Objective: The present study was to investigate the effect of intravenous lidocaine combined with intratracheal dexmedetomidine on postoperative sore throat in patients undergoing thyroid cancer surgery.

Methods: Investigators enrolled 144 patients with American Society of Anesthesiologists (ASA) physical status I and II, aged 18-65 years, and scheduled for elective undergoing thyroid cancer surgery with general anesthesia. The participants were randomly assigned into four groups(n=36 each group): Group L received lidocaine 1.5 mg/kg was injected intravenously 3 min before endotracheal intubation and tracheal spray with 0.8% ropivacaine 40 mg (5 mL) for surface anesthesia. Group D received equal volume normal saline was injected intravenously 3 min before tracheal intubation and tracheal spray with dexmedetomidine (1 μg/kg) mixed with 0.8% ropivacaine 40 mg (5 mL). Group LD received lidocaine 1.5 mg/kg was injected intravenously 3 min before endotracheal intubation and tracheal spray with dexmedetomidine (1 μg/kg) mixed with 0.8% ropivacaine 40 mg (5 mL). Group C received equal volume normal saline was injected intravenously 3 min before tracheal intubation and tracheal spray with 0.8% ropivacaine 40 mg (5 mL) for surface anesthesia.The incidence and severity of postoperative sore throat were recorded in four groups at 1 h, 2 h, 6 h, 24 h and 48 h after operation.

Inclusion Criteria:

• Thyroid cancer surgery with ASA grades I-II
• Aged 18-65 years
• The patient's communication is normal and they have a certain learning ability

Exclusion Criteria:

• Severe respiratory and circulatory system diseases
• There was bradycardia (HR < 60 beats/minute) or atrioventricular block before the operation
• Nervous system disease
• Mental and psychological disorders
• Abnormal liver and kidney functions
• Pregnant and lactating women