Monopolar Instruments Transfer Stray Energy During Robotic Surgery

Douglas M Overbey, MD2, Edward L Jones, MD, MS1, Douglas Hirth, MD2, Teresa S Jones, MD, MS1, Thomas N Robinson, MD, MS1. 2University of Colorado, Department of Surgery, 1Denver Veteran’s Affairs Hospital, Department of Surgery

Introduction: Stray energy transfer from monopolar instruments during laparoscopy can be potentially catastrophic. Robotic surgery is increasing in popularity however the risk of stray energy transfer during robotic surgery is unknown. The PURPOSE of this study was (1) to quantify stray energy transfer using robotic instrumentation, (2) to determine strategies to minimize the transfer of energy, and (3) to compare robotic stray energy transfer to traditional laparoscopy.

Methods and Procedures: In a laparoscopic trainer box, the monopolar instrument was activated using both robotic instrumentation (da vinci® system) and traditional laparoscopic instruments. In both set-ups, energy was delivered through an L-hook. A camera telescope and assistant grasper were inserted into the trainer. During energy activation to the L-hook, each nonelectrical instrument (camera and grasper) tips were placed adjacent to the simulated tissue. The primary outcome variable was an increase in simulated tissue temperature (°C) placed adjacent to the non-electrical grasper and camera tips.  Temperature was measured with a thermal camera.   

Results: Simulated tissue increased in temperature nearest the tip of the robotic assistant port grasper (18.3±5.8°C; p=<0.001) but not nearest the robotic camera tip (2.3±3.6°C; P=0.08). Strategies to decrease energy transfer included: using desiccation technique in preference to open-air activation (0.15±0.2 vs. 18.3±5.8°C, p<0.001); decreasing power setting from 30 Watts to 15 Watts (18.3±5.8 vs. 2.6±2.8, p<0.001); and using low voltage cut mode in preference to coag mode (3.1±2.1 vs 18.3±5.8, p<0.001). When compared to traditional laparoscopy, stray energy transfer to the grasper was not statistically different between robotic and laparoscopic instruments (18.3±5.8 vs 16.9±6.6, p=0.6). However, significantly more energy transferred to the laparoscopic camera tip compared to the robotic camera tip (18.7±5.3 vs 2.3±3.6°C, p<0.001).

Conclusions: Unintentional energy transfer occurs during robotic surgery. In contrast to traditional laparoscopy, the assistant grasper is the highest risk for thermal injury due to stray energy transfer. Strategies to reduce stray energy transfer in robotic surgery include avoiding activation without tissue contact, lowering generator power setting and using low voltage cut mode in preference to coag mode. These practical findings can aid surgeons using the robotic surgical approach to minimize inadvertent energy transfer.  

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