The Influence Of Different Targeted Effect-site Concentration Of Sufentanil On Popofol EC50 At Loss Of Consciousness

As a result of further understanding of the pharmacokinetics and pharmacodynamics, total intravenous anesthesia (TIVA) gradually get popularization in modern age. To keep a balance between opioids and propofol is the core idea in TIVA, so the combined application of them become a mainstream in modern TIVA. The application of target controlled infusion and the invention of bispectral index not only promoted the TIVA clinical practice rapidly, but also made scientific research become simple.The appearance of sufentanil, fentanyl, propofol and other new types of intravenous anesthesia drugs gradually replace the original drugs. These drugs performs unique characteristics in induction,maintenance and recovery from anesthesia. We can precisely calculate the absorption, distribution, elimination of the drugs with the soft ware planted in the TCI system. Therefore, the research of TIVA will focus on the interaction between these drugs, and our work is to get the optimal anesthesia effect by controlling the interaction between these drugs.Numerous researches demonstrated that opioids can reduce the minimum alveolar concentration of inhalation anesthetics by synergistic interaction, and they have an obvious dose-dependent relationship. Opioids and propofol also has the similar nature of synergistic interaction, it has an obvious significance in clinical practice in induction,maintenance and recovery from anesthesia. Researches showed that synergistic interaction is closely related to the intensity of noxious stimulation, the greater the intensity of stimulation, the more obvious synergistic interaction exhibits. Opioids can increase the hypnotic effect of propofol during induction, propofol can also enhance the opioid-induced respiratory depression and combination of opioids during surgery have a capacity in in strengthening the anesthesia effect of propofol.Recently, sufentanil has introduced into clinical practice, it shows a better performance in analgesia and in maintaining cardiovascular stability. Current research of sufentanil mainly focused on its analgesic effect and cardiovascular stability, there has little studies on its dose effect relationship with propofol. Hence, it has an obvious significance in studying the synergistic interaction between sufentanil and propofol. Clinical application of sufentanil often based on 10:1 with fentanyl as an equipotent, and it lack of a certain accuracy.Objective: under the monitoring of bispectral index, using various target effect-site concentration of sufentanil, to investigate the synergistic interaction characteristics between sufentanil and propofol and explore the dose ratio between sufentanil and fentanyl as an equipotent, to provide reference for the clinical work.Methods: sixty patients with ASA physical statusⅠ~Ⅱscheduled for elective surgery, were randomly allocated into three groups of 15 patients each: group I,group II and groupШ. Group I received intravenous target effect-site concentration of sufentanil 0.3 ng/ml and group II received sufentanil 0.5 ng/ml and groupШreceived fentanyl 3ng/ml. When the plasma concentration of sufentanil and fentanyl came into ballence with effect-site concentration, then TCI propofol in a up and down method. At the time loss of consciousness, the plasma concentration of propofol and the BIS were recorded. Then use the regression method to calculate the propofol EC50 at the time loss of consciousness. Propofol was infused continuously, when the BIS decreased lower than 60, vecuronium at a dose of 0.12mg/kg was injected, after that tracheal intubation was performed. The HR,BP,MAP,SPO2,BIS were recorded at the time the patient entering operating room (t1),the plasma concentration of sufentanil and fentanyl came into ballence with effect-site concentration (t2),the preset plasma concentration of propofol attained (t3) and right after tracheal intubation was accomplished (t4).Results: patients characteristics were similar in all groups. 1. Cardiovascular response: (1). Compared to group F and S1, group S2 has significant differences in HR,SBP,DBP and MAP at t4, P<0.01. (2). There was also an obvious difference between group F and S1 at t4, P<0.01. 2. BIS index: (1).Compared to t1, there were significant differences among all the groups at the same time point. (2). Compared to group F and S1, there were significant differences at t2,t3 and t4 in group S2. (3). There were no significant differences between group F and group S1 at t4 except t2. 3. The propofol EC50 at loss of consciousness was 4.18μg /ml, 4.13μg /ml and 3.58μg/ml in each group, and the 95% confidence interval was 3.98~4.39μg /ml, 3.95~4.32μg /ml and 3.39~3.76μg /ml, respectively.Conclusion, along with the increase of effect site target concentration of sufentanil, the EC50 of propofol at loss of consciousness decreased. Sufentainil has stronger synergistic interaction with propofol compared with fentanyl. The equipotent dose between sufentanil and fentanyl changes with the intensity of stimulation at a range of 6~10:1.