The effect of intravenous lidocaine on ED50 and ED95 of propofol, which causes unconsciousness, is unclear. In addition, it is not clear whether the depth of anesthesia induced by propofol changes when lidocaine is used in combination. Therefore, the purpose of this study was to study the effects of intravenous lidocaine on ED50, ED95 and NTI values of propofol induced unconsciousness .

Intravenous lidocaine has many advantages in perioperative period, in addition to reducing the amount of opioids and propofol, thus reducing the incidence of adverse reactions caused by them, it also has the effect on organ protection, can shorten the length of hospital stay, and promote postoperative recovery. The effect of intravenous lidocaine on ED50 and ED95 of propofol, which causes unconsciousness, is unclear. In addition, it is not clear whether the depth of anesthesia induced by propofol changes when lidocaine is used in combination. Therefore, the purpose of this study was to study the effects of intravenous lidocaine on ED50, ED95 and NTI values of propofol induced unconsciousness .

Inclusion Criteria:

1. The informed consent is signed
2. Aged 18 to 65 years old
3. ASA is rated from I to II
4. Body mass index ranged from 18.5 to 24.9 kg/m2

Exclusion Criteria:

1. Unwilling to sign informed consent or refuse to participate in the study
2. Patients with serious arrhythmia and organic heart disease before surgery
3. Sedative and analgesic drugs were taken within 1 week before surgery
4. Lidocaine allergy
5. Patients with mental and neurological diseases
6. Patients with difficult airway
7. People with hearing impairment