Optimum dose of dexmedetomidine combined with propofol and remifentanil for anesthesia during laparotomy in patients with mild liver dysfunction

Objective To determine the optimum dose of dexmedetomidine through evaluating the effects of different doses of dexmedetomidine combined with propofol and remifentanil for anesthesia during laparotomy in patients with mild liver dysfunction.Methods Sixty ASA physical status Ⅱ patients of both sexes,aged 18-60 yr,with body mass index 20-26kg/m2,Child-Pugh grade A,undergoing radical resection for stomach or colon cancer,were randomly assigned into 3 groups (n=20 each):propofol and remifentanil group (group Ⅰ),low-dose dexmedetomidine combined with propofol and remifentanil group (group Ⅱ) and high-dose dexmedetomidine combined with propofol and remifentanil group (group Ⅲ).In Ⅱ and Ⅲ groups,dexmedetomidine was infused at a rate of 0.2 μg·kg-1 · h-1 and 0.4 μg·kg 1 · h-1,respectively,until 30 min before the end of surgery after a loading dose of dexmedetomidine 0.4 μg/kg and 0.8 μg/kg,respectively,was infused at 10 min before induction of anesthesia.The patients were mechanically ventilated after tracheal intubation.Anesthesia was maintained with target-controlled infusion of propofol (target plasma concentration 2-4 μg/ml),iv infusion of remifentanil 0.2 μμg·kg-1 · h-1 and intermittent iv boluses of rocuronium 0.15 mg/kg.BIS value was maintained at 40-60.Before dexmedetomidine infusion (T0),at 2 min before intubation (T1),at 1 min after intubation (T2),immediatay after zskin incision (T3),and at 30 min of surgery (T4),arterial blood samples were taken for measurement of concentrations of plasma norepinephrine (NE) and epinephrine (E).The emergence time,adverse cardiovascular events,and the development of nausea and vomiting and restlessness during recovery from anesthesia were recorded.Results Compared with group Ⅰ,the plasma concentration of propofol was significantly decreased,and the incidence of tachycardia and restlessness during recovery from anesthesia were significantly decreased in Ⅱ and Ⅲ groups,and the incidence of bradycardia during operation was significantly increased,and the incidence of hypertension during recovery from anesthesia was significantly decreased,and the emergence time was prolonged in group Ⅲ (P ＜ 0.05).Compared with group Ⅱ,the plasma concentration of propofol was significantly decreased,the incidence of bradycardia during operation was increased,and the emergence time was prolonged in group Ⅲ (P ＜0.05).The plasma NE and E concentrations were significantly higher at T2.3 in group Ⅰ,and were lower at T1-4 in Ⅰ and Ⅲ groups than those at T0 (P ＜ 0.05).Conclusion 0.4 μg/kg injected before induction of anesthesia followed by infusion at 0.2 μg·kg-1 · h-1 is the recommended optimum method for application of dexmedetomidine when combined with propofol and remifentanil for anesthesia during laparotomy in patients with mild liver dysfunction. Key words: Dexmedetomidine ;  Propofol ;  Piperdines ;  Hepatic insufficiency ;  Anesthesia, intravenous