BackgroundPropofol-based sedations are widely used in elderly patients for endoscopic retrograde cholangiopancreatography (ERCP) procedure, but respiratory depression and cardiovascular adverse events commonly occur. Magnesium administered intravenously can alleviate pain and decrease propofol requirements during surgery. We hypothesized that intravenous magnesium was used as adjuvant to propofol might be beneficial in elderly patients undergoing ERCP procedures.MethodsEighty patients aged from 65 to 79 years who were scheduled for ERCP were enrolled. All patients were intravenously administered 0.1 µg/kg sufentanil as premedication. The patients were randomized to receive either intravenous magnesium sulfate 40 mg/kg (group M,n= 40) or the same volume of normal saline (group N,n= 40) over 15 min before the start of sedation. Intraoperative sedation was provided by propofol. Total propofol requirement during ERCP was the primary outcome.ResultsThe total propofol consumption were reduced by 21.4% in the group M compared with the group N (151.2 ± 53.3 mg vs. 192.3 ± 72.1 mg,P= 0.001). The incidences of respiratory depression episodes and involuntary movement were less in the group M than those in the group N (0/40 vs. 6/40,P= 0.011; 4/40 vs. 11/40,P= 0.045; respectively). In the group M, the patients experienced less pain than those in the group N at 30 min after the procedure (1 [0–1] vs. 2 [1–2],P< 0.001). Correspondingly, the patients’ satisfaction was clearly higher in the group M (P= 0.005). There was a tendency towards lower intraoperative heart rate and mean arterial pressure in group M.ConclusionsA single bolus of 40 mg/kg of intravenous magnesium can significantly reduce propofol consumption during ERCP, with higher sedation success and lower adverse events.Trial RegistrationID UMIN000044737. Registered 02/07/2021.