Effect of intravenous lidocaine on the response to insertion during painless gastroscopy

INTERVENTION: Lidocaine Group(L Group):Following routine monitoring, all patients received an intravenous injection of fentanyl 0.5 µg/kg (administered over a period of no less than 30 seconds). According to their group assignment, lidocaine 1.5 mg/kg was then administered intravenously (also over a period of no less than 30 seconds). Two to three minutes later, propofol 1.0‐2.0 mg/kg was slowly administered by intravenous bolus.;Saline control group (Group C):Following routine monitoring, all patients received an intravenous injection of fentanyl 0.5 µg/kg (administered over a period of no less than 30 seconds). According to their group assignment, an equivalent volume of normal saline was then administered intravenously (also over a period of no less than 30 seconds). Two to three minutes later, propofol 1.0‐2.0 mg/kg was slowly administered by intravenous bolus.; CONDITION: Effect of intravenous lidocaine on the response to insertion during painless gastroscopy PRIMARY OUTCOME: Positive rate of insertion response during gastroscopy; SECONDARY OUTCOME: Propofol dosing (induction dose, total dose) ;Hemodynamic changes (heart rate and blood pressure measured before, during, and within 1 minute after insertion);Coughing and body movement;Respiratory Depression;Hypotension;PONV, dizziness and headache;Endoscopist satisfaction; INCLUSION CRITERIA: 1.Aged 18 to 65 years; 2.Scheduled to undergo elective, diagnostic painless gastroscopy based on clinical needs; 3.American Society of Anesthesiologists (ASA) Physical Status Classification of I to III; 4.Body Mass Inde X(BMI) between 18 and 28 kg/m^2; 5.Voluntarily agrees to participate and provides signed informed consent; 6.Not concurrently participating in any other interventional clinical trial.