The Effects Of Different Target Concentrations Of Remifentanil On MAC_BAR Of Sevoflurane And Minimum Plasma Concentration Of Catecholamine (NE_BAR,E_BAR) In Gynecological Patients With Laparoscopic Surgery

ObjectiveTo investigate the effects of different target plasma concentrations of remifentanil on the minimum alveolar concentreation of sevoflurane (MACBAR) and minimum plasma concentration of catecholamine (NEBAR, EBAR) for blocking adrenergic response in gynecological patients undergoing laparoscopic surgery, And to investigate the effects of the changes of blood pressure (BP) and heart rate (HR) on auditory evoked potential index(AEPindex) and evaluate the reliability of auditory evoked potential index as an anesthesia depth monitor.MethodsGeneral materials and methods 61 gynecological patients with ASAⅠ-Ⅱ,aged 20～45yr, undergoing laparoscopic surgery, were randomly assigned to three groups: control group (R0) and 2 remifentanil groups (R1, R2). Based on remifentanil target controlled infusion (2ng/ml), anesthesia was induced with etomidate 0.3mg/kg, vecuronium 0.1mg/kg. After tracheal intubation anesthesia was maintained with inhaled sevoflurane. The fresh oxygen flow rate was set at 1.5L.min-1. The target end-tidal sevoflurane concentration was maintained stable at least 20 min. In control group, the target controlled infusion of remifentanil was stopped immediately after intubation. During maintenance, in group R1 , the target plasma concentration of remifentanil was adjusted to 1ng/ml, but in group R2, it still maintained at 2ng/ml. In each group, the end-tidal sevoflurane concentration was adjusted by using an up-and-down method and maintained stable at least 20 min before each determination. The MACBAR of sevoflurane was determined by using a sequential design and pneumoperitoneum stimulation in each group, and blood samples were adopted at corresponding time points for the determination of catecholamine concentrations. Experiment was ended by obtained 6 crossovers (positive response versus negative response).Observation Heart rate (HR) , mean arterial blood pressure (MAP) and auditory evoked potential index (AEPindex) were recorded at 3min and 1min before Pneumoperitoneum incision and 1min, 3min after Pneumoperitoneum incision. Blood samples were adopted at 3min after Pneumoperitoneum incision for the determination of catecholamine concentrations.Results1.In group R0, R1 and R2, the MACBARs of sevoflurane were (4.60±0.30) %, (2.37±0.21) % and (1.70±0.28) %, respectively. 2.No significant differences were found in NEBAR, EBAR, minimum MAP and minimum HR among the 3 groups.3. In each group, no significant differences were found in the values of AEPindex between after and before pneumoperitoneum stimulation either in the patients whose haemodynamic responses to pneumoperitoneum stimulation are positive or negative.Conclusions1.The target plasma remifentanil concentrations of 1 ng/ml and 2 ng/ml can significantly reduce MACBAR of sevoflurane by 48% and 63% respectively in gynecological patients undergoing laparoscopic surgery.2.The hemodynamic changes were the same when half patients'adrenergic responses were blocked among the three groups.3.The changes of BP and HR can not directly reflect the change of the depth of anesthesia. AEPindex can effectively reflect the depth of anesthesia on the level of sedation and loss of consciousness, but could not predict the response to noxious stimulus.