Final answer:
Anaphylactic reactions to a blood transfusion are severe immune responses to incompatible RBCs, which can cause symptoms like fever, chills, and low blood pressure, leading to anaphylactic shock and potentially death if not promptly treated.
Step-by-step explanation:
Anaphylactic reactions to a blood transfusion occur when a patient receives blood that is not compatible with their own type and antibodies in their blood react to the new, incompatible red blood cells (RBCs). For example, a person with type B blood who receives a transfusion of type A blood will have their anti-A antibodies bind to and agglutinate the transfused RBCs. This results in a severe immune response, including the activation of the classical complement cascade, leading to a systemic type I hypersensitivity reaction, or anaphylaxis. The patient can suffer from fever, chills, pruritus (itching), urticaria (hives), dyspnea, hemoglobinuria, and dangerously low blood pressure. These symptoms can quickly escalate to anaphylactic shock, presenting a life-threatening situation that can lead to shock, multi-organ failure, and death if not immediately treated with epinephrine and other emergency interventions.