Blood selection/Procedures in Crossmatching Flashcards
Possible causes of:
Positive antibody screen
Incompatible crossmatch
Negative autocontrol
Due to a mixture of antibodies or an antibody to a high frequency antigen
In emergency situations, when the patient’s sample has not been obtained but transfusion is critical for patient survival, what is the best choice for donor compatibility? What steps must be taken prior to giving the blood unit, after the unit has left the lab?
O neg units given in emergencies. Most facilities have policies in place the require the attending physician to sign approval for giving uncrossmatched blood. A patient specimen should be collected as soon as possible. Type and cross must be performed. Once the patient’s ABO/Rh have been determined, the decision must be made to switch back to patient’s type if applicable
If type specific blood is not available, what is the best course of action in an emergency situation?
Attending physician must determine the situation. If O neg units are not available, Rh neg units are given
What test must be done on the recipient’s blood before transfusion?
ABO, Rh, antibody scree, immediate spin crossmatch if screen is negative
How long must patient’s blood specimen and donor blood specimen be retained?
7 days after transfusion
If the patients blood is AB and AB blood is not available, what blood should be used and why?
Most likely A packed cells because of the availability of A compared to B
How do you calculate the probability of compatible units when the patient has a single antibody?
The number of random units needed for antigen screening is calculated by dividing the number of antigen-neg units desired by the incidence of antigen-neg individuals in the population
What is the purpose of performing a crossmatch?
To ensure the safest transfusion possible
When do you need to do all phases of testing for the crossmatch procedure?
If the patient has a positive antibody screen or an ABO discrepancy
If an antibody was previously detected on a patient and is now not evident, what would be the proper course to take if 2 units were ordered on this patient?
Type the donor units for the specific antigen and crossmatch with those antigen negative donor units
List the causes of a major crossmatch incompatibility at room temp
Specifically ABO incompatibilities or any other IgM antibody that may be reacting at RT
If blood donor units are “checked out” of the blood bank and then returned 30 minutes later unused, what is the proper protocol to follow?
If the donor unit is maintained at room temp, the blood is no longer acceptable to be used for transfusion and must be properly disposed of.
If the donor unit has been properly maintained at 1-10 degree C, the unit may be accepted back into the bank with proper documentation and reissued at a later date, providing the bag has not been entered and the unit is intact
Review the effect that one unit of packed cells has on raising the hemoglobin and hematocrit in a patient
One unit of blood can be expected to raise the hematocrit 3% and raise the hemoglobin by 1 g/dL
Define massive transfusion
The replacement of the patient’s total blood volume or more within a 24 hour period
Effects of giving non-type specific blood in massive transfusions
Evaluation of switching types must be made and the patient’s age, sex, and current blood supply must be considered. Once a D-neg patient receives one or more units of D pos blood, there is little advantage to returning to a D neg blood.
What considerations must be made regarding coag studies in massive transfusions?
The platelet count must be monitored during massive transfusions due to dilutional effects. Coag factors are also “diluted” during and thus the PT, PTT may be prolonged and the fibrinogen may be decreased.
How much blood loss is considered to be a massive blood loss?
When 25% or more of the patient’s total blood volume is lost rapidly
What is the usual massive transfusion protocol?
- 2 units group O RBC’s uncrossmatched
- Massive transfusion protocol pack
- Monitor CBC, platelets, PT/INR, PTT, fibrinogen
- Add or subtract components in pack based on lab values
List the possible causes for a crossmatch incompatibility at AHG phase
Unexpected alloantibodies that are IgG
After the patient sample collection, what is the maximum amount of time before a new sample of blood is needed for compatibility testing?
3 days
If the patient is Rh pos, what donor Rh types may be selected
Rh pos and Rh neg
If the patient is Rh neg, what donor types may be selected?
Rh neg only
Specificity in antibody screen
If the antibody screen test is negative when the patient doesn’t have an antibody
Sensitivity in antibody screen
If the antibody screen test is positive when the patient has an alloantibody
What testing must be done by the receiving institution of a shipment of donor units from a blood center?
ABO and Rh type
What is the purpose of the immediate spin phase in crossmatch testing?
ABO compatibility
What is the purpose of the 37 degree phase in crossmatch testing when the patient has an IgG alloantibody?
Allow sensitization of the patient’s antibody onto the donor antigen if present
What is the purpose of the AHG phase in crossmatch testing when the patient has an IgG alloantibody?
Allow the bridging of sensitized RBCs if the patient’s antibody is reaching to the donor antigen
What testing must be performed on an autologous unit
ABO and Rh
Where is the antigen from in the crossmatch test?
Donor RBCs
Where is the antibody from in the crossmatch test?
Recipient’s serum/plasma
How long can testing be performed before a scheduled transfusion if the patient has either been pregnant or received a transfusion within the last three months?
3 days
If a recipient is type A and has been given several packed cell units of type O and needs additional units in a few days, what determines if they should revert back to type A units instead of continuing with type O?
Fresh patient serum in compatible with A donor cells in a cross match
