Effective Defibrillation in a Wet Environment: A Preliminary Study

Abstract

A new hypothermia treatment, the Thermosuit TM consists of the application of a thin layer of water to the body surface. Hypothermic-induced patients are often postresuscitative and may experience sequential fibrillation. Therefore, we examined whether defibrillation could be administered safely and effectively in such a wet environment. A 35 kg swine was anesthetized and placed inside the Thermosuit TM system. This consists of a water containing surround and pumping system. Defibrillation voltage and current were measured. 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. There were several 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 normally required less than 220 joules. There was only a small difference measured in the overall defibrillation voltage and current as applied to the electrodes for the several cases. Thus, under-water defibrillation is safe and can be performed effectively.