Effects Of Obesity On Median-effective Target Plasma Concentration Of Propofol By TCI For Loss Of Consciousness

Objective:To investigate the effect of Obesity on Median-effective targetplasma concentration of Propofol by TCI for loss of consciousness.Methods: All sixty subjects were ASA physical status I or II, aged35～55yr, and were scheduled for elective procedures under general anesthesia.Subjects were excluded from study if they had any evidence ofcardiopulmonary disease, hepatic disease, or renal dysfunction. Additionally,subjects with extreme anxiety, or whose preoperative medication regimenincluded benzodiazepines,opioids,or any prescribed or over-the-counter sleepmedications were excluded.Subjects with nervous，mental system diseases orhearing impairment were also excluded.According to BMI(body mass index),patients were divided into three groups: the control group of BMI<25kg/m2(C),the obesity were randomized by sealed envelope into2groups of20，eachreceive propofol for induction of anesthesia based on either total body weight(T,n=20)or lean body weight(L,n=20).No patients of the three groups received premedication.The patientsentered the operating room,the peripheral intravenous pathways was placed,the heart rate (HR), electrocardiogram,pulse oxygen saturation and bispectralindex (BIS) were monitored, and then when patients were in local anesthesiathe radial artery puncture and intubation was conducted, and invasive arterypressure could be monitored.The Fresenius Infusion System TCI of propofolwas started at a target plasma concentration of1.2μg/ml,followed byincrements of0.3μg/ml at30s intervals and was stopped once LOC wasachieved.A quantal response model(probit analysis)was used to calculate thetarget plasma EC50and95％confidence interval of propofol．HR，MAP andBIS were monitored and recorded before and during anesthesia.Total propofoldose and the time to lost consciousness were also recorded. Result:1The comparison of the ages, gender ratios of the three groups had nostatistical significance(P>0.05);2There were no significant differences (P>0.05) among the comparisonof heart rates, mean arterial pressures and BIS values beforeinduction(P>0.05);3The target plasma EC50and95％confidence interval of propofol at lossof consciousness were3.82（3.73～3.90）μg/ml、3.29（3.20～3.37）μg/ml、3.90（3.80～3.91）μg/ml.There were significant differences between Group Cand Group T(P<0.05).However,the comparison of propofol at loss ofconsciousness between Group C and Group L,there were no significantdifferences(P>0.05);4The time to loss of consciousness were362±6s,308±8s,367±5s inGroup C,Group T and Group L,which was shorter in Group T. Compared withGroup C and Group L,there were no significant differences (P>0.05).Conclusions:The target plasma EC50of propofol at loss of consciousnessare3.29（3.20～3.37）μg/ml、3.90（3.80～3.91）μg/ml in total and lean Bodyweight groups respectively.The obesity who receive propofol based on TBWcan reduce EC50of propofol by target-controlled infusion(TCI) for loss ofconsciousness.