Final answer:
Dyspnea, restlessness, and crackles during a blood transfusion may indicate a hemolytic transfusion reaction, a serious complication arising from receiving incompatible blood.
Step-by-step explanation:
During a blood transfusion, symptoms such as dyspnea (difficulty breathing), restlessness, and crackles (abnormal lung sounds) may indicate a serious complication known as a hemolytic transfusion reaction (HTR). This is a type II hypersensitivity cytotoxic response that can occur when a person receives a transfusion of blood that is not compatible with their own blood type. The immune system attacks the mismatched red blood cells (RBCs), leading to their destruction by complement and antibodies. This reaction causes a cascade of symptoms including the ones mentioned, along with fever, chills, hemoglobinuria (presence of hemoglobin in urine), and hypotension (low blood pressure). In severe cases, this can lead to shock, multi-organ failure, and potentially death.