Flashcards in Transfusion Medicine Deck (19)
What are the major concerns of blood donor recruitment?
Donation is only done by donation, not for pay. Volunteers are screened by interviews, ROS, analysis for high risk behavior, and asked to call if they develop any symptoms of infection. They are given a brief physical exam and a platelet count. Skin prep and phlebotomy technique are also concerns.
What are some conditions that are routinely screened for?
Syphilis, Hepatitis A, B, & C, HIV, West Nile Virus (WNV), CJD, EBV
What determines blood groups?
The Polysaccharides expressed on the surface of each cell. Only fucose = Type O (universal donor). Fucose & galactosamine = Type A. Fucose & D-galactose = Type B. AB blood has both galactosamine and D-galactose on it's surface.
What antibodies are present in the serum of people with different blood types?
By year 1, individuals develop antibodies to the antigens they don't express. Type O = A and B antibodies, Type A = B antibodies, Type B = A antibodies, Type AB = no antibodies (universal acceptor).
What are the Rh antigens?
C/c, D/-, and E/e. Two genes are responsible for our Rh blood group: RHD and RHCE. Only D is routinely tested for resulting in Rh(+) (means D is present, 85% caucasian pop), or Rh(-) (means D is absent, 15% caucasian pop).
Why are antibody screens done on donor and recipient blood if they are the same blood type?
Antibody screens look for antibodies to antigens on RBCs other than the ABO antigens.
What is a major crossmatch test?
Recipient's serum and donor's cells are combined to monitor for agglutination. Coombs reagent (anti-antibody) may also be used in the test.
What are alternatives to crossmatch testing in an emergent or "time stressed" situation?
O negative blood may be used in an emergent situation. Males and non-child bearing females may accept O positive. A time stressed situation may allow blood matched to the recipient (ABO, Rh types) to be administered while crossmatch is being conducted. 1:17,000 risk of an adverse event occurring.
If the antibody screen is positive, what are the classifications of the Ab and how do transfusions proceed with each?
Ab are classified as either alloantibodies or autoantibodies. Alloantibodies require antigen free blood determined by major crossmatch testing. Autoantibodies require using the "least incompatible" blood transfused with "in vivo" crossmatching - give small amount of blood to patient and watch for adverse effects.
How are "warm" antibodies screened for?
Warm antibodies attach to RBCs in the warmer regions of the body. Testing is strong for IgG, may show some weak signs of complement activation. Highest concentration at body temp, not specific to antigens ('panagglutinin'). Leads to extravascular hemolysis (Ig bound RBCs are attacked by macrophages in the spleen). Treated by immunemodulation or suppression.
How are "cold" antibodies screened for?
"Cold" antibodies (typically IgM) bind RBC antigens in the colder regions of the body (toes, e.g.) but fall off as they return to warmer regions. Testing is strong for complement activation (IgM) but no antibody is ever found, max test results at 4 c specific for I/i antigen. Complement activation triggers C5-9 lytic phases, leads to mostly intravascular hemolysis. Blocking spleen does not help, only immunosuppressive therapy or plasma exchange.
What is the Donath Landsteiner Scheme?
A workup for another cold antibody, this time an IgG that binds like an IgM in the cold regions, specific for P antigen. Leads to intravascular hemolysis (complement activation). Treat with supportive care, warm patient, will resolve with infection.
What can 500ml of whole blood be processed into?
I unit of whole blood or packed RBC (PRBC), Fresh Frozen Plasma (FFP), and 1 aliquot Platelets
How long does whole blood last? PRBC? FFP?
Whole blood: 35 days. PRBC: 35-42 days depending on preservatives. FFP: Up to 1 year at -18 deg C.
How long does cryoprecipitate last? Whole blood platelets? Apheresis platelets?
Cryoprecipitate: Up to 1 year at -18deg C. Whole blood platelets: 5 days. Apheresis platelets: 5 days (apheresis machine produces many more units of platelets per donor - from .2 units from whole blood to 10 units apheresis).
What is whole blood used for? PRBCs?
Whole blood is used for massive transfusions, patient needs O2 carrying capacity and volume. PRBCs are used when the patient needs O2 capacity, such as very low HCT levels/chronic anemia.
What is FFP used for? Cryoprecipitate?
Fresh Frozen Plasma is used in cases of coagulant deficiencies. Cryoprecipitate is used for low fibrinogen conditions.
What are platelets used for? Granulocytes?
Platelet transfusions are used in situations involving bleeding or platelet dysfunction. Granulocyte transfusions are used in patients with severe infections and neutrophil counts <500 unresponsive to other treatments.