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