Emergency Cardiac Ventricular Defibrillation

Abstract

Survival after sudden ventricular fibrillation is likely when defibrillator shock is properly applied. Both equipment and techniques are important keys to success. Recent equipment options include portability, battery power, built-in monitors, and telemetry. These make defibrillators useful in ambulances. Modern equipment more efficiently delivers the stored energy; when set for 400 joules, most defibrillators deliver at least 300. More powerful shocks may damage the heart. All devices should be regularly checked for actual output. DC equipment should replace older, AC devices, as AC shock can damage operators and patients' hearts. Optimum waveform remains in dispute. Proper technique is to verify fibrillation by ECG, apply gel to electrodes, position electrodes on chest, select energy dose, press down on electrodes, apply the shock, check rhythm on ECG, and repeat the procedure if necessary. Low resistivity gel should be used. Current thought is that 8- to 14-cm diameter elecrodes should be used for adults, smaller electrodes for children. Energy dose is controver-sial; for adults we recommend an initial dose of 300 joules, followed by larger doses if necessary. Firm pressure on electrodes improves shock delivery. Shock can be applied before CPR if given within 1 minute after fibrillation starts. If fibrillation has persisted for as long as 3 minutes, it may be best to apply CPR for 1 minute prior to the shock. Ongoing research is investigating new waveforms, current density distribution, and cardiac protection by drugs.