Blood Transfusions Flashcards
What does the donor screening involve?
- extensive questionnaire
2. multiple criteria for deferral
What are the 3 main serum tests for infectious agents when donating blood?
HIV, HCV, HBV
What are packed red blood cells (prbc)?
when one separates red cells from plasma and platelets
How much prbc are in each unit?
250ml, 1 unit will increase Hgb 1g/dL
How long can one store blood?
42 days
What is leukoreduced prbc?
when you remove leukocytes from rbcs
What kinds of Ags are on a RBC surface?
- proteins
2. complex carbs on lipids or proteins
What is the basic O antigen made up off?
Spingosine connected to 5 sugars (GalNac, Gal,GalNac, Glu, Fucose)
What is the role of ABO glycosyltransferase?
attach a 6th sugar to the O antigen
Which blood groups have the enzyme and what does it do for the blood group?
- A alleles - adds GalNac to O Ag
- B alleles - adds Gal to O Ag
- O alleles - enzymes is inactive
Type A blood makes what Abs?
Abs to B Ag
What subclass of Igs are the Abs against blood groups?
IgM
What can happen is a recipient is transfused with ABO-incompatible red cells?
- lyse them all very quickly
- acute hemolytic transfusion rxns
- can be fatal
What blood groups can donate to O recipient?
O donors
Who can donate to A blood types?
O and A
Who can donate to B blood types?
O and B
Who can donate to AB blood types?
All blood types
What is antigenicity?
a measure of how likely it is that a potential Ab binding site wil actually induce an Ab response
What are the RBC Ags encoded by?
genes that show substantial allelic variation
What is the most antigenic protein on the red cell surface?
RhD – over 80% of D- individuals transfused with D+ red cells develop Abs
What is the most common RhD?
a complete deletion of the coding sequence
Why is RHD protein significant in obstetrics?
- RhD (-) mother having a RhD (+) baby can cause complications for future pregnancies because mother makes Rh-Ab that can cross the placenta.
How do you treat the problem with RhD-Abs in pregnancy?
give mother RhoGam – basically an immunization
Who do you never give D+ red cells if they are D-?
girls and women of childbearing age
What are minor red cell Ags?
currently over 350 known Ag-Ab combinations exist due to minor red cell Ags (i.e. RhCE)
What should the blood bank do for minor red cell Ags?
screen recipients for ANY Abs to these Ags before any transfusion and identify
What are the steps of compatibility testing?
- provide current blood speciment for a type and screen
- Crossmatch is performed - mix donor cells w/ patient plasma and look for agglutination
- if Ab screen is negative give blood
- in emergency use O negative blood
When should one give blood speicmen to blood bank for surgery?
at least day before surgery but no more than 3 days before the surgery
What is the objective of red cell transfusion?
to increase the patient’s O2 carrying capacit
What is measured for the O2 carrying capacity?
Hgb mainly but sometimes can look at Hct
When should you give a red cell transfusion?
- when patient is symptomatic and anemic (increased HR, RR, confusion, weakness, dizziness)
- Acute blood loss, rapid volume expansion
- During or following an MI
- Hgb trendline
When shouldn’t you give a red cell transfusion?
- patient is old and frail
- asympotmatic coronary artery disease
- expand blood volume
- promote wound healing
Is anemia a diagnosis?
no – need to determine why patient has anemia
When will you need to give a rationale for transfusion at the VA?
if lab indications are questionable (such as Hgb > 8.0
What is the average blood volume?
5 L
How much are 2 units of prbc in terms of cc?
500, 10% of blood volume
What are some risks associated w/ red cell transfusion?
- CMV seroconversion
- Fever w/out hemolysis
- Anti-RBC Ab development
- Urticaria
- circulatory overload
How do hemolytic rxns present?
fever, chills, chest pain, hypotension
- overall nonspecific so if you see this after a transfusion, stop transfusion and ask blood bank to do work up for a transfusion rxn
What does the blood bank do for a transfusion rxn?
- clerical check
- look at serum (pink = acute hemolysis, yellow= icteric, subabcute/chronic hemolysis)
- recheck ABO of patient and donor
- repeat crossmatch
- repeat Ab screen
- preform a DAT
What is the most common cause of immediate hemolytic rxns?
clerical error
What is the common cause of delayed hemolytic rxns? How to minimize risk for future?
- du to Ab to minor red cell ag
educate patient about Abti-RBC ab so it doesn’t happen in future
Allergic rxns to plasma components?
urticaria (1-2%) and anaphylaxis rarely
How to minimize allergic rxn?
-premedicate w/ antihistamines for subsequent transfusion, or request washed red cells for any subsequent transfusions
