Glossary

Massive Transfusion

Defined loosely as the rapid administration of a volume of red blood cells roughly equivalent to a “normal” person’s RBC volume. The most common definition is the receipt of 10 units of RBCs within 24 hours, but alternative definitions include: 4 to 5 RBC transfusions within 1 hour, replacement of one-half the patient’s blood volume within 3 hours, or bleeding at a rate of greater than 150 ml/min. The problems with massive transfusion are many, and include more than just whatever issue caused the large-scale hemorrhage leading to a massive transfusion! The list includes coagulation abnormalities, electrolyte imbalances (including calcium and potassium problems, especially), and hypothermia, to name a few.

Problems with coagulation secondary to massive transfusion have been studied extensively, with formula-driven “massive transfusion protocols” (specifying ratios of units of red cells to plasma and sometimes platelets) under evaluation. Currently, standard U.S. practice includes the target of a red cell to plasma often expanded to “1:1:1” (with a single unit of whole blood-derived platelets as the last “1”; since few places use whole blood platelets, that means 1 apheresis platelet for every 6 RBCs and 6 plasmas, more like “6:6:1”). A major study of this issue published in 2015 called “PROPPR” (JAMA 2015;313(5):471-482) failed to show a substantial difference in mortality at 24 hours between patients receiving a 1:1:1 vs. those receiving more RBCs at a 2:1:1 ratio (that interpretation is not without controversy), but the study did show a decrease in acute hemorrhagic deaths.

Editorial comment: I totally agree that massive transfusion protocols are essential, because they help everyone both in the transfusion service and in the ED and OR understand exactly what to expect and what products to give. However, I am NOT sure that a strict 1:1 red cell to plasma transfusion ratio is mandatory! People sometimes get very compulsive about the ratios, but I think that the data we have so far suggests that as long as you are reasonably close, the outcomes are likely to be similar to what you would expect with a strict 1:1 protocol. Further, I think that the recent reintroduction of low-titer group O whole blood (LTOWB) has potential to significantly impact trauma resuscitation in the near future (see my discussions in episodes 040CE and 073 of the Blood Bank Guy Essentials Podcast for more on LTOWB).

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