Effects of different doses of dexmedetomidine administered intranasally on EC50 of propofol inhibiting responses to laryngeal mask airway insertion in pediatric patients

Objective To evaluate the effects of different doses of dexmedetomidine administered intranasally on the median effective target plasma concentration(EC50)of propofol inhibiting responses to laryngeal mask airway(LMA)insertion in the pediatric patients. Methods American Society of Anesthesiologists physical statusⅠor Ⅱ pediatric patients of both sexes, aged 1-3 yr, with body mass index of 20-26 kg/m2, scheduled for elective surgery under general anesthesia, were divided into 3 groups using a random number table: control group(group C), dexmedetomidine 1 μg/kg group(group D1)and dexmedetomidine 2 μg/kg group(group D2). At 20 min before induction of anesthesia, dexmedetomidine 1 and 2 μg/kg(diluted to 1 ml in normal saline)were intranasally administered in DI and D2 groups, respectively, and the equal volume of normal saline was intranasally administered in group C. Children were separated from their parents at 20 min after intranasal administration and admitted to the operating room.The target plasma concentration of propofol was determined by modified Dixon′s up-and-down method.The initial target plasma concentration of propofol was set at 5.4 μg/ml.The target plasma concentration of propofol was increased/decreased by 10% in the next patient according to the response to LMA insertion, and the ratio between the two successive concentrations was 1.1.Patients′ sedation status and LMA acceptance were evaluated when patients were separated from their parents.Patient′s satisfaction with sedation and with LMA acceptance was recorded.Probit analysis was used to calculate the EC50 of propofol inhibiting responses to LMA insertion. Results Compared with group C, the satisfactory rates of sedation and LMA acceptance were significantly increased, and EC50 of propofol inhibiting responses to LMA insertion was decreased in D1 and D2 groups(P<0.05). Compared with group D1, the satisfactory rates of sedation and LMA acceptance were significantly increased, and the EC50 of propofol inhibiting responses to LMA insertion was decreased in group D2(P<0.05). Conclusion Dexmedetomidine 1 and 2 μg/kg administered intranasally both can decrease the EC50 of propofol inhibiting responses to LMA insertion in the pediatric patients, and 2 μg/kg produces better efficacy. Key words: Dexmedetomidine; Administration, intranasal; Propofol; Dose-response relationship, drug; Laryngeal masks; Child