Tag Archives: whole blood

Best Of EAST 2024 #8: Whole Blood And VTE

The pendulum has swung from the use of whole blood in the early 20th century, to component therapy in the 1960s, and now a gradual move toward incorporating whole blood again. More and more papers are being published, and many trauma centers are looking for ways to integrate whole blood into their massive transfusion protocols.

Much of the literature has been dedicated to safety and effectiveness, but little has examined thrombotic complications from its use.  The trauma group at the University of Texas in Houston performed what looks to be a retrospective review of whole blood usage at two Level I trauma centers. Adult patients receiving at least one emergency-release whole blood unit were compared with those receiving only component therapy. They looked at the incidence of venous thromboembolic (VTE) complications such as pulmonary embolism (PE) or deep venous thrombosis (DVT).

Here are the factoids:

  • Nearly 3,500 patients were enrolled and were fairly evenly split between whole blood and component therapy only
  • Whole blood patients were slightly younger, were much more likely to have penetrating injury, and had significantly higher ISS (26 vs 19)
  • The whole blood patients were also significantly more likely to receive TXA, VTE chemoprophylaxis within 48 hours (86% vs. 79%) and lower 30-day survival (74% vs 84%)
  • Crude incidence of VTE was similar (7% whole blood vs. 9% component), but logistic regression “revealed that whole blood was protective of VTE,” while red cell transfusion and TXA increased VTE risk
  • Each unit of red cells increased VTE risk by 3%

The authors concluded that whole blood was associated with a 30% reduction in VTE, and TX was associated with a 2.5x increase in risk. They cautioned against the use of TXA in the setting of whole-blood resuscitation.

Bottom line: A lot is going on here. First, this is a retrospective study, which limits the number of variables that can be collected reliably. It also makes it much more difficult to perform regression analysis because there are many other possible variables to control for than just the ones collected. 

Next, as quoted in bullet point 4 above, this study can’t show that whole blood was protective, only that it was (maybe) associated with decreased VTE when the variables they collected were controlled. 

Most of the confidence intervals for the “significant” results were very close to the 1.0 line. This leaves the possibility that the result could easily be changed by adding other pertinent variables not included in the data. The only impressive one was the association of TXA exposure and VTE. I think this demands further work.

The authors need to answer several questions in their presentation to help explain the results:

  • Was there any relationship between the number of units of packed cells given and the likelihood of VTE?
  • Similarly, was there a relationship between the number of units of whole blood and possible “protection” from VTE?
  • Did you examine other physiologic or anatomic variables and their relationship with VTE? Specific ones that come to mind are shock, long bone or spine fractures, and TBI. These are some of the variables that need to be included in the regression model to improve it.

Overall, this is an interesting abstract that makes one think. But it either needs some good explanations during the presentation or additional data analysis to make it even more interesting.

Reference: Does whole blood resuscitation increase risk for venous thromboembolism in trauma patients? A comparison of component therapy vs whole blood in 3468 patients. EAST 2024, Podium paper 33.

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

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.

Best Of EAST 2023 #4: Whole Blood In Patients With Shock And TBI

We know that even a brief shock episode in patients with severe TBI dramatically increases mortality. Therefore, standard practice is to ensure good oxygenation with supplemental O2 and an adequate airway ASAP and to guard against hypotension with crystalloids and blood if needed.

Many papers (and several abstracts in this bunch) have been written about the benefits of whole blood transfusion. The group at the University of Texas in Houston compiled a prospective database of their experience with emergency release blood product usage in patients with hemorrhagic shock.

They massaged this database, analyzing a subset of patients with severe TBI, defined as AIS Head of 3. They specifically looked at mortality and outcome  differences between those who received whole blood and those who received component therapy.

Here are the factoids:

  • A total of 564 patients met the TBI + shock criteria, and 341 (60%) received whole blood
  • Patients receiving whole blood  had higher ISS (34 vs. 29), lower blood pressure (104 vs. 118), and higher lactate (4.3 vs. 3.6), all indicators of more severe injury
  • Initial univariate analysis did not identify any mortality difference, but using a weighted multivariate model teased out decreases in overall mortality, death from the TBI, and blood product usage
  • Neither statistical model demonstrated any difference in discharge disposition of ventilator days

The authors concluded that whole blood transfusion in patients with both hemorrhagic shock and TBI was associated with decreased mortality and blood product utilization.

