Body weight does not affect defibrillation, resuscitation, or survival in patients with out-of-hospital cardiac arrest treated with a nonescalating biphasic waveform defibrillator.

BACKGROUND This is a study of the influence of body weight on defibrillation, resuscitation, and survival in patients with out-of-hospital cardiac arrest treated with a nonescalating impedance-compensating 150-J biphasic waveform defibrillator. METHODS Cardiac arrest data from Rochester, MN, emergency medical services over a 6-yr period was retrospectively analyzed. Patient weight data were available for 62 of the 68 patients who were treated initially by basic life support personnel and who presented with a shockable rhythm. For each defibrillation and resuscitation outcome variable, we tested for differences in body weight for successful vs. unsuccessful outcome. RESULTS Initial shocks defibrillated 92% (83% to 97%) of patients. Cumulative success with two shocks was 98% (confidence interval, 92% to 100%) and with three shocks was 100% (confidence interval, 95% to 100%). The mean shock impedance was 90 +/- 21 ohms. The average body weight was 84 +/- 17 kg (minimum, 53 kg; maximum, 135 kg) and was normally distributed. Based on the body mass index for 46 patients, approximately 41% were classified as overweight (body mass index, > or = 25), 24% obese (body mass index, > or = 30), and 4% extremely obese (body mass index, > or = 40). The remaining 31% were classified as normal or underweight. First-shock success, cumulative success through two shocks, and cumulative success through the first-shock series were unrelated to body weight, as were basic life support restoration of spontaneous circulation, prehospital restoration of spontaneous circulation, hospital admission, and discharge. CONCLUSIONS Overweight patients were defibrillated by the biphasic waveform used in this study at high rates, with a fixed energy of 150 J, and without energy escalation.