Cardiac arrest outcomes before and after the 2005 resuscitation guidelines implementation: evidence of improvement?

Background: Previous studies have reported improvements in out-of-hospital cardiac arrest (OHCA) outcomes with the introduction of the 2005 cardiopulmonary resuscitation guidelines however they have not adjusted for underlying trends in OHCA survival. We compare outcomes before and after the 2005 guideline changes adjusting for underlying trends in OHCA survival.

Methods: The Victorian Ambulance Cardiac Arrest Registry (VACAR) was searched for adult (≥16 years) OHCA of presumed cardiac aetiology, unwitnessed by paramedics with attempted resuscitation. Outcomes for OHCA occurring between 2003 and 2005 were compared with 2007-2009. Segmented regression analysis of interrupted time series data was performed, adjusting for known predictors, to examine changes in survival to hospital and survival to hospital discharge.

Results: For the pre- and post- guideline periods there were 3115 and 3248 OHCAs, respectively. Asystole increased as presenting rhythm (33-43%, p<0.001) as did median EMS response times (7.1-7.8 min, p<0.001) over the two periods. VF/VT arrests decreased (40-35.5%, p=0.001) as did bystander witnessed arrests (63-59%, p=0.002). On univariate analysis survival to hospital discharge improved between the two periods (9.4-11.8%, p=0.002) due to improved outcomes in VF/VT (19-28%, p<0.001). Segmented regression analysis of interrupted time series data showed improvement in the rate of survival to get to hospital for shockable and non-shockable rhythms [OR (95% CI)=1.54 (1.10-2.15, p=0.01) and 1.45 (1.10-2.00, p=0.02), respectively] following implementation of the guidelines however survival to hospital discharge did not improve [OR=1.07 (0.70-1.62, p=0.70) and 1.40 (0.69-2.85, p=0.40), respectively].

Conclusions: OHCA outcomes have improved since introduction of the 2005 CPR guidelines, but multivariable segmented regression analysis adjusting for pre-existing trends in survival suggests that this improvement may not be due to implementation of the 2005 resuscitation guidelines.