title: Safety analysis of vagal nerve stimulation for continuous nerve monitoring during thyroid surgery.
abstract: OBJECTIVE
  Intraoperative neuromonitoring (IONM) facilitates recurrent laryngeal nerve (RLN) identification, but various studies affirm virtually unchanged postoperative RLN palsy rates. Several authors meanwhile suggest continuous intraoperative neuromonitoring (CIONM) via vagal nerve stimulation (VNS) to improve RLN protection. However, knowledge of side effects of electrical VNS derives mainly from its therapeutic applications in the fields of neurology and psychiatry. The presented study was conducted to further evaluate the safety of CIONM and identify possible VNS related side effects.
  
  
  METHODS
  Prospective nonrandomized controlled trail.
  
  
  METHODS
  Forty patients scheduled for thyroid or parathyroid surgery were enrolled in the trail. The intervention group consisted of 22 patients receiving VNS for CIONM. Eighteen patients were operated on with routine IONM. To assess VNS-induced effects on the autonomic nervous system (ANS), heart rate variability analysis (HRVA) was applied. Serum cytokine levels of tumor necrosis factor (TNF)-α were monitored to evaluate immunomodulatory effects of VNS.
  
  
  RESULTS
  HRVA revealed significantly increased vagal activity during CIONM. This parasympathetic predominance was not countered by the sympathetic nervous system. Despite a significant increase of vagal tone, no hemodynamic events occurred; in fact, no significant changes in median heart rate or in median arterial blood pressure were detected. Even though anti-inflammatory effects of VNS have been reported, no attenuation of cytokine release of TNF-α was measured.
  
  
  CONCLUSIONS
  VNS for CIONM resulted in increased vagal activity assessable via HRVA. The increased parasympathetic tone affected neither hemodynamics nor levels of the proinflammatory cytokine TNF-α. VNS for CIONM appears safe with the applied settings.
authors.affiliation: Department of General and Visceral Surgery, Robert Bosch Hospital, Stuttgart, Germany. cmfriedrich@gmx.de
authors.forename: Colin
authors.initials: C
authors.lastname: Friedrich
authors.forename: Christoph
authors.initials: C
authors.lastname: Ulmer
authors.forename: Fabian
authors.initials: F
authors.lastname: Rieber
authors.forename: Eva
authors.initials: E
authors.lastname: Kern
authors.forename: Andrea
authors.initials: A
authors.lastname: Kohler
authors.forename: Karolina
authors.initials: K
authors.lastname: Schymik
authors.forename: Klaus-Peter
authors.initials: KP
authors.lastname: Thon
authors.forename: Wolfram
authors.initials: W
authors.lastname: Lamadé
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D005858:Germany; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D011446:Prospective Studies; D012016:Reference Values; D018570:Risk Assessment; D017751:Safety Management; D018709:Statistics, Nonparametric; D013959:Thyroid Diseases / Q000473:pathology / Q000601:surgery*; D013965:Thyroidectomy / Q000009:adverse effects / Q000379:methods*; D016896:Treatment Outcome; D055536:Vagus Nerve Stimulation / Q000009:adverse effects / Q000379:methods*; D014826:Vocal Cord Paralysis / Q000453:epidemiology / Q000517:prevention & control*; D055815:Young Adult