Epidemiological characteristics and factors associated with out-of-hospital cardiac arrest attended by bystanders before ambulance arrival

BACKGROUND: The aim of this study is to analyze the characteristics of out-of-hospital cardiac arrests based on whether patients received bystander resuscitation before ambulance arrival, and to describe the factors associated with resuscitation attempts by bystanders. METHODS: A retrospective observational study was performed. Clinical data from cardiac arrest patients in the Basque Country (Spain) were collected over a period of five years. Epidemiological characteristics compared resuscitation started by bystanders with resuscitation carried out by ambulance caregivers. The relation between no resuscitation started by bystander and different exposure factors was explored by multiple logistic regression analysis. RESULTS: We analyzed 3,278 cardiac arrests. Of them, 61.9 % were not attended by bystanders and this was associated with the absence of instructions from Emergency Centre (OR: 6.25, 95%CI: 5.15-7.58, p < 0.001), home location (OR: 2.94, 95%CI: 2.48-3.48, p < 0.001), unwitnessed cardiac arrest (OR: 1.56, 95%CI: 1.28-1.89, p < 0.001), victims of 65 years or older (OR: 1.48, 95%CI: 1.26-1.74, p < 0.001) and suburban locations (OR: 1.29, 95%CI: 1.04-1.62, p = 0.023). CONCLUSION: There are differences in cardiac arrests depending on whether they have been resuscitated by bystanders. These characteristics may influence the bystander’s decision to initiate resuscitation maneuvers (or not) and evolution.