| Background and objectives: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 rate of successful resuscitation is low. Though epinephrine has been used as a first-line drug in CA for many years, the efficacy of the drug is still not completely satisfactory., and this forced people to continuously study and search for more effective resuscitation drug. In recent years, 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,and started trying to apply CPR vasopressin, and achieved certain results.Epinephrine is a non-selectiveα,βreceptor agonists, in the CPR when that excitedαreceptor high blood pressure, but also excitedβ-adrenergic receptor, the latter that increase myocardial oxygen consumption, and increase of malignant arrhythmia the incidence, reducing the success rate of resuscitation. And vasopressin is a peptide hormone, through the direct effect of V1a receptor in the vasoconstrictor effect caused to aortic diastolic pressure and coronary perfusion pressure to increase; with epinephrine compared to noβ-adrenergic receptor exciting and difficult to arouse negative effects, such as malignant arrhythmias. In theory, vasopressin in CPR may be better than the effect of epinephrine. However, with in-depth study, a growing number of scholars found: vasopressin and epinephrine in CPR efficacy in the very different. Have a mechanism for this phenomenon is unclear.A long period of time, CPR when ventricular fibrillation appeared to give conventional defibrillation. In fact, the resuscitation drug efficacy and the results of the comprehensive effects of defibrillation, difficult to evaluate the true effect of resuscitation drug. Therefore, ours study for rats experiments of, electric stimulation to establish CA model, use of the different traditional methods and set of experimental design, observation and a series of one time application of epinephrine or vasopressin in the non-defibrillator under the conditions of recovery effect, seeks to clarify what kind of drugs more easily induced in CPR and / or increase the ectopic arrhythmia, from the perspective of academic research to explore the two drugs may exist mechanism in the CPR. Methods:1. Reproduce CA rat model of ventricular fibrillation, as compared epinephrine and vasopressin the efficacy,under the conditions of non- defibrillators once drug in the model. Health of 40 male SD rats, weight 200-300g, were randomly divided into 4 groups (n=10) , saline group; epinephrine group; vasopressin group and combination group. 5F to a cardiac pacing electrode (2 pole) was inserted into the mouth of rat esophagus, with AC (50HZ, 20V) stimulate to copy the CA model of ventricular fibrillation. from AC stimulation 5 min after start CPR, when the recovery time to 1min, 4 group rats were respectively given intravenous normal saline 1 ml, epinephrine 0.04mg/kg, vasopressin 0.8u/kg, and epinephrine 0.04mg/kg+vasopressin 0.8u/kg the Single time, to observe the rats in the cardiac rhythm during CPR changes, compared the Restoration of spotaneous circulation(ROSC), as well as early recovery situations. 2. Under the conditions of non-defibrillator several times drug comparison the effect in the rat model of ventricular fibrillation: Healthy of 30 male SD rats were randomly divided into 3 groups (n=10) epinephrine group; vasopressin group and combination group, using the same method of Reproduce ventricular fibrillation CA rat model . from AC stimulate 5min after start CPR, when the resuscitation 1min, 4min, 7min respectively given the epinephrine 0.04mg/kg, vasopressin 0.8u/kg and 0.04mg/kg epinephrine+vasopressin 0.8u/kg, ROSC but not enough three times drug to stop given. Observation of the rats in the cardiac rhythm during CPR and the ROSC rate changes, observation hemodynamics after administration of the change, as well as the recovery of survival after resuscitation successful.Results:1. when the cessation of AC stimulation, saline group; epinephrine group; vasopressin group and combination group, respectively, the incidence of ventricular fibrillation is the 9/10, 8/10, 9/10 and 8/10, among the groups no significant difference; with the time, each group of rats to ventricular fibrillation most changed to pulse electrical activity or heart arrest, pre-CPR each group the rats heart of rhythm of changes comparison and no significant difference; the end of the CPR vasopressin and saline group all rats were ventricular fibrillation, epinephrine and with combined treatment group rats the incidence of ventricular fibrillation is 3/10, 3/10, maintain or new occurrence the probability of ventricular fibrillation was significantly lower than vasopressin group (P <0.01); epinephrine and with combined treatment group were 5/10 and 6/10 the rate of ROSC, ROSC rates of two groups was significantly higher than vasopressin and saline group (P<0.05); Although epinephrine group and the combination group ROSC rate compared no significant difference (P=0.392), but epinephrine ROSC time was significantly longer than the combination group (P = 0.037).2. In 30 transesophageal AC stimulation copy of ventricular fibrillation CA rat model, after repeated application of the resuscitation drug, epinephrine group, vasopressin group and combination group at the end of the resuscitation. Three group rats still sustained ventricular fibrillation probability is 3/10, 8/10 and 3/10 respectively. The ventricular fibrillation occurrence rate of vasopressin group was significantly higher than the other two groups (P<0.05); three group ROSC rates were 6/10, 1/10 and 7/10, vasopressin group was significantly lower than epinephrine group and combination group (P=0.019, P=0.006). Epinephrine group and combination group of the ROSC rate between no significant difference (P>0.05), but epinephrine group ROSC time is still longer than the combined treatment group (P = 0.046).Conclusion:1 .Under the conditions of the non-defibrillator, whether single or repeated drug administration, by electrical stimulation in the rat model of ventricular fibrillation , epinephrine in the recovery effect was significantly better than vasopressin. Epinephrine does not increase the incidence of ectopic arrhythmias, on the contrary, during CPR epinephrine may appear the automatic termination of ventricular fibrillation or automatic conversion to sinus rhythm tendency. The mechanism may be excited with theβ-adrenergic receptor resulted in sinus node and self-discipline and increased excitability, which may to some extent in favor of the termination of ventricular fibrillation.2. Repeated application of vasopressin in CPR not be maintained at a higher level of coronary perfusion pressure, and vasopressin does not reduce the incidence of ventricular fibrillation and ventricular fibrillation duration, suggesting that vasopressin may be in the model did not cause the termination of ventricular fibrillation automatically change to sinus rhythm effects.3. Vasopressin combined with epinephrine ROSC time can be shortened, but does not increase the rate of ROSC, indicating that the model in the combination application of these two drugs increased the resuscitation of the net effect is very limited.4. In the CPR, even if ventricular fibrillation is not defibrillation given to the experