Transfusion of blood components containing ABO-incompatible plasma does not lead to higher mortality in civilian trauma patients

Seheult JN, Dunbar NM, Hess JR, et al. (on behalf of the Biomedical Excellence for Safer Transfusion [BEST] collaborative) Transfusion. 2020;1–12.

Reviewed by Mary Berg, MD

The authors conducted a retrospective study, gathering information from nine level I trauma centers regarding trauma patients who required emergency transfusion.  They separated them into categories, depending on whether or not they received incompatible plasma.  The trauma centers provided information regarding the nature of the trauma (blunt force versus penetrating), amount of blood & components infused, patient demographics, and patient outcomes.  The amount of plasma infused per product was standardized, with the following values assigned: 40 mLs per RBC unit, 342 mLs per whole blood unit, 234 mLs per plasma unit, 68 mLs per whole blood derived platelet, 239 mLs per apheresis platelet, and 23 mLs per cryoprecipitate unit.  For example, if a non-group O patient received a unit of low-titer O whole blood (LTOWB), they were listed as receiving 342 mLs of incompatible plasma; if a group B patient received a unit of A liquid plasma and an O RBC unit, they would be recorded as having received 234 + 40 = 274 mLs of incompatible plasma.  Most patients who received incompatible plasma also received compatible plasma.   The median amount of incompatible plasma infused was 342 mLs.  Comparisons were made between the patients who only received compatible plasma and those who received incompatible plasma; the incompatible plasma was further divided into those who got less than or equal to 342 mLs and those who got more than 342 mLs.

The statistical analysis showed that the patients who received only compatible plasma had similar demographics to the patients who received incompatible plasma.  There was no statistical significance in their injury severity scores or in their mortality at 6 hours, 24 hours, or 30 days.  As would be expected, group O patients were only represented in the compatible plasma transfusion patients so there was a difference in ABO types between the two categories of patients.

When comparing the compatible plasma patients only to those who received more than 342 mLs of incompatible plasma, differences were seen in that the >342 mL incompatible plasma group received more transfusions overall (e.g. 71% received platelets, compared to 53.5% of compatible plasma patients who received platelets). For the >342 mL incompatible patients, 36.1% received > 10 RBC and/or LTOWB units in 24 hours and had higher injury severity scores, compared to 19.5% of the compatible plasma patients who also had lower injury severity scores.  With that background, it might not be surprising that mortality in the >342 mL incompatible plasma patients was higher than that of the compatible plasma patients (7.5% versus 4.5% at 6 hours, 14.2% versus 9.0 % at 24 hours, and 28.0% versus 19.6% at 30 days).  No comparison was made between the patients who received >342 mLs of only compatible plasma and those who received > 342 mLs of incompatible plasma.

The authors point out several reasons as to why patients who received higher amounts of incompatible plasma might have done worse than those received only compatible plasma.  It might have been that patients received more incompatible plasma because they received more plasma overall, due to higher injury severity scores.  Laboratory parameters were not included with the patient data, so coagulopathy or degree of anemia could not be assessed, but might have played a role.  Bearing in mind that data was collected from nine sites, differences in practices might have affected how patients were transfused & thus how much incompatible plasma they received.  As an example, only three sites reported giving LTOWB, with one site giving it to 3 patients and another site giving it to 172 patients.  Differences such as this could have contributed to the amount of incompatible plasma given especially if, for example, LTOWB was only given to the most severely injured patients.

The authors emphasized that no difference in mortality was noted between the compatible and incompatible plasma patients when all patients where considered.  They also emphasized the need for additional studies to investigate whether giving higher volumes of incompatible plasma might be clinically significant.

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