title: Electrophysiologic monitoring correlates of recurrent laryngeal nerve heat thermal injury in a porcine model.
abstract: OBJECTIVE
  Thermal injury to the recurrent laryngeal nerve (RLN) may not be visually apparent and may go unrecognized intraoperatively. This study aimed to investigate the heat thermal tolerance of RLN and evaluate the electrophysiologic correlates of electromyographic (EMG) signal change during an acute RLN heat damage.
  
  
  METHODS
  Prospective porcine model with continuous intraoperative neuromonitoring (CIONM).
  
  
  METHODS
  Ten pigs (20 RLNs) undergoing CIONM had their EMG tracings recorded and correlated with heated normal saline (NS) irrigation of varying temperature and duration.
  
  
  RESULTS
  In the initial pilot study, the EMG was without change during incremental heated NS irrigation (40/45/50/55 °C for 60 seconds), but adverse EMG combined events (CE) (amplitude decrease with a concordant latency increase) occurred and degraded to loss of signal (LOS) (by 17.5 ± 1.3 seconds) when the temperature was elevated to 60 °C (n = 4). Another 16 RLNs were evaluated to further compare the EMG pattern after various degrees of thermal stress (60/70 °C for 30/20 seconds). Electromyographic recordings showed CEs and LOS in all RLNs, and only six of eight RLNs with 60 °C exposure showed slight EMG amplitude recovery (16%-35%) after 20 minutes. None of the injured nerve segments were visually apparent, but all were detectable by IONM.
  
  
  CONCLUSIONS
  Sixty degrees Celsius is a critical temperature to cause RLN thermal injury. Continuous intraoperative neuromonitoring can be used as a tool for the early detection of acute thermal stress and may guide use of energy-based devices during thyroid procedures.
  
  
  METHODS
  N/A.
authors.affiliation: Graduate Institute of Clinical Medicine, Faculty of Medicine, College of Medicine, Department of Otorhinolaryngology-Head and Neck Surgery, Kaohsiung, Taiwan.
authors.forename: Yi-Chu
authors.initials: YC
authors.lastname: Lin
authors.affiliation: First Division of Surgery, Research Center for Endocrine Surgery, Department of Surgical Sciences and Human Morphology, University of Insubria (Como-Varese), Varese, Italy.
authors.forename: Gianlorenzo
authors.initials: G
authors.lastname: Dionigi
authors.affiliation: Division of Thyroid and Parathyroid Endocrine Surgery, Department of Laryngology and Otology, Massachusetts Eye and Ear Infirmary, Endocrine Surgery Service, Division of Surgical Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Randolph
authors.affiliation: Department of Anesthesiology, Kaohsiung Medical University Hospital, (KMU), Kaohsiung, Taiwan.
authors.forename: I-Cheng
authors.initials: IC
authors.lastname: Lu
authors.affiliation: Department of Anesthesiology, Kaohsiung Medical University Hospital, (KMU), Kaohsiung, Taiwan.
authors.forename: Pi-Ying
authors.initials: PY
authors.lastname: Chang
authors.affiliation: Department of Pathology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Shan-Yin
authors.initials: SY
authors.lastname: Tsai
authors.affiliation: Department of Surgery, KUMC Thyroid Center, Korea University Hospital, Korea University College of Medicine, Seoul, Korea.
authors.forename: Hoon Yub
authors.initials: HY
authors.lastname: Kim
authors.affiliation: Department of Surgery, KUMC Thyroid Center, Korea University Hospital, Korea University College of Medicine, Seoul, Korea.
authors.forename: Hye Yoon
authors.initials: HY
authors.lastname: Lee
authors.affiliation: Division of Head and Neck Endocrine Surgery, Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland, U.S.A.
authors.forename: Ralph P
authors.initials: RP
authors.lastname: Tufano
authors.affiliation: Department of Thyroid and Parathyroid Surgery, China-Japan Union Hospital, Jilin University and Jilin Provincial Key Laboratory of Surgical Translational Medicine, Changchun, Jilin Province, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Sun
authors.affiliation: Department of Thyroid and Parathyroid Surgery, China-Japan Union Hospital, Jilin University and Jilin Provincial Key Laboratory of Surgical Translational Medicine, Changchun, Jilin Province, China.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Liu
authors.affiliation: Graduate Institute of Clinical Medicine, Faculty of Medicine, College of Medicine, Department of Otorhinolaryngology-Head and Neck Surgery, Kaohsiung, Taiwan.
authors.forename: Feng-Yu
authors.initials: FY
authors.lastname: Chiang
authors.affiliation: Graduate Institute of Clinical Medicine, Faculty of Medicine, College of Medicine, Department of Otorhinolaryngology-Head and Neck Surgery, Kaohsiung, Taiwan.
authors.forename: Che-Wei
authors.initials: CW
authors.lastname: Wu
mesh_terms: D000818:Animals; D001831:Body Temperature; D002056:Burns / Q000175:diagnosis* / Q000503:physiopathology; D017115:Catheter Ablation / Q000009:adverse effects*; D004195:Disease Models, Animal; D004576:Electromyography / Q000379:methods*; D005500:Follow-Up Studies; D007431:Intraoperative Complications / Q000175:diagnosis / Q000517:prevention & control*; D008991:Monitoring, Physiologic / Q000379:methods*; D010865:Pilot Projects; D011446:Prospective Studies; D061226:Recurrent Laryngeal Nerve Injuries / Q000175:diagnosis* / Q000503:physiopathology; D015203:Reproducibility of Results; D013552:Swine; D013965:Thyroidectomy / Q000009:adverse effects* / Q000379:methods
keywords: Recurrent laryngeal nerve; continuous intraoperative neuromonitoring; energy-based devices; nerve thermal injury; thyroid surgery