Category Archives: Abstracts

Abstracts

EAST 2018 #2: Blood Product Age And Mortality

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Ever since the start of the modern transfusion age (which was really only about 75 years ago), we’ve been trying to extend the life of banked blood products. Currently, we get about 6 weeks of useful life from packed red blood cells, and varying amounts from other frozen or non-frozen products.

What happens at day 42 for red cells? Or day 5 for platelets or thawed plasma? It’s not like a switch gets flipped and it suddenly goes bad. Each of these products slowly degrades over time, and the myriad components that make them up (proteins, clotting factors, etc) do so at varying rates. It has been recognized for years that some of these products “don’t work so well” when they age, and this has been termed the “storage lesion” of blood.

The next EAST paper I’ll review looks for associations between use of older blood products which probably have a storage lesion, and mortality in trauma patients. It re-analyzed the prospectively collected data on the 680 patients enrolled in the PROPPR trial, which was originally designed to examine the mortality difference between patients with specific FFP:platelet:PRBC ratios given during massive transfusion. In this re-analysis, the authors looked at the mortality after 6 hrs, 24 hrs, and 30 days in patients undergoing massive transfusion, and examined the impact of using “older” blood products. “Old” was defined using the median age of the product; RBCs were old after 20/42 days, plasma after 2/5 days, and platelets after 4/5 days.

Here are the factoids:

  • Plasma age decreased with increasing transfusion. There was no similar change in average platelet or RBC age, though.
  • Patients receiving older RBC and younger plasma had higher mortality
  • Receiving older PRBC was associated with mortality at 6 and 24 hrs, but not 30 days

Bottom line: First, this is an association study, not a causation one. Don’t read anything more into it than you see. And what do you think when you see random mortality numbers like this? For me, either mortality is too crude of a variable to use, or the association is just too weak. If you look at the data table for the study, the confidence intervals of the computed “hazard ratios” barely clear the 1.0 line. To me, this looks like an interesting mathematical exercise, but I can’t tease any clinical significance out of it at all. And I don’t think that re-analyzing this dataset will provide any further clarity.

Here are some questions for the authors to consider before their presentation:

  • Did you try to calculate the statistical power of your dataset? As mentioned above, the associations look weak at best.
  • Did you look at other potential factors like injury severity score or massive transfusion volumes? These would seem to have a much more significant impact on the three survival cohorts?
  • Big picture questions: Where can you go from here? What kind of study could you do to see if this is a real effect vs just a statistical anomaly?

Reference: EAST 2018 Podium paper #3.

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Abstracts

EAST 2018 #1: Plasma Over-Resuscitation And Mortality In Pediatric TBI

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The first EAST abstract I will discuss is the very first to be presented at the annual meeting. This is a prospective, observational studied that was carried out at the University of Pittsburgh. It looked at the association between repeated rapid thromboelastography (rTEG) results in pediatric patients and their death and disability after plasma administration. They specifically looked at the degree of fibrinolysis 30 minutes after maximum clot amplitude and tried to correlate this to mortality.

For those of you who need a refresher on TEG, the funny sunfish shape above shows the clot amplitude as it increases from nothing at the end of R, hits its maximum at TMA, then begins to lyse. The percent that has lysed at 30 mins (LY30%) gives an indication if the clot is dissolving too quickly (LY30% > 3%) or too slowly (LY30% < 0.8%).

The authors selected pediatric patients with TBI and performed an initial rTEG, then one every day afterward. They looked at correlations with transfusion of blood, plasma, and platelets.

Here are the factoids:

  • A total of 101 patients under age 18 were studied, with a median age of 8, median ISS of 25, and 47% with severe TBI (head AIS > 3)
  • Overall mortality was 16%, with 45% having discharge disability
  • On initial analysis, it appeared that transfusion of any product impeded fibrinolysis, but when controlling for the head injury, only plasma infusion correlated with this
  • Increasing plasma infusion was associated with increasing shutdown of fibrinolysis
  • The combination of severe TBI and plasma transfusion showed sustained fibrinolysis shutdown, and was associated with 75% mortality and 100% disability in the remaining survivors
  • The authors conclude that transfusing plasma in pediatric patients with severe TBI may lead to poor outcomes, and that TEG should be used for guidance rather than INR values.

Bottom line: There is a lot that is not explained well in this abstract. It looks like an attempt at justification for using TEG in place of chasing INR in pediatric TBI patients. This may be a legitimate thing, but I can’t really come to any conclusions based on what has been printed in this abstract so far.

