The Effects Of Pretreatment With Lipid Emulsion On Bupivacaine, Ropivacaine Infusion Induced Cardiac Toxicity In Rats

Objective:To investigate the effect of lipid emulsion on bupivacain,ropivacain infusion induced cardiac toxicity and to explore its mechanism.Methods:72 SD adult male rats weighting about 220-250g,were randomly divided into five groups,non-treatment control group(group A)(n=8),bupivacaine control group(group B), bupi-vacaine+ lipid emulsion pretreatment group(group C), ropivacain control group(group D), ropi-vacain+ lipid emulsion pretreatment group(group E), each group of B,C,D,E group are divided into two sub-groups based on the death group (group 1) and the material group (group 2) (n=8 each). The rats were anesthetized with 10%Chloral hydrate (0.3ml/100g)that was injected by in-traperitoneal.Two-lead ECG being monitored by inserting three acupuncture needles into the bo-th upper limbs and left lower limb subcutaneouly.The right internal jugular vein and the femo-ral vein was isolated to pump liquid.The left common carotid vein was isolated and connected to the pressure transducer to measure mean arterial pressure(MAP) which was then connected to the computer with bio-function experimental system.(1) Group A 0.9% normal saline(3ml/kg/min)was pumped in intrvenous injection continuously heart was quickly removed after 6 minutes.(2) Group B1 0.9% normal saline(3ml/kg/min)was pumped in intravenous injection 5 minutes continuously,then 0.5% bupivacaine 2mg/kg/min was not pumped in intravenous injection continuously until cardiac arrest.(3) Group B2 0.9% normal saline(3ml/kg/min)was pumped in intravenous injection 5 minutes continuously,then 0.5% bupivacaine 2mg/kg/min was pumped in intravenous injection 1 minutes continuously then the heart was quickly removed.(4) Group C1 20% fat emulsion(3ml/kg/min)was pumped in intravenous injection 5 minutes continuously,then 0.5% bupivacaine 2mg/kg/min was not pumped in intravenous injection continuously until cardiac arrest.(5) Group C2 20% fat emulsion(3ml/kg/min)was pumped in intravenous injection 5 minutes continuously,then 0.5% bupivacaine 2mg/kg/min was pumped in intravenous injection 1 minutes continuously then the heart was quickly removed.(6) Group D1 0.9% normal saline(3ml/kg/min)was pumped in intravenous injection 5 minutes continuously,then 0.5% ropivacaine 2mg/kg/min was not pumped in intravenous injection continuously until cardiac arrest.(7) Group D2 0.9% normal saline(3ml/kg/min)was pumped in intravenous injection 5 minutes continuously,then 0.5% ropivacaine 2mg/kg/min was pumped in intravenous injection 1 minutes continuously then the heart was quickly removed.(8) Group E1 20% fat emulsion(3ml/kg/min)was pumped in intravenous injection 5 minutes continuously,then 0.5% ropivacaine 2mg/kg/min was not pumped in intravenous injection continuously until cardiac arrest.(9) Group E2 20% fat emulsion(3ml/kg/min)was pumped in intravenous injection 5 minutes continuously,then 0.5% ropivacaine 2mg/kg/min was pumped in intravenous injection 1 minutes continuously then the heart was quickly removed.MAP,ECG and HR were monitored continuous, animal's mean arterial pressure(MAP) was recorded before the drugs were given,and the heart rate (HR) were recored at the same time.By tracing normal ECG and the wave of BP,the time when arrhythmia(QRS>90 ms) was appeared in these animals was recored, and the time when the cardiac arrest in the death group.The electric wave has been observed after disappearing of it for 1 minute.The accumulated dose of corresponding local anesthetics was calculated at every point.The rats in the group A and the material group are quiekly done to die by cutting head. ATP would be measured with the refrigerant heart from the died rats.Result:1.weight There was no statistic difference on weight between nine groups(P>0.05).2.elementary value of haemodynamics There was no statistic difference on elementary value of haemodynamics (MAP,HR) between nine groups (P>0.05).3.The different time points and dose corresponding to the time in the death groupThe time points,arrhythmia(T2) and cardiac arrest(T3) about group C1,group D1 and group El is appeared later than the group B1(P<0.05).The accumulated dose of corresponding local anesthetics in group C1,group D1 and group E1 is larger than in group B1(P<0.05), the difference has statistical significance. The time points,arrhythmia(T2) and cardiac arrest(T3) about group D1 and group E1 is appeared later than the group C1(P<0.05). The accumulated dose of corresponding local anesthetics in group D1 and group El is larger than in group C1(P<0.05), the difference has statistical significance, but the time points,arrhythmia(T2) and cardiac arrest(T3) and the accumulated dose of corresponding ropivacaine was no statistic difference between group Dl and group El(P>0.05). 4.The change of content of myocardial ATPThe comparison between each groups'content of ATP:group A>group D2>group C2> group B2,the differences were significant(P<0.05),but there was no statistic difference between group D2 and group E2(P>0.05).Conclusion:The mechanisms of the lipid emulsion reduce the cardiac toxicity of bupivaca-ine may be due to increase contene in myocardial ATP,the lipid emulsion was able to reduce the cardiac toxicity of bupivacaine in rats, but has no effects on that of ropivacaine.