Comparison of Lateral Thermal Spread Using Monopolar and Bipolar Diathermy, and the Bipolar Vessel Sealing System ThermoStapler™ During Thyroidectomy

Abstract

Electric devices enabling the maintenance of haemostasis during surgery have found application in modern thyroidectomy procedures. The haemostatic effect is associated with generation of heat, which apart from the intended result may bring about thermal tissue injury. The aim of the study was to determine the thermal spread around the active tip of electric devices in the operating field during total thyroidectomy, and the safe temperature range during the operation of studied devices. Over 14 months from December 2009 until January 2011, 76 total thyroidectomy procedures were analysed. The surgeries employed mono- and bipolar diathermy as well as the ThermoStapler™ bipolar vessel sealing system. During the procedures, the thermal spread around the active tips of used electric devices was recorded with the use of high-definition camera. Comparable 5-second periods of electric device use at two power ranges (30 W and 50 W) were selected from the recorded material. The highest temperature of the active tip of electric devices was determined, and the 42°C isotherm was found with the use of computer image analysis, thus determining the safe distance of important anatomic structures from the active tip of the electric device. The temperature spread around the active tips of electric devices was recorded and the 42°C isotherm was determined. The diameter of this isotherm at the end of operation differed statistically significantly depending on the type of electric devices and power settings. The highest temperature, at both power ranges, was recorded for the bipolar vessel sealing system, while the lowest - for bipolar diathermy; at the same time a significantly lower 42°C isotherm diameter was found for ThermoStapler™ as compared with other devices. In all studied cases, the largest heat spread was found for monopolar diathermy. The mean safe distance of the active tip of an electric device from important anatomic structures is 5 mm and depends on the device type and its power settings. Monopolar diathermy causes the strongest heating of surrounding tissues, and the ThermoStapler™ bipolar vessel sealing system, despite producing the highest temperature during operation, causes relatively small thermal injury to the surrounding tissues.