The Efficacy And Safety Of Targed-controlled Infusions Of Remifentanil And Predictive Performance Of Targed-controlled Infusions System During Thoracic Surgery

Objective: To compare the efficacy and safety oftarget-controlled infusion(TCI) of remifentanil in threedifferent doses during thoracic surgery and predictive TCIperformance of remifentanil using pharmacokinetic parametersreported by Minto in Chinese.Methods: Forty-five ASA Ⅰ～Ⅱpatients aged 40～60yr and weighed 50⁷5Kg undergoing thoracic surgery wererandomly divided into three groups.The patients were givenmidazolam 0.05mg·kg^-1 and artropine 0.5 mg·kg^-1 intram-uscular before anesthesia.Perioperative monitoring includedelectrocardiogram and heartrate(HR),invasivel(artery) meanarterial blood pressure(MAP), systolic blood pressure (SBP),diastolic arterial blood pressure(DBP), peripheral oxygensaturation(SpO₂), heart rate variablity(HRV), bispectral index(BIS), and P_ETCO₂. Anesthesia was induced with remifentaniland propofol both given by TCI simultaneously.The targetconcentration of propofol was set at 3μg·ml^-1 and remifentanilat 4, 6, 8ng·ml^-1(grouprR4, R6, R8). When the patients lostconscionsness, vecuronium 0.1mg·kg^-1 was given intravenouslyto facilitate intubation. The patients were mechanicallyventilated and PETCO2 was maintained between 30～40mmHg.Anesthesia was maintained with TCI of propofol-remifentaniland intermittent intravenously boluses of vecuronium.Remifentanil target concentration not changed duringanesthesia. BIS index was maintained between 45～55 bymodify propofol target concentration. When the surgery wascompleted, the remifentanil and propofol infusions werestopped abrutly. When patients gain their conscionsness andsatifying spontaneous respiration (respiratory rate>10breaths/min, P_ETCO₂<50mmHg), the trachea was extubated.Hemodynamic values, BIS index, and HRV index wereseparately recorded at the following times: befor induction ofanesthesia(T₀), immediately before tracheal intubation(T₁),immediately after tracheal intubation(T₂), skin incision(T₃),chest exploration(T₄), skin closuer(T₅), immediately afterextubation (T₆). Vein blood samples were taken at T₀, T₂, T₃, T₄,T₅ and T₆ for determination of plasma concentration ofepinephrine(E) and norepinephrine(NE) by ELASA. Arterialblood samples were taken before and after TCI remifentanil 5,10, 20, 40, 60, 90, 120min for measuring of bloodconcentration of remifentanil by High performance liquidchromarography (HPLC). The performance error(PE) wasdetermined for each measured blood remifentanil concen-tration.The performance in the population was determined bythe median absolute performance error(MDAPE), the medianperformance error (MDPE), and the Wobble(the medianabsolute deviation of each PE from the MDPE). Time of lossconscionsness, extubation (from end of anesthesia toextubation of the trachea), and response to verbalcommands("open your eyes"asked in a normal tone) wererecorded.Results: Patients conditions was similar in the threegroups before induction of anesthesia. SBP, DBP, MAP, andHR were increased signifiantly in group R4 after intubation,skin incision, chest explortation, skin closure, andextubation(P<0.05 or 0.01). After induction, blood pressureand HR decresed singnifiantly in group R8 than groupR4(P<0.05 or 0.01). LF and LF/HF were increased signifiantlyin group R4 at intubation, skin incision, exploration, skinclouser and extubation(P<0.05 or 0.01). LF at intubation, chestexploration, skin closure, extubation and LF/HF at skinincision, chest exploration, extubation were higher in group R4than group R8 (P<0.05). NE concentration increasedsignifiantly in group R4 after intubation, and in group R6,R8after skin incision(P<0.05 or 0.01). in group R6 and R8 , theNE concentration were lower at intubation than group R4(P<0.05). E concentration increased signiftiantly in group R4at all the points after skin incision(P<0.05 or 0.01), but ingroup R6 and R8 were lower than group R4 (P<0.05).Themeasured concentration(Cm) of remifentanil in group R4, R6and R8 were 2.8⁹.2ng·mL^-1, 3.1¹1.6ng·mL^-1and...