SIP

Subject: Blood Banking
Topic: Bone Marrow Transplantation (BMT)

Bone marrow contains immature cells (stem cells), which develops into RBCs, WBCs & platelets

Purpose: To replace unhealthy cells with healthy ones in order to survive

Patients: People with diseases of the blood, bone marrow, or certain types of cancer, (e,g., Hodgkin's disease, mulitple myeloma, leukaemia, etc.)

Conditioning/preparative regimen: Treatment with high doses of chemotherapy or total body irradiation, given immediately prior to a transplant.

Purpose: To help remove the patient's disease prior to the BMT & to suppress immune reactions. It also has an immunosuppressive effect which prevents rejection of the BMT by the recipient's immune system.

If donor's bone marrow doesn not match, it'll treat the patient's body as foreign material to be attacked & destroyed, which results in graft vs host disease (GVHD). This is when patient's own immune system destroy the new bone marrow (graft rejection).

During the period when patient waits for the transplanted bone marrow to migrate to the cavities of large bones, setting up 'engraft' to the stage where it begins to produce normal blood cells, the patient is susceptible to infection & excessive bleeding. Platelets are transfused to patients who are bleeding.

Until the donor marrow engrafts, RBCs & platelets will be needed to keep the hemoglobin level above 9g/dl and platelet count > 20,000/ul. Engraftment takes place in 2 to 4 weeks but may be delayed if complications occur.

As a result of the total body irradiation & chemotherapy required for preparation for transplantation, patients are immunosuppressed & susceptible to GVHD, if transfused with blood components that contains live lymphocytes, which are capable of dividing. Tranfusion related GVHD can be prevented by irradiating all blood components.

Why use irradiated & filtered (leucodepleted) blood products?

To prevent patients from febrile non-hemolytic transfusion reaction due to leucocytes & leucocytes fragments in whole blood or packed cells.

Blood cell gamma irradiator is used for irradiating blood components such as red cell or platelet concentrates. The gamma rays effectively stop cells dividing by mitotic division, preventing lymphocyte proliferation.

Since alloimmunisation is caused by leucocytes contained in the blood components, leucodepleted red cells has been used to minimise the likelihood of inducing alloimmunisation.

The immunosuppression also results in great susceptibility to infectious diseases. Most patients will receive anitbiotics, antifungal agents & intravenous immunoglobulin to help prevent fight infection.

ABO Incompatible Transplants:
ABO incompatible transplants may be done when there is patient antibody directed against donor cells (major incompatibility; e.g., patient O, donor A) or donor antibody directed against the patient's red cells (minor incompatibility; e.g., patient A, donor O).

Example 1:
Patient 1's blood group: A+
Donor 1's blood group: O+

Blood product (irradiated & filtered): Packed cell: O+
Platelet/CSP: Group A+ (1st choice)/Group O+

Problem: Continued production of antibody by the new donor lymphocytes while there are original patient's cells continuing to circulate. Thus, the group O donor cells may begin to produce anti-A while the orginal patient A red cells remains, leading to hemolysis.

Solution: This can be lessened by red cell exchange transfusion if necessary.

Group A Recipient with Group O Donor:

Anti-A	Anti-B	Anti-AB	A Cells	B Cells	O Cells	Interpretation
+	-	+	-	+	-	Group A
+/-	-	-	-	+	-	Incomplete Group A
-	-	-	+/-	+	-	Incomplete Group O
-	-	-	+	+	-	Complete Group O

ABO blood grouping of transfused patient:
For incomplete group A, there will be a mixed field reaction when tested with anti-A. Some of the red cells are agglutinated while others are not. The anti-sera will appear to be cloudy due to some free red cells. This occurs when the patient's blood group (A+) is slowly switching to the new donor's blood type (O+).

Example 2:
Patient 2's blood group: O+
Donor 2's blood group: A+

Blood product (irradiated & filtered): Packed cell: O+
Platelet/CSP: Group A+ (1st choice)/Group AB+

Problem: When ABO-incompatible marrow is to be transfused into a patient with circulating antibodies against the donor's ABO type, hemolysis of the red cells in the marrow can be expected.

Prevention: By processing the marrow to remove the red cells.

Following transplant & after engraftment, the patient will become A+ but cannot begin to receive group A red cells until the circulating anti-A has disappeared. Anti-A persists longer than anti-B. Thus, even after transfusion of type A marrow, the patient continues to receive type O red cells containing additonal anti-A that can slow down the appearance of type A red cells.

If delayed red cell engraftment is occurring, the titer of anti-A should be determined & a DAT done to determine if high levels of circulating anti-A are hemolysing newly forming A red cells.

In making the decision when to convert to the new donor ABO type for red cell transfusion, we use the crossmatch to determine the absence of circulating ABO antibody incompatible with the patient's original type. The patient's serum should be tested in the antiglobulin phase to ensure the absence of free ABO-incompatible antibody.

When the ABO antibody to donor type is undetectable & DAT is negative, this is a satisfactory indicator of the safety to begin transfusion the new donor ABO type red cells.

Group O Recipient with Group A Donor:

Anti-A	Anti-B	Anti-AB	A Cells	B Cells	O Cells	Interpretation
-	-	-	+	+	-	Group O
+/-	-	+/-	-	+	-	Incomplete Group A
+	-	+	-	+	-	Complete Group A

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