What are the signs of a possible hemolytic reaction after a blood transfusion?

The signs of a possible hemolytic reaction after a blood transfusion are characterized by fever, chills, flank pain, and dark urine. This specific combination of symptoms is indicative of the immune system's response to foreign blood cells, where the body recognizes the transfused red blood cells as non-self and mounts an attack against them.

Fever and chills often occur as the body responds to the transfusion, reflecting the release of pyrogens due to the destruction of red blood cells. Flank pain is particularly associated with hemolysis as it may arise from kidney involvement, especially if hemoglobin is released into the bloodstream and subsequently filtered by the kidneys. Dark urine results from hemoglobinuria, which occurs when free hemoglobin from lysed red blood cells is excreted in the urine, giving it a darker appearance.

Recognizing these symptoms is crucial in clinical practice, as timely intervention can help prevent more serious complications.