Bottom line: This is yet another study trying to tease out the benefits of giving whole blood. The results are intriguing and show an association between whole blood use and survival. But remember, this type of study does not establish causality. It’s not possible to rule out other variables that were not available or not considered that could be the cause of the difference.

In this type of study, it’s essential to look at the design. Was it possible to create the study to record a complete set of variables that the researchers thought might contribute to the outcomes? Or is it a retrospective analysis of someone else’s data that contains just a few of them? This study falls into the latter category, so we have fewer data elements to work with and the likelihood that others that are not present could contribute to the outcomes.

The details of the multivariate analysis are also important. The authors stated that weighted multivariate analyses were performed. It’s not possible to provide details in a standard abstract, but these will be important for the audience to understand.

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

  • Tell us more about the database you used for the analysis. What was the purpose? How many data elements did you collect, and how are they related to your research questions?
  • How did you decide which variables to include in your multivariate analysis? And how did you determine the weights? These can have a significant effect on your results.
  • This is a preliminary proof of idea study. How should this be followed up to move from association to causation?

This is just one of many exciting studies trying to shed light on the forgotten benefits of whole blood in trauma. I’m looking forward to seeing the final manuscript!


Best Of EAST 2023 #3: The Cost Of Whole Blood vs Component Therapy

Decades ago, blood banks discovered they could fractionate units of whole blood into components for focused use. This was useful for patients who were thrombocytopenic or needed specific plasma factors. But trauma patients bleed whole blood, and trying to reassemble whole blood from components does not work well. Have a look at this chart:

It all comes down to money. Blood banks found they could charge more for the sum of the components of a unit of whole blood rather than the one unit itself. But now, with whole blood in trauma becoming a thing again, it’s essential to reexamine costs.

The University of Texas at San Antonio group examined transfusion-related charges for trauma patients receiving either component therapy or low-titer O+ whole blood within six hours of arrival. This was a retrospective review of prospectively collected data. During the first two years, only component therapy was given. Whole blood was introduced during the last four years.

Here are the factoids:

  • Once the trauma center switched to whole blood, total annual transfusion charges, as well as component charges decreased by 17% overall
  • In both adults and children, whole blood was associated with a significantly lower cost per ml delivered and cost per patient throughout all phases of care
  • In severely injured patients (ISS>15), the same significantly lower costs were also noted
  • Patients who triggered the massive transfusion protocol also had a lower cost per ml of product in the ED and the first 24 hours

The authors concluded that whole blood was associated with lower charges and “improved logistics,” especially in massive transfusion patients.

Bottom line: This is an interesting and important paper. However, several questions still need to be answered. I recognize that there is limited space in an abstract, so I will list them below in hopes the authors will answer them during the presentation.

The first issue is that the numbers of patients and quantities of blood products given need to be listed. These are very important because the figures list only total charges and maybe costs. These numbers are not per unit of product, so the data may be skewed if the number of patients was different between the groups. For example, if 100 patients received component therapy and only 10 got whole blood, costs or charges could definitely be skewed.

And then there is the cost vs. charge confusion. The abstract seems to use them interchangeably. The methods section of the abstract states that charges were analyzed. Yet cost is mentioned in the results, and figure two shows “cost” on the axes, but the caption states that charges were listed. 

We all know that hospitals can charge whatever they like, and that amount may vary based on insurance and other factors. The relationship between the charge and the cost is tenuous at best. Hopefully, the authors will clarify this at the start of the presentation.

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

  • Please clarify the concept of charges vs. costs at the presentation’s beginning. If you truly analyzed only charges, do they bear any relationship to the actual costs of the units?
  • Shouldn’t your analysis of annual “charges” for product expenditures in Figure 1 be per unit? Otherwise, the costs and charges could be lower if fewer products were given after whole blood was introduced.
  • Was the switch to whole blood absolute, or was component therapy still given in some cases after 2018? If the switch was not total, there could be a selection bias in patients who received whole blood.
  • Figure 2 also appears to be total charges (or costs), not per patient or unit. But, again, without numbers it is difficult to say if the dollar differences are significant.
  • What are the “improved logistics” mentioned in the conclusion section? And how could they lower charges (or costs) in your study?

Lots of questions. I think you will need to provide a lot of explanation up front to justify your findings. Nevertheless, I’m excited about the presentation.


