Sedative interaction between dexmedetomidine and propofol

Abstract

Objective To evaluate the sedative interaction between dexmedetomidine and propofol. Methods Sixty-four American Society of Anesthesiologists physical status Ⅰ or Ⅱ patients, aged 20-60 yr, with body mass index of 19.0-25.0 kg/m2, scheduled for elective surgery under general anesthesia, were allocated into 4 groups (n=16 each) using a random number table: different target concentrations of dexmedetomidine groups (D1-4 groups). Dexmedetomidine was administered by target-controlled infusion (TCI) with the Markku model.The target plasma concentrations of dexmedetomidine were 0, 0.4, 0.6 and 0.8 ng/ml in D1-4 groups, respectively.At 15 min of dexmedetomidine TCI, propofol was given by TCI with Schnider model, and the initial target effect-site concentration was set at 1.0 μg/ml.After the target effect-site and plasma concentrations were balanced, the target effect-site concentration of propofol was gradually increased in increments of 0.2 μg/ml until loss of consciousness (Observer′s Assessment of Alertness/Sedation Scale score was 1). The model of pharmacodynamic interaction was used to analyze the sedative interaction between the two drugs. Results There was no statistically significant difference in residual sums of squares fitted by using the model of pharmacodynamic interaction between the target effect-site concentration of propofol and target plasma concentration of dexmedetomidine at loss of consciousness (P> 0.05). The linear dimensionless parameter of pharmacodynamic interaction was 0.The median effective effect-site concentration of propofol was 2.38 μg/ml at loss of consciousness, and the median effective plasma concentration of dexmedetomidine was 2.03 ng/ml at loss of consciousness. Conclusion Dexmedetomidine and propofol interact additively in terms of sedation. Key words: Dexmedetomidine; Propofol; Conscious sedation; Drug interactions