Single Incision Laparoscopic Surgery Increases the Risk of Unintentional Thermal Injury From the Monopolar “bovie” in Comparison to Traditional Laparoscopy

Nicole T Townsend, MD, MS, Edward L Jones, MD, MS, Douglas M Overbey, MD, Thomas N Robinson. University of Colorado

INTRODUCTION: Single incision laparoscopic surgery (SILS) places multiple instruments in close, parallel proximity; an orientation that has been shown to increase stray energy transfer from the monopolar “Bovie” instrument to nearby instruments during traditional laparoscopy. The purpose of this study was to compare the energy transferred during simulated cholecystectomy via SILS to traditional four port laparoscopy (TRD). Our hypothesis is that close proximity and parallel orientation of the SILS instruments will result in increased energy transfer.

METHODS AND PROCEDURES: In a laparoscopic simulator, instruments were inserted via SILS or TRD set-up. The monopolar generator delivered energy to a laparoscopic L-hook instrument for 5-second activations on 30Watts coag mode. The primary outcome (stray current) was quantified by measuring the heat of liver tissue held adjacent to the non-electrically active 10mm telescope tip and Maryland grasper in both the SILS and TRD set-ups. To control for the potential confounder of stray energy coupling via wires outside the surgical field, the camera, light cord and active electrode cord were bundled in parallel or completely separated.

RESULTS: SILS and TRD set-ups create similar amounts of stray current as measured by increased tissue temperature at the non-electrically active telescope tip (41±12°C versus 39±10°C; p=0.71) when the active electrode and camera/light cords are bundled. Stray current was greater in SILS compared to TRD at the tip of the non-electrically active Maryland forceps (38±9°C versus 20±10°C; p<0.01). Separation of the active electrode and camera cords did not change the amount of stray energy in the SILS orientation for either telescope (39±10? bundled versus 36±10? separated; p=0.40) or grasper (38±9? bundled versus 34±11? separated; p=0.19) but did significantly reduce energy transfer in the TRD orientation (41±12 bundled vs. 24±10 separated; p<0.01). When SILS was compared to TRD with the cords separated, SILS increased stray energy at both the telescope tip and grasper tip more than TRD laparoscopy (36±10ºC vs. 24±10ºC; p<0.01 and 34±11ºC vs. 17±8ºC; p<0.01 respectively).

CONCLUSION: Single incision laparoscopic surgery transfers nearly twice as much stray energy as traditional laparoscopy when using the monopolar “Bovie.” Separation of the active electrode and camera cords significantly reduces stray energy transfer during TRD laparoscopy but does not significantly affect SILS due to the forced parallel alignment and close proximity of the instruments. This unavoidable increased risk of injury during SILS should be considered when choosing the best type of surgery for each patient.

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