Final answer:
The nurse should immediately stop the transfusion, maintain a patent IV line with saline, check vital signs, and report to the physician as these symptoms may indicate a hemolytic transfusion reaction.
Step-by-step explanation:
When a client complains of chest pain, difficulty breathing, and feeling cold shortly after starting a transfusion of packed red blood cells, the first action the nurse should take is to stop the transfusion immediately. This could be a sign of a hemolytic transfusion reaction, which is a serious and potentially life-threatening condition. After stopping the transfusion, the nurse should maintain a patent IV line with saline, check the client's vital signs, and report the reaction to the physician. Further actions will depend on the client's condition and physician's orders, which may include administering medications such as antihistamines, corticosteroids, or epinephrine, and conducting laboratory tests to confirm the reaction.