RESUMO
Objective To determine the ED50 of dexmedetomidine for suppressing cardiovascular responses to placement of laryngeal mask airway (LMA) in patients undergoing gynecological laparoscopic surgery with induction of propofol. Methods ASA I or II Patients aged 18 to 55 undergoing elective gynecological laparoscopic surgery were enrolled. After an bolus dose of dexmedetomidine over 10 min , anaesthesia was induced with target-controled propofol, and then bolus of vecuronium of 0.1 mg/kg was injected when the BIS was between 45 and 55. LM palcement was performed 3 minutes after vecuronium injection. The modified Dixon ’ s up-and-down method was used to determine the bolus dose of dexmedetomidine , starting from 1.0 μg/kg (step size:0.1 μg/kg). Cardiovascular response was defined as an increase in SBP and/or HR by 15% of baseline within 2 min after placement of LMA. The test ended after at least 7 crossovers ( successive ‘response’ or ‘non-response’) were obtained. Probit analysis was used to calculate ED50, ED95 and 95% confidence interval (CI). Results The ED50 and ED95 (95% confidence interval) of dexmedetomidine for suppressing cardiovascular responses to placement of LMA was 0.65 μg/kg (0.44-0.80) μg/kg and 0.94 μg/kg (0.79-2.47) μg/kg. Conclusion Under induction of target-controled propofol , the ED50 of dexmedetomidine is 0.65 μg/kg for suppressing cardiovascular responses to placement of LMA in female patients.