Paramedic exposure to cardiac arrest and patient survival: does practice make perfect?

Abstract

Background: Out-of-hospital cardiac arrest (OHCA) is a common cause of premature death and the rate of survival is low. Early defibrillation and high quality chest compressions are known to influence OHCA survival and it is likely that paramedics who are frequently exposed to OHCA cases will perform more competently these vital components of resuscitation. Given that resuscitation skills decline over time and paramedic treatment of OHCA often falls short of the recommended standard, the number of OHCAs that paramedics are exposed to may be contributing to low and varied OHCA survival rates. Therefore, the broad aim of this thesis was to examine the association between paramedic exposure to OHCA and patient survival. Methods: Firstly, I performed a systematic review of the literature which identified that the association between paramedic exposure to OHCA and patient survival was a clear knowledge gap. To address this knowledge gap, I undertook a survey of emergency medical services (EMS) and conducted three epidemiological studies. The survey investigated the methods that EMS in Australia and New Zealand use to develop and maintain paramedic competency in resuscitation. The epidemiological studies were conducted in the setting of a large, statewide, two-tiered EMS agency, Ambulance Victoria (AV), and high quality data were sourced from the Victorian Ambulance Cardiac Arrest Registry as well as routinely collected data from AV. I measured typical paramedic exposure to OHCA. Then, using multivariable regression analysis, adjusting for internationally accepted covariates, I analysed the association between paramedic exposure to OHCA and patient survival. To determine whether increasing paramedic exposure is associated with better performance – the potential intermediary factor between exposure and outcomes, the association between paramedic exposure to endotracheal intubation (ETI) and performance (as measured by successful endotracheal tube [ETT] placement) was examined. I chose to investigate performance in ETI because it is one of the most technical individual skills carried out by paramedics during OHCA resuscitation. Results: The survey found that EMS agencies provided paramedics with minimal refresher training and rarely used other evidence-based methods of maintaining resuscitation competency. Paramedics were typically exposed to 1.4 (interquartile range [IQR]: 0.0-3.0) OHCAs per year and OHCA exposure declined over time. It would take paramedics an average of 163 days to be exposed to an OHCA and up to a decade for paediatric and traumatic OHCAs, which occur relatively rarely. OHCA exposure was lower in paramedics who were employed part-time, in rural areas, and with lower qualifications. Compared to patients treated by paramedics with a median of ≤6 exposures during the previous three years (7% survival), the odds of survival were higher for patients treated by paramedics with >6-11 (12%, adjusted odds ratio [AOR] :1.26, 95% confidence interval [CI] :1.04-1.54), >11-17 (14%, AOR:1.29, 95% CI:1.04-1.59) and >17 exposures (17%, AOR:1.50, 95% CI:1.22-1.86). I found that paramedic exposure to an individual component of OHCA resuscitation, namely ETI, was associated with better performance (AOR for successful ETT placement: 1.04, 95%CI: 1.03-1.05) but not OHCA patient survival. Intensive care paramedics typically performed 3 (IQR: 1-6) ETIs per year, the majority of which were performed on OHCAs (66%). Conclusions: Individual paramedics are rarely exposed to OHCA and increasing exposure is associated with improved patient survival. In addition, paramedic exposure to a single complex component of resuscitation, ETI, was associated with improved performance but not OHCA survival. The poor performance and patient outcomes commonly reported for OHCA may in part be the consequence of inadequate opportunities for paramedics to practise their resuscitation skills. These findings suggest that paramedic exposure to OHCA and resuscitation procedures need to be monitored and strategies to supplement low exposure, such as simulation training, should be explored.