Larger plasma volumes increase transfusion thrombosis risk




SAN FRANCISCO – Venous thromboembolism is about 50% more likely when trauma patients are transfused with more than 1 unit of fresh frozen plasma for every 2 units of red blood cells, according to a retrospective review of 139,842 adult patients in the National Trauma Data Bank, all of whom received at least 1 unit of red blood cells from 2007 to 2012.

The risk quadrupled when patients received 6 or more red blood cell (RBC) units; for those patients, the only independent risk factor for venous thromboembolism (VTE) was transfusion with more than 1 unit of fresh frozen plasma (FFP) per 2 units of RBCs (odds ratio, 4.12; P = .011).

Dr. Gregory Magee

Dr. Gregory Magee

When patients get that much plasma, they “should be monitored closely for deep vein thrombosis [DVT] and pulmonary embolism [PE], and started on VTE prophylaxis as soon as possible,” said lead investigator Dr. Gregory Magee, a trauma and critical care fellow at the University of Southern California, Los Angeles. The findings complicate an emerging idea of how best to transfuse trauma patients. A 2013 investigation found that 6-hour survival is significantly higher when patients get more plasma with their RBCs than they might have in the past, at least 1 FFP unit for every 2 RBC units. Some research suggests that a 1:1 ratio might be even better (JAMA Surg. 2013;148:127-36). “You need to do what you need to do to help your patients survive,” but there should be a “balancing act to make sure they have enough clotting factors [onboard] to stop the bleeding, but not enough to cause thrombosis,” Dr. Magee said at the annual clinical congress of the American College of Surgeons.

The rate of transfusion-associated PEs in his study was 0.4%, and the rate of DVTs 0.8%. How serious they were is not known; the information was unavailable in the database review. Though low, the incidence of thrombosis increased with increasing volumes of transfused RBCs.

In addition to the 50% increased risk of VTE with higher volumes of transfused plasma (OR 1.47, P < .001), VTE was independently associated with transfusions of 6 or more RBC units (OR 2.10, P = .001); blunt trauma (OR 1.49, P = .001); male gender (OR 1.29, P < .001); and Abbreviated Injury Scale (AIS) scores of 3 or higher for chest injuries (OR 1.30, P < .001), head injuries (OR 1.18, P = .032), and lower extremity injuries (OR 1.16, P = .034).

Several of Dr. Magee’s colleagues are coinvestigators on a recently concluded randomized transfusion trial that pitted plasma, platelet, and RBC ratios of 1:1:1 and 1:1:2 against each other, looking for survival and complication differences. They hope to publish their results soon, he said. The randomized study was the only way to counter the survival bias that might have been at work in the 2013 investigation, which was a prospective cohort study. Higher volumes of plasma might have improved survival, but it’s possible that patients who lived longer were more likely to get FFP, since it’s often administered well after RBC transfusions are underway.

For now, “we don’t know which one is best or if it makes a difference,” Dr. Magee said.

Dr. Magee had no disclosures. The work was funded in part by the National Institutes of Health.

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