Final answer:
In the context of a blood transfusion, the presence of urticaria (hives) would indicate an allergic reaction to the transfused packed RBCs.
Step-by-step explanation:
A nurse is caring for a client who is receiving one unit of packed RBCs. Among the potential complications, if a client is experiencing an allergic reaction to a blood transfusion, one main indicator would be the presence of urticaria (also known as hives). Urticaria manifests as raised, itchy welts on the skin and is a common symptom of allergic reactions, which can occur when a person's immune system reacts against the proteins in the transfused blood. Other symptoms of transfusion reactions can include fever, low-back pain, or distended neck veins, but these are more commonly associated with other types of transfusion reactions such as hemolytic, febrile non-hemolytic, or volume overload. Anaphylaxis is a serious allergic reaction that can also occur, but it is not as common as other types of reactions and would include symptoms beyond just skin manifestations, such as breathing difficulties and a drop in blood pressure.