I have always been taught to abide be the strictest requirements, as long as it is from a reliable source. That being said, according to the most recent Technical Manual 16 Ed. Page 617 under Delay in Starting Transfusion, it states that the unit must be infused within 4hrs of the time that it was issued from the transfusion service, or it must be discarded. We are dealing with this problem currently. We have asked the the order be written to transfuse the unit no greater than 3hrs to allow them time to pick-up the unit, perform all of the necessary checks and get it started. Mabel is correct in that the Admin Set cannot be used for >4hrs.