Low-dose Rocuronium Provides Adequate Muscle Relaxation and Increases the Effectiveness of Intraoperative Neural Monitoring in Thyroid Surgery

Intraoperative Neuromonitoring (IONM) was started to be used by surgeons to help prevent laryngeal nerve (RLN) damage during thyroid and parathyroid operations. IONM can be used to localize and identify RLN intraoperatively, to evaluate vocal function after thyroid resection, and to explain the mechanism of RLN injury. However, an important problem in the routine use of IONM is the effect of neuromuscular blocking agents (NMBAs). The use of NMBAs in general anesthesia is essential to provide clinically acceptable tracheal intubation conditions and to prevent laryngeal trauma. However, NMBAs may be the potential cause of a false-negative response during the IONM. Randolph et al. proposed short-acting 1-2 mg/kg succinylcholine for enough relaxation and the ease of electromyographic (EMG) endotracheal tube intubation during the IONM. However, succinylcholine, a depolarizing NMBA, is associated with various adverse effects such as cardiac arrhythmia, hyperkalemia, and malignant hyperthermia. Nondepolarizing NMBAs are widely used by most anesthesiologists due to their safe effects, but to the best our knowledge, there is no very short-acting nondepolarizing NMBA. This deficiency creates a problem because the dose and the time point of nerve stimulation are critical for a successful IONM. However, some studies have reported the feasibility of IONM following the administration of nondepolarizing NMBAs during a thyroid operation. Rocuronium is a short-acting and nondepolarizing NMBA type which is widely used for induction in general anesthesia. Although 0.6 mg/kg rocuronium is recommended for standard intubation dose, the ease of intubation can also be provided with 0.3 mg/kg rocuronium or 1.5 mg/kg succinylcholine. Therefore, the present study was designed to compare the effects of IONM with low and standard rocuronium doses in the induction of general anesthesia.