Platelets Flashcards
how is whole blood processed
centrifuged as hard spin separating red cells and plasma
500 ml is collected and 40 is diverted to reduce risk of contamination, it is used for testing
How many buffy coats are pooled together
7 from the same ABO group
and leukoreduced
What is pooled platelets psoralen treated concentrate?
-platelet concentrate made by separating the buffy coat from 480 ml of whole blood in 70 ml of CPD
-7 ABO matched platelet concentrates are pooled with 280 mL of platelet additive solution (PAS-E)
-LR by filtration
-pathogen reduced with Cerus INTERCEPT which includes the addition of synthetic psoralen and using UVA light
-residual amotosalen and free photoproducts are removed with adsorption
-double dose unit is split into two single units
-pooled platelet component is labelled as Rh negative only when all donors are RH negative
What is the difference between new method of buffy coat separation and old
- smaller volume
-higher concentration
-Less plasma so that reduces febrile and allergic reactions
-no DEHP so safer plastic
-units dont need to be irradiated
What is apheresis platelets
-obtain therpeutic dose from one donor
-labelled as Single donor platelets
-Platelets are class I HLA
-rare to have identical HLA-A and B from unrelated ppl
-match doesnt have to be exact but enough so that you can overcome the refractory state (from relative )
-platelets can demonstrate platelet AG which can give a reaction from patient receiving the donation
-if patient has Platelet AB they need HPA matched units
What is an apheresis platelet unit consist of
- 19 ml ACD-A in automated technique that includes LR and PAS-E addition
-contains residual red blood cells
-only indication for apheresis platelets is to collect matched platelets for pts with Anti-HLA or Anti HPA
What the sample tested for
-ABO group, Rh and AB
-titers for Anti A and Anti B are tested , we always want the low titre
-ABO and Rh are on the label
-before blood components are provided for transfusion they must be non reactive for
1)Antibodies to HIV-1 and HIV-2, HCV, Human Tcell lymphotropic virus, type I and II, HBcore
2) HBsAg
3) Presence of viral RNA HIV-1 and HCV
4) Presence of viral DNA of HBV
5) Syphilis
How are platelets stored
-20-24C with continuous gentle agitation
-if the agitation stops during transport for 24 hours thats okay
-Shelf life is 7 days
-must be gas exchange during storage to support platelet metabolism
-does not need to be irradiated if it is already PSA treated but for apheresis collection they will need to be irradiated
What is most associated with bacterial sepsis
Blood product because the platelets are pooled
What do platelets do for us
maintain vacular integrity
-initiate platelet plug formation
-stabilize the plug with fibrin formation
-normal platelet function and numbers are needed for hemostasis
What is the role of transfused platelets
- participate in primary hemostasis by providing normal platelets
-helps to prevent or treat bleeding due to platelet def or dysfunction
-treating pts with bleeding and low platelet counts is secondary to dilutional thrombocytopenia
-transfusion of platelet is noted for pts with platelet destructive conditions or functionally abnormal platelets before a procedure
What type of patients are indicated for transfusions
- post op bleeding
-ppl on chemo
-ppl with alloimmune regractoriness HLA/HPA matched apheresis (when people dont take platelets well, they have an AB that destroys plts )
-if platelets are being destroyed because of DIC, ITP, hypersplenism etc then HLA or HPA matched apheresis platelets arent any more effective then unmatched
What are prophylactic platelet transfusions be used for
- very low platelet counts secondary to decreased production
How long do transfused platelets circulate
3-4 days , support is needed
-espcially ppl on chemo
-assessing plalet transfusion is needed to determine if pateint is refractory or unresponsive to transfusions
-Immune = HLA antibodies, platelet antibodies, and autoantibodies
-Nonimmune = Splenomegaly, medications, sepsis, active bleeding, DIC and even fever
When should you not use platelet componenets
- if bleeding is not related to decreased numbers of abnormally functional platelets
-not recommended for pts with platelet destruction like in ITP, TTP, HIT unless the pt is hemorrhaging
-if patient has Anti IgA then they need to receive IgA deficient platelets (washed)
When is pool platelets Psoralen Treated not used
-pts with history of hypersensitivity to amotosalen or other psoralen
-neonates being treated with phototherapy due to potential erythema caused by a reaction between UV light and amotosalen
What are warnings to using Pooled Platelets Psoralen Treated
-suspended in 40% and 60% PASE
-Plasma is from 7 donors in pooled platelet concentrate
-too many transfusions of PASE can lead to overdose of K and MG - must monitor electrolytes
What is an uncommon complication of plasma ABO incompatibility with platelet transfusion
Hemolysis
-RH pos platelets to Rh Neg ppts can cause sensitization - given RHOGAM
-donor selection does not eliminate hazard of transmitting diseases
Transfusion lab
Requirements
Group and Screen
Ideally ABO and Rh Identical
Should be Compatible
If platelets are in short supply,
Lab will follow their policy for
ABO blood group substitution
What is PTP
Post Transfusion Purpura
-complication of platelet transfusion
-thrombocytopenia due to anamnestic production of platelet alloantibody
-AB produced from exposure to HPA
-occurs in multiparous women
-time between transfusion and thrombocytopenia is 7-14 days
-AB found is Anti-HPA-1A
-PTP = platelet antibody destruction of platelets after transfusion
How do platelet elicit an immune response
-with inherited membrane proteins
-platelet AB are not found as often because it has less AG variability
–most common AB is directed against HPA AG
What is FNAIT
Fetal and Neonatal Alloimmune Thrombocytopenia
-AB to platelet AG
-due to previous pregnancies maternal allo AB are produced against AB inherited from the father and cause destruction of fetal platelets - IgG AB
-cause megakaryocyte suppression and leads to thrombocytopenia in the fetus and increased risk of bleeding.
-must find HPA-Ia negative platelets (antigen negative platelets) for transfusion
how do you know how many LR units you give
- depends on patients situation
-response to platelet transfusions is assessed by observing whether the bleeding stops and by measuring post trans platelet counts
-EACH DOSE increases pt platelet by 15-25x 10^9L
-must be transfused in 4 hours
What is a modification for Apheresis platelets
Irradiation - gamma radiate the cells
-for immunocomped that get components from closely matched HLA or related/directed donors
-prevents GVHD risk
do not do for psa e treated ones
