractures included 51 vertebral body fractures, 6 burst fractures, 3 facet fractures, and 2 pedicle fractures
  • No unstable fractures were missed on CT CAP
  • More MRIs were performed in the patients who had recons, there were more spine consultations, and 11% underwent operative fixation vs. 2% for CTA only (!!)

The authors concluded that CT CAP alone was sufficient to identify clinically significant thoracic and lumbar fractures. They also stated that clinically insignificant injuries identified with reconstructions were more likely to undergo MRI and use excess resources. They urged us to be selective with the use of T&L reformats.

Bottom line: Wow! I have a lot of questions about this abstract! And I really disagree with the findings.

You studied fewer than 500 patients with T or L spine fractures over a six year period. This is only about 80 per year, which seems very low. This suggests that many, many patients were being scanned without recons to start with. How did patients get selected out to get recons? Were there specific criteria? I worry that this could add some bias to your study.

The number of fractures seen only on the recon views besides transverse process fractures were deemed “statistically insignificant.” However, looking at the list of them (see bullet point 5 above) they don’t look clinically insignificant. It’s no wonder that recons resulted in more consults, MRI scans, and spine operations!

I worry that your conclusion is telling us to stop looking for fractures so we won’t use so many additional resources. But their use may be in the best interest of the patients!

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

  • Why did you decide to do this study? I didn’t realize that not doing the recons was a thing in major blunt trauma. Was there some concern that resources were being wasted? Was there an additional cost for the reconstructions?
  • How many patients only received CT CAP? The greater the number of these, the higher the probability that some non-random selection process is going on that might bias your findings.
  • How did you get separate reports for the non-reconstructed images? Did you have new reads by separate radiologists? Typically, the report contains the impression for the entire study. It would be unusual for the radiologist to comment on the non-recon images, then add additional findings from just the reconstructions.
  • Doesn’t the increased numbers of spine consults, MRIs, and operative procedures in the patients with reconstructions imply that these otherwise occult fractures needed clinically important additional attention? 

I worry that readers of this abstract might take away the wrong message. Unless there is some additional compelling data presented, this study is certainly not enough to make me change my practice!

Reference: UTILITY OF CT THORACOLUMBAR SPINAL RECONSTRUCTION IMAGING IN BLUNT TRAUMA. EAST 2023 Podium paper #20.

Best Of EAST 2023 #8: Use Of AI To Detect Rib Fractures On CT

Artificial intelligence systems (AI) are increasingly finding their way into medical practice. They have been used to assist pathologists in screening microscope specimens for years. Although still amazingly complicated, one of the most obvious applications for trauma is in reading x-rays. Counting rib fractures may be helpful for care planning, and characterizing fracture patterns may assist our orthopedic colleagues in evaluating and planning rib plating procedures.

The trauma group at Stanford developed a computer vision system to assist in identifying fractures and their percent displacement.  They used a variation on a neural network deep learning system and trained it on a publicly available CT scan dataset.  They used an index of radiographic similarity (DICE score) to test how well their model matched up against the reading of an actual radiologist.

Here are the factoids:

  • The AI network was trained on a dataset of 5,000 images in 660 chest CT scans that had been annotated by radiologists
  • The model achieved a DICE score of 0.88 after training
  • With a little jiggering of the model (reweighting), the receiver operating characteristic curve improved to 0.99, which is nearly perfect

The left side shows a CT scan rotated 90 degrees; the right side shows the processed data after a fracture was detected.

Bottom line: This paper describes what lies ahead for healthcare in general. The increasing sophistication and accuracy of AI applications will assist trauma professionals in doing their jobs better. But rest easy, they will not take our jobs anytime soon. What we do (for the most part) takes very complex processing and decision making. It will be quite some time before these systems can do anything more that augment what we do.

Expect to see these AI products integrated with PACS viewing systems at some point in the not so distant future. The radiologist will interpret images in conjunction with the AI, which will highlight suspicious areas on the images as an assist. The radiologist can then make sure they have reported on all regions that both they and the AI have flagged.

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

  • How can you be sure that your model isn’t only good for analyzing your training and test datasets? If neural networks are overtrained, they get very good at the original datasets but are not so good analyzing novel datasets. Have you tried the on your own data yet?
  • Explain what “class reweighting” is and how it improved your model. I presume you used this technique to compensate for the potential issue mentioned above. But be sure to explain this in simple terms to the audience.
  • Don’t lose the audience with the net details. You will need to give a basic description of how deep learning nets are developed and how they work, but not get too fancy.

This is an interesting glimpse into what is coming to a theater near you, so to speak. Expect to see applications appearing in the next few years.

Reference: AUTOMATED RIB FRACTURE DETECTION AND CHARACTERIZATION ON COMPUTED TOMOGRAPHY SCANS USING COMPUTER VISION. EAST 2023 Podium paper #16.