Temperature distribution beneath pediatric electrosurgical dispersive electrodes: a model study.

Concerns have been raised about the safety and the thermal performances of commercially available electrosurgical dispersive electrodes. A model system was designed to simulate the thermal effects observed in humans. The following critical factors affecting the thermal performances of pediatric electrodes were investigated: the intensity and duration of the applied current, the electrical resistivity of the test medium, the contact interface area between the electrode and the test medium, and the water content of the adhesive gel of the electrode. The maximum temperature rises (delta Tm) under the electrodes were 0.6 +/- 0.1 degrees C, 2.8 +/- 0.2 degrees C, and 5.2 +/- 0.3 degrees C when 60 s of 1 A, 2 A, and 3 A currents, respectively, were applied. delta Tm increased linearly with the increase of the duration of applied current and the resistivities of the test medium. When dispersive electrodes with reduced areas or reduction of water content of the adhesive gel of the electrodes were used, delta Tm increased with the areas or the water contents decreased. The currents and durations used in this study were in excess of those routinely used in electrosurgery. The study confirmed that the maximum temperature increase under the electrode is inversely proportional to the square of the perimeter of the electrode, rather than the square of the surface area. The test methods described can be used to evaluate the thermal performances of other electrosurgical dispersive electrodes. Monitoring the impedance at the interface between the dispersive electrode and the tissue in contact would reduce the risk of burns.