Tag Archives: MTP

Can We Use Type A Plasma For Emergency Transfusion?

Trauma patients tend to try to bleed to death. And trauma professionals try to stop that bleeding. They also frequently have to replace the blood products that were lost, which includes red blood cells, plasma, platelets, and more.

From a red blood cell standpoint, we have a long history of using group O- packed red cells as the so-called universal donor product. The problem is that only about 5% of the world population has this blood type, so it can be scarce.

To address this, many centers have moved toward using O+ blood for select patients. This blood type is much more prevalent (about 50% worldwide). The only difference is the positive Rh factor which has little impact on males, or females who are not in their child-bearing years. If an allergic reaction occurs, it is typically mild.

But what about plasma? This is interesting stuff. When selecting red cells, we want them to have no ABO group antigens on them so they don’t provoke a reaction. But plasma is just the opposite. We don’t want any ABO group antibodies in it. And the only plasma without antibodies comes from people who have all of them (A and B) on their red cells. This means people with type AB+ blood. Unfortunately, this is the other rare blood type, so there’s not a lot to go around. Worldwide, about 5% of people are AB+ and less than 1% are AB-.

So why couldn’t we do something like we did with packed red cells and substitute a more common blood type that evokes little immune response? The American Association of Blood Banks (AABB) has authorized both AB and A plasma for use in emergency situations. Unfortunately, the safety profile for using group A has not been very well studied, particularly in trauma patients needing massive transfusion.

The authors of the PROPPR study re-analyzed the data from it to try to answer this question. As you may recall, PROPPR was published in 2015 and compared safety and effectiveness of transfusion ratios at 1:1:1 to 1:1:2 (plasma : platelets : red cells).

The study group selected patients from the dataset who received at least one unit of emergency release plasma (ERP), defined as product given before the patient’s ABO type had been determined. Nicely enough, 12 sites transfused group AB ERP and 9 sites gave group A. One site gave both A and AB.

The authors looked at in-hospital mortality at 30 days, and a host of complications. Here are the factoids:

  • A total of 584 of the 680 patients in the PROPPR study received emergency release plasma
  • The median number of units given was 4, and there was no difference between A and AB groups
  • There were statistically significant baseline differences between the groups, including blood type, SBP, percent in shock (SBP<90), blunt mechanism, positive FAST that were probably not very clinically significant
  • The number of transfusions of all products were significantly  higher in the A plasma group
  • Complications were significantly higher in the A plasma group, specifically from SIRS, pulmonary problems, and venous thromboembolism (VTE)
  • There were no acute hemolytic transfusion reactions and three febrile reactions

The authors concluded that, statistically, the use of group A plasma was not inferior to the use of group AB. The authors stated that cautious use of group A is an acceptable option, especially if group AB is not readily available.

Bottom line: Here we go again. Always be careful when reading a study that suggests non-inferiority of one thing compared to another. There are a lot of potential issues here:

  • The PROPPR trial data was not designed to answer questions about plasma usage, so the data is being highjacked a bit
  • Participating centers did not have a standardized way to determine the group that received ERP, so some data anomalies will be present
  • The A and AB study groups were different in many ways at baseline, particularly with respect to how much product they received
  • The primary outcome, 30-day mortality, was underpowered and could never show a significant difference

So with significant baseline differences in study groups and a potentially underpowered study, don’t read non-inferiority as meaning that use of group A plasma is okay. We still just don’t know. What this study really shows is that you can “get away with” using low titer group A plasma if you run out of AB. But it shouldn’t be your go to product yet. To figure out the real safety profile, we need to do a real “PROPPR” study. Get it?

Reference: Group A emergency-release plasma in trauma patients requiring massive transfusion, J Trauma 89(6):1961-1067, 2020.

Best of AAST #1: What Has The MTP Bought Us?

