Effect of intravenous lidocaine on the ED(50) of propofol for inserting gastroscope without body movement in adult patients: a randomized, controlled study

BACKGROUND: Circulatory and respiratory depression are common problems that occur in propofol alone sedation during gastroscopy. As a widely used analgesic adjuvant, intravenous lidocaine can reduce the consumption of propofol during Endoscopic retrograde cholangiopancreatography (ERCP) or colonoscopy. However, it is still unknown the median effective dose (ED(50)) of propofol when combined with lidocaine intravenously. This study aimed to compare the ED(50) of propofol with or without intravenous lidocaine for inserting gastrointestinal endoscope successfully. METHODS: Fifty nine patients undergoing gastroscopy or gastrointestinal (GI) endoscopy were randomly divided into control group (Group C, normal saline + propofol) or lidocaine group (Group L, lidocaine + propofol). Patients were initially injected a bolus of 1.5 mg/kg lidocaine in Group L, whereas equivalent volume of 0.9% saline in Group C. Anaesthesia was then induced with a single bolus of propofol in all subjects. The induction dose of propofol was determined by the modified Dixon’s up-and-down method, and the initial dose was 1.5 mg/kg in both groups. The primary outcome was the ED(50) of propofol induction dose with or without intravenous lidocaine. The secondary outcomes were the induction time, the first propofol bolus time (FPBT: from MOAA/S score ≤ 1 to first rescue bolus propofol), and adverse events (AEs: hypoxemia, bradycardia, hypotension, and body movements). RESULTS: Totally, 59 patients were enrolled and completed this study. The ED(50) of propofol combined with lidocaine was 1.68 ± 0.11 mg/kg, significantly reduced compared with the normal saline group, 1.88 ± 0.13 mg/kg (P = 0.002). There was no statistical difference in induction time (P = 0.115) and the FPBT (P = 0.655) between the two groups. There was no significantly difference about the AEs between the two groups. CONCLUSION: The ED(50) of propofol combined with intravenous lidocaine for successful endoscope insertion in adult patients, was 1.68 ± 0.11 mg/kg significantly reduced compared with the control group. TRIAL REGISTRATION: Chinese Clinical Trial Registry, No: ChiCTR2200059450. Registered on 29 April 2022. Prospective registration. http://www.chictr.org.cn.