Safety of Continuous Intraoperative Neuromonitoring (C-IONM) in Thyroid Surgery

Excerpt

Terris [1] reported nine cases operated with continuous neuromonitoring (CIONM). We are concerned with some of aspects reported. Several hundred cases of CIONM have been published without reporting related side effects [2]. The anesthesia description is not precisely presented. Which anesthetic protocol was used during induction and maintenance? How was the depth of anesthesia measured? What was the pharmacological approach to treating the effects on autonomic nervous system (ANS)? ANS alterations are frequently encountered but unrelated to vagal stimulation [3]. The use of continuous propofol infusion reduces blood pressure and parasympathetic tone in direct proportion to the depth of anesthesia, while sevoflurane use exerts only minor effects on the parasympathetic tone [3]. Greater parasympathetic tone in case of bispectral index values >50 is expected with propofol and bradyarrhytmias may occur [3]. Totally intravenous anesthesia technique with opioids influences the autonomic heart rate response [3]. Sevoflurane effects on the nervous system are characterized by an overall reduction in activity of the sympathetic and parasympathetic nervous system, without “imbalance” between the two components of the ANS [3]. With these overwhelming influences, it is difficult to implicate CIONM. The hemodynamic instability described in 2nd complication is difficult to clearly be attributable to a vagal reaction to anesthesia or vagal nerve (VN) manipulation or CIONM stimulation. Figure 3 shows heart rate reaction at “APS off” not at “APS on,” text is discrepant [1]. …