A client experiences an ABO incompatibility reaction after multiple blood transfusions. Which finding should the nurse report immediately to the healthcare provider (HCP)?

A. Delayed painful rash with urticaria: Urticaria is associated with mild allergic transfusion reactions caused by sensitivity to donor plasma proteins. These reactions usually present with itching, hives, or rash and are uncomfortable but rarely life-threatening. While it should be documented and monitored, it does not indicate a severe hemolytic transfusion reaction. B. Arthritic joint changes and chronic pain: Chronic joint pain or arthritic changes are not typical manifestations of an acute ABO incompatibility transfusion reaction. Such symptoms are more consistent with long-term inflammatory or autoimmune disorders rather than acute transfusion complications. They would not require urgent reporting in this situation. C. Lower back pain and hypotension: These are classic signs of an acute hemolytic transfusion reaction caused by ABO incompatibility. In this condition, recipient antibodies rapidly destroy donor red blood cells, leading to intravascular hemolysis, hemoglobin release, renal injury, and circulatory collapse. These findings indicate a potentially life-threatening reaction that requires immediate cessation of the transfusion and urgent notification of the healthcare provider. D. Acute rhinitis and nasal stuffiness: Nasal congestion and rhinitis may occur in mild allergic reactions related to blood product exposure. These symptoms are self-limiting and are not indicative of severe hemolysis or systemic instability. Although they should be monitored, they do not signal a life-threatening transfusion complication that requires immediate intervention.