Electrical impedance properties of the body and the problem of alternate-site burns during electrosurgery

The radiofrequency (RF) impedance at 500 kHz was measured between multiple contact points on the bodies of six healthy volunteers by a tetrapolar measurement technique. The impedance between various contact points was predictable and could increase by a factor of two, depending on the sites selected for electrode application. These results were related to a simple resistive model of RF current distribution through the body. Based on the model and on data from human subjects, a hierarchy of optimal locations was developed to minimize the impedance between a surgical site and a dispersive electrode site and to reduce the potential for alternate-site burns from electrosurgery.