Stray Energy Transfer During Endoscopy: A New Mechanism for Complications

Edward L Jones, MD1, Amin Madani, MD2, Douglas M Overbey, MD1, Asimina Kiourti, PhD3, Satheesh Bojja-Venkatakrishnan, MS3, Dean J Mikami, MD3, Jeffrey W Hazey, MD3, Thomas N Robinson, MD1. 1University of Colorado and Denver VA Medical Center, 2McGill University, 3The Ohio State University

INTRODUCTION: Endoscopy is the standard tool for the evaluation and treatment of gastrointestinal disorders. While the risk of complications during endoscopy is low, the risk increases 100-fold when energy is used. Little is known about the mechanism of increased injury or what impact, if any, stray energy transfer has on endoscopy complications. The purpose of this study was to determine if stray energy transfer occurs during routine endoscopy and if so, to define strategies to minimize stray energy transfer.

METHODS AND PROCEDURES: A standard therapeutic upper endoscope was introduced into the stomach of an anesthetized pig. A monopolar generator delivered energy via an endoscopic snare for 5 seconds without the tip of the energy device contacting adjacent tissue or the endoscope itself. Baseline generator settings included a power level of 60 Watts on coag mode. Power level, mode and endoscope tip orientation were then varied to mimic in vivo use. The primary outcome (stray current) was quantified as change in temperature (°C) from baseline at the tissue nearest the tip of the endoscope via thermal imaging. Experiments were repeated 10 times and compared to a control (no energy activation). Data is expressed as mean ± standard deviation.

RESULTS: Tissue adjacent to the tip of the endoscope increased by 24.6±5.7°C compared to baseline (p<0.001) when using a hot biopsy forceps. When comparing temperature at three locations on the tip of the endoscope (when using a hot snare), tissue temperature increased 12.1±3.5°C nearest the camera lens (p<0.001 vs. all others), 2.1±0.8°C nearest the light lens, and 1.7±0.4°C nearest the working channel. Strategies to reduce stray energy transfer included: lowering power setting to 30 Watts and 15 Watts (12.1±3.5 vs. 9.5±0.8°C, p=0.04 and 12.1±3.5 vs. 8.0±0.8°C, p=0.002 respectively); and using low voltage cut mode (12.1±3.5 vs. 6.6±0.5°C, p<0.001).

CONCLUSION: Stray energy transfers from the monopolar instrument to the endoscope itself and can heat tissue nearest the tip of the endoscope by at least 25°C. The camera lens is the location of greatest energy transfer. Decreasing the power setting and using cut mode in preference to coag mode decreases stray energy transfer. This study provides the first evidence of stray energy transfer within the endoscope itself and provides an explanation for unexplained endoscopic complications during energy use. 

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