What finding would indicate a potential transfusion reaction when monitoring a client during a transfusion?

A rash or hives during a blood transfusion can indicate a potential transfusion reaction, particularly an allergic reaction to the blood product. This is a key sign that the body is responding negatively to the transfusion, leading to the activation of the immune system and the release of histamines. The presence of skin reactions such as hives typically arises due to sensitization to allergens present in the donor blood, including proteins.

Monitoring for symptoms like rash or hives is crucial because it allows healthcare providers to take immediate action, such as stopping the transfusion and administering antihistamines or other interventions as required. In contrast, other options do not reflect signs that would indicate a transfusion reaction. For example, a temperature decrease is not commonly associated with transfusion reactions, while increased urine output typically signifies normal renal function and is not an indicator of a reaction. Improved oxygen saturation would suggest that the transfusion is beneficial and effectively improving the patient's oxygen delivery rather than indicating any adverse reaction.