according to aorn (recommended practices, 2010), there is no specific amount of time that a sterile field is considered usable after set up; it is event related. however, an open sterile field should be continually monitored by authorized or personnel to ensure that the set up is not contaminated. obviously, a case should not be set up until it is absolutely necessary. common sense should be used. however, if there is a delay of 2, 4, 6 hours, etc., just monitor the set up, limit traffic in/out of the room, monitor environmental controls, etc. finally, remember that your vigilance and practice of surgical conscience is for the good of the patient.