Transthoracic Incremental Monophasic Versus Biphasic Defibrillation by Emergency Responders (TIMBER)

Abstract

Background-Although biphasic, as compared with monophasic, waveform defibrillation for cardiac arrest is increasing in use and popularity, whether it is truly a more lifesaving waveform is unproven. Methods and Results-Consecutive adults with nontraumatic out-of-hospital ventricular fibrillation cardiac arrest were randomly allocated to defibrillation according to the waveform from automated external defibrillators administered by prehospital medical providers. The primary event of interest was admission alive to the hospital. Secondary events included return of rhythm and circulation, survival, and neurological outcome. Providers were blinded to automated defibrillator waveform. Of 168 randomized patients, 80 (48%) and 68 (40%) consistently received only monophasic or biphasic waveform shocks, respectively, throughout resuscitation. The prevalence of ventricular fibrillation, asystole, or organized rhythms at 5, 10, or 20 seconds after each shock did not differ significantly between treatment groups. The proportion of patients admitted alive to the hospital was relatively high: 73% in monophasic and 76% in biphasic treatment groups (Pϭ0.58). Several favorable trends were consistently associated with receipt of biphasic waveform shock, none of which reached statistical significance. Notably, 27 of 80 monophasic shock recipients (34%), compared with 28 of 68 biphasic shock recipients (41%), survived (Pϭ0.35). Neurological outcome was similar in both treatment groups (Pϭ0.4). Earlier administration of shock did not significantly alter the performance of one waveform relative to the other, nor did shock waveform predict any clinical outcome after multivariate adjustment. Conclusions-No statistically significant differences in outcome could be ascribed to use of one waveform over another when out-of-hospital ventricular fibrillation was treated.

Part 6: Defibrillation

“…One randomized study comparing transthoracic incremental monophasic with biphasic defibrillation for out-of-hospital pulseless VT/VF cardiac arrest failed to demonstrate any significant differences in any outcome (LOE 1). 69 A single-cohort study (LOE 3) 70 using the 2000 International Guidelines 71 demonstrated better hospital discharge and neurological survival with biphasic than with monophasic waveforms. However, there were confounding factors in that the intervals between the first and second shocks (of 3-stacked shocks) were shorter with the biphasic defibrillators.…”

Amiodarone, Lidocaine, or Placebo in Out-of-Hospital Cardiac Arrest

“…Although ventricular fibrillation or pulseless ventricular tachycardia is regarded as the most treatable presentation of out-of-hospital cardiac arrest because of its responsiveness to shock, 2 most defibrillation attempts do not result in sustained return of spontaneous circulation. 3 Ventricular fibrillation or pulseless ventricular tachycardia commonly persists or recurs after shock, and there is a significant inverse relationship between the duration of ventricular fibrillation or pulseless ventricular tachycardia, or the frequency of acute recurrences, and resuscitation outcome. [4][5][6] Amiodarone and lidocaine are used commonly to promote successful defibrillation of shockrefractory ventricular fibrillation or pulseless ventricular tachycardia and prevent recurrences.…”

Part 6: Electrical Therapies

“…[21][22][23][24][25] Although the optimal energy level for defibrillation using any of the monophasic or biphasic waveforms has not been determined, a recommendation for higher initial energy when using a monophasic waveform was weighed by expert consensus with consideration of the potential negative effects of a high first-shock energy versus the negative effects of prolonged VF. The consensus was that rescuers using monophasic defibrillators should give an initial shock of 360 J; if VF persists after the first shock, second and subsequent shocks of 360 J should be given.…”