The Optimal Dosage of Neuromuscular Blocking Agent for Intraoperative Neuromonitoring During Thyroid Surgery

Recurrent laryngeal nerve (RLN) palsy is the most common and serious complication after thyroid surgery, and ranks among the leading reasons for medicolegal litigation of surgeons. Intraoperative neuromonitoring (IONM) are being applied to prevent RLN injury during thyroid surgery. IONM has been used as a means not only to localize and identify the RLN, but also to predict cord function and elucidate the surgical pitfalls during preparation of RLN.

Muscle relaxant is necessary for general anesthesia; it can facilitate tracheal intubation and stable conditions for surgery. However, the use of muscle relaxant might diminish the EMG response during IONM and interfere with the interpretation of IONM results. Eighty patients were randomized to receive one (group 1, n=40) or two (group 2, n=40) effective dose (ED95) of rocuronium to facilitate EMG endotracheal tube insertion. Evoked potentials were obtained per 5 minutes by stimulating vagus nerve from the time point of 30 to 70 minutes after administration of rocuronium. The magnitude of evoked potential at each time point and tracheal intubating condition were compared between groups. Accelerometry [twitch (% TW)] was used to monitor the quantitative degree of neuromuscular transmission. The aim of this study was to explore an alternative non-depolarizing muscle relaxant (Rocuronium) and its optimal dosage to replace succinylcholine for IONM. The ED95 of rocuronium is 0.3mg/kg and 2×ED95 is generally recommended as a standard intubation dosage.