Here are some questions for the authors to consider before their presentation:

  • There seem to be a lot of typos, especially with < and > signs in the methods.
  • Disability is a vague term. What was it exactly? Was it related to TBI or the other injuries as well?
  • These children also appear to have had other injuries, otherwise why would they need what looks like massive transfusion activation? Why did they need so much blood? Could that be the reason for their fibrinolysis changes and poor outcomes?
  • I can see the value of the initial rTEG, and maybe one the next day. But why daily? What did you learn from the extra days of measurements? Would a pre- and post-resuscitation pair have been sufficient?
  • Plasma is the focus of this abstract, but it does not describe how much plasma was given, or whether there was any departure from the usual acceptable ratios of PRBC to plasma administration.
  • Big picture questions: Most importantly, why would you think that poor outcomes, which are the focus of this paper, are related to plasma administration? Why haven’t we noticed this correlation before? And how does daily TEG testing help you identify and/or avoid this? What questions raised here are you going to pursue?

Reference: EAST 2018 Podium paper #1.

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Abstracts

The EAST Annual Meeting Is Coming!

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The EAST Annual Scientific Assembly is just around the corner. The meeting takes place January 9-13 at Disney World in Orlando. As in previous years, I am going to select some of the more interesting (to me) podium abstracts and analyze them, one per day until the meeting. I will pick them apart, provide some clinical perspective, and most importantly, provide a bullet list of questions the presenter may hear at the podium. Hint, hint.

On Christmas day, I’ll publish the list of abstracts that I’ll be reviewing. Then daily, until the meeting is over, I’ll tease one apart for you. Stay tuned!

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Abstracts, Critical care

EAST 2017 #4: A More Restrictive Transfusion Trigger?

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For many years, patients were automatically given not one, but two units of blood anytime they got “anemic” while in the hospital. And anemia was defined as a hemoglobin (Hgb) value < 10. Wow! Then we recognized that blood was a dangerous drug, with many potential complications.

We’ve come a long way, with our transfusion trigger slowly dropping and giving just one unit of blood at a time when needed. Many trauma centers use a transfusion trigger Hgb of 7 in younger, healthier patients. The question is, how low can you (safely) go?

The trauma program at Wake Forest University analyzed their data, and found that there was no “physiologic advantage” to transfusions in patients with Hgb of 6.5 to 7. Therefore, they lowered their transfusion trigger from 7 to 6.5 and retrospectively studied the results for the six months before and six months after the switch. Patients with hemorrhage, anticipated surgical procedures, or unreconstructed coronary artery disease were excluded.

Here are the factoids:

  • Of 852 patients admitted to the ICU, 131 met criteria and had a Hgb < 7
  • 72 patients were transfused with a trigger of 7, and 59 with a trigger of 6.5
  • There was no difference in ventilator, ICU, or hospital days, or mortality
  • The transfusion rate dropped by 27%, saving 72 units of blood

Bottom line: We continue to determine how low we can go with this. In healthy patients, the magic number is probably even lower. But we are increasingly seeing older, less healthy trauma patients. The next step is to start looking at subsets to determine what is safe for each group.

Questions and comments for the authors/presenter

  • Tell us the nature of the “preliminary work” that led to this paper. Was it animal data, or some kind of analysis of your patient data?
  • Since coronary artery disease was an exclusion criterion, how did you know a patient had it? By history alone?
  • Please show an age histogram of all units given at each threshold. This will let us see if there is any age bias present.
  • How low did the Hgb actually get in both groups? A histogram would be nice on this one, too.
  • Do you have any recommendations regarding selection based on age, frailty, or other parameters? What is your practice now?
  • Your outcome measures are somewhat crude, meaning that one would not really expect much of a change in those variables due to an extra unit or two of blood. What about adverse reactions that necessitated a fever workup or other intervention? Any differences between the groups there?

Click here to go the the EAST 2017 page to see comments on other abstracts.

Related posts:

Reference:   Effects of a more restrictive transfusion trigger in trauma patients. Poster #38, EAST 2017.

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Abstracts

AAST 2016 Is Coming Soon!

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The 75th annual meeting of the American Association for the Surgery of Trauma (AAST) is just around the corner. It’s being held on the big island of Hawaii, which pretty much guarantees a large turnout. Hard to resist a little vacation time tacked on to the meeting!

Starting tomorrow, there are 17 weekdays left until the end of the meeting. This year, there are a lot of interesting abstracts, and I’ll be posting info and my commentary about the best of the best (and maybe some worst of the worst?).

Here are some of the topics I’ll be covering:

  • Which is better for pulmonary embolism prevention: Unfractionated vs low molecular weight heparin?
  • The cardiac “box”
  • Which ICU is better for neurotrauma patients: neuro-ICU, trauma-ICU, or med/surg-ICU?
  • A scoring system for identifying appropriate patients for air transport
  • The Cribari Matrix and over/undertriage
  • Preperitoneal pelvic packing
  • Are graduating surgery residents qualified to take trauma call?
  • VTE prophylaxis in children
  • and about 9 more!!

Stay tuned starting tomorrow!

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