Successful defibrillation in water: a preliminary study

Mild hypothermia (32-34 deg C) treatment alleviates vital organ damage after cardiac arrest. A new cooling device, the Thermosuit operates by applying of a thin layer of water directly to the body surface. Hypothermic patients may experience sequential fibrillation. Therefore, we examined whether defibrillation could be administered safely and effectively in water. A 35 kg swine was anesthetized and placed inside the Thermosuit system. This consists of a water containing surround and pumping system. Conventional AED disposable defibrillation electrodes were applied to the animal's chest. Fibrillation was created by applying a 50-volt signal to a pacing wire introduced into the heart. Following a 30-second period of fibrillation, defibrillation was attempted using Medtronic AED 1000 defibrillator. Defibrillation voltage and current were measured. There were three test cases: dry in the system, wet in the functioning system, and damp. Cooling water in the system was contaminated with saline to simulate potential conditions in clinical application. In each fibrillation-defibrillation sequence, the heart was restarted successfully; this required less than 220 joules. Only a small difference was measured in the overall defibrillation voltage and current as applied to the electrodes for the different cases. Thus, underwater defibrillation is safe and can be performed effectively.