| Background and ObjectivePropofol is an intravenous anesthetic with rapid onset of anesthesia, recovery quickly and improve functional recovery, lower incidence of postoperative nausea and vomiting,etc. It is widely used in clinical anesthesia, sedation and assisted analgesia. TCI is an infusion system which bases on pharmacokinetics and pharmacodynamics and combines with the computer. It calculates the individual dosage regimen by drug-compartment model according to the specific situation of patients. Target-controlled hemodynamic stability during induction, easy to control depth of anesthesia, anesthesia process smooth, you can predict a patient awake and the recovery time, easy to use, accurate, and controllable. Both induction and maintenance are continuous process of administration. It is not only to reduce the amount of anesthetic to ensure the accuracy of pharmacokinetics, but avoiding the induction of a single dose after treatment due to failure to increase the depth of anesthesia caused by intraoperative awareness. The pharmacokinetics characteristic of propofol is very suitable for TCI. In recent years, TCI of propofol is widely used in clinical anesthesia. Laryngeal mask airway(LMA)is the tool between intubation and mask. It is easy to learn and to operate. It does not need laryngoscopy and muscle relaxation. It is irritation of the body and brings great convenience for clinical treatment. So it can avoid the traditional complications caused by tracheal intubation. According to the recommended dose, the EC50 of intubation is 4-6μg/ml.It can cause the larger Hemodynamic changes during LMA such as blood pressure and heart rate decrease and serious complications. This study observes the EC50 of propofol of target-controlled infusion during the insertion of LMA at the moment of anesthesia induction, in order to provide a theoretical basis for clinical treatment. So reduce complications and ensure patient's safety.Materials and MethodsTwenty cases of general anesthesia patients for elective surgery (ASAⅠ-Ⅱgrade). The difference in age, sex, weight, body mass index is no statistics significance. The initial concentration of propofol was 4.0μg/ml. LMA was inserted successfully. These twenty cases were used target-controlled infused of propofol 2.0-3.5μg/ml, remifentanil 0.15-0.20μg/(kg·min) intravenously to maintain the depth of anesthesia. Adjusted the speed of drug infusion according to the value of BIS, while maintain BIS at 45-55 during the surgery. The ECG, MAP, SpO2 and BIS of the patients were monitored. Record the time points:before induction (T1), before LMA insertion while after induction (T2), at the moment of LMA insertion (T3),3 minutes after LMA insertion (T4),5 minutes after LMA insertion (T5),10 minutes after LMA insertion (T6). To determine the plasma concentration of target-controlled of propofol by Dixon's sequential. If there was LMA reaction, the previous concentration was selected; if not, the next level of concentration was selected. The ratio between adjacent levels was 1:1. For example, if the initial plasma concentration of propofol were 4.0μg/ml, others would be 3.6μg/ml, 3.3μg/ml, 3.0μg/ml, 2.7μg/ml,2.5μg/ml,2.3μg/ml,2.1μg/ml and so on respectively. Datas were analyzed statistically using SPSS 17.0 package. Measurement informations and data are displayed by mean±standard deviation x±s. The differences of the monitoring indicators at each time point use repeated measures analysis of variance. P<0.05 was considered statistically significant. Results1. Twenty patients which eleven cases of males and nine females, aged 18 to 65 years old, weighing 54～74kg, body mass index of 20.61-25.00kg/m2 were selected. The surgery lasted 75-155 minutes. The surgery types included liver and gallbladder surgery, neurosurgery, general surgery, intervention surgery and laparoscopy surgery. There were no significant differences between and within groups.2. The initial target concentration of propofol was 4.0μg/ml during the induction of anesthesia, the concentration was lowered sequentially at the ratio of induction 1.1. There was LMA reaction when the target concentration was 2.3μg/ml. Select the previous concentration (2.5μg/ml) as the first case. There were two cases at the target concentration of 2.7μg/ml, which the cases with no LMA reaction were effective. There were nine cases at the target concentration of 2.5μg/ml, of which seven were effective and two cases were ineffective. There were eight cases at the target concentration of 2.3μg/ml, of which one was effective and seven cases were ineffective. There was one case at the target concentration of 2.1μg/ml, which was regarded as invalid.3. Calculated by Dixon's sequential:EC50 was 2.43±0.0381μg/ml,95% confidence interval was 2.05～2.89μg/ml.4. Twenty cases were randomly divided into two groups:effective group and ineffective group, each group contain ten cases. Compared hemodynamic parameters at different time points, there were no significant differences between two groups at T1, T2, T4, T5 and T6 (P>0.05)which has no statistical significance, while at T3 was in the opposite (P<0.05). No significant differences were noted with regard to age, gender, weight, body mass index, primary disease, the function of heart, liver and kidney and combined drug use (P>0.05) between two groups.Conclusions1. The EC50 of target-controlled infusion of propofol during the insertion of LMA is 2.43±0.0381μg/ml,while 95％confidence interval is 2.05-2.89μg/ml. |
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