title: Antenna coupling explains unintended thermal injury caused by common operating room monitoring devices.
abstract: BACKGROUND
  Unintended thermal injury from patient monitoring devices (eg, electrocardiogram pads, neuromonitoring leads) results in third-degree burns. A mechanism for these injuries is not clear. The monopolar "bovie" emits radiofrequency energy that transfers to nearby, nonelectrically active cables or wires without direct contact by capacitive and antenna coupling. The purpose of this study was to determine if, and to what extent, radiofrequency energy couples to common patient monitoring devices.
  
  
  METHODS
  In an ex vivo porcine model, monopolar radiofrequency energy was delivered to a handheld "bovie" pencil. Nonelectrically active neuromonitoring and cardiac-monitoring leads were placed in proximity to the monopolar pencil and its cord. Temperature changes of tissue touched by the monitoring lead were measured using a thermal camera immediately after a 5-second activation. The energy-device cords were then separated by 15 cm, the power was reduced from 30 W coag to 15 W coag and different cord angulation was tested. An advanced bipolar device, a plasma-based device, and an ultrasonic device were also tested at standard settings.
  
  
  RESULTS
  The neuromonitoring lead increased tissue temperature at the insertion site by 39 ± 13°C (P<0.001) creating visible char at the skin. The electrocardiogram lead raised tissue temperature by 1.3 ± 0.5°C (P<0.001). Decreasing generator power from 30 W to 15 W and separating the bovie cord from the neuromonitoring cord by 15 cm significantly reduced the temperature change (39 ± 13°C vs. 26±5°C; P<0.001 and 39 ± 13°C vs. 10 ± 5°C; P<0.001, respectively). Lastly, monopolar energy increased tissue temperatures significantly more than argon beam energy (34 ± 15°C), advanced bipolar energy (0.2 ± 0.4°C), and ultrasonic energy (0 ± 0.3°C) (all P<0.001).
  
  
  CONCLUSIONS
  Stray energy couples to commonly used patient monitoring devices resulting in potentially significant thermal injury. The handheld bovie cord transfers energy via antenna coupling to neuromonitoring leads that can raise tissue temperatures over 100°F (39°C) using standard settings. The most effective ways to decrease this energy coupling is to reduce generator power, increase the separation between wires, or utilize lower voltage energy devices such as ultrasonic or bipolar energy.
authors: *Department of Surgery, University of Colorado School of Medicine, Aurora §Covidien, Boulder, CO †Department of Surgery, The Ohio State University, Columbus, OH ‡University of Kansas School of Medicine, Kansas City, KS.
authors: Nicole T
authors: NT
authors: Townsend
authors: Edward L
authors: EL
authors: Jones
authors: Alessandro
authors: A
authors: Paniccia
authors: Joel
authors: J
authors: Vandervelde
authors: Jennifer R
authors: JR
authors: McHenry
authors: Thomas N
authors: TN
authors: Robinson
mesh_terms: D000818:Animals; D002058:Burns, Electric / Q000209:etiology*; D004195:Disease Models, Animal; D004564:Electrocoagulation / Q000009:adverse effects* / Q000295:instrumentation*; D004868:Equipment Failure; D006358:Hot Temperature / Q000009:adverse effects*; D007431:Intraoperative Complications; D009873:Operating Rooms; D013552:Swine