A 24 year old A negative female was transfused with approximately 65 CC of an A positive RBC unit. How many vials of RhIG should this woman receive?

A 24 year old A negative female was transfused with approximately 65 CC of an A positive RBC unit. How many vials of RhIG should this woman receive?

• A. 5
• B. 1
• C. 3
• D. 7

Answer: (A)

Rh immune globulin is given to an Rh-negative person after exposure to Rh-positive red cells to prevent the formation of anti-D antibodies. The amount of RhIG needed is estimated from how many milliliters of Rh-positive red cells were involved; one 300 μg vial of RhIG neutralizes about 15 mL of Rh-positive fetal RBCs. In this case, about 65 mL of Rh-positive RBCs were transfused. Dividing 65 by 15 gives roughly 4.3, so you round up to five vials to ensure complete neutralization.

Rh immune globulin is given to an Rh-negative person after exposure to Rh-positive red cells to prevent the formation of anti-D antibodies. The amount of RhIG needed is estimated from how many milliliters of Rh-positive red cells were involved; one 300 μg vial of RhIG neutralizes about 15 mL of Rh-positive fetal RBCs. In this case, about 65 mL of Rh-positive RBCs were transfused. Dividing 65 by 15 gives roughly 4.3, so you round up to five vials to ensure complete neutralization.