Evaluating the impact of implementing an early warning score system on incidence of in-hospital cardiac arrest.

Aim: To evaluate the introduction of an early warning score (EWS) system on incidence of in-hospital adult cardiac arrest.

Methods: A before-after evaluation of an EWS system (in the form of a patient observation chart with escalation protocol) in a 600 bed tertiary teaching hospital in New Zealand during the two 12-month periods between March 2009 and March 2011. Difference in incidence rates was compared using Student's t test.

Results: There were 168 cardiac arrests during the 24 month period. The incidence rate of cardiac arrests per 1000 admissions was 4.67 during 2009-2010 and 2.91 during 2010-2011 (mean difference of 1.77, 95%CI 0.59-2.94). The number of cardiac arrests dropped from an average of 8.5 arrests per month during 2009-2010 to 5.5 arrests per month during 2010-2011 following the introduction of ADDS (mean difference 3.0, 95%CI 0.78-5.22). There was no significant increase in the number of medical emergency calls (7.5 calls versus 9.1 calls per month).

Conclusion: Introduction of an EWS system in addition to an existing cardiac arrest team response decreased the incidence of in-hospital cardiac arrests in a tertiary hospital in New Zealand.