Typically composed of an ICU doctor, nurse and other appropriate personnel, Medical Emergency Teams (METs) were first introduced in certain hospitals in the 1990s. Since then METs have been widely implemented; their mission is to provide a medically-based critical care resource to critically ill patients wherever in the hospital it is needed. METs should be able to be summoned to a medical emergency in a similar manner and with comparable urgency as a traditional cardiac arrest team. Although METs seem on the surface to make intuitive common-sense, the data regarding their benefits are not clear-cut, and can even show them to be inefficacious. A recent paper by Price and Cuthbertson evaluated the cases for and against METs [1]; this article presents their principal conclusions.   

The basic rationale for the creation of dedicated Medical Emergency Teams (METs) is to address the situation that can occur if a patient on a general ward develops critical illness and there are insufficient resources (both in terms of personnel and equipment) to meet the clinical need.  In response to these considerations, the concept of a Rapid Response System (RRS) has emerged. In addition to being known as MET, the responding team can also be known as a rapid response team (RRT) or critical care outreach (CCO) but whatever the name, all are designed to provide early intervention by individuals with critical care competencies. The recommendations of an international consensus conference on METs were that hospitals should implement a rapid response system, consisting of four elements [2]. These are an afferent, “crisis detection” and “response triggering” mechanism; an efferent, predetermined rapid response team; a governance/administrative structure to supply and organise resources; and a mechanism to evaluate crisis antecedents and promote hospital process improvement to prevent future events.

The case for METS
The rationale for a MET is both obvious and intuitive: the provision of a rapidly responding team should overcome the situation in many hospitals, where there are inevitable delays within a hierarchical structure that consists of individuals who may not possess the appropriate skills for the treatment of deteriorating patients. With a MET, costs may thus be saved via a reduction in the length of  ICU and hospital stays. Many studies have been set up to try to quantitate the benefits of the implementation of METs and some have demonstrated a positive effect. However, from an evidence-based medicine point of view the level of evidence is frequently weak and most of these studies can be considered as Level 2 evidence at best, with a significant likelihood of bias. At least there does not seem to be any suggestion within the literature that METs are actually harmful in some way.

The case against METs
One of the most fundamental arguments against METs is that surprisingly there is no clear-cut evidence in favour of cardiac arrest team systems, which have served as the model on which most METs have been designed. The more detailed evidence against METs comes from a rigorous analysis of the studies that on the face of it purported to show benefits. The question being raised is simply this: are the data in such studies flawed to the extent that they cannot be trusted. For example, some studies involved the comparison of hospitals using the MET system with others that didn’t. Clearly differences between the basic case composition of the different hospitals could bias the results. A priori, the use of studies in the same hospital before and after the introduction of METs should minimise this problem, but even here problems still exist, such as seasonal variations, differences in case mix and general changes with time of the overall health care provision.

Accepting the limitations of such “before and after studies”, two studies have shown that there is no demonstrable benefits to the introduction of METs. In a UK study, Kenward et al [3] looked at the effect of the introduction of a MET on the incidence of cardiac arrest and in-hospital death. The study was carried out over a period of one year before and one year after the introduction of MET. For both outcome parameters, no benefit was shown for the existence of METs.

The MERIT study (Medical Early Response. Intervention and Therapy)  is the largest and most robust study of METS and involved 23 hospitals in a prospective cluster-randomised trial [4], with the primary outcome being the composite of unexpected death, cardiac arrest and unplanned ICU admission.  The studies were designed such that for each hospital there was a baseline period of two months prior to the introduction of  METs in the test group of hospitals. Of course, in the control group of hospitals, no METs were set up after the baseline period. It was found that a significant improvement in the outcomes between the baseline period and test only occurred in the control group of hospitals (i.e. those with no METs)! Direct comparison of the test and control hospitals showed no statistically significant improvement in those hospitals using METs. Various theories have been advanced to explain the apparent lack of efficacy in the MERIT studies. One is that the triggers used to call the MET [Table 1} were not specific or sensitive enough. Likewise the use of a composite outcome criterion of  unexpected death, cardiac arrest and unplanned ICU admission may have been inappropriate. Other explanations could be inappropriate staffing or inappropriate or inadequate interventions. However until clear evidence for the benefits of METs is presented,  the case for their implementation remains seriously flawed.
 
References
1. Price RJ and Cuthbertson BH. Should hosiptals have a medical emergency team? in Controversies in Intensive Care medicine ed by Kuhlen R, Moreno R, Ranieri M and Rhodes A, pub by Medizinisch Wissenshftliche Verlagsgesellschaft 2008
2. DeVita MA et al. Findings of the first consensus conference on medical emergency teams Crit Care Med 2006; 34: 2463.
3. Kenward G et al. Evaluation of a Medical Emergency Team one yearafter implementation. Resuscitation:; 2004: 61: 257.
4. Hillman K et al. Introduction of the medical emergency team (MET) system: a cluster-randomised controlled trial. Lancet 2005; 365:2091.