Final answer:
The nurse should first verify the patient's blood type and Rh factor to ensure compatibility between the donor blood and the patient, which is critical to preventing a hemolytic transfusion reaction.
Step-by-step explanation:
The first action a nurse should take when preparing to transfuse a unit of packed RBCs to a patient who has anemia is to verify the patient's blood type and Rh factor.
This step is crucial to ensure compatibility between the donor blood and the recipient. It involves using commercially prepared antibodies against the A, B, and Rh antigens to confirm that both the blood unit and the patient's blood type match.
If the donor blood, for instance, is A-positive, it will exhibit agglutination with the anti-A antibodies, confirming the presence of A antigens.
Subsequent actions, following the initial verification, include assessing the patient's vital signs, instructing the patient to report any adverse reactions, and priming the blood administration set.
However, verifying blood compatibility through blood type and Rh factor is the most immediate and critical step to prevent a potential hemolytic transfusion reaction, which can be life-threatening.