Study design
All participants were randomly divided into lidocaine or normal saline group in a 1:1 ratio by the investigator using a computer-generated sequence. The sequential numbers from 1 to 70 for participants were marked outside of each individual envelope. Based on the computer-generated sequence, 35 paper slips marked with #1 (normal saline group) and 35 slips marked with #2 (lidocaine group) were sealed inside of envelopes. On the day of study, a nurse who was not involved in the administration and observation opened an envelope with the smallest sequential number and prepared the medicines based on the number appeared on the slip, either #1 or #2. Then, the medicines were handed over to an anesthesiologist who would administrate it and perform general anesthesia. The normal saline was matched to the lidocaine for color, smell, volume and method of administration. Patients, the anesthesiologist who performed anesthesia and another designated anesthetist who observed and recorded the data were all blinded to the study arms. All operations involved in the study were completed between 08:00 am and 12:00 noon.After entering into the operating room, all patients were monitored for electrocardiograph (ECG), pulse oximeter (SpOThe patients were then intubated, and general anesthesia was maintained with 1.5–2% sevoflurane in an oxygen/air mixture and 0.1–2 µg·kg