J. Wang1, C. Nessim1, B. Dingley1, R. Auer1,2 1University Of Ottawa, Department Of Surgery, Ottawa, Ontario, Canada 2The Ottawa Hospital Research Institute, Ottawa, ON, Canada
Introduction:
Modern electrosurgery utilizes alternating current (AC) in the 300-500 kHz range to achieve a cutting or cauterization effect on tissue. Pinch burning is a common surgical technique used to achieve hemostasis with monopolar cautery. Cautery is applied to metal forceps rather than directly to tissue which creates a coagulation effect through the larger contact surface area. From anecdotal experience, the authors have found the effect of pinch burning is mitigated when the user holding the forceps leans against the metal bed railing. A potential explanation for this is via current leak through the gloved hand into the bed. The layers of forceps, glove, and hand functionally create an electrical component called a capacitor. Capacitors are able to transmit AC current despite the presence of the insulating layer. The effect is heightened at higher current frequencies. This phenomenon, called capacitive coupling, is well described in laparoscopic electrosurgery. This experiment was done to investigate if pinch burning current is reduced when the user holding forceps leans against the bed railing.
Methods:
We created a circuit to measure the voltage across simulated tissue represented by a 2000 Ω resistor. This value was chosen based on human tissue impedances reported in the literature. The circuit was shorted with forceps held by a hand wearing a single pair of latex surgical gloves. The voltage across the resistor was measured when the user holding the forceps was standing away from the surgical table versus touching the table at the waist or forearm.
Results:
The voltage measured over the resistor decreased from 14.4 to 12.2 V (16%) when touching the table with the waist and from 14.4 to 10.7 V (26%) at the forearm (p < 0.0001). This corresponded to a 1.1 and 1.8 mA current drop, and power loss of 28.5mW (29%) and 43.9mW (45%) respectively.
Conclusion:
When a surgeon is pinch burning in the operating room and in contact with the OR bed, they can create a short circuit through the forceps, into the body and into the bed. Despite the insulating properties of surgical gloves, AC current electrosurgery allows this effect to occur via a phenomenon called capacitive coupling. We have demonstrated in a simulated setting that this can result in current losses up to 26% and power losses up to 45%. In difficult technical situations where hemostasis is paramount, one strategy to improve pinch burning efficacy is to avoid contact with the OR table.
