ABSTRACT
Objective To evaluate the effects of different doses of dexmedetomidine administered intranasally on the median effective concentration (EC50) of sevoflurane inhibiting responses to laryngeal mask airway (LMA) insertion in the pediatric patients.Methods American Society of Anesthesiologists physical status Ⅰ or Ⅱ pediatric patients of both sexes, aged 1-3 yr, with body mass index of 20-25 kg/m2, scheduled for elective surgery under general anesthesia, were randomly divided into 3 groups: control group (group C) , dexmedetomidine 1 μg/kg group (group D1) , and dexmedetomidine 2 μg/kg group (group D2).In D1 and D2 groups, dexmedetomidine 1 and 2 μg/kg (in 1 ml of normal saline) were administered intranasally at 1 h before induction of anesthesia, respectively.Group C received the equal volume of normal saline administered intranasally.The children were separated from their parents at 45-60 min after intranasal administration and admitted to the operating room.The children inhaled 8％ sevoflurane until they lost consciousness.After loss of consciousness, the end-tidal concentration of sevoflurane was determined using the modified Dixon's up-and-down method.The initial end-tidal concentration of sevoflurane was set at 2％.The concentration was increased/decreased by 0.2％ in the next patient according to the response to LMA insertion.The patient's sedation status and with LMA acceptance were evaluated, and the patient's satisfaction with sedation and with LMA acceptance was recorded.Probit analysis was used to calculate the EC50 and 95％ confidence interval of sevoflurane inhibiting responses to LMA insertion.Results The patient's satisfaction with sedation and with LMA acceptance was significantly higher in D1 and D2 groups than in group C, and in group D2 than in group D1 (P＜0.05).The EC50 (95％ confidence interval) of sevoflurane inhibiting responses to LMA insertion was 2.03％ (1.91％-2.15％), 1.76％ (1.65％-1.87％) and 1.63％ (1.53％-1.73％) in C, D1 and D2 groups, respectively.The EC50 was significantly lower in D1 and D2 groups than in group C, and in group D2 than in group D1 (P＜0.05).Conclusion Dexmedetomidine 1 and 2 μg/kg administered intranasally can decrease the EC50 of sevoflurane inhibiting responses to LMA insertion in the pediatric patients, and 2 μg/kg produces better efficacy.
ABSTRACT
Objective To investigate the sedative and hypnotic interaction between remifentanil and propofol by target-controlled infusion (TCI) during induction of anesthesia.Methods Third-two ASA Ⅰ or Ⅱpatients,aged 22-63 yr,body mass index 18-25 kg/m2,scheduled for elective surgery under general anesthesia,were randomly divided into 4 groups(n=8 each).Group Ⅰ only received TCI pmpofol.GroupⅡ,Ⅲ,and Ⅳreceived a target concentration of 2,4 or 6 ng/ml remifentanil respectively.While the blood-effect site concentrations of remifentanil were equilibrated,patients received TCI of propefol,with an initial target concentration of 0.5μg/ml.After the blood-effect site concentrations of propofol were equilibrated then with 0.5μg/ml increments until the loss consciousness was achieved.The eyelash reflex and state of consciousness were assessed and radial arterial blood sample 6 ml was taken every 3 min to determine the remifentanil and propofol concentrations in blood.Propofol and remifentanil concentrations in blood were measured by reversed-phase high-performance liquid chromatography and high-performance liquid chromatography with ultraviolet detection respectively.The sedative and hypnotic interaction between propofol and remifentanil was determined with a pharmacodynamie interaction model by regression analysis and determined using the isobolographic method.Results Propofol concentrations in blood were lower in group Ⅱ,Ⅲ and Ⅳ than group Ⅰ(P<0.05).The propofol concentratopms in blood were significantly decreased in trun with the increase in the remifentanil concentrations in blood in group Ⅱ-Ⅳ(P<0.05).At loss of eyelash reflex and loss of consciousness of patients,the pharmacodynamic interaction model by curve fitting was superior to linear regression (P<0.05).At loss of eyelash reflex of patients,the curve fitting result showed EC50,prop=2.77μg/ml and EC50,rem=26.67 ng/ml,and the isobolographic method equation is ECprop/2.77+ECrem/26.67=0.69.At loss of consciousness of patients,the curve fitting result showed EC50,prop==3.76μg/ml and EC50,rem=31.56ng/ml,and the isobolographic method equation is Ecprop/3.76+Ecrem/31.56=0.65.Conclusion Remifentanil (Cp 2-6 ng/ml) and propofol by TCI shows a synergistic type of pharmacodynamic interaction on the sedative and hypnotic during induction of anesthesia.