Effects Of Lipid Emulsion In Reversing The Cardiotoxicity Caused By Bupivacaine

Bupivacaine is one of lipid soluble amide long-acting local anesthetics which iscommenly used in clinic, and it can cause severe cardiovascular toxicity if it is strayed intothe vein or overdose when it playing a role in peripheral nerve block, epidural block andsubarachnoid block. While lacking of specific antagonists, the main treatment washeteropathy. It has been demonstrated previously that LE is very effective in resuscitationfrom cardiac arrest that results from bupivacaine toxicity in animal models as well as inpatients. Whether the effect of epinephrine which was widely used in clinic while cardiacarrest in resuscitating the cardiac toxicity caused by bupivacaine is superior than LE has notbeen proved. So our study bases on the hypothesis of whether the effect of LE reversing thecardiotoxicity caused by bupivacaine is better than epinephrine. In spite of the provenefficacy of LE in resuscitating bupivacaine-induced cardiac arrest, the underlying mechanismbehind the interaction of LE and bupivacaine is not fully understood. Here we examined thehypothesis that the protective action of LE is associated with inhibition of the apoptosis ofH9C2cells caused by bupivacaine.Experiment1: Evaluate lipid emulsion in resuscitating the cardiac toxicity caused bybupivacaine in dogs Objective Aim of this study was to compare effectiveness of Lipid Emulsion (LE) andcombination of LE and Epinephrine (EPI) for the treatment of severe hemodynamiccompromise owing to bupivacaine (BPV) intoxication in dogs. Methods Bupivacaine,0.75%,10mg Kg-1, was administered intravenously through femoral vein over10s to fasteddogs under pentobarbital sodium general anesthesia, restored spontaneous breath.resuscitation started when MAP dropped to50%of the initial value and ECG showedabnormal QRS waves, then animals were given mechanical ventilation maintained with100%oxygen and external chest compressions followed with saline (Group S),20%LE(Group L) and20%LE plus10μg Kg-1epinephrine (Group C) infusion, EPI was repeatedevery5min, administered as a4mg Kg-1bolus followed by continuous infusion at0.25mL Kg-1min-1until the CPR ended. Survival, hemodynamic course containing MAP,HR, PR duration, QRS duration and QT duration were recorded. Results Twenty-one dogs,devided into three groups were investigated. Six animals in Group L but only one of sevendogs in Group S and Group C respectively, survived. Comparison within and amonggroups has statistical difference（P <0.05）. Hemodynamic course in Group L was better thanthat of other two groups. Conclusions Cardiac toxicity model induced by bupivacaine wassuccessfully built up. For the treatment of severe hemodynamic compromise owing tobupivacaine intoxication in dogs,20%LE was more effective than first-line rescue withepinephrine10μg Kg-1with regard to survival as well as hemodynamic course.Experiment2: The effect of LE acting on apoptosis caused by bupivacaine in H9C2cellsObjectives To investigate the effect of lipid emulsion on apoptosis induced bybupivacaine. Methods group1: To observe the survival rate (determined by MTT method)after24hrs cultivation in lipid emulsion group (concentrations were0.25%,0.5%,0.1%,2% respectively) and bupivacaine group (concentration were0.38,0.54,0.77,1.54mMrespectively), to find out the best concentration of myocardial cells proliferation induced bylipid emulsion. Group2: The cell proliferraion was determined in control group,1%lipidemulsion group and the combination of1%lipid emulsion and1.54mM bupivacaine afterthe cultivation of6hrs,12hrs and24hrs, then Hoechst33258staining was used to observethe apoptosis under fluorescence microscope, finally the flow cytometry was used to detectthe degree of apoptosis. Results The different levels of cytotoxicity induced by bupivacainewas observed in H9C2cells, and majority cells were with the result of apoptosis or deathinduced by bupivacaine after24hrs incubation in the concentration of1.54mM, while theinhibiton of cell growth was not seen in lipid emulsion group, and the cells proliferation atthe concentration of1%were superior than the other concentrations.1%lipid emulsioncould reduce the myocardial cells apotosis or death caused by bupivacaine at theconcentration1.54mM by using Hoechst33258staining, the apoptosis&necrosis in group1.54mM bupivacaine combined1%lipid emulsion was less than in1.54mM bupivacaine butmore than the control group or1%lipid emulsion alone(P <0.05). Conclusion The apoptosiscaused by bupivacaine can sharply reduced by lipid emulsion and showed the effect ofcardiopretection.