What is the most common adverse effect of transfusing packed red blood cells?

The most common adverse effect of transfusing packed red blood cells is pyrexia, often referred to as a fever. This reaction typically occurs in approximately 1-2% of transfusions and is primarily caused by the recipient's immune response to white blood cells or cytokines in the transfused blood.

Pyrexia is generally a benign reaction and may occur hours after the transfusion has started. It's important to monitor patients for this fever, as it is a common and expected outcome of receiving blood products, particularly if the blood was not leukoreduced (filtered to remove white cells).

Understanding the potential for pyrexia highlights the importance of careful patient monitoring during and after transfusions. While other adverse effects such as allergic reactions, transfusion-related acute lung injury, and iron overload can occur, they are less frequent compared to the incidence of pyrexia associated with blood transfusions. Hence, recognizing pyrexia as the most common reaction emphasizes the need for thorough pre-transfusion assessments and appropriately managing patient expectations.