Effect Of Electroacupuncture Pretreatment On Bupivacaine Cardiotoxicity In Rats

Objective: Bupivacaine is frequently used in local anesthesia. However, the cardiotoxicity is a severe side effect of bupivacaine. Evidence revealed that electroacupuncture(EA) could decrease arrhythmia and myocardial injury induced by myocardial ischemia-reperfusion. However, Whether EA could alleviate bupivacaine-induced cardiotoxicity still remains unknown. To observe the effect of EA pretreatment on hemodynamic changes and resuscitation outcomes induced by bupivacaine overdose in rats.Method: Thirty-six adult male SD rats, weighing 180-240 g, aging 2 months, were randomized assigned into three groups: EA60, EA30 and only bupivacaine(B)(n=12). Rats in EA60 and EA30 group received EA at bilateral ―Neiguan‖(PC6), ―Zusanli‖(ST36) and ―Fenglong‖(ST40) for 60 min and 30 min, respectively, while B received nothing to EA. Then Lead 2 of the electrocardiograph was monitored, catheter was inserted into the femoral vein for drug administration and into the right carotid artery for arterial blood pressure monitoring. Three hours after EA, all rats received 0.5% bupivacaine 10 mg/kg via femoral vein catheter at a rate of 5 mg·kg-1 ·min-1. The mean arterial pressure(MAP), heart rate(HR) and electrocardiography(ECG) were recorded automatically by PowerLab system. The specific time points when 20% prolongation in QRS, QT, and respiratory, cardiac arrest occurs were marked. The time consumed for successful resuscitation and final survival rates were calculated. Arterial blood samples(0.3 mL) were taken at baseline and and the end of experiment in survived rats for blood gas analysis. Cardiac muscle tissue was harvested from each rat. Carnitine concentration in myocardial cytoplasm and myocardial mitochondria was further measured.Results: After bupivacaine injection, Time to 20% prolongation of QRS, QT interval in EA 60 groupwere increased compared with EA30 group and B group(P<0.05); MAP and HR in EA60 group were higher than EA30 group and B group in most recorded points(P<0.05); It took significantly less time for successful resuscitation in EA60 group, compare to EA30 and B group(P<0.05), but not statistical differences among EA30 and B group(P>0.05); the incidences of cardiac arrest were 7/12, 10/12,and 11/12 in EA60, EA30 and B group, respectively. The rates of cardiac arrest were not statistical differences among three group(P>0.05); The rates final animal survival in EA60 group was higher than other B group(P<0.05). The carnitine concentration in myocardial cytoplasm was higher in B group than EA60 group and EA30 group, while the carnitine concentration in myocardial mitochondria is higher in EA60 group than EA30 group and B group(P<0.05).Conclusion: EA pretreatment decreases vulnerability of bupivacaine-induced heart arrest in rats, with 60 min pretreatment leading to better therapeutic effect than 30 min. EA pretreatment may play its role through myocardial protection by increasing the concentration of mitochondria carnitine.