A sterile field is an area kept free of microorganisms to protect the health and safety of a patient during a medical procedure, usually a surgery. This environment is aseptic; all items in the sterile field are sterilized and should not contain microorganisms. Maintaining aseptic conditions is critical for surgical safety, as an infection could be very dangerous for the patient. Medical care providers learn how to create and maintain a safe surgery environment during their training.
Sterile fields can include people and tools, all of which are aseptic. The process of creating such a field starts with the operating room, which should be kept in very clean condition. When a patient prepares for surgery, nurses will scrub the surgical site with antiseptics, and when the patient goes into the operating room, nurses set up a series of sterile drapes to isolate the site of the surgery. This is the start of the sterile field. Instruments will be laid out for the surgeon on another sterile drape, and each should be inside a sterilization pouch with an indicator showing that it has passed through the autoclave.
Any personnel who work in a sterile field must scrub their hands and arms thoroughly, and wear gowns and gloves as well as cover their hair. While in surgery, they maintain sterility by making sure they do not touch any people or objects that are not sterile. If a surgeon drops a tool on the floor, it is no longer sterile. If she bends down to look at it, she isn't sterile either, because she has passed outside the boundaries of the sterilized area.
A nurse known as a circulator monitors conditions in the sterile field. He is not sterile, and can walk freely around the operating room to look out for health and safety concerns. The general rule of thumb is that if the aseptic status of a person or tool is unclear, it should be considered nonsterile. If a nonsterile person or tool enters the sterile field, the field is contaminated and must be resterilized.
Visitors to operating rooms, like interns and student nurses in their training, may find that they run afoul of the sterile field rules. Operating room visitors can reduce the risk of creating a problem by standing well clear unless specifically invited to move closer. They should not touch the personnel who are "scrubbed in" to work in the sterile area, and should ask for permission before undertaking an activity like picking up a fallen instrument.