J Endocr Surg.  2018 Mar;18(1):21-36. 10.16956/jes.2018.18.1.21.

Improving Safety of Neural Monitoring in Thyroid Surgery: Educational Considerations in Learning New Procedure

• Dionigi G
• Bartolo V
• Rizzo AG
• Marullo M
• Fabiano V
• Catalfamo
• Pergolizzi FP
• Cancellieri A
• Melita G

• KMID: 2414420
• DOI: http://doi.org/10.16956/jes.2018.18.1.21

Abstract

Literature on intraoperative neuro monitoring (IONM) during endocrine surgery have increased over recent years. A comprehensive understanding of the role of IONM for prevention of nerve injuries is critical to maximize safety during surgery of the anterior compartment of the neck. Neuromonitoring techniques are currently considered safe technique and technology; however, albeit sporadically, have been reported some complications and related side effects using such methods. The complications described can be related to the electrodes positioned at the larynx, at the obstruction of the endotracheal tube, the drugs used for anesthesia and the effects of electrical stimulation on nerve structures and systemic levels. This review will explore the safety issues of IONM to improve the outcomes among patients undergoing monitored thyroidectomy.

Keyword

Safety; Neural monitoring; Thyroidectomy; Endocrine Surgical Procedures

MeSH Terms

Anesthesia
Electric Stimulation
Electrodes
Endocrine Surgical Procedures
Humans
Larynx
Learning*
Neck
Thyroid Gland*
Thyroidectomy

Figure

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  Fig. 1 ETT-based surface electrode (Trivantage EMG; Medtronic Xomed Inc., Jacksonville, FL, USA). Tube is ID available in 5, 6, 7, 8, and 9 size. Is standard, non re-enforced tube. Gray area is the electrode area that pick-up EMG. Each EMG channel has an electrode placed anterior above the VF and posterior below the VF. Each length are; anterior electrode length: 25.4 mm, posterior: 30 mm, overall working length: 49 mm. Blue area is an intubation marker only. The tube will work about 5 mm beyond the blue depth marker. Tube is available in EU, USA, and Canada. ETT = endotracheal tube; EMG = electromyography; VF = vocal fold.

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  Fig. 2 Ground and return electrodes are usually placed in a deltoid or in presternal region.

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  Fig. 3 The awareness of the possibility of EMG reinforced ETT herniation is of paramount importance for patient health, as for any other tube adopting. In patients intubated, any event suggesting sudden ventilation blockage should be managed initially by prompt deflation of the cuff. The cuff should be inflated at the minimal necessary volume, and it should be kept in mind that the pilot balloon is not a reliable indicator of cuff pressure. The staff should pay maximum attention to the stability of endotracheal and breathing tubes. EMG = electromyography; ETT = endotracheal tube.

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  Fig. 4 EMG profile with amplitude (green), latency (red), and duration (blue) values definition. The EMG waveform is biphasic. The graphic represents pre-dissectional right vagal nerve stimulation (V1), with amplitude value of 676 mcV. Vocal cord depolarization amplitudes are about 100–800 μV during normal awake volitional speech (Blitzer et al. Otolaryngol Head Neck Surg 2009). EMG = electromyography; RLN = recurrent laryngeal nerve.

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  Fig. 5 Single use, incrementing prass stimulating probe, monopolar, standard flexible and ball tip (product No.8225490; Medtronic Xomed Inc., Jacksonville, FL, USA). Ball tip design is atraumatic for anatomical structures.

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  Fig. 6 EMG curve profile from Wu et al.'s study (23). ENG = electromyography; RLN = recurrent laryngeal nerve.

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  Fig. 7 Vagal nerve branches. SLN = superior laryngeal nerve; VN = vagus nerve; RLN = recurrent laryngeal nerve.

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  Fig. 8 Ventricular asystolia at the initial stimulus test in a patient with epilepsy. It is modified by Ali et al. (29).

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  Fig. 9 Vagal nerve dissection for intermitted and continuous monitoring. VN = vagus nerve; I-IONM = intermitted intraoperative neural monitoring; C-IONM = continuous intraoperative neuro monitoring.

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  Fig. 10 Vagal nerve identification, dissection and subsequent C-IONM probe positioning. We recommend caution when dissection the vagal nerve and C-IONM probe placement. Energy based devices should not be used near the vagal nerve for possible thermal spread injury. C-IONM = continuous intraoperative neuro monitoring.

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  Fig. 11 Positioning of C-IONM electrode. Open design electrode, requires partial VN dissection, tripolar mode of stimulation, size 54×8×0.8 mm (Dr. Langer Medical, GmbH, Waldkirch, Germany). C-IONM = continuous intraoperative neuro monitoring; VN = vagus nerve.

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  Fig. 12 Positioning of C-IONM electrode. Closed design electrode, requires 360° VN dissection, monopolar mode of stimulation, 2 size 2 and 3 mm APS (Medtronic Xomed Inc., Jacksonville, FL, USA). C-IONM = continuous intraoperative neuro monitoring; VN = vagus nerve.

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