Which patient change should the technician report immediately after a blood transfusion begins?

The correct answer highlights a critical situation that requires immediate attention following a blood transfusion. Complaints of back pain accompanied by chills can be indicative of a transfusion reaction, which can develop quickly after the commencement of a blood transfusion. This type of reaction may involve the immune system responding negatively to the foreign blood components, leading to severe consequences if not addressed promptly.

In contrast, the other signs mentioned, such as a few blotches on the skin, feelings of tiredness and fatigue, or minimal urine output, could be related to various patient responses that do not necessarily indicate an immediate life-threatening situation. While these symptoms may still require monitoring and further evaluation, they do not carry the same urgency as the potential indicators of a transfusion reaction, making the reported back pain and chills a priority for immediate reporting and intervention. Ensuring patient safety is paramount, so understanding and recognizing key symptoms of adverse reactions is essential in clinical practice.