Let’s kick off my reviews of AAST 2020 abstracts with a paper on the results of recent advances in hemorrhage control. Over the past 10+ years we have seen the following new (and old) tools move into more widespread use:

  • Massive transfusion protocol (MTP) with a goal of 1:1 ratios of red cells to plasma
  • Availability of liquid plasma for more rapid use in the MTP
  • Addition of tranexamic acid (TXA) to resuscitation
  • Resurgence of tourniquet use by prehospital providers
  • Adoption of REBOA and TEG
  • Transfusion with whole blood

The authors analyzed their experience after serially introducing these tools to their resuscitation strategies, and studied their impact on overall mortality.

They retrospectively reviewed the experience over a 12 year period at their large Level I trauma center. Here are the factoids:

  • The reviewed a total of 824 MTP events. To put this into perspective from a volume standpoint, this is a little over one MTP activation per week.
  • Patients were primarily young (median age 31), male (81%), with a penetrating mechanism (68%). Median ISS was 25
  • Prehospital times were significantly longer at the end of the study, but the authors state that there was no correlation with an increase in in-hospital mortality
  • During the entire study, overall mortality ranged from 38% to 57%, and logistic regression did not identify an effect from any of the interventions

The authors concluded that their mortality rates have not improved despite all of the advancements we have added over the past decade. They suggest that future efforts should attempt to move targeted hemorrhage control backwards in time, out of the ED and toward to injury scene.

Here are my comments: This is an interesting and simple-appearing study. Overall, the authors didn’t really show that any of our “modern” resuscitation interventions did much for their patients at all.  There was a suggestion that tourniquet implementation and use of whole blood tended toward improving things.

But don’t be fooled by simplicity. There are many, many factors that enter into whether an individual patient lives or dies. When you fail to see a significant result in a study, first look at the methods and tools used for measurement. Are they powerful enough to discern changes? Do they cover enough of the factors that promote survival, not just our resuscitative advances? Or is the tool looking at the wrong things?

One big difference at this center is the sheer volume of penetrating trauma. This could have a major impact on survival, and may be very different from the experience of most centers that have predominantly blunt injury mechanisms.

And some questions for the authors:

  • What exactly is your definition of mortality? Made it out of the ED? Lived twenty four hours? Thirty days? This makes a big difference in how you look at the results.
  • Since you have only about one MTP event per week, do you think your numbers are large enough to actually detect a mortality difference? 
  • Did you consider looking at your unexpected survivors to see if there were any common threads in their care that might have made the difference? Maybe some of our resuscitative advances do make a difference, but only in specific subsets of patients.
  • Can you speculate about the reasons for longer prehospital times, and the impact on mortality?
  • How would you recommend pushing hemorrhage control back toward the scene? New tools for prehospital providers? More advanced providers in the rigs? This is an intriguing concept and it would be interesting to hear your thoughts.

This is a thought provoking paper that questions our assumptions about our time-honored resuscitation tools. I look forward to hearing it live next month!

Reference: After 800 MTP events, mortality due to hemorrhagic shock remains higha nd unchanged despite several hemorrhage control advancements; is it time to move the pendulum? AAST 2020 Oral Abstract #1.

Massive Transfusion: What’s The Right Ratio?

In my last post, I analyzed a survey that studied the massive transfusion protocol (MTP) practices of academic Level I trauma centers in the US. What centers do is one thing. But what does the literature actually support? A group from Monash University in Melbourne, Australia and the National Health Service in the UK teamed up to review the literature available through 2016 regarding optimal dose, timing, and ratio of products given during MTP.

One would think that this was easy. However, the search for high quality ran into the usual roadblock: the fact that there is not very much of it. The authors scanned MEDLINE for randomized, controlled studies on this topic, and found very few of them. Out of 131 articles that were eligible, only 16 were found to be suitable for inclusion, and 10 of them were still in progress. And only three specifically dealt with the ratio question. Even they  were difficult to compare in a strict apples to apples fashion.

