Comparison Of Vasopressin And Epinephrine For Cardiopulmonary Resuscitation In A Rabbit Model Of Ventricular Fibrillation

Background and objective:Cardiac arrest(CA)is an emergent incident and needs to be treated with cardiopulmonary resuscitation(CPR)immediately.Although CPR has been performed for many years,the resuscitation rate is still low.Myriads of researches have been completed,in which several adjuvant cardiac medication drugs and techniques have been advocated during advanced cardiac life support to improve resuscitation rate.Though epinephrine has been used as a standard first-line drug in CA for many years,the efficacy of the drug is still not completely satisfactory.Searching more effective medicines has been the highlight.Some scholars found that plasma vasopressin concentrations were higher in resuscitated patients than in nonresuscitated ones during CPR.This result provocated greatly the interest of scientifical researcher,in which they try to identify whether vasopressin could improve the outcomes of CA during CPR. Unfortunately,the different efficacy of vasopressin during CPR were reported frequently.It was described that vasopressin was superior to epinephrine in a pig model of ventricular fibrilation(VF),but inferior to epinephrine in a rabbit asphyxia model.These controversial results provoked us to suspect whether the various efficacy of vasopressin during CPR related to the discrepancy of biological species or the different type of deseases.Since VF model in rabbit is relatively less and the efficiency of vasopressin during rabbit VF model has not been reported until now,the purposes of the study was,therefore,to test the feasibility of induction of VF in rabbit by alternating current(AC)stimulation subcutaneously and then compare the efficacy of vasopressin,epinephrine or both of them during CPR in this model.Method:1.Establishing a rabbit model of VF.Eighteen healthy male rabbits were chosen to induce VF via AC stimulation subcutaneously.Firstly,two potentials of AC(20V and 30V)were delivered to the rabbit and test whether VF could be induced by this technique.Two series of 5 seconds burst stimulation were performed at each potential with 2 minutes rest interval between each burst series.If VF occurred,even if only once,we judged that the technique could induce VF in rabbits.Secondly,30V was conducted and maintained for at least 30 seconds to prevented spontaneous defibrillation.If necessary,additional 15 seconds of AC stimulation was performed.CPR was initated after 4 min of untreated CA.Incidences of VF at each potential,time of AC stimulation and ECG following the post-stimulation were recorded.2.The effecacy of medication in this model.Sixty healthy male rabbits else were randomed into 3 groups(n=20 each):epinephrine group recevied epinephrine 0.2mg/kg intravenously,vasopressin group recevied 0.8U/kg intravenously and the drug combination group recevied the combination of epinephrine(0.2mg/kg)and vasopressin(0.8U/kg)respectively.VF was induced through AC stimulation subcutaneously in animals.After 4 min of untreated CA, animals were subjected to CPR.The rate of ROSC and the survival time were observed in each group. Result:1.VF was induced via AC stimulation subcutaneously in 18 rabbits.The incidences of VF were 55.6%and 100%in two of potentials(20V and 30V) respectively,and were more higher in 30V than in 20V(P＜0.05).With the prolongation of AC stimulation,the incidences of spontaneous defibrillation in the rabbits decreased substantially,whereas incidences of PEA increased accordingly.Time of AC stimulation with 30V was 50.83±46.75s.Following termination of prolonged AC(30V)stimulation,ECG indicated that VF occurred in 14 of 18 rabbits,PEA in 3 of 18 rabbits and asystole in 1 of 18 rabbits.Prior to CPR,sustained VF occurred in 10 animals,PEA in 8 animals.Following CPR, 11 of 18 animals were successfully resuscitated(61.1%).2.In 60 rabbits,the rate of ROSC was 61.1%in epinephrine group,21.1% in vasopressin group and 57.9%in drug combination group.The rate of ROSC was significantly lower in the vasopressin group than those in the epinephrine group and the drug combination group(P=0.02 or P=0.045).The survival time of resuscitated rabbits was 60(60,180)min in the epinephrine group,40(11, 465)min in the vasopressin group and 19(14,60)min in the drug combination group.The survival time was shorter in the drug combination group than that in the epinephrine group(P＜0.05).Conclusion:1.VF could be induced in rabbits by AC stimulation subcutaneously. Development of a rabbit VF model by AC stimulation subcutaneously is a simpler and noninvasive procedure,which may have practical significance for conducting a profound pathophysiologic study regarding CA and CPR.2.The effect of vasopressin is inferior to that of epinephrine in the rabbit model of ventricular fibrillation,which is consistent with the result in a rabbit asphyxia model,but inconsistent with that in a pig model of VF.The mechanism of the phenomenon remains unclear.The species discrepancy may be responsible for the diversity of the results.