Changing cardiac arrest and hospital mortality rates through a medical emergency team takes time and constant review

Abstract

Objective: To determine the long-term impact of a medical emergency team on survival and to assess the utility of administrative data to monitor outcomes.

Design: Prospective study of cardiac arrests and survival. Retrospective study of administrative data.

Setting: University affiliated tertiary referral hospital in Melbourne, Australia.

Patients: All patients admitted to hospital in three 6-month periods between 2002-2007 (prospective) and 1993-2007 (retrospective).

Intervention: Implementation of a medical emergency team in November 2002.

Measurements and main results: In the prospective analysis, rates of unexpected cardiac arrest and hospital mortality (referenced to 1000 patient-care days) were measured before (July-August 2002) and after (December 2002-May 2003, December 2004-May 2005, December 2006-May 2007) the introduction of the medical emergency team. Cardiac arrest rates decreased progressively from 0.78 per 1000 (95% confidence interval, 0.50-1.16) to 0.25 per 1000 (95% confidence interval, 0.15-0.39, p < .001), and hospital mortality from 0.58 per 1000 (95% confidence interval, 0.35-0.92) to 0.30 per 1000 (95% confidence interval, 0.20-0.46, p < .05); cardiac arrest rates achieved statistical significance at 2 yrs and hospital mortality at 4 yrs. Using administrative data adjusted for age, sex, case-mix, and comorbidity, hazard ratios for mortality for the three post implementation periods were statistically lower than for the 10 yrs pre implementation (0.85, 0.74, 0.65). The intensity of calling (calls/1000 patient-days) inversely correlated with cardiac arrest rate, unexpected mortality rate, and total hospital mortality rate.

Conclusions: The introduction of a medical emergency team was associated with a progressive decline of unexpected cardiac arrests within 2 yrs, and of unexpected mortality within 4 yrs. This suggests that changes to organizational practice take time and benefits may not be immediately obvious. Such changes are reflected in total hospital mortality measured from administrative data and make monitoring simpler in the longer term. Finally, efforts to increase calling of emergency teams should reduce cardiac arrests and mortality.