Antenna coupling--a novel mechanism of radiofrequency electrosurgery complication: practical implications.
OBJECTIVE
(1) To determine if antenna coupling occurs in common operating room scenarios. (2) To define modifiable clinical variables that reduce the magnitude of antenna coupling.


BACKGROUND
Mechanisms of electrosurgical burns where monitoring devices contact the surgical patient are unclear. Antenna coupling occurs when the "bovie" active electrode (electrically active transmitting antenna) emits energy, which is captured by a nonelectrically active wire (electrically inactive receiving antenna) in close proximity without direct contact.


METHODS
Monopolar radiofrequency energy was delivered to a laparoscopic instrument (electrically active transmitting antenna), whereas other nonelectrically active wires (electrically inactive receiving antenna) including electrocardiogram (EKG) lead, nonactive "bovie" pencil, and nerve electrode monitor were placed in proximity. Temperature changes of tissue placed adjacent to the electrically inactive receiving antennae were measured.


RESULTS
Nonelectrically active wires (receiving antenna) increase tissue temperature when lying parallel to the active electrode cord: EKG pad 2.4°C ± 1.2°C (P = 0.002), "bovie" pencil tip 90°C ± 9°C (P < 0.001), and nerve electrode monitor 106°C ± 12°C (P < 0.001). Factors that reduced the heat generated by antenna coupling included the following: increasing angulation between transmitting and receiving antennae (parallel = 90°C ± 9°C; 45° angle = 53°C ± 10°C; perpendicular = 35°C ± 11°C; P < .001), increasing separation distance between parallel transmitting and receiving antenna (<1 cm = 90°C ± 9°C; 15 cm = 44°C ± 18°C; 30 cm = 39°C ± 2°C; P < .001); and decreasing generator power setting (15 W = 59°C ± 11°C; 30 W = 90°C ± 9°C; 45 W = 98°C ± 8°C; P < .001).


CONCLUSIONS
Antenna coupling occurs in common operating room scenarios. Simple, practical measures by the surgeon, such as orienting the receiving antenna at a greater angle and with greater separation to the active electrode cord, or lowering the generator power setting reduce antenna coupling.
Department of Surgery, University of Colorado School of Medicine, Aurora, CO, USA. thomas.robinson@ucdenver.edu
Thomas N
TN
Robinson
Kelli S
KS
Barnes
Henry R
HR
Govekar
Greg V
GV
Stiegmann
Christina L
CL
Dunn
Francis T
FT
McGreevy
D001831:Body Temperature; D002058:Burns, Electric / Q000209:etiology* / Q000517:prevention & control; D004566:Electrodes; D004598:Electrosurgery / Q000009:adverse effects*; D006801:Humans; D007431:Intraoperative Complications; D010535:Laparoscopy / Q000009:adverse effects*; D009873:Operating Rooms