Tag Archives: AAST2023

Abstracts, Resuscitation

Best Of AAST #8: Whole Blood At The Scene Of Injury

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Here’s another abstract with a promising title that suffers from low subject numbers. Whole blood is the new darling of trauma resuscitation. Assembling a unit of whole blood from the components it was broken down into produces an inferior product from the standpoint of resuscitation.

It makes sense from a coagulation standpoint, but there are a few pesky issues that need to be considered, such as antibody titers. So I understand the enthusiasm to get some papers out there that describe the value of it.

A group in the Czech Republic performed a prospective study that assigned patients to receive scene resuscitation with either one unit of packed cells plus one unit of plasma, or two units of low titer group O whole blood. They had a host of primary outcomes, including feasibility, 24-hour and 30-day mortality, 24-hour blood use and fluid balance, and initial INR. They compared the two groups to matched cohort controls from a trauma registry. The study was performed over a three year period.

Here are the factoids:

  • Three groups of about 50 patients each were enrolled
  • There was no difference in 24-hour mortality, but the authors claimed that the 30-day mortality was “better.” However, the numbers were not statistically significant.
  • They found a statistically significant decrease in 24-hour transfusion volume of about 500cc, which is not clinically significant
  • Similarly, there was an increase in fluid balance of about 2L
  • They also found a “significant” decrease in INR from 1.17 to 1.10, which is also not clinically significant
  • There were no transfusion reactions

The authors concluded that whole blood was safe to give at the scene and that there were improvements in the measured parameters.

Bottom line: Sorry, but the abstract does not really support the title. This study is woefully small, and confusing to read. The purpose of the registry control cohort was not clear, and the extra results further muddied the picture. The statistical analyses were not included, and I am skeptical that they fully support the conclusions. There is just no statistical power to achieve significance with the number of subjects in this study. And many of the differences, even if they were statistically significant, were not clinically significant.

I don’t want to be a downer here. I do believe that whole blood is a good thing. Unfortunately, the whole blood in this study could have been better used doing a much bigger, multicenter study to truly show us the benefits.

Reference: Whole blood on the scene of injury improves clinical outcome of the bleeding trauma patient. AAST 2023, Plenary paper #28.

Abstracts, Resuscitation

Best Of AAST #7: How Do You Like Your Platelets – Warm Or Cold?

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Until the last few years, massive transfusion in trauma consisted of component therapy, an admixture of packed red cells, plasma, and platelets. Whole blood transfusion is making inroads again, but it is used in a minority of centers.

Of the three components, platelets have classically required different handling than the others. They are generally kept at room temperature, while the red cells and plasma are kept very cold to preserve their shelf life. A few centers have toyed with the use of cold platelets, but there have been concerns about their ability to clot and their useful life after transfusion.

Researchers from the US Army performed a retrospective registry study on a sample of military casualties over four years. They identified soldiers who received either room-temperature or cold-stored platelets. The primary outcome was mortality, and secondary outcomes included the need for surgery, fluid and blood infusions, and the use of a massive transfusion protocol.

Here are the factoids:

  • A total of 300 patients were identified, nearly equally split between room temp platelets and cold-stored
  • Demographics of the two groups were similar, but the ISS was somewhat higher in the cold-stored platelet group
  • Significantly fewer cold-stored platelet patients underwent surgery (13% vs. 24%)
  • Survival was the same at 87-88%
  • Blood and product administration was significantly higher in the cold-stored group, as was the use of the MTP (54% vs. 34%)

The authors concluded that the use of cold-stored platelets were not inferior to room temperature platelets.

Bottom line: Huh?? Yes, survival was the same despite a higher ISS in the cold platelet group. But they required more blood and needed massive transfusion significantly more often.

I see two major issues with this study. The most important is that it is a non-inferiority study. To believe that both arms are equal, a power analysis is required. The sample size here is too small to achieve significance unless differences are extreme, like the transfusion and MTP numbers.

The second problem is that this is an association study. Attempting to show that the type of platelets used is a major determinant of survival, need for surgery, or blood product use is shortsighted. There are a myriad of other factors that have more of an impact.

Far more subjects need to be studied, and a retrospective study with limited data points is not enough. I’m surprised that a military registry could only come up with 75 patients a year to analyze. These low numbers and the nature of this particular registry could inject significant bias as well.

Stay with the room temp platelets for now, and wait for a well-powered prospective analysis before changing your MTP.

Reference: An analysis of the use of cold-stored platelets in combat trauma. AAST 2023 Plenary paper #29.

Abstracts, Complications

Best Of AAST #6: Chronic Disease In Young Trauma Patients

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Worldwide, the proportion of older people is growing. With that is an increase in the number of older folks with medical comorbidities like diabetes, hypertension, and obesity. Trauma professionals recognize these conditions’ negative impact on recovery after injury.

