Inhibiting GPIbα Shedding Preserves Post-Transfusion Recovery and Hemostatic Function of Platelets After Prolonged Storage.

OBJECTIVE: The platelet storage lesion accelerates platelet clearance after transfusion, but the underlying molecular mechanism remains elusive. Although inhibiting sheddase activity hampers clearance of platelets with storage lesion, the target platelet protein responsible for ectodomain shedding-induced clearance is not definitively identified. Monoclonal antibody 5G6 was developed recently to bind specifically human platelet receptor glycoprotein (GP)Ibα and inhibit its shedding but not shedding of other receptors. Here, the role of GPIbα shedding in platelet clearance after transfusion was addressed. APPROACH AND RESULTS: Both human leukoreduced apheresis-derived platelets and transgenic mouse platelets expressing human GPIbα were stored at room temperature in the presence and absence of 5G6 Fab fragment. At various time points, aliquots of stored platelets were analyzed and compared. 5G6 Fab inhibited GPIbα shedding in both platelets during storage and preserved higher level of GPIbα on the platelet surface. Compared with age-matched control platelets, 5G6 Fab-stored platelets exhibited similar levels of platelet activation, degranulation, and agonist-induced aggregation. 5G6 Fab-stored human GPIbα platelets exhibited significantly higher post-transfusion recovery and in vivo hemostatic function in recipient mice than control platelets. Consistently, 5G6 Fab-stored, 8-day-old human platelets produced similar improvement in post-transfusion recovery in immunodeficient mice and in ex vivo thrombus formation over collagen under shear flow. CONCLUSIONS: Specific inhibition of GPIbα shedding in the stored platelets improves post-transfusion platelet recovery and hemostatic function, providing clear evidence for GPIbα shedding as a cause of platelet clearance. These results suggest that specific inhibition of GPIbα shedding may be used to optimize platelet storage conditions.

Implementation of a pediatric trauma massive transfusion protocol: one institution's experience.

BACKGROUND: Massive transfusion protocols (MTPs) with fixed ratios of blood products may improve outcomes in coagulopathic adult trauma patients. However, there is a paucity of data on transfusion support protocols for pediatric trauma patients, whose mechanisms of injury may differ from those seen in adults. We hypothesized that an MTP would improve outcomes in children, through a balanced blood product resuscitation. STUDY DESIGN AND METHODS: A pediatric trauma MTP, with a fixed ratio of red blood cells (RBCs):fresh-frozen plasma (FFP):platelets:cryoprecipitate in quantities based on the patient's weight, was initiated at a pediatric hospital. Data on clinical status, resuscitation volumes, and hospital course were collected and compared to data from pre-MTP trauma patients requiring transfusion. RESULTS: Fifty-three patients were enrolled over a 15-month period and compared to 49 pre-MTP patients. Seventy-two percent of MTP patients had at least one coagulation value outside of the normal range upon emergency department (ED) arrival, and the median time to FFP transfusion decreased fourfold after MTP implementation (p<0.0001). A total of 49% of MTP patients received greater than 70 mL/kg blood products, and the 24-hour median FFP:RBC transfusion ratio was twofold higher in these patients than the pre-MTP cohort (median, 1:1.8 vs. 1:3.6; p=0.002). No improvement in mortality was observed after MTP implementation, taking into consideration injury severity, prothrombin time, and partial thromboplastin time. CONCLUSIONS: A pediatric trauma MTP is feasible and allows for rapid provision of balanced blood products for transfusion to coagulopathic children. Larger studies are warranted to determine whether such protocols will improve outcomes for pediatric trauma patients.

Transfusion management of sickle cell patients during bone marrow transplantation with matched sibling donor.

BACKGROUND: Sickle cell disease (SCD) patients have unique transfusion considerations during bone marrow transplantation (BMT), including prophylaxis against stroke and alloimmunization. Characterization of transfusion requirements is important for blood bank and clinician patient management. STUDY DESIGN AND METHODS: A retrospective analysis of red blood cell (RBC) and platelet (PLT) transfusion of SCD patients during myeloablative matched sibling donor (MSD) BMT at one institution from 1993 to 2007 was performed. Patient characteristics (RBC blood group antibodies, ABO-incompatible donor, BMT-related morbidity) and transfusion practices (RBC phenotype matching, transfusion threshold, and blood age) were assessed for effect on total RBC transfusion volumes. RESULTS: Twenty-seven patients received MSD BMT with 96% survival and 0% rejection. Six alloimmunized patients received RBCs with extended phenotype matching (C, c, E, e, K, Fy(a), Jk(b)), 14 nonalloimmunized received limited matching (C, c, E, e, K), and 7 did not have phenotype matching. Among 26 survivors, a median seven RBC transfusions (range, 3-15) and 13.5 PLT transfusions (range, 4-48) per patient were administered, equivalent to 64 mL/kg RBCs (range, 22-122 mL/kg) and 106 mL/kg PLTs (range, 26-343 mL/kg). BMT-related morbidity predicted increased RBC transfusions (p = 0.006). Venoocclusive disease was associated with greater RBC (p = 0.016) and PLT transfusion volumes (p = 0.016). Greater phenotype matching was associated with decreased RBC transfusions (p = 0.0247). CONCLUSIONS: SCD patients have high transfusion support during MSD BMT. Communication of BMT complications to the blood bank is essential for transfusion inventory management. Phenotype matching decreased RBC transfusions in this cohort and warrants further investigation in SCD transfusion therapy.