Here are the factoids that could be gleaned from them:

  • There was no difference in 24-hour or 30-day mortality between a ratio of 1:1:1 (FFP:platelets:RBC) vs 1:1:2
  • However, a significantly higher number of patients  achieved hemostasis in the 1:1:1 group (86% vs 78%)
  • There was no difference in morbidity or transfusion reactions in the two groups
  • One study compared 1:1 component therapy with whole blood transfusion and found no difference in short-term or long-term mortality or morbidity

Bottom line: As usual, the quality of available data is poor if one limits the field to randomized, controlled studies. Ratios of 1:1:1 and 1:1:2 appear to be equally effective given the limited information available. A number of papers not included in this review (because of their less rigorous design) do seem to indicate that higher ratios of RBC (1:3-4) appear to be detrimental. And as time passes, more and hopefully better studies will be published.

What does this all mean for your MTP? Basically, we still don’t know the best ratio. However, it is recommended that your final ratios of FFP:RBC end up somewhere between 1:1 and 1:2. The only way to ensure this is to set up your MTP coolers so the the ratio of product they contain is better than 1:2. This means more plasma than 1 unit per 2 units of red cells. 

If you set it at the outside limit of 1:2, then that is the best ratio you can ever get assuming everything goes perfectly. However, if you have to thaw frozen plasma, use too much emergency release PRBC before activating MTP, or someone cherry-picks the coolers to transfuse what they think the patient needs, the ratios will quickly exceed this boundary.

So be sure to load your coolers with ratios that are closer to 1:1 to ensure that your final ratios once MTP is complete are what you want them to be. And monitor the final numbers of every one of your MTP activations through your trauma performance improvement program so you know what your patients are really receiving.

Reference: Optimal Dose, Timing and Ratio of Blood Products in Massive
Transfusion: Results from a Systematic Review. Transfusion Med Reviews 32:6-15, 2018.

Massive Transfusion: What Ratios Are People Using?

This is the first of a two-part series on massive transfusion protocol (MTP) ratios. Today, I’ll write about what ratios trauma centers around the country are using. Tomorrow I’ll review the literature we have to date on what the correct ratio should be. Are we all doing the right thing or not?

Back in the old days (which I remember fondly), we didn’t pay too much attention to the ratio of blood to plasma. We gave a bunch of bags of red cells, then at some point we remembered that we should give some plasma. And platelets? We were lucky to give any! And to top it all off, we gave LOTS of crystalloid. Turns out this was not exactly the best practice.

But things have changed. Some good research has shown us that a nice mix of blood component products is good and too much crystalloid is bad. But what exactly is the ideal mix of blood products? And what is everybody else doing? I’ll try to answer these questions in this series.

So first, what are all the other trauma centers doing? An interesting medley of anesthesia and pathology groups from the University of Chicago, a Dallas-based anesthesia group, and a blood center in my home base of St. Paul, conducted a survey of academic medical centers in 2016. They wanted to find out how many actually had a MTP and to scrutinize the details.

They constructed a SurveyMonkey survey and sent it to hospitals with accredited pathology residencies across the US. There were 32 questions in the survey, which asked for a lot of detail. As you can probably personally attest, the longer and more complicated the survey, the less likely you are to respond. That certainly happened here. Of 107 surveys sent out, it took a lot of nagging (initial email plus two nags) to get a total of 56 back.

Here are the factoids:

  • Most were larger hospitals, with 74% having 500 or more beds
  • All had massive transfusion protocols
  • Trauma center level: Level I (77%), Level II (4%), Level III (4%), Level IV (2%), no level (14%)
  • Nearly all (98%) used a fixed ratio MTP; very few used any lab-directed (e.g. TEG/ROTEM) resuscitation
  • Target RBC:plasma ratio: 1:1 (70%), 1.5:1 (9%), 2:1 (9%), other (9%)
  • Only 58% had the same RBC:plasma ratio in each MTP cooler
  • More than 86% had thawed plasma available (remember, these were generally large academic centers)
  • Half stored uncrossmatched type O PRBCs outside the blood bank, usually in the ED; only 1 stored thawed plasma in the ED
  • A total of 41% had more than one MTP (trauma, OB, GI, etc.)
  • 84% had some type of formal review process once the MTP was complete
  • About 68% had modified their MTP since the original implementation. Some increased or decreased ratios, expanded MTP to non-trauma services, decreased the number of units in each pack, changed to group A plasma from AB, or switched from ratio to TEG/ROTEM or back.

