Original article
Factors Associated With Mortality in Out-of-hospital Cardiac Arrests Attended in Basic Life Support Units in the Basque Country (Spain)Factores asociados a la mortalidad extrahospitalaria de las paradas cardiorrespiratorias atendidas por unidades de soporte vital básico en el País Vasco

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Abstract

Introduction and objectives

To describe the epidemiological characteristics of cardiac arrests attended in basic life support units in the Basque Country (Spain) and look for factors associated with failure of cardiopulmonary resuscitation.

Methods

We conducted an observational study during 18 months, including all out-of-hospital cardiopulmonary resuscitation provided by basic life support units. The variables defined in the Utstein-style were considered as independent and mortality as the dependent variable. We applied descriptive and analytical statistics and evaluated the magnitude of the association using a logistic regression model, which included variables with P<.05 in the bivariate analysis.

Results

Of 1050 cardiac arrests attended, 15.7% of patients were revived in situ. The presumed etiology was cardiac in 55.3% of cases and 71.4% occurred at home. Cardiopulmonary resuscitation was started before the arrival of the ambulance in 22.9% of cases and in 18.2% the rhythm of presentation was shockable. Variables associated with lower mortality were: shockable rhythms (relative risk=0.44; P=.003), patient aged<65 years (relative risk=0.44; P=.002), time to cardiopulmonary resuscitation<8 min (relative risk=0.56; P=.039), and out-of-home events (relative risk=0.55; P=.031).

Conclusions

Cardiac arrest survival was low. Cardiopulmonary resuscitation before the arrival of the ambulance was rare. A shockable rhythm, age younger than 65 years, early cardiopulmonary resuscitation efforts, and a location away from home were associated with longer survival. It is necessary to develop strategies designed to reduce ambulance response time and educate the public in basic resuscitation.

Resumen

Introducción y objetivos

Describir las características epidemiológicas de las paradas cardiorrespiratorias atendidas por las unidades de soporte vital básico del País Vasco y determinar los factores asociados al fracaso de las maniobras de reanimación.

Métodos

Estudio observacional sobre el total de paradas cardiorrespiratorias asistidas por las unidades de soporte vital básico del País Vasco durante 18 meses. Se tomaron como variables independientes las definidas en el estilo Utstein y como variable dependiente la mortalidad extrahospitalaria. Se aplicó estadística descriptiva y analítica, evaluando la magnitud de asociación mediante el riesgo relativo aplicando un modelo de regresión logística.

Resultados

Se atendieron en total 1.050 paradas, de las que se reanimó in situ el 15,7%. El 55,3% de las paradas fueron de etiología cardiológica y el 71,4% aconteció en el hogar. Se intentó la reanimación antes de la llegada de la ambulancia en el 22,9% de los casos y en el 18,2% el ritmo de presentación fue desfibrilable. Las variables asociadas a menor mortalidad fueron ritmo desfibrilable (riesgo relativo = 0,44; p = 0,003), edad del paciente < 65 años (riesgo relativo = 0,44; p = 0,002), tiempo hasta la reanimación < 8 min (riesgo relativo = 0,56; p = 0,039) y eventos extradomiciliarios (riesgo relativo = 0,55; p = 0,031).

Conclusiones

La probabilidad de sobrevivir a una parada cardiorrespiratoria es baja. Se realizan pocos intentos de reanimación antes de la llegada de la ambulancia. Un ritmo desfibrilable, edades inferiores a 65 años, el inicio precoz de la reanimación y la localización fuera del domicilio se asocian a mayor supervivencia. Deben crearse estrategias dirigidas a disminuir los intervalos de respuesta e instruir a la población en reanimación básica.

Section snippets

INTRODUCTION

Out-of-hospital cardiopulmonary arrest (OHCA) is an important health problem because the probability of recovery is small even though the process is potentially reversible.

The exact incidence of this condition in Spain is still not known. National estimates range from 10 0001 to 50 000 events per year.2 This lack of data is due to the lack of a specific central registry and of national studies on OHCA, to the methodological limitations of the available studies, and to differences in the

METHODS

The study sample comprised all cases of OHCA between July 1, 2009 and December 31, 2010 in which CPR was initiated by a BLSU of the emergency health transport system of the Basque Country with semiautomatic external defibrillators at their disposal (either as the only resource available or in combination with an ALSU).

The data were taken from the central OHCA database maintained by Emergentziak-Osakidetza. Entries to this database are made using the clinical information collected with a

RESULTS

During the 18 months of the study period, 1272 OHCA events with resuscitation attempts were recorded in the database; in 1050 (82.5%) of these, a basic life support resource was deployed. Case details and general characteristics are shown in Figure 1. The remaining cases (222) were attended exclusively by advanced life support resources and so were excluded from this study.

CPR outside the hospital measures were successful in 15.7% of the interventions, and the patients were transferred to

DISCUSSION

Based on the consideration that the data source for OHCA used for this study considers all resuscitations performed by emergency health resources in the Basque Country, the ratio of OHCA cases of any etiology attended during the study period (1272) and the resident population in this autonomous community, it is possible to calculate an approximate incidence of 3.9 (95%CI, 3.6-4.2) events per 10 000 inhabitants or 18 400 cases per year if the data were extrapolated to the entire Spanish population.

CONCLUSIONS

The findings of this study show that the chances of surviving CRA in the Basque Country are low and that CPR is very seldom attempted prior to arrival of the ambulance. A shockable rhythm, age<65 years, early initiation of life support measures, and occurrence at a site outside the home were associated with increased survival until transfer to hospital.

In addition, the findings of the present study highlight the need to strive to create strategies aimed at reducing EMS response time and

CONFLICTS OF INTEREST

None declared.

Acknowledgments

We thank all members of the basic life support resources in the network of emergency transport of the Basque Country (Red Cross, DYA [Detente y Ayuda], Transporte Sanitario Bizkaia, Ambulancias Euskadi, Larrialdiak, Gipuzkoa Emergentziak and Ambulancias Gipuzkoa) for their cooperation in collecting and sending the data, and to Emergentziak Osakidetza for providing us with access.

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