All posts by The Trauma Pro

Abstracts, Pharmacy

Best of AAST #1: Aspirin Vs Low Molecular Weight Heparin For VTE Prophylaxis

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The 82nd Annual Meeting of the American Association for the Surgery of Trauma begins next week. As is my custom, I will be reviewing some of the more interesting (to me) oral presentation abstracts until the last day of the meeting.

When reading abstracts, keep in mind that you are seeing just a snippet of a finished manuscript. The authors are given very little print space to fully describe their research idea, their methods, and their results’ significance. Sometimes, what is seen in the abstract varies significantly from what is actually heard at the meeting. But mercifully, this does not happen often. The abstract is usually an intriguing look at some new and exciting work.

Having said all that, an abstract should not be a reason to change your practice! It is usually early work and needs to be fully vetted at peer review. Even then, it needs to be taken in context with past, similar research before trickling down to patient care.

The first abstract is fascinating. Our orthopedic surgery colleagues have been trying to use aspirin for venous thromboembolism (VTE) prophylaxis for decades. Frequently, they are thwarted by the trauma surgeons, who are thoroughly indoctrinated in the low molecular weight heparin (LMWH) camp.

This work comes from the Shock Trauma Center in Baltimore and is a follow on to a paper published in the New England Journal of Medicine earlier this year. The paper demonstrates that aspirin is not inferior to LMWH when used for VTE prophylaxis of patients. There was no difference in death from all causes, VTE occurrence, wound complications, or bleeding events.

The abstract is a follow-on to that manuscript. The authors performed a secondary analysis of the initial data to see if aspirin provided the same apparent level of protection in patients with high risk for VTE as measured by the Caprini score.

Here are the factoids:

  • A total of 12,211 patients were enrolled in this multi-center, and the same outcomes listed above were monitored for 90 days
  • Of the total group, 3052 were judged to be high risk: 46% had a femur fracture, 42% had a pelvic/acetabular fracture, 48% had a thoracic injury, 39% had a spinal injury, and 35% had a head injury
  • There was no difference in death, deep venous thrombosis, pulmonary embolism, or bleeding in the two groups
  • Patient-reported satisfaction was significantly better by 68% in the aspirin group

The authors concluded that outcomes for aspirin vs. LMWH are similar, even in patients at high risk for VTE.

Bottom line: This is an intriguing abstract, pointing me to the original paper published in NEJM. This multi-center study was performed in conjunction with the research coordinating center at Johns Hopkins, which designs some top-notch research. This study was no exception.

I am fascinated with this work because it shows that our orthopedic colleagues were right! They’ve been trying to get us to use aspirin for a long time. It’s very cheap compared to LMWH, by a ratio of about 50,000:1. 

If you’ve followed me for a long time, you would know I have been skeptical of the VTE prophylaxis establishment. Looking historically at its evolution over the last 40+ years, the incidence of DVT and fatal PE have changed very little despite the introduction of heparin, low molecular weight heparin, and anti Factor Xa monitoring. But it’s been established practice, so we’ve had to abide by the rules. Now, a cheaper alternative to all of this is being shown to be just as (in)effective. 

I suspect that if others bear out this work, we will be able to use a cheaper prophylaxis drug that does not require injection. But we still need to work on figuring out the basis for this problem to hopefully reduce it to near zero someday.

References: 

  • Risk-stratified thromboprophylaxis effects of aspirin versus low-molecular-weight heparin in orthopaedic trauma patients. AAST 2023 Plenary Paper 3.
  • Aspirin or Low-Molecular-Weight Heparin for Thromboprophylaxis after a Fracture. N Engl J Med 2023; 388:203-213.
Critical care

The Decision To Stop In Geriatric Trauma – Part 2

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In my previous post, I reviewed a recent paper analyzing which geriatric patients were more likely to have care withdrawn after serious injury. The authors noted that those with significant limitations to daily living activities, increasing age and/or frailty, and ventilator dependence were major factors.

Today’s paper was written by a multi-institutional group from several Ohio trauma centers. Like the previous paper, the authors used TQIP data for two of the same three years. Patients were at least 65, and deaths within the first 24 hours were excluded. The authors focused on patient groups with and without injuries that limited activities of daily living, so it dovetails with and further refines the conclusions of the previous paper.

Nearly 600,000 patients were identified, with about 550,000 without and 50,000 patients with injuries limiting activities of daily living. The study used propensity matching to examine 39,138 patients with and without these injuries.

Here are the factoids:

  • Patients with an activity-limiting injury were 3x more likely to have care withdrawn (7.5% vs 2.5%)
  • Several additional factors were discovered that were even more predictive of withdrawal of care:
    • Severe injury (ISS > 25) – 23x more likely
    • Unplanned admission to an ICU – 3.3x more likely
    • In-hospital cardiac arrest – 5x

The authors concluded that even if your patient does not have injuries that might limit their daily activities, it is still important to discuss goals of care with our elderly trauma patients.

Bottom line: These two papers, taken together, are saying the same thing. Injured geriatric patients have a higher mortality than similarly injured younger people. Certain factors are associated with ultimate withdrawal of care, including injuries that limit activities of daily living, increasing age and frailty, and unexpected serious events in the hospital, like cardiac arrest and admission to the ICU.

The point is that injuries limiting daily activities are a predictable factor for withdrawal of care. But this is only a small factor. Other unpredictable events, like cardiac arrest or an issue severe enough to require unexpected ICU admission, may be even more predictive. But unless we have a discussion with the patient and their family well in advance, the opportunity will be missed and may result in unwanted and futile care.

Reference: Are we waiting for the sky to fall? Predictors of withdrawal of
life-sustaining support in older trauma patients: A retrospective analysis. J Trauma 94(3):385-391, 2023.

Critical care

The Decision To Stop In Geriatric Trauma

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Traumatic injury is a continuum ranging from very minor to immediately fatal. The mortality rate along that continuum rises exponentially as the Injury Severity Score (ISS) increases. We long ago moved away from the philosophy of keeping someone alive at all costs to embracing the concept of quality of life. We have become more thoughtful about considering patient and family input in difficult cases.

This occurs more frequently when we treat geriatric patients. The mortality for a given ISS increases even more steeply than in younger patients and continues to accelerate for each decade of life. It is becoming routine to have goals of care discussions with patients and their families in most areas of medicine. Although commonplace in specialties like oncology, it is not as common in trauma care.

Withdrawal of life support is one of the endpoints of these goals of care discussions. However, making such a decision with the patient and/or family is challenging. Too soon, and there may be missed opportunities for recovery. Too late, and the patient and family may be further traumatized by futile or undesired care.

Is it possible to identify the common factors that predict appropriate withdrawal of care? The University of Arizona at Tucson group analyzed the Trauma Quality Improvement Program (TQIP) database on withdrawal of care from 2017-2019. The authors included only patients aged 65 and older. They sought to identify the predictors of care withdrawal. They also calculated their frailty index to gauge its impact on withdrawal decision-making.

Here are the factoids:

  • Over 150K patients were included in the analysis, with a mean age of 77 and predominantly blunt mechanism (97%)
  • About 19% were judged to be frail by applying an 11-variable frailty index
  • About 1 in 10 had withdrawal of support
  • Factors that increased the likelihood of support withdrawal were increasing age (1.4x more likely), frailty (1.4x), impaired activities of daily living (ADLs) (2.6x), and ventilator requirement (13x)
  • There was no difference between Level I and Level II trauma centers
  • Only 9% of patients had an advance directive
  • Interestingly, 19% of patients who had support withdrawn did not die

Bottom line: The authors only attempted to describe what factors were more likely to be present in patients who underwent withdrawal of care. A simple TQIP database analysis does not contain the data necessary to reliably develop suggested criteria. However, this study is very valuable because it offers a possible basic framework.

Age, frailty, ADLs, and vent dependence were the major variables noted. This alone may make the trauma professional more confident in approaching the family in cases where there is no advance directive. Which, unfortunately, is the majority of patients. 

But more importantly, we really need to define when the most appropriate time for the withdrawal discussion to occur. It requires a careful balance between potentially stopping too soon and persisting into futility.

In my next post, I’ll review another paper on this topic, using TQIP data, also published earlier this year. I’ll compare and contrast the results and see if we can get a clearer picture of how to proceed in the challenging cases.

Reference: The final decision among the injured elderly, to stop or to continue? Predictors of withdrawal of life-supporting treatment. J Trauma Acute Care Surg. 2023 Jun 1;94(6):778-783. 

Practice guidelines, Solid organ

New EAST Practice Guideline: Spleen Vaccines After Angioembolization

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I am trying to figure out how I missed it! The Eastern Association for the Surgery of Trauma (EAST) snuck a new practice management guideline into the Injury journal last fall. And it desperately tries to answer a question that has been hanging around for several years. Do we vaccinate spleen injury patients who undergo angioembolization or not?

I’ve been pondering this for some time and have reached my own conclusion based on some very old literature. Decades ago, we figured out that removing the spleen significantly affects immune function. Splenectomy patients are known to be more susceptible to encapsulated bacteria like Neisseria meningiditis, Streptococcus pneumoniae, and Haemophilus influenzae. Most trauma centers routinely vaccinate these patients before they are discharged home.

With the more recent emphasis on splenic salvage and nonoperative management of injury to this organ, angioembolization has become commonplace. This technique can be done in two ways: proximal and distal. Proximal embolization blocks the splenic artery, so there is no further blood flow to the spleen through it. Distal embolization (selective or super-selective) strives to block flow to very specific areas of the organ.

Do we need to give the vaccines if we cut off blood flow to pieces of the spleen or the main splenic artery? Based on my appreciation of very old splenectomy and partial splenectomy papers, it looked like we should in some cases. One report showed that splenic protection from encapsulated bacteria required about 50% of the spleen to be present and perfused by the splenic artery. This caveat stems from a time when we would perform a trauma splenectomy, dice the spleen up on the back table, and then implant a bunch of spleen cubes into the mesentery to try to provide some immune protection. Turns out that the pieces lived but didn’t do a damn thing.

My practice, then, has been to look at the fluoro images and estimate how much of the spleen was left. I would order the vaccines if a main splenic artery embolization (proximal) was performed. If a distal embolization were performed, I would eyeball the amount of devascularized spleen and give the vaccines if it looked like more than half was dark. Not very precise, I know.

But what would EAST say? They tried to perform a systematic review and meta-analysis of studies that compared outcomes in splenectomy vs. angioembolization patients. Unfortunately, there isn’t a lot of research material out there. So they settled on looking at papers that analyzed immune function, typically using B-cells, T-cells, and antibodies. The authors performed two comparisons: angioembolization vs. splenectomy and angioembolization vs. control.

Angioembolization vs. Splenectomy

These papers compared embolization patients who may or may not have spleen function to splenectomy patients who definitely have none. Embolization patients had fewer infectious complications during their hospital stay and better immune function using the indirect methods noted above. Unfortunately, the data quality was poor, with a significant risk of bias. There was no stratification of proximal vs. distal embolization. Nevertheless, this suggests that, at least overall, the embolization patients retained immune function.

Angioembolization vs. Controls

What about comparing embolization patients to spleen-injured patients who did not undergo any procedure? They should have normal function. Again, the quality of the very few papers available was low. But overall, there was no difference in immune function between the groups.

Bottom line: The EAST review team conditionally recommended against routine spleen vaccines after angioembolization for spleen injury. They concluded that immune function was maintained, so it should not be necessary.

What, you ask, about patients with proximal splenic embolization? The reality is that this only stops inflow from the splenic artery, and only for a few days or weeks. It may slowly resume over time. And it does nothing to the inflow from the short gastric arteries. Apparently, this is enough to provide immune protection against infection.

Whether this is actually true is open to debate. We have no idea if the numbers of T- and B-cells seen and the antibody titers are actually enough to avoid overwhelming post-splenectomy sepsis. And unfortunately, this condition is so rare that we will never accumulate enough cases to make a definitive statement.

But for now, it is probably okay to forgo the vaccines in patients undergoing angioembolization. Besides, the differing guidelines on which vaccines to use, when to give them, and when to schedule boosters were getting way out of hand! Please keep it simple!

Reference: Vaccination after spleen embolization: a practice management guideline from the Eastern Association for the Surgery of Trauma. Injury 53:3569-3574, 2022.

General

Crafting And Refining Your Massive Transfusion Protocol – Part 4

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It’s more on the massive transfusion protocol (MTP). I’ll continue today with MTP activation triggers.

What criteria should trigger your massive transfusion protocol? Sometimes, it’s obvious. The EMS report indicates that your incoming patient is in shock. Or there was notable blood loss at the scene. Or they have a mangled extremity and will need blood products in the OR, if not sooner.

But sometimes the need for ongoing and large quantities of blood sneaks up on you. The patient is doing well but has an unexplained pressure dip. And it happens again. You give one of your  uncrossmatched units of blood. It happens again. At some point, you come to the realization that you’ve given six units of blood and no plasma or other products! Ouch!

Many trauma centers have adopted MTP criteria like:

  • More than 4 units given over 4 hours
  • More that 10 units to be given over 24 hours
  • Loss of half a blood volume over 24 hours

I call these the “psychic power” criteria, because one must surely be prescient to know this information just shortly after the patient arrives. Don’t include criteria like these at your center!

Instead use some sort of objective criteria. A simple one is the use of any of your blood refrigerator products or emergency release blood, or a calculated score such as the ABC score or shock index (SI).

ABC score is the Assessment of Blood Consumption score and gives one point each for a heart rate > 120, SBP < 90, positive FAST, penetrating mechanism.  ACS score > 2 was predictive of requiring MTP with sensitivity and specificity of about 85%. Overtriage was about 15%.

Shock index (SI) is defined as the heart rate divided by the SBP. Normal values are in the range of 0.5 to 0.7. Need for MTP was found to increase to 2x for SI of 0.9, 4x with an SI of 1.1, and 7x with SI 1.3.

One paper compared these two systems retrospectively on 645 trauma activations over a 5-year period. They found that they both worked well with the following results:

  • Shock index > 1 – 68% sensitive 81% specific
  • ABC > 2 – 47% sensitive, 90% specific

The study suggests that shock index is more sensitive, and takes less technical skill to calculate. Bottom line: just pick the some objective criterion you are most comfortable with and use it!

Reference: Accuracy of shock index versus ABC score to predict need for massive transfusion in trauma patients. Injury 49(1): 15-19, 2018

Well folks, that’s it for the MTP series! Hope you enjoyed it. Feel free to email or leave a comment with any questions or suggestions!