Part 3: Defibrillation

Abstract

The 2005 Consensus Conference considered questions related to the sequence of shock delivery and the use and effectiveness of various waveforms and energies. These questions have been grouped into the following categories: (1) strategies before defibrillation, (2) use of automated external defibrillators (AEDs), (3) electrode-patient interface, (4) use of the electrocardiographic (ECG) waveform to alter management, (5) waveform and energy levels for the initial shock, (6) sequence after failure of the initial shock (ie, second and subsequent shocks), and (7) other related topics. The ECC Guidelines 2000 1 state that defibrillation should be attempted as soon as ventricular fibrillation (VF) is detected, regardless of the response interval (ie, time between collapse and arrival of the AED). If the response interval is >4 to 5 minutes, however, there is evidence that 1½ to 3 minutes of CPR before attempted defibrillation may improve the victim’s chance of survival. The data in support of out-of-hospital AED programs continues to accumulate, and there is some evidence supporting the use of AEDs in the hospital. Analysis of the VF waveform enables prediction of the likelihood of defibrillation success; with this information the rescuer can be instructed to give CPR or attempt defibrillation. This technology was developed by analysis of downloads from AEDs; it has yet to be applied prospectively to improve defibrillation success and is not available outside research programs. All new defibrillators deliver a shock with a biphasic waveform. There are several varieties of biphasic waveform, but the best variant and the optimal energy level and shock strategy (fixed versus escalating) have yet to be determined. Biphasic devices achieve higher first-shock success rates than monophasic defibrillators. This fact, combined with the knowledge that interruptions to chest compressions are harmful, suggests that a 1-shock strategy (1 shock followed immediately by CPR) may be preferable to …