Best Of EAST #13: Whole Blood And Hypocalcemia

Hypocalcemia has long been known to exacerbate coagulopathy. Calcium is involved at several points in the coagulation cascade. Once serum levels drop below about 0.25 mmol/L (normal value 1.2-1.4 mmol/L) thrombin generation and clot formation cease. Although levels this low are probably rare, anything between this low and the normal level can significantly lower clot strength.

Trauma patients are more likely to have bleeding issues than most, and trauma professionals do their best to avoid coagulopathy. Unfortunately, the products we use to replace shed blood are preserved with citrate, which binds calcium. Given in even modest to large quantities, transfusion itself can lead to hypocalcemia.

Most blood transfused in the US has been broken down into separate components (packed cells (PRBC), plasma, platelets) and the effect on calcium levels is well known. The trauma group at Oregon Health Sciences University studied the impact on calcium of whole blood transfusions.

They performed a retrospective review of data collected prospectively over a 2.5 year period on patients receiving whole blood. This included the number of transfusions, ionized calcium levels, and calcium replacements administered. Patients were divided into two groups, those who received whole blood only and those who were given whole blood and component therapy. Outcomes evaluated were ionized calcium levels, hypocalcemia correction, and death.

Here are the factoids:

  • During the study period, 335 patients received whole blood, but only 67% met inclusion criteria
  • About half (103) received a median of 2 units of whole blood (only!)
  • The authors do not state how many component units the whole blood plus component therapy group received
  • There was no difference in calcium levels based on average ISS in the two groups, although ISS does not differentiate injuries that bleed very well
  • Hypocalcemia occurred in only 4% of whole blood patients vs 15% of whole blood + components, which was significant
  • Hypocalcemia within the first hour was significantly associated with death in the first 24 hours and 30 days, although the standard deviation or SEM of this value was large
  • Whole blood only patients received less calcium replacement, and failure to correct was associated with 24 hour mortality
  • Median time to death in patients that “failed to correct” was 7.5 hours after admission

The authors conclude that hypocalcemia rarely occurs in whole blood only resuscitation, and that adding components increases its incidence and overall mortality. They state that aggressive calcium supplementation should be prioritized if component therapy is used.

Bottom line: There’s a lot to “unpack” here! Packed red cells are preserved with 3g of citrate per unit, whereas whole blood units contain only half that amount (1.66g to be exact). One would expect that one unit of packed cells would have twice the anticoagulant effect as a unit of whole blood.

This study is a blended model, where every patient got some whole blood, but some got components as well. Why? Is there a blood refrigerator in the ED stocked with whole blood, and when it is exhausted there is a switch to components? This model makes it more difficult to tease out the impact of the components given. Perhaps it could be done by matching patients with a given amount of whole blood. That is, comparing patients with 3 whole blood with those who received 3 whole blood + 2 PRBC.

There was no room in the abstract to explain why one third of patients were excluded from the study. This needs to be provided to ensure that the remaining two thirds are representative and can legitimately be analyzed. 

The number of units of whole blood per patient was low, with a median of two units given. Is it surprising that these patients did better than ones who received many more? Remember, from a citrate anticoagulant perspective, hanging two units of whole blood is the same as giving just one unit of PRBC.

This abstract raises a lot of questions, and the most important ones deal with how it was designed and the exact numbers of product given. Only then can we be confident that the rest of the associations described are significant.

Here are my questions for the authors and presenter:

  • Why did you choose the whole blood vs whole blood + components for your study? Wouldn’t it have been cleaner to do whole blood only vs components only? Perhaps all of your patients get whole blood? It seems like this might make the results more difficult to tease out.
  • How is whole blood made available for your trauma patients, and did this have an impact on your study? Do you have a limited number beyond which component therapy is used?
  • What were the inclusion criteria? These were not stated in the abstract, but a third of patients were excluded from the study based on them.
  • Could excluding a third of patients have skewed your results, and how?
  • How many component units were given along with the whole blood in the combination group? This was not provided in the abstract and will have a major impact on outcomes if the median total product numbers are significantly higher.
  • What does “failed to correct” mean? Were the patients not responding to large amounts of administered calcium, or were they not receiving large amounts of it?

I am very interested in the fine details in this abstract and will be listening intently to the presentation!