Going from A to B : the safety of incompatible group A plasma for emergency release in trauma and massive transfusion patients

L ike the Halloween nor’easter of 1991, AB plasma is currently facing a perfect storm of competing forces that is exacerbating the availability of an already limited resource. One force is AABB Standard 5.4.1.2, which becomes effective for all plasma and whole blood collected after April 1, 2014. Although TRALI reduction strategies have already been widely implemented for group A, B, and O donors for several years, they have generally not been applied to group AB donors due to concerns of AB plasma availability. The riskbenefit of exempting AB donors was recently reassessed in the face of epidemiology studies examining the efficacy of TRALI reduction strategies. In general, TRALI cases and TRALI fatalities have decreased dramatically over the past several years for most products with the striking exception of AB plasma. In a recent 4-year retrospective study of TRALI cases reported to the American Red Cross, the odds of TRALI with AB plasma were 14.5-fold higher than that of plasma from other blood types (26.3 vs. 1.8 cases per million units). The application of Standard 5.4.1.2 to AB donors is projected to decrease AB plasma availability by 27% to 33%, with AB donors making up only 2.6% of active donors. The second storm battering the AB plasma supply is the widespread adoption of massive transfusion protocols (MTPs), which advocate early and aggressive plasma resuscitation. In an informal poll of recent AABB annual meeting attendees, 93% had MTPs with fixed plasma:RBC ratios. Moreover, 73% maintain a thawed plasma inventory with most hospitals providing only AB plasma to patients without a current or historical ABO type. Because many trauma patients require transfer to large regional trauma centers, these patients are more likely to initially receive AB plasma due to the absence of a historical ABO type on file at the receiving facility. The direct consequence is overutilization of AB plasma since most patients will be group A, O, or B. In addition, the use of fixed plasma:RBC ratios often leads to plasma overtransfusion. In one study, 86% of transfused trauma patients did not meet the definition of massive transfusion, averaging only three RBC transfusions in the first 12 hours. Finally, the need to maintain thawed AB plasma inventories increases AB utilization and transfusion to non-AB patients, as unused plasma is diverted to other patients to prevent wastage. An analysis at Dartmouth determined that maintenance of a thawed, 2-unit AB plasma inventory would increase yearly AB utilization by at least 25%. This estimate closely mirrors the overall increase in AB plasma use nationwide, which has risen 27% since 2006. Several suggestions have been offered to minimize the impact of Standard 5.4.1.2 on AB plasma supplies. Among the most controversial proposals is the initial use of prethawed group A plasma for emergency release in trauma and other MTP patients. Proponents of the practice argue that most patients will be compatible with group A plasma, based on the known distribution of ABO types in the population. Moreover, anti-B titers are relatively low in most group A donors, especially male-only donors who should lack immune-stimulated anti-B. Secretors may have additional protection from hemolysis due to the presence of B substance capable of adsorbing anti-B from transfused plasma. As evidence, they point to the rarity of hemolytic transfusion reactions due to incompatible group A PLT transfusions. Finally, patients requiring an emergent MTP “pack” are also receiving several units of group O RBCs, which further decreases the risk of hemolysis. In this issue, Chhibber and colleagues describe their 5-year experience using prethawed group A plasma for emergency release at the University of Massachusets. To monitor the safety of the policy, patients receiving incompatible plasma were prospectively monitored for clinical and laboratory signs of hemolysis. Between 2008 and 2013, a total of 358 patients required emergency release, group A plasma, representing less than 1% of their emergency room admissions (135,000 per year). As expected, most patients (84%) were group A or group O and therefore ABO compatible with group A plasma. Group A plasma was dispensed to 54 group B and AB patients; however, only 23 (6%) patients actually received group A–incompatible plasma. Most patients received less than 4 units of plasma including 10 patients who required plasma for warfarin reversal with little or no group O RBC support. Nearly half of patients (11/23, 48%) also received group O RBCs, with nine of 11 receiving at least 4 units. Only three patients, however, approached the definition of massive transfusion, receiving between 8 and 12 units of group O RBCs. There was no overt evidence of acute hemolytic transfusion reactions although three patients had weak positive posttransfusion DATs. © 2014 AABB