Early warning score
An early warning score (EWS) is a guide used by medical services to quickly determine the degree of illness of a patient. It is based on the vital signs (respiratory rate, oxygen saturation, temperature, blood pressure, pulse/heart rate, AVPU response). Scores were developed in the late 1990s when studies showed that in-hospital deterioration and cardiac arrest were often preceded by a period of increasing abnormalities in the vital signs. Principles The resulting observations are compared to a normal range to generate a single composite score, for instance based on the following diagram (an early modified EWS): A score of five or more is statistically linked to increased likelihood of death or admission to an intensive care unit. Within hospitals, the EWS is used as part of a "track-and-trigger" system whereby an increasing score produces an escalated response varying from increasing the frequency of patient's observations (for a low score) up to urgent review by a rapid response or Medical Emergency Team (MET call). Concerns by nursing staff may also be used to trigger such call, as concerns may precede changes in vital signs. Optimal use Throughout the world the EWS is based on the principle that clinical deterioration can be