What is a critical nursing action for a patient undergoing a blood transfusion?

Monitoring vital signs is a critical nursing action for a patient undergoing a blood transfusion due to the risk of transfusion reactions, which can occur at any time during the transfusion process. By closely observing vital signs such as temperature, heart rate, blood pressure, and respiratory rate, nurses can detect any changes that may indicate an adverse reaction.

Elevations in temperature might suggest a febrile reaction, while changes in heart rate or blood pressure could indicate hemolytic reactions or allergic responses. Vital signs should be assessed before the transfusion starts, at intervals during the transfusion, and after the transfusion is completed, ensuring any potential issues are identified and addressed promptly.

The other options may also be relevant to patient care but do not have the same immediate critical nature during a blood transfusion. Administering medication or performing a physical assessment may be necessary for overall care, but they do not directly address the acute risks associated with the transfusion itself, making monitoring vital signs the priority action in this scenario.