Sometimes it is necessary to transfuse platelets from an Rh-positive donor to an Rh-negative recipient. The amount of red blood cells in a platelet pool is sufficient to alloimmunize the patient, especially if multiple units are given. Rh Immune Globulin (RhoGAM, RhIG) can be given to prevent alloimmunization.


NOTE: Rh antigen is not present on platelets, and survival of platelets from an Rh-positive donor is normal in a patient with anti-D.


Amount of Packed RBC

random concentrate

0.5 mL per unit (2 mL in pool of 4 units to 4 mL in pool of 8 units)

pheresis product

2 mL


1 unit of RhoGAM is immunoprophylactic for up to 15 mL of Rh-positive packed RBCs:

(1) for up to 30 random concentrates

(2) for up to 7 platelet pheresis products


NOTE: Micro-RhoGAM can be given for up to 2.5 mL of Rh-positive red blood cells, However, I am not sure that there is a significant cost savings, while it is unlikely that a patient requiring platelet transfusions that badly would require only 1 pheresis product or 5 random concentrates.


If hematoma development at the site of intramuscular injection is a concern, an intravenous injectable form is available.


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