The nursing policy should say that the unit must be transfused within 4 hrs, so if there is a delay in starting the unit, they know it still must be finished within 4 hrs of receiving it on the floor. There is no more 30 min rule in the AABB Technical manual and in fact if your laboratory is accredited by College of American Pathologists [CAP], one of the checklist questions deals with return units and reissuing. What ever time you decide must be validated because inspectors ask to see documentation. When I did the validation for our hospital BB [300 bed], we found that after 15 min, the blood warms above 6 C so we changed our time to 15 min unspiked.