Objective To observe the influences of continuous infusion of different doses of dexmedetomidine for 10 min before anesthesia induction on hemodynamics and myocardium oxygen consumption in patients undergoing off-pump coronary artery bypass grafting and discus the comparatively proper loading dose of dexmedetomidine.Methods Seventy-five patients,aged 45-70 years,weighing 55-80 kg,with BMI18.5-24.5 kg/m2,ASA?or?,NYHA?or?and left ventricular ejection fraction?45%,undergoing off-pump coronary artery bypass grafting,were randomly divided into groups D3,D6 and D9 using a random number table.There was no bradycardia?heart rate<50 times/min?or atrioventricular block above level II,no serious systematic diseases?liver and renal injury or serious respiratory diseases?and no anesthetic drug allergy history among these included patients.Dexmedetomidine 0.3,0.6 and 0.9?g/kg were infused intravenously for 10 min before induction of anesthesia in groups D3,D6and D9,respectively.Anesthesia was induced with lidocaine 1.5 mg/kg,midazolam 0.08mg/kg and sufentanil 0.6?g/kg.As BIS value?75,0.12 mg/kg vecuronium bromide was infused intravenously.After induction of anesthesia,patients were tracheal intubated and mechanically ventilated when BIS value?55.As BIS value?60,0.5-1.0 mg/kg propofol was injected intravenously.The respiration parameters including tidal volume?VT?8-10ml/kg,inspiratory/expiratory?I:E?1:2,respiratory rate?RR?10-12 times/min were set.General conditions including gender,weight,age,BMI,number of grafts and LVEF of patients were recorded.before dexmedetomidine infusion.2.HR,SBP,DBP and rate pressure product?RPP?which calculated using the formula RPP=HR×SBP were recorded before dexmedetomidine infusion?T0?,5 and 10 min after dexmedetomidine infusion?T1-2?,immediately before intubation?T3?and 1,3,5 min after intubation(T4-6)3.The incidence of adverse cardiovascular events including hypotension,hypertension and bradycardia and respiratory depression were also recorded during anesthesia induction.Results Compared with T0,HR was significantly decreased at T1-T 6 and RPP was significantly decreased at T2-T6 in groups D6 and D9?P<0.05?,SBP and DBP were significantly increased at T1 in group D9?P<0.05?,while decreased at T3 in all three groups?P<0.05?,and HR and RPP were increased at T4 in group D3?P<0.05?.Compared with T3,the HR,SBP,DBP and RPP were significantly increased at T4 and T5 in group D3?P<0.05?.Compared with group D3,SBP and DBP of groups D6 and D9 were significantly increased at T3?P<0.05?,while HR and RPP were decreased at T4?P<0.05?.The rate of hypotension was significantly lower in groups D6 and D9 than that in group D3?P<0.05?.While the incidence of hypertension,bradycardia and respiratory depression were significantly increased in group D9 than those in groups D3 and D6?P<0.05?.Conclusion Compared with 0.3 and 0.9?g/kg,dexmedetomidine 0.6?g/kg intravenous infusion is optimal to keep the stability of hemodynamics and the balance of myocardial oxygen delivery and consumption during anesthesia induction in patients undergoing coronary artery bypass grafting. |