Clinical paperCardiac arrest outcomes before and after the 2005 resuscitation guidelines implementation: Evidence of improvement?☆
Introduction
Major changes in cardiopulmonary resuscitation (CPR) guidelines occurred in 20051, 2 focusing on good quality chest compressions and avoiding unnecessary interruptions of compressions. The major changes were removal of stacked shocks, immediate chest compressions following each shock and increasing the compression to ventilation ratio to 30:2 in non-intubated patients. These changes were intended to reduce pauses in chest compressions and improve vital organ perfusion. Fewer pauses and better chest compression quality was anticipated to improve overall survival following cardiac arrest. The Chain of Survival was also modified to incorporate post resuscitation care including therapeutic hypothermia.3
Previous studies have reported improved outcomes in out-of-hospital cardiac arrest (OHCA) with the introduction of the 2005 guidelines; some showing improvements17, 18 others showing little change4, 19, 20 (Table 1). However, OHCA survival over the last decade was arguably steadily improving in advance of the 2005 guidelines being introduced11, 12, 13 and failure to adjust for this trend in observational research is likely to show improved survival when any two time periods are compared. In addition, some previous studies were limited by sample size and failure to adjust for confounders.
Using the Victorian Ambulance Cardiac Arrest Registry (VACAR), we sought to compare OHCA outcomes for time periods pre- and post- the 2005 guideline implementation to establish whether the new guidelines brought about improvements in achieving return of spontaneous circulation (ROSC) and survival to hospital discharge while controlling for baseline survival trend (Table 2).
Section snippets
Setting
The study setting was Melbourne, Australia which has an area of 10,000 square kilometers and a current population of 4 million. Ambulance Victoria provides the emergency ambulance service for this entire population.
Emergency Medical System and Victorian Ambulance Cardiac Arrest Registry
The Emergency Medical System (EMS) for Melbourne is two-tiered with approximately 2500 ambulance paramedics who have some adult advanced life support skills (CPR, defibrillation, laryngeal mask airway, intravenous epinephrine) and mobile intensive care ambulance (MICA) paramedics who
Statistical analysis
Univariate analyses were undertaken to compare the profile of cases in the pre-implementation period with cases in the post-implementation period; chi-square tests were used to compare categorical variables and continuous variables were compared using the t-test (if they followed approximately a normal distribution) or Mann–Whitney test (skewed distribution).
Segmented regression analysis of interrupted time series data was used to analyze the effect of the guideline changes on survival to reach
Results
Ambulance Victoria attended 20,823 OHCAs during the combined time periods (Fig. 1). There were 6363 presumed cardiac aetiology OHCAs unwitnessed by EMS in patients 16 years and over who had an attempted resuscitation, 3115 in the period pre and 3248 in the period post 2005 guideline implementation. Changes between the time periods were; a decrease in the proportion of VF (40.0% vs. 35.5%, p < 0.001), PEA (26% vs. 21%, p < 0.001), and witnessed arrests (63% vs. 59%, p < 0.001) and increases in the
Discussion
This is the largest study to examine the effect of the 2005 guidelines to date and the first to use a segmented regression analysis of interrupted time series data to adjust for underlying improvements in OHCA survival. While this study shows increased ROSC associated with implementation of the 2005 guidelines, associated increased survival to hospital discharge is not seen.
Before-and-after observational studies are subject to a variety of confounding influences that may affect the validity of
Conclusions
Improvements in OHCA outcomes, both survival to hospital and survival to hospital discharge rates, have been seen in the time since introduction of the 2005 CPR guidelines. However, multivariable segmented regression analysis does not confirm that the improvements are due to the implementation of the 2005 resuscitation guidelines.
Conflict of interest statement
None.
Acknowledgements
We would like to acknowledge the VACAR team (Vanessa Barnes and Marian Lodder) the paramedics at Ambulance Victoria for their role in improving survival in cardiac arrest and Dr Belinda Gabbe for statistical advice and manuscript comments.
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A Spanish translated version of the abstract of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2011.04.005.
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On behalf of the VACAR Steering Committee.