Various aspects of treatment in cardiac arrest prior to hospital arrival

Abstract

Background and aims: Out-of-hospital cardiac arrest (OHCA) is a major public health issue, affecting almost 300,000 victims per year in Europe, who have an overall survival rate of about 10 per cent. In general, the current Emergency Medical Services (EMS) do not have the capacity to act quickly and effectively enough in regard to this vast group of patients. The objectives of the current work were: to study the importance of bystander cardiopulmonary resuscitation (CPR) from a national perspective; to determine the safety, feasibility and efficacy of trans-nasal evaporative cooling initiated during CPR; to investigate the effects of dual dispatch of fire-fighters and EMS on short- and long-term survival; to explore regional differences in response times and survival rates in relation to dual dispatch of fire-fighters and EMS in cases of OHCA.

Methods and results: Study I. Observational study of 34,125 patients. From 1992 to 2005, bystander CPR significantly increased, especially when performed by laypersons, in witnessed (40% to 55%, p<0.0001) and unwitnessed (22% to 44%, p<0.0001) OHCA. Bystander CPR was associated with higher ventricular fibrillation (VF) rates (adjusted OR 1.73, 95% CI 1.62–1.86) and improved 30-day survival (adj. OR 2.20, 95% CI 1.68–2.90). Study II. Randomised trial concerning 200 cases of witnessed OHCA. Trans-nasal evaporative cooling was feasible in pre-hospital arrests. Eighteen device-related adverse events were reported, where one case of epistaxis was defined as serious. Time to target temperature of 34°C was shorter in the treatment group for both tympanic (102 vs. 282 minutes, p=0.03) and core (155 vs. 284 minutes, p=0.13) temperature. Study III. Intervention study (trained fire-fighters dispatched in cases of OHCA) using historical controls. When dispatched, fire-fighters were first on the scene and connected an automated external defibrillator (AED) in 41% of the cases. Thirty-day survival improved from 3.9% (control) to 7.6 % (intervention) (p=0.001, adjusted OR 2.8, 95% CI 1.6–4.9). Survival to 3 years increased from 2.4% to 6.5% respectively (p<0.001, adjusted OR 3.8, 95% CI 1.9–7.6). Study IV. Intervention study using historical controls, assessing the regional impact of Study III in areas with different population densities. Median response times shortened significantly in all subgroups, ranging from 0.8 (downtown) to 3.2 minutes (rural). The effect on 30-day survival rates varied depending on population density, with the lowest impact in rural areas.

Conclusions: Bystander CPR, especially when performed by laypersons, increased in Sweden between 1992 and 2005 and is associated with increased VF and survival rates. Intra-arrest trans-nasal cooling in cases of OHCA is safe and feasible and it shortened the time interval required to cool patients. Implementation of a dual dispatch system (fire-fighters and EMS) in cases of OHCA was associated with increased 30-day- and 3-year survival. Shortened response times were seen in sparsely as well as in highly populated regions. The lowest impact of a dual dispatch system on survival was seen in rural areas.