Study Of Real-time Intraoperative Monitoring Of Recurrent Laryngeal Nerve

Objective (1) To study the influence of several types of nerve injuries during operation on the function of recurrent laryngeal nerve (RLN) in rabbits. (2) To evaluate the clinical significance and application value of the real-time intraoperative monitoring (RTIM) technique in preventing RLN from injury during operation. ( 3 ) To study the monitoring indications, methods, technical parameters of nerve-identifying. (4) To observe the influence of general anesthesia on the RTIM procedure.Methods (1) Twenty New Zealand rabbits were randomly divided into four groups ( i.e. stretch, ligation, clamping and electrocautery group), and each group had 10 RLNs in five rabbits. The exposed RLN before injury was used as the control groups. We imitated four common types of injuries in cervical segment of RLN in thyroid gland surgery (TGS) and established experimental animal models with damaged RLN under various conditions. We also recorded the compound muscle action potential (cMAP) by the bipolar electrodes inserted into muscle by means of nerve integrity monitor (NIM). The minimal stimulus current intensity threshold (MSCIT) of evoked electromyography (EMG)in larynx muscle was obtained after injury of RLN. (2) The RTIM of RLNs by NIM were used in 38 cases who underwent thyroid surgery under general anesthesia from Nov. 2002 to April 2005. (3) The endotracheal intubation tube with laryngeal electrode sited on the tube (NIM?EMG) were adopted for general anesthesia.Results (l)The average MSCIT of RLNs in rabbits before injury was 0.05 mA. No significant difference among groups was observed by t test (P>0.05). The average MSCIT of damaged groups (stretch, ligation, clamping and electrocautery group) was 0.24 mA, 1.04 mA, ≥3.0 mA and 2.81 mA respectively. The average MSCIT was significant difference in each experimental group (P<0.05), except stretch group versus control group, clamping group versus electrocautery group. (2) The spontaneous non-in-phase cMAP of larynx muscle in both vocal cords was recorded in all 38 cases who underwent thyroid surgery under general anesthesia. The RLNs in 7 cases were exposed and explored in 5 cases. The evoked in-phase cMAP of larynx muscle could be recorded while stimulating the exposed RLNs by monopolar electrode. The MSCIT ranged from 0.08mA to 0.35 mA (average: 0.25 mA). The range of suitable stimulating current intensity was from 0.2 mA to 1.0 mA and the MaxSCIT used in operation was 2.0 mA. The function of RLNs in 37 cases (97.4%) remained well and was consistent with that of pre-operation. Only one patient's left RLN(2.6%) was damaged during operation. The left RLN paralysis was...