A unit of Fresh Frozen Plasma was inadvertently thawed and then immediately refrigerated at 4°C. On Tuesday evening, this unit may still be transfused as a replacement for:

The reasoning behind the correct choice relates to the stability of various coagulation factors under different temperature conditions post-thawing. Fresh Frozen Plasma (FFP) is typically stored at -18°C or below and retains all its coagulation factors until thawed. Once thawed, it can be refrigerated at 4°C for a limited time before the factors start to degrade.

Among the coagulation factors present in FFP, Factor IX is the most stable when FFP is stored at 4°C after thawing. Factor IX, primarily involved in the intrinsic pathway of blood coagulation, can remain functional for a longer duration when compared to other factors. This stability allows Factor IX to retain its activity even if the FFP was inadvertently thawed and then refrigerated, making it a potential replacement.

On the other hand, Factor V and Factor VIII are more sensitive to temperature changes and degradation after the thawing process. Both factors are considerably less stable when stored at 4°C, leading to a significant reduction in their activity levels. Therefore, while some factors might be present in diminished capacities, the option that remains viable as an effective replacement post-refrigeration is Factor IX.