SBB test preparation Exam - Clinical Immunohematology and Transfusion (questions and answers)
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Course
SBB
Institution
SBB
SBB test preparation Exam - Clinical
Immunohematology and Transfusion
(questions and answers)
degree of matching for HLA-matched platelets - CORRECT ANSWER-Match Grade A:
All four antigens identical
Match Grade B1U: Only three antigens detected in donor, all present in recipient
Match Grad...
SBB test preparation Exam - Clinical
Immunohematology and Transfusion
(questions and answers)
degree of matching for HLA-matched platelets - CORRECT ANSWER-Match Grade A:
All four antigens identical
Match Grade B1U: Only three antigens detected in donor, all present in recipient
Match Grade B2U: Only two antigens detected in donor, both present in recipient
Match Grade B1X: Three donor antigens identical to recipient, fourth antigen
crossreactive with recipient
Match Grade B2X: Two donor antigens identical to recipient, third & fourth antigen
cross-reactive with recipient
Match Grade C: One antigen of donor not present in recipient & not cross-reactive with
recipient
**Best Transfusion Response with Grade A; Next Best
With B1U & B2U; Then B1X, B2X. C-Grade Least Preferred
Overall Failure Rate With HLA-Matched Platelets: 40-50%
Product Considerations HLA-Matched Platelets - CORRECT ANSWER-Patient May
Need Irradiated, CMV-Negative, and/or
Leukocyte-Reduced Platelets Making It Difficult to Find
Suitable Donors
Some HLA Antigens Are Not Fully Expressed on Platelets
HLA-A2 Positive Donors Should Be Avoided for HLA-A2-
Negative Recipients Because Anti-HLA-A2 Antibody Is
Commonly Produced
ABO/Rh Compatibility May Have to be Sacrificed to
Provide Better HLA-Matched Platelets
Donor Could Be Selected Based on Response to Prior
Transfusion of Platelets from the Donor
Family Members, Especially Siblings May be Completely
Matched for HLA Antigens and Could Serve As Platelet
Donors
Massive Transfusion - CORRECT ANSWER-Greater than 10 units of blood
, Replacement of one blood volume in 24 hours
Replacement of >30% blood volume in 3 hours
or less
Complications when >2 times blood volume
Comorbid factors lower the threshold
Dilutional Coagulopathy - CORRECT ANSWER-One blood volume transfusion dilutes
plasma &
platelets by 65%
93% of patients have abnormal coagulation studies
Increased microvascular bleeding when platelet
count <50,000/ul or fibrinogen <50 mg/dl
Prophylactic transfusions (platelet & FFP) based
on fixed volume of RBC transfused is
unnecessary
Periodic monitoring of platelet count, PT, PTT
and fibrinogen recommended during massive
transfusion
Citrate Toxicity - CORRECT ANSWER-Sodium Citrate for all blood component
Packed RBC: 54-181 mg/dl
Fresh Frozen Plasma: 384-436 mg/dl
Citrate binds divalent cations including
calcium & magnesium
Citrate is rapidly metabolized by liver
Metabolic alkalosis due accumulation of
metabolic by-product bicarbonate
Mild citrate symptoms are seen in donors during
apheresis procedures
Citrate Toxicity Hyocalcemia - CORRECT ANSWER-Prolongation of QT interval
Depressed left ventricular function
Increased neuomuscular excitability
In liver transplants: During ahepatic phase, decreased left ventricular function &
hypotension may be seen
Hypomagnesemia can cause "torsades des pointes" (Malignant form of cardiac
arrhythmia)
Treat hypocalcemia when ionized Ca level
falls below 50% of its normal value &
with symptoms
Disturbance in Acid-Base Balance - CORRECT ANSWER-Stored blood is acidic due to
citrate anticoagulant
Stored blood also contains lactic acid
Post-transfusion acidemia is rare
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