Bottom line: This is an intriguing snapshot of MTP practices around the country that is about four years old. Also remember, this is a somewhat skewed dataset. The survey was directed toward hospitals with academic pathology programs, not trauma centers. However, there is enough overlap that the results are probably generalizable. 

Most centers are (were) using MTP packs containing six units of PRBCs, and were attempting to achieve a fixed 1:1 ratio. Half of hospitals had the same number of units in each cooler, half varied them by cooler number. Nearly half had multiple flavors of MTP for different specialties. Very few used TEG/ROTEM during the initial phased of MTP. Most modified their MTP over time.

I’ve written quite a lot on most of these issues. See the links to my “MTP Week” series from earlier this year, below.

Tomorrow, I’ll review what we know and don’t know about the proper ratios to use in your MTP.

Reference: Massive Transfusion Protocols: A Survey of Academic
Medical Centers in the United States. Anesth & Analg 124(1):277-281, 2017.

MTP week series:

What’s The Best Trigger For Your Massive Transfusion Protocol?

Every trauma center verified by the American College of Surgeons Committee on Trauma (ACS-COT) must have a massive transfusion protocol (MTP). The details and logistics of the protocol are up to the individual center. The difficult question is: how is a trauma professional to know that the MTP should be activated?

Sometimes it’s extremely obvious. The patient is very hypotensive. Blood is spurting all over the room. But sometimes it’s more subtle and the need just seems to creep up on you. And frequently, this delays activation and the actual arrival of the blood that is so desperately needed.

I’ve previously written about common triggers for the MTP, including psychic powers, shock index, and ABC index. See the links below to read my MTP week posts. But is one better than the other? The group at Vancouver General Hospital in British Columbia, Canada performed a systematic review of the literature to try to answer this question.

A total of 45 pertinent articles were identified in the literature up to 2017. Fifteen different scoring systems were evaluated involving combinations of clinical assessment, laboratory tests, and ultrasound evaluation.

Here are the factoids:

  • The best validated score using clinical assessment plus ultrasound was the Assessment of Blood Consumption score (click here for my post). This was the easiest to score compared to other systems using ultrasound.
  • Shock index (SI) was the only validated system using just the clinical exam
  • Some other studies were promising, with excellent areas under the receiver operating characteristic curve (AUROC), but had not been validated. The best of the bunch was one from Mina et al, but it is complicated enough to require a smartphone tool for calculation.
  • Other promising studies required laboratory evaluations which preclude their use at the time of patient arrival
  • Scoring systems that used more variables generally showed better correlation with actual need for MTP, but were more less likely to provide suficiently early predictions
  • Most validation studies involved single centers
  • No studies were designed to or able to show improved outcomes

Bottom line: There are many, many systems out there for predicting need for activation of the MTP (at least 15 to date)! This review concludes that the system used should be tailored to the center implementing it.

Simpler is better. I still recommend either Shock Index (SI) or ABC. Shock index is quickly calculated based on physical exam as heart rate divided by systolic blood pressure. The normal range is 0.5 to 0.7. The likelihood of MTP escalates 2x with SI > 0.9, 4x if SI > 1.1, and 7x with SI > 1.3. The ratio can easily be calculated based on numbers available from EMS providers prior to arrival. Basically, pick your threshold.

The Assessment of Blood Consumption (ABC) uses four parameters, three of which could be reported prior to patient arrival:

  • Heart rate > 120
  • Systolic blood pressure < 90
  • FAST positive
  • Penetrating mechanism

If two or more criteria are met, the patient has a 41% likelihood of needing MTP.

So basically, use a system that works for you. From my experience, centers that use a system tend to use ABC. But definitely pick a system, don’t leave it up to chance with the trauma surgeon. And use your trauma PI program to assess utilization to see if it’s the best tool for your center.

Related posts:

Reference: Systematic Reviews of Scores and Predictors to Trigger Activation of Massive Transfusion Protocols. Accepted ahead of print, J Trauma, 2019.