As required versus fixed schedule analgesic administration for postoperative pain in children.

Acute postoperative pain occurs as a result of tissue damage following surgery. Administering the appropriate analgesia to children is a complex process and it is unclear whether children's postoperative pain is more successfully treated by using 'as required' (when pain occurs) (termed 'pro re nata' or PRN) or (irrespective of pain at the time of administration).