A nurse is monitoring a client who is receiving a transfusion of packed RBCs. The client reports chills, headache, low-back pain, and a feeling of "tightness" in his chest. The nurse should identify that the client has developed which of the following types of transfusion reactions?

An acute hemolytic transfusion reaction is the most life-threatening transfusion reaction and occurs when ABO-incompatible blood is transfused, triggering rapid destruction of donor red blood cells by the recipient's immune system. Classic signs include chills, fever, headache, low back pain (from renal involvement as hemoglobin deposits in the kidneys), flank pain, chest tightness, hypotension, tachycardia, and hemoglobinuria. The combination of low-back pain and chest tightness described in this stem is particularly characteristic of the acute hemolytic type. A febrile nonhemolytic reaction typically presents with fever and chills but does not include low-back pain or chest tightness and is caused by antibodies against donor leukocytes. A bacterial reaction involves fever, severe hypotension, and shock due to contaminated blood products, not the classic low-back pain picture. An allergic reaction is characterized by urticaria, flushing, and pruritus, and in severe cases anaphylaxis, but not low-back pain. The nurse must stop the transfusion immediately, maintain IV access with normal saline, and notify the provider and blood bank when an acute hemolytic reaction is suspected.