Effects of early defibrillation of out-of-hospital cardiac arrest patients by ambulance personnel.

During the year of this study, the specially trained ambulance personnel initiated cardiopulmonary resuscitation in 307 out of hospital cardiac arrest patients. All arrests, regardless of aetiology, age or other circumstances, were studied. The mean age for the arrest patients was 66 years. The majority of arrests occurred in elderly patients at home. Although as many as 70% of the arrests were witnessed, cardiopulmonary resuscitation had been initiated in only 15% of patients before the arrival of the ambulance. One hundred and forty patients had rapid ventricular tachycardia or ventricular fibrillation when the ambulance arrived (mean delay of 7.8 +/- 3.7 min). The effects of defibrillation could be fully evaluated in 135 patients. QRS complexes, with a rate between 20 and 110 min-1, were seen after defibrillation in 94 patients, persistent asystole in 26 patients and persistent ventricular fibrillation, despite one or more 360 J DC shocks, in 15 patients. Nineteen of the 94 patients who had a return of QRS complexes also had a return of pulse shortly after defibrillation without further advanced life support measures, while another six patients had a return of pulse after further life support therapy. Six of the 32 ventricular fibrillation patients (19%) reached within 4 min and three of the 63 ventricular fibrillation patients (5%) reached between 4-8 min survived. An estimated 4.2 lives per 100,000 inhabitants a year were saved when early defibrillation was used as the only addition to the basic life support provided by the present ambulance service.