What is the proper action for a nurse if a blood unit is returned but left outside of refrigeration?

If a blood unit is returned but has been left outside of refrigeration, the appropriate action is to discard the unit. This is due to the crucial requirement that blood products be stored at specific temperatures to maintain their viability and safety for transfusion. When blood products are not kept at the recommended temperature, especially above 6 degrees Celsius for red blood cells, there is a risk of bacterial growth and a decrease in red cell integrity. These factors can lead to serious complications if the unit is transfused into a patient.

Thus, the protocol calls for the unit to be discarded rather than returned for reuse, used for transfusion, or kept for further testing, which could pose a significant risk to patient safety. The focus on patient safety and ensuring the quality of blood products is a fundamental component of blood banking practices.