But is being young becoming the new old? The trauma group at WakeMed performed a retrospective multi-center study to tease out an estimate of the prevalence of these conditions (plus one more: alcohol/substance use) in injured young(er) people. They studied trauma patients aged 18-40 over three years, examining their charts for evidence of the conditions listed that had been previously undiagnosed.

Here are the factoids:

  • Of the 6,307 patients included, a startling 4,843 (77%) had at least one underlying disease, usually hypertension or obesity
  • Using their multivariate models, they found that age was (barely) a predictor, as were male sex ( 1.43x) and uninsured status (1.6x)
  • Only a quarter of patients had a primary care physician (PCP), but this did not increase the presence of underlying disease
  • Patients found to have these conditions were twice as likely to be referred to a PCP, although this referral rate was still very low (14% vs. 8%)
  • There was no difference in inpatient complications or hospital length of stay

The authors concluded that the undiagnosed disease burden in young adult trauma patients is high. They recommend rigorous screening measures and appropriate referrals.

Bottom line: This is an interesting abstract revealing what we all probably subconsciously recognize. Younger people are not as healthy as they once were. The numbers with obesity, diabetes, hypertension, and substance use are now staggering, with over three-quarters of patients in this convenience study impacted.

Abnormalities are often found on the lab panels drawn during a trauma activation or upon admission. Unfortunately, we do not always act on them since they don’t appear to have anything to do with the trauma.

This abstract makes it clear that the disease burden in this group is high. It is very likely that those affected will probably develop complications at an earlier age and will suffer a decrease in their overall healthspan as they age. The only and most important thing we can do is pay attention and set our patients up with a primary care physician on discharge to begin working on their potential health problems.

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, Thorax

Best Of AAST #3: When To Place A Chest Tube For Hemothorax

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There is an art to deciding when to place a  chest tube for either hemothorax or pneumothorax. For the most part, the trauma professional examines the imaging and then uses some unknown internal metric to declare that it is “too big.” Then it’s time to insert some type of chest drain.

There have been attempts over the years to make this decision more quantitative. One of the better-known ones is the 2-cm rule for pneumothorax. If the distance from the chest wall to the lung on the chest x-ray is >2cm, it is “too big.”

But what about hemothorax? The Medical College of Wisconsin trauma group performed a retrospective review of 391 patient charts to test a new 300cc rule defining when a hemothorax is “too big.” This guideline was implemented in 2018-2019, and patients presenting before implementation were compared to those arriving after.

The 300cc threshold is determined by using Mergo’s formula for calculating the volume of a square prism. Obviously, this requires a CT scan for calculation, so patients who had a tube placed before scanning or did not have one were excluded. They were also excluded from the study if their pneumothorax met the 2-cm rule. The authors studied how many patients could be observed, how many needed tube drainage, observation failure, and later need for a VATS procedure or thoracotomy.

Here are the factoids:

  • About 60% of the study group was admitted after the new criteria were implemented, and both groups were demographically similar
  • After implementation, the number of patients that were just observed increased significantly from 52% to 71%
  • Of course, this means that the number of chest tubes inserted was significantly less (42% vs. 61%)
  • There was no difference in observation failure (delayed placement of a tube), 18% vs. 24%
  • There were also no differences in pulmonary complications, 30-day readmissions, or 30-day mortality
  • The average ICU and hospital length of stays were significantly shorter as well

The authors concluded that implementing their 300cc guidelines correlated with decreased length of stay and no increase in failure or complication rates.

Bottom line: Although this is a relatively small series, the differences between the groups quickly achieved significance. There are three major questions that I have. First, how was the 300cc threshold arrived at? Was this borne of clinical judgment, or did some previous work suggest it?

My next question has to deal with the accuracy of the volume calculation. Mergo’s formula was used to determine the volume of a rectangular solid. As we all know, hemothoraces and pneumothoraces are not cubes. They can be very irregular and influenced by patient position. However, I did find a paper from the University of Florida that found the correlation coefficient between the volume calculated by Mergo’s formula vs. using 3-D software estimation was 0.9, which is excellent. So this approximation appears to be a very good one.

Finally, using the 300cc rule is predicated on getting a CT scan. Does every patient need a chest CT? Part of the resuscitation process for major trauma involves obtaining a chest X-ray. The obviously large hemothorax can justify inserting a chest tube at that point. But the reality is that most of these patients do go on to chest CT, so this is a minor change in practice for most. 

Although I love to see confirmatory studies before practice changes, this one study can lead us to change our practice guidelines now. It is a relatively minor one and will allow us to avoid placement of a few more chest tubes and to shave off a few days of hospital stay. The logical follow-up study for the authors is to extend the post-discharge window for complications to 60 or 90 days to ensure that delayed procedures were not required in the observation group.

References:

  • Implementing the 300-cc rule safely decreases chest tube placement in traumatic hemothorax. AAST 2023 Plenary paper #22.
  • New formula for quantification of pleural effusions from computed tomography. J Thorac Imaging. 1999 Apr;14(2):122-5.