Abstract

It is clinically intuitive that physiological deterioration precedes critical illness, and there is growing research evidence to support this belief. The use of track and trigger early-warning systems to facilitate the early recognition of the acutely deteriorating patient outside the critical care area of a hospital is based on this premise. The first such scoring system, based on a single parameter trigger, was developed in Liverpool, Australia as part of the Medical Emergency Team (MET) concept. This was followed by the development of a range of similar systems that have entered clinical practice around the world. These incorporate a variety of physiological variables in scoring, and trigger algorithms that are often more complex than the original MET's calling criteria. They use a wide range of weightings and cut-off points to develop a score designed to trigger activation of a response system. However, most parameters and cut-off points are still based on clinical intuition, rather than the use of rigorous derivation and validation methodologies.