Chapter 107. Transfusion Biology and Therapy (Part 4)

Apheresis technology is used for the collection of multiple units of platelets from a single donor. These single-donor apheresis platelets (SDAP) contain the equivalent of at least six units of RD platelets and have fewer contaminating leukocytes than pooled RD platelets.Plasma may also be collected by apheresis. Plasma derivatives such as albumin, intravenous immunoglobulin, antithrombin, and coagulation factor concentrates are prepared from pooled plasma from many donors and are treated to eliminate infectious agents.Whole BloodWhole blood provides both oxygen-carrying capacity and volume expansion. ...
Nội dung trích xuất từ tài liệu:
Chapter 107. Transfusion Biology and Therapy (Part 4) Chapter 107. Transfusion Biology and Therapy (Part 4) Apheresis technology is used for the collection of multiple units of plateletsfrom a single donor. These single-donor apheresis platelets (SDAP) contain theequivalent of at least six units of RD platelets and have fewer contaminatingleukocytes than pooled RD platelets. Plasma may also be collected by apheresis. Plasma derivatives such asalbumin, intravenous immunoglobulin, antithrombin, and coagulation factorconcentrates are prepared from pooled plasma from many donors and are treatedto eliminate infectious agents. Whole Blood Whole blood provides both oxygen-carrying capacity and volumeexpansion. It is the ideal component for patients who have sustained acutehemorrhage of ≥25% total blood volume loss. Whole blood is stored at 4°C tomaintain erythrocyte viability, but platelet dysfunction and degradation of somecoagulation factors occurs. In addition, 2,3-bisphosphoglycerate levels fall overtime, leading to an increase in the oxygen affinity of the hemoglobin and adecreased capacity to deliver oxygen to the tissues, a problem with all red cellstorage. Whole blood is not readily available since it is routinely processed intocomponents. Packed Red Blood Cells This product increases oxygen-carrying capacity in the anemic patient.Adequate oxygenation can be maintained with a hemoglobin content of 70 g/L inthe normovolemic patient without cardiac disease; however, comorbid factorsoften necessitate transfusion at a higher threshold. The decision to transfuse shouldbe guided by the clinical situation and not by an arbitrary laboratory value. In thecritical care setting, liberal use of transfusions to maintain near-normal levels ofhemoglobin may have unexpected negative effects on survival. In most patientsrequiring transfusion, levels of hemoglobin of 100 g/L are sufficient to keepoxygen supply from being critically low. PRBCs may be modified to prevent certain adverse reactions. Leukocytereduction of cellular blood products is increasingly common, and universalprestorage leukocyte reduction has been recommended. Prestorage filtrationappears superior to bedside filtration as smaller amounts of cytokines aregenerated in the stored product. These PRBC units contain transfused, and each unit is anticipated to increase the platelet count 5000–10,000/µL. Patients who have received multiple transfusions may bealloimmunized to many HLA- and platelet-specific antigens and have little or noincrease in their posttransfusion platelet counts. Patients who may require multipletransfusions are best served by receiving SDAP and leukocyte-reducedcomponents to lower the risk of alloimmunization. Refractoriness to platelet transfusion may be evaluated using the correctedcount increment (CCI): where BSA is body surface area measured in square meters. The plateletcount performed 1 h after the transfusion is acceptable if the CCI is 10 x 10 9/mL,and after 18–24 h an increment of 7.5 x 109/mL is expected. Patients who havesuboptimal responses are likely to have received multiple transfusions and haveantibodies directed against class I HLA antigens. Refractoriness can beinvestigated by detecting anti-HLA antibodies in the recipients serum. Patientswho are sensitized will often react with 100% of the lymphocytes used for theHLA-antibody screen, and HLA-matched SDAPs should be considered for thosepatients who require transfusion. Although ABO-identical HLA-matched SDAPsprovide the best chance for increasing the platelet count, locating these products isdifficult. Platelet cross-matching is available in some centers. Additional clinicalcauses for a low platelet CCI include fever, bleeding, splenomegaly, DIC, ormedications in the recipient.