RESUMEN
Dexmedetomidine [DEX] induces a dose dependent sedation and has been widely used as an adjuvant sedative during regional anesthesia recently. We aimed to investigate the effective dose of intravenous single-dose DEX to induce consciousness inhibition in patients of different ages undergoing lower limb surgery with epidural anesthesia. Ninety-two patients were divided into three groups according to their ages. Patients aged 18-45 years, 46-64 years and 65-85 years in group Y, group M and group O, respectively. With the accomplishment of epidural anesthesia, a pre-calculated dose of DEX was infused for more than 10 minutes and the sedative state was assessed by Observer's Assessment of Alertness/Sedation [OAA/S] scale 30 minutes after the infusion. A modified Dixon's up-and-down method was applied to decided the dose of DEX for each sequential patient. The 50% effective dose [ED50] of DEX in the three groups were 0.40, 0.76 and 1.03 microg/kg, respectively. The 95% effective dose [ED95] in group O [0.54 microg/kg] was 45% of group Y [1.21microg/kg] and 64% of group M [0.84microg/kg]. Besides, the incidence of bradycardia was more frequent with the increase of age. The present study indicated that the appropriate single-dose of DEX to induce consciousness inhibition should reduce with the increase of age in patients undering lower limb surgery with epidural anesthesia, especially in patients over 64 years old. This result may protect the old patients from excessive sedation and dose-dependent adverse reactions
RESUMEN
Objective To determine the 95 ％ effective target plasma concentration (EC95) of remifentanil for tracheal tube tolerance during the recovery period from anesthesia following cervical spine surgery.Methods Thirty ASA Ⅰ or Ⅱ patients,aged 18-60 yr,weighing 50-80 kg,scheduled for elective cervical spine surgery under total intravenous anesthesia,were enrolled in this study.Anesthesia was induced with iv injection of propofol,sufentanil and rocuronium.The patients were tracheal intubated and mechanically ventilated.Anesthesia was maintained with iv infusion of propofol and target-controlled infusion of remifentanil.The target plasma concentration (Cp) of remifentanil was set at 4-6 μg/L.BIS value was maintained at 40-60.Infusion of propofol was stopped at the end of surgery.Participants were allocated to a dose of remifentanil by 3-patient cohorts.Six Cps were selected from 1.0-3.5 μg/L before beginning and they were 1.0,1.5,2.0,2.5,3.0,3.5 μg/L.The Cp of remifentanil was 3.0 μg/L in the first cohort.After completion of the trial in each cohort,the posterior probability of each concentration was calculated according to the condition of sedation/analgesia and anterior probability of each concentration.The concentration with the posterior probability closest to 95 ％ was chosen as Cp in the next cohort.The concentration-probability curve was made according to the posterior probability of each concentration,and then EC95 and 95 ％ confidence interval of remifentanil were calculated.Results The EC95 and 95 ％ confidence interval of remifentanil were 2.77μg/L (2.65-2.83 μg/L) for tracheal tube tolerance during the recovery period from anesthesia following cervical spine surgery.Conclusion The EC95 of remifentanil for tracheal tube tolerance during the recovery period from anesthesia is 2.77 μg/L in patients undergoing cervical spine surgery.