Abstract
Background : Dexmedetomidine could be an ideal adjuvant to
propofol during gastrointestinal endoscopy because it provides both
analgesia and sedation without respiratory depression. This study
investigates the effect of different doses of dexmedetomidine on the
median effective concentration of propofol during gastrointestinal
endoscopy. Methods : 90 adult patients were randomly assigned to
Group Control , Group DEX0.5 (0.5 μg/kg dexmedetomidine), or Group
DEX1.0 (1.0 μg/kg dexmedetomidine) . Anaesthesia during endoscopy was
implemented by plasma target-controlled infusion (TCI) of propofol with
different doses of dexmedetomidine. TCI concentration of the first
patient for each group was 2.5 μg/ml and the consecutive adjacent
concentration gradient was 0.5 μg/mL. EC50 of TCI
propofol for gastrointestinal endoscopy was determined by using the
modified Dixon’s up-and-down method. Cardiovascular variables were also
measured. Results : EC50 of TCI propofol and
95% confidence interval (CI) for gastrointestinal endoscopy were, 3.77
(3.48-4.09), 2.51 (2.27-2.78) and 2.10 (1.90-2.33) μg/mL in Group
Control, Group DEX0.5 and Group DEX1.0. The average percent change from
baseline in HR was 2.8 (8.9), -7.4 (7.7) and -10.5 (8.8)
(P <0.001), and the average percent change from baseline in MAP
was -10.6 [-24.7; 3.5], -9.5 [-29.2; 11.4] and -4.0 [-27.3;
15.5] (P = 0.034) in Group Control, Group DEX0.5 and Group
DEX1.0, respectively. Conclusions: Dexmedetomidine reduced the
EC50 of TCI propofol. A 0.5-1 μg/kg dexmedetomidine
caused a decrease in HR without bradycardia. The decrease in dosage of
propofol with increasing doses of dexmedetomidine caused more stable
MAP. Dexmedetomidine is an ideal adjuvant drug to propofol during
gastrointestinal endoscopy.
Keywords : The median effective concentration, Propofol,
Dexmedetomidine, Gastrointestinal endoscopy.