There is a significant body of research demonstrating that many hospitalized patients exhibit signs of clinical deterioration prior to experiencing a cardiopulmonary arrest (CPA).This qualitative study used the critical decision method to describe the cues and factors employed by nurses to identify and interrupt a potentially preventable CPA. The cues that nurses used in identifying a patient at risk for CPA were altered level of consciousness and other selected triggers from the Early Warning Scoring System (EWSS) combined with knowledge of the patient and the contextual features of the decision situation. Nurse characteristics that assisted in interrupting an adverse event included previous experiences in prearrest situations, and the ability to function as part of a team. Organizational characteristics that supported the nurse to interrupt included the availability of nurse-initiated monitoring equipment, experience and flexibility of staff, working with a collaborative team, and access to knowledge resources.