Utstein style analysis of out-of-hospital cardiac arrest--bystander CPR and end expired carbon dioxide.

INTRODUCTION: The aim of this prospective cohort study was to describe the outcome for patients with out-of-hospital cardiac arrest in Maribor (Slovenia) over a 4 year period using a modified Utstein style, and to investigate elementary knowledge of basic life support among potential bystanders in our community. PATIENTS AND METHODS: Through the prehospital and the hospital database system we followed up a consecutive group of patients with out-of-hospital cardiac arrest (OHCA) between January 2001 and December 2004. We investigated the effects of various factors on outcome in OHCA, especially partial end-tidal CO2 pressure (petCO2), efficacy of bystander CPR and their elementary knowledge of basic life support (BLS). We also examined motivation among potential bystanders and possible implementation for BLS education in our community.
RESULTS: OHCA was confirmed in 592 patients. Advanced cardiac life support was initiated in 389 patients, of which 277 were of cardiac aetiology. In 287 patients the event was bystanders witnessed and lay-bystander basic life support was performed only in 83 (23%). After treating OHCA by a physician-based prehospital medical team ROSC was obtained in 61%, the ROSC on admission was 50% and the overall survival to discharge was 21%. Initial petCO2 (OR: 22.04; 95%CI: 11.41-42.55), ventricular fibrillation or pulseless ventricular tachycardia as initial rhythm (OR: 2.13; 95%CI: 1.17-4.22), bystander CPR (OR: 2.55; 95%CI: 1.13-5.73), female sex (OR: 3.08; 95%CI: 1.49-6.38) and arrival time (OR: 1.29; 95%CI: 1.11-1.82) were associated with improved ROSC when using multivariate analysis. Using the same method we found that bystander CPR (OR: 5.05; 95%CI: 2.24-11.39), witnessed arrest (OR: 9.98; 95%CI: 2.89-34.44), final petCO2 (OR: 2.37; 95%CI: 1.67-3.37), initial petCO2 (OR: 1.61; 95%CI: 1.28-2.64) and arrival time (OR: 1.39; 95%CI: 1.33-1.60) were associated with improved survival. A questionnaire to potential bystanders has revealed disappointing knowledge about BLS fundamentals. On the other side, there is a welcomed willingness of potential bystanders to take BLS training and to follow dispatchers instructions by telephone on how to perform CPR.
CONCLUSION: After OHCA in a physician-based prehospital setting in our region, the overall survival to discharge was 21%. The potential bystander in our community is generally poorly educated in performing CPR, but willing to gain knowledge and skills in BLS and to follow dispatchers instructions. Arrival time, witnessed arrest, bystander CPR, initial petCO2 and final petCO2 were significantly positively related with ROSC on admission and with survival. Prehospital data from this and previous studies provide strong support for a petCO2 of 1.33 kPa to be a resuscitation threshold in the field. In our opinion the initial value of petCO2 should be included in every Utstein style analysis.