Low-Dose Dexmedetomidine Reduces Median Effective Doses of Propofol Required for Successful Gastroscope Insertion: A Prospective Randomized Controlled Dose-Finding Trial

Purpose: Patients undergoing painless gastrointestinal endoscopy (GIE) typically receive propofol-based sedation. However, the exact dose of propofol when combined with low-dose dexmedetomidine for this procedure remains unclear. The objective of this study was to determine and compare the median effective doses (ED 50 , the doses required for successful gastroscope insertion in 50% of the subjects) of propofol when used with low-dose dexmedetomidine (0.3 μg/kg) premedication versus propofol alone during painless GIE. Patients and Methods: Adult outpatients aged 18 to 65 years scheduled for GIE were enrolled. Participants were randomized to receive either 0.9% saline (Group S) or 0.3 μg/kg of dexmedetomidine (Group D) intravenously over 5 min before induction with propofol. Using modified Dixon’s up-and-down method (MDUDM), the initial induction dose of propofol was 1.5 mg/kg, adjusted in a step size of 0.1 mg/kg. ED 50 of propofol required for successful endoscope insertion was calculated by averaging the midpoints of all sequential crossovers. Using isotonic regression analysis, ED 50 and ED 95 (the effective doses required for successful gastroscope insertion in 95% of the subjects) were then extrapolated. All adverse events during painless GIE were recorded. Results: Thirty patients were enrolled per group. Using MDUDM, the ED 50 of propofol for successful gastroscope insertion was significantly lower in Group D (1.48 ± 0.10 mg/kg) than in Group S (1.82 ± 0.16 mg/kg; P < 0.001). The ED 50 and ED 95 of propofol were extrapolated to 1.80 mg/kg (83% confidence interval [CI], 1.649– 1.882) and 2.10 mg/kg (83% CI, 2.081– 2.124) for Group S, respectively, using isotonic regression analysis. These values were significantly lower in Group D, at 1.40 mg/kg (83% CI, 1.297– 1.452) and 1.70 mg/kg (83% CI, 1.667– 1.753). Conclusion: Premedication with low-dose dexmedetomidine (0.3 μg/kg) significantly reduces the median effective doses of propofol required for successful gastroscope insertion during painless GIE. Keywords: dexmedetomidine, propofol, effective dose, gastrointestinal endoscopy, sedation