RESUMO
Objective To evaluate the effects of dexmedetomidine on hemodynamics during induction of anesthesia in the patients with atrial fibrillation with rapid ventricular rate undergoing noncardiac surgery.Methods Fifty patients with rheumatic valvular heart disease complicated with atrial fibrillation,aged 45-64 yr,weighing 50-75 kg,with ventricular rate ≥ 90 bpm,of ASA physical status Ⅱ or Ⅲll (NYHA Ⅱ or Ⅲ),scheduled for elective surgery,were randomly divided into 2 groups (n =25 each) using a random number table:control group (group C) and dexmedetomidine group (group D).Dexmedetomidine 0.6 μg/kg was infused intravenously at 10 min prior to induction of anesthesia in group D.Anesthesia was induced with iv midazolam 0.06 mg/kg,sufentanil 0.6 μg/kg,and vecuronium 0.12 mg/kg.Tracheal intubation was performed when the BIS value≤≤ 55After admission to operating room (T0,baseline),immediately after the end of dexmedetomidine infusion (T1),immediately before intubation (T2),and at 1,3 and 5 min after intubation (T3-5),SP,DP,MAP and HR were recorded.The adverse cardiovascular events were recorded starting from induction of anesthesia to 5 min after intubation.Results Compared with the baseline value at T0,HR was significantly decreased at T2,5,while increased at T3,4 in group C,and HR was decreased at T1-5 in group D; SP,DP and MAP were decreased at T2,5,while increased at T3 in group C,and no significant changes were found in the indices mentioned above in group D.Compared with group C,the incidence of hypotension,hypertension and tachycardia was significantly decreased,and no significant changes were found in theincidence of bradycardia in group D.Conclusion Dexmedetomidine 0.6 μg/kg infused intravously is helpful in maintaining the hemadynamics stable during induction of anesthesia in the patients with atrial fibrillation with rapid ventricular rate underging noncardiac surgery.
RESUMO
Objective To investigate the effect of different doses of dexmedetomidine on the median effective concentration (EC50) of propofol required to prevent the response to Supreme laryngeal mask airway (LMA) insertion in aged patients.Methods ASA Ⅰ or Ⅱ patients of both sexes,aged ≥ 65 yr,with a body mass index of 20-28 kg/m2,undergoing knee operation under general anesthesia,were randomly divided into 3 groups:control group (group C),small dose dexmedetomidine group (group D1 ) and large dose dexmedetomidine group (group D2 ).Dexmedetomidine 0.4 and 0.8 μg/kg were infused intravenously over 10 min in groups D1 and D2 respectively,while group C received the equal volume of normal saline instead.Anesthesia was induced with target-controlled infusion of propofol.The initial target plasma concentration of propofol was set at 3.5,3.0 and 2.6 μg/ml in groups C,D1 and D2 respectively.Following equilibration between the plasma and effect-site concentration of propofol,LMA was inserted when BIS value was 50-60.EC50 was determined by up-and-down sequential trial.The target plasma concentration of propofol increased/decreased by 10％ in the next patient depending on whether or not the LMA insertion response occurred.Positive LMA insertion response was defined as body movement,comer of the mouth movement,biting LMA,bucking and/or wallowing during insertion.The EC50 and 95％ confidence interval (CI) of propofol required to prevent LMA insertion response were calculated with sequential method.Results EC50(95％ CI) of propofol was 3.57 μg/ml (2.91-3.87 μg/ml),3.09 μg/ml (2.66-3.53 μg/ml) and 2.62 μg/ml (2.30-3.15 μg/ml) in groups C,D1 and D2 respectively.EC50 was significantly lower in groups D1 and D2 than in group C,and in group D2 than in group D1 ( P ＜ 0.05 ).Conclusion Dexmedetomidine 0.4 and 0.8 μg/kg infused intravenously can reduce the EC50 of propofol required to prevent the response to Supreme LMA insertion in aged patients,and the effect of 0.8 μg/kg is more obvious.