Tag Archives: VTE

Abstracts, Pharmacy

Best Of AAST #5: Door-To-Prophylaxis Time

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Today’s abstract continues the theme of VTE prophylaxis. The authors introduce another timing parameter in this one: the “door-to-prophylaxis” time. Just as it sounds, this is the time interval between admission to the ED and initiating chemo-prophylaxis. Just like some centers struggle with how long to wait to start it after a solid organ injury (see previous post here), many find it challenging to get it ordered in the first place.

The authors retrospectively reviewed their registry data over four years. They compared adult patients who arrived as a highest-level of activation and received blood during their resuscitation. They were divided into two groups: those with DVT or pulmonary embolism (VTE group) and those without (no VTE group). The door-to-prophylaxis time was defined as the time from hospital arrival to the first dose of medication.

Here are the factoids:

  • Just over 2,000 patients met inclusion criteria, with 106 experiencing VTE and 1,941 without it
  • VTE patients had higher ISS (29 vs. 24), higher lactate levels (4.6 vs. 3.9), and more post-ED blood transfusions (8 vs. 2)
  • There was no difference in the need for dose adjustment or missed doses between the groups
  • Door-to-prophylaxis time was significantly longer in the VTE group (35 vs. 25 hours)
  • When controlling for age, sex, ISS, lactate, and post-ED transfusions, each hour of delay increased the likelihood of VTE by 1.5%

The authors concluded that the door-to-prophylaxis time was significantly associated with increased incidence of VTE. They suggest that the door-to-prophylaxis time should be utilized as a performance improvement metric for this condition.

Bottom line: Unfortunately, we need a lot more information here. There was not enough room for details about the statistical analysis in the abstract, but they will be essential to know. And the authors remind us that this study shows association, not causation. 

Severe injury and blood transfusion are already known to be associated with a higher likelihood of VTE. The fact that the longer door-to-prophylaxis group had more frequent VTE may very well be due to their higher ISS and greater number of transfusions. Those events themselves may have led to the hesitation in starting a heparin.

Early prophylaxis is certainly a desirable goal in any trauma patient. But we need more than a new metric. We need more concrete information on the specific reasons for the delay and to prove that it is safe to give the drug early in patients who have those potential delaying factors.

Reference: “Door-to-prophylaxis” time as a novel quality improvement metric in preventing venous thromboembolism following traumatic injury. AAST 2023, Plenary paper #38.

Abdomen, Abstracts, Pharmacy

Best Of AAST #4: Starting VTE Prophylaxis After Solid Organ Injury

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Venous thromboembolic disease (VTE) continues to be a major issue in trauma patients. Most trauma centers have prophylaxis guidelines to try to reduce this problem. These guidelines typically recognize specific injuries that increase the risk of bleeding if anticoagulants are given. Typical ones include hemorrhagic injuries to the brain, pelvic and spine fractures, and solid organ injuries.

Typically, VTE prophylaxis starts immediately upon admission. But when these high-risk injuries are present, it is usually delayed for a period of time. Unfortunately, that period may be highly variable. Many centers have adopted 2-3 days to delay administration of low molecular weight heparin in patients with solid organ injury.

The AAST initiated a prospective multi-institutional trial comparing early (<48 hours after admission) and late (>48 hours) administration of prophylactic agents. Patients were older than 16 years, had any number of liver, spleen, or kidney injuries, and were initially treated nonoperatively. Patients who were transferred, died in the ED, were pregnant, had a bleeding disorder, or were taking anticoagulants or platelet inhibitors were excluded. A power analysis was performed, and more than the needed number of patients were enrolled.

Here are the factoids:

  • A total of 1173 patients were enrolled, and there were 589 liver injuries, 569 spleen injuries, and 289 kidney injuries
  • About 75% of patients (864) had early prophylaxis
  • Patients were younger (median 34 years), and two-thirds were male, with a median ISS of 22
  • Early VTE prophylaxis patients had significantly lower rates of VTE (3% vs. 7%)
  • There was no significant difference in failure of nonoperative management (5% early vs. 7% late)
  • The early prophylaxis group received fewer units of blood after prophylaxis started (17% vs. 23%)
  • Patients receiving VTE prophylaxis after 48 hours were 2.2x more likely to develop VTE

The authors concluded that early VTE chemoprophylaxis was associated with lower rates of VTE with no increase in complications. They recommended that it should become the standard of care for these patients.

Bottom line: Seeing such a well-designed and nicely executed study is refreshing. If the facts are borne out in the final manuscript review, this should become the standard of care for VTE prophylaxis in patients with solid organ injuries. 

I wish the authors would have stipulated that the chemoprophylaxis was required to be low molecular weight heparin. Unfortunately, there are still more than a few centers using unfractionated heparin. There could be a difference in efficacy and failure rates between the two. This could complicate the statistical analysis. Hopefully, the presenter will address this during the meeting.

I would also like to see a breakdown of when the early VTE prophylaxis actually started. Were they all close to 48 hours? Or were there enough at 24 hours to show this is also safe and effective?

It’s time for everyone to review their VTE prophylaxis guidelines. Get ready to make some major changes in your patients with solid organ injury!

Reference: When is it safe to start VTE prophylaxis after blunt solid organ injury? A prospective AAST multi-institutional trial. AAST 2023, Plenary paper #23.

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.
Complications

Predicting VTE Risk In Children

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There’s a lot of debate about if and at what age injured children develop significant risk for venous thromboembolism (VTE). In the adult world, it’s a little more clear cut, and nearly every patient gets some type of prophylactic device or drug. Kids, we’re not so certain about at all.

The Children’s Hospital of Wisconsin tried to tease out these factors to develop and implement a practice guideline for pediatric VTE prophylaxis. They prospectively reviewed over 4000 pediatric patients admitted over a 6 year period.

It looks like the guideline was developed using some or all of this data, then tested using regression models to determine which factors were significant. The guideline was then tweaked and a final model was implemented.

Here are the factoids:

  • 588 of the patients (14%) were admitted to the ICU, and 199 of these were identified as high-risk by the guidelines
  • Median age was 10 (this is always important in these studies)
  • VTE occurred in 4% of the ICU patients, and 10% of the high-risk ones
  • Significant risk factors included presence of central venous catheter, use of inotropes, immobilization, and GCS < 9

Bottom line: This abstract confuses me. How were the guidelines developed? What were they, exactly? And the results seem to pertain to the ICU patients only. What about the non-ICU kids? The abstract just can’t convey enough information to do the study justice. Hopefully, the oral presentation will explain all.

I prefer a very nice analysis done at the Oregon Health Science University in Portland. I wrote about this study earlier this year. The authors developed a very useful calculator that includes most of the risk factors in this model, and a few more. Input the specific risks, and out comes a nice score. The only issue is, what is the score threshold to begin prophylaxis and monitoring? Much more practical (and understandable) than this abstract. Check it out at the link below.

References:

  1. Evaluation of guidelines for injured children at high risk for venous thromboembolism: A prospective observational study. J Trauma Acute Care Surg. 2017 May;82(5):836-844.
  2. A Clinical Tool for the Prediction of Venous Thromboembolism in Pediatric Trauma Patients. JAMA Surg 151(1):50-57, 2016.
Abstracts, Complications, Head

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

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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.