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Objective To determine the median effective concentration (EC50) of remifentanil inhibiting responses to tracheal extubation in patients of Uygur nationality.Methods The patients of Uygur nationality,aged 18-60 yr,of ASA physical status Ⅰ or [Ⅱ,scheduled for elective surgery,were enrolled in this study.After the end of surgery,remifentanil was given by target-controlled infusion until tracheal extubation.The initial target plasma concentration (Cp) of remifentanil was 2.0 ng/ml.The response was defined as positive when MAP and/or HR increased by ＞ 15％ of the level at the end of operation and the duration ＞ 15 s during extubation.Each time the target Cp increased/decreased if the cardiovascular response was positive or negative.The ratio between the two successive concentrations was 1.1.The EC50 and 95 ％ confidence interval of remifentanil blunting responses to extubation was calculated by Probit method.Results Twenty-eight patients completed the study.The EC50 and 95 ％ confidence interval of remifentanil required for inhibiting the responses to extubation was 1.75 ng/ml and 1.45-2.01 ng/ml.Conclusion The EC50 of remifentanil inhibiting the responses to tracheal extubation is 1.75 ng/ ml in patients of Uygur nationality.
ABSTRACT
Objective To determine the median effective target effect-site concentration (EC50) of sufentanil inhibiting cardiovascular response to tracheal intubation when combined with propofol in patients of Uygur nationality.Methods Thirty-one ASA Ⅰ or Ⅱ Uighurs of both sexes,aged 21-59 yr,with body mass index 18-28 kg/m2,undergoing elective surgery,were enrolled in this study.Anesthesia was induced and maintained with propofol and sufentanil target-controlled infusion and iv injection of cisatracurium 0.2 mg/kg.The target effect-site concentration (Ce) of propofol was set at 3.0 μg/ml.Tracheal intubation was performed after the target Ce and plasma concentrations were balanced.The target Ce was set at 0.8 ng/ml in the first patient.Each time Ce increased/decreased by 10％ in the next patient depending on whether or not the cardiovascular response to tracheal intubation occurred.The positive cardiovascular response was defined as increase in systolic blood pressure by 15％ and/or HR＞ 90 bpm lasting for ＞ 15 s.The EC50(95％ confidence interval) of sufentanil blunting cardiovascular responses to trancheal intubation was calculated by Probit analysis.Results EC50 (95 ％ confidence interval) of sufentanil inhibiting cardiovascular response to tracheal intubation when combined with 3.0 μg/ml propofol was 0.46 (0.43-0.49) ng/ml.Conclusion EC50 of sufentanil inhibiting cardiovascular response to tracheal intubation is 0.46 ng/ml in patients of Uygur nationality when combined with propofol.
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Objective To investigate the effects of remifentanil on sinoatrial (SA) node autorhythmicity in rabbits.Methods Twenty-four healthy rabbits of both sexes weighing 1.8-2.2 kg were sacrificed.Their hearts were removed and sinoatrial nodes were dissected and placed in Tyrode solution saturated with 95 ％ O2-5 ％ CO2 at 36 ℃.The action potentials of the sinus node pacemaker cells were recorded by intracellular glass microelectrode technique.The experiment was performed in 3 parts (n =8 each).Part Ⅰ:the sinoatrial node was exposed to remifentanil 2,4,8,16 and 32 ng/ml respectively.The action potentials were recorded after the sinoatrial nodes were exposed to each concentration of remifentanil for 15 min.Part Ⅱ and Ⅲ:the sinoatrial nodes were first exposed to Ca2+ channel agonist Bay K8644 0.5 μmol/L or K+ channel blocker TEA 20 nmol/L for 15 min.Then remifentanil was added until the concentration reached 16 ng/ml (final concentration) and 15 min later the action potentials were recorded.The action potential parameters included,amplitude of action potential (APA),rate of pacemaker firing (RPF),action potential duration at 90％ repolarization (APD90) and velocity of diastolic depolarization (VDD).Results Remifentanil significantly decreased,APA,RPF,VDD and prolonged APD90 in a concentration dependent manner as compared with the baseline values.Pretreatment with Bay K8644 could block the effects of remifentanil on SA node pacemaker cells,while TEA did not affect the electrophysiologic effects of remifentanil on SA node pacemaker cells.Conclusion Remifentanil exerts a negative chronotropic action on SA node pacemaker cells.These effects are likely produced by decrease in Ca2+ current,while opening of K + channels is not involved in these effects.
ABSTRACT
Objective To determine the median effective plasma concentration of remifentanil (EC50) inhibiting cardiovascular response to tracheal intubation and skin incision when combined with propofol in patients of Uighur nationality.Methods Thirty ASA Ⅰ or Ⅱ Uighurs aged 20-60 yr with body mass index of 18-30 kg/m2 undergoing elective laparoscopic cholecystectomy were enrolled in this study.Anesthesia was induced and maintained with propofol infusion.BIS value was maintained at 40-50.TCI of remifentanil was then started.The initial target plasma concentration (Cp) was 6.0 ng/ml.EC50 of remifentanil was determined by modified Dixon' s upand-down sequential experiment.Each time Cp increased/decreased by 0.5 ng/ml.Tracheal intubation was facili.tated with cisatracurium 0.2 mg/kg at 2 min after a new Cp was set when target effect-site concentration (Ce) was balanced with Cp.Positive cardiovascular response was defined as increase in SBP by 15％ and/or HR ＞ 90 bpm lasting＞15 s.The EC50 (95％ confidence interval) of remifentanil blunting responses to tracheal intubation and skin incision was calculated.Results EC50 (95 ％ confidence interval) of remifentanil inhibiting cardiovascular response to tracheal intubation and skin incision when combined with propofol was 3.4 (2.3-4.5) ng/ml and 3.8 (2.8-4.9) ng/ml respectively.Conclusion When depth of anesthesia was maintained at BIS value 40-50 with propofol infusion,the EC50 of remifentanil inhibiting cardiovascular response to tracheal intubation and skin incision is 3.4 and 3.8 ng/ml respectively.