The Questionable Benefit of Medical Emergency Teams
Hillman K, Chen J, Cretikos M, et al. Introduction of the medical emergency team (MET) system: a cluster-randomised controlled trial. MERIT study investigators. Lancet. 2005;365:2091-2097.
Previous studies have reported that the MET system reduces the incidence of cardiac arrests, deaths, and unplanned ICU admissions. A MET is a preplanned group of healthcare practitioners who respond to acute patient deteriorations in hospitalized patients.
METs are usually identical to hospital code teams, with the exception that they respond prior to a patient’s developing cardiac arrest. This early response has been shown to significantly decrease unexpected hospital mortality in hospitals in the United States, Australia, and Great Britain. Even though the system has been reported since 1995, few hospitals have knowledge of or experience with METs.
Unexpected hospital deaths and cardiac arrests are often preceded by clinical warning signs. In addition, unplanned ICU admissions may be foreshadowed by abnormalities in the patient’s vital signs that may progress if appropriate interventions are not undertaken. METs assess patients with abnormal physical findings or when there is a concern about the patient’s condition. These patients have findings that may precede a serious event or cardiac arrest, but otherwise don’t meet existing criteria to call a code.
The theory is that if a MET responds to see a patient who is becoming unstable (see “Table 1: MET Calling Criteria,” at left), early interventions may reduce the likelihood of arrest. Published studies have shown a reduction in cardiac arrests and ICU length of stay in virtually all systems in which MET has been introduced (although most studies are hampered by the use of historical controls).
The MERIT study randomized 23 hospitals in Australia to continue functioning as usual (n=11) or to introduce a MET system (n=12). The study sites included a wide range of tertiary, metropolitan, and non-metropolitan hospitals in different states across Australia. The primary outcome was the composite of cardiac arrest, unexpected death, or unplanned ICU admission during the six-month study period after MET activation, using intention to treat analysis.
A four-month educational period was undertaken with the MET centers prior to initiation of the trial. Control hospitals did not receive any education about the MET concept. This was followed by a six-month trial period. Cardiac arrest teams were maintained at all hospitals. The MET consisted of at least one doctor and a nurse from the ED or ICU.
The eligible patients included those residing on a medical ward (including critical care units); the ICUs, OR, postoperative recovery areas, and ED areas were not regarded as general wards.
The primary outcome for the study was the composite outcome of the incidence (events divided by number of eligible patients admitted to the hospital and residing on a medical ward during the study period) of:
- Cardiac arrests without a pre-existing “not-for-resuscitation” (NFR) order;
- Unplanned ICU admissions; and
- Unexpected deaths (those without a pre-existing NFR order).
The results of the study:
- During the study period, the overall rate of calls for the cardiac arrest team or MET was significantly higher in intervention hospitals than in control hospitals. Calls not associated with events were more common in MET hospitals than in controls. Half of the total calls were not associated with a cardiac arrest or unexpected death, whereas in MET hospitals more than 80% of calls were not associated with a cardiac arrest or death (P<0.0001).
- In patients with documented MET calling criteria in association with cardiac arrest or unexpected death, the call rate was similar in MET and control hospitals.
- There were no significant differences between the MET and control hospitals for any outcome.
- The response to changes in vital signs was not adequate—even in MET centers.