Blood Bank Chapter 16
16.3 When should the posttransfusion count be done?
1 hour after the end of the transfusion additional can be ordered at 24 hours
16.1 How do we collect platelets?
1 unit from 1 person via apheresis or pool 6 units worth to make 1 dose of platelets
16.7 Explain the platelet crossmatch
12 - 18 ABO identical platelet units are screened. Combine with patient plasma. Stir, incubate, coverslip. Antibodies = clumps/agglutinate = do not use
16.3 What is the threshold for indicating platelet refectoriness?
CCI below 7,500 at 1 hour indicates platelet refractoriness
16.8 Define immune/idiopathic thrombocytopenia purpura
Cappillary is broken. Blood seeps out under the skin but there's not enough platelets to plug the hole so it keeps bleeding and results in purplish spots
16.3 Calculate platelet refractoriness using the corrected count increment
body surface area time the difference of the post minus pre transfusion platelet count over the number of platelets transfused
16.3 What is the CCI and what does it tell us?
corrected count increment; To determine if the platelet transfusion was therapeutic
16.5 Explain the process of alloimmunization that leads to platelet refractoriness
the more platelets somebody gets, the greater their chance of becoming immune
16.1 Define the term "platelet refractoriness"
unresponsive to platelet transfusion exists in about 20% of patients that are chronically transfused
•After the first couple months of life, will the newborn's condition get better or worse?
Better its no longer being exposed to antibodies from the placenta
16.2 Immune causes of thrombocytopenia
antibody is involved that is destroying the platelets, allo or auto
16.6 Describe how platelets are selected for those that are refractory for platelets
HLA type specific platelet units that lack the antigens for which the patient has an antibody can be used for transfusion
16.7 When do you order a platelet crossmatch
If the HLA and HPA antibodies have not been identified and the patient's HLA type is unknown
16.3 When should the pretransfusion count be done?
Immediately prior to the transfusion so it will be more accurate
16.4 Describe immune mediated platelet refractoriness
Mostly alloantibodies directed to either against human platelet antigens and human leukocyte antigens (HPAs and HLAs)
16.2 Identify two main causes of platelet refractoriness
Nonimmune and Immune
16.5 How has the incidence of alloimmunization to HLA antigens decreased?
Now nearly everyone leukoreduces the blood units
16.1 What population of people may exhibit platelet refractoriness?
People who have transfusions on a regular basis. ie. chemotherapy patients who dont make many on their own but receive platelets a lot
16.2 Nonimmune causes of thrombocytopenia
Sequestration - platelets are gathered up & stored in the spleen Consumption - platelets are used up quickly (DIC) Prothrombotic - heparin induced
16.5 What occurs in persons that are type O but are mismatched and receive type A or B platelets?
a transient platelet refractoriness
16.9 Describe the types of thrombocytopenia purpura
idiopathic, drug induced, post transfusion, Neonatal Alloimmune