The patient with A+ blood type can only receive blood from donors with blood types A+, A-, O+, and O-. Therefore, the nurse must hold the AB- blood and contact the blood bank to request A+ blood. The nurse must not administer the AB- blood which would likely result in a transfusion reaction. Diphenhydramine may be indicated in the treatment of a transfusion reaction, but using it as pre-medication before administering the AB- blood is not an appropriate strategy. The patient cannot receive AB+ blood, so this intervention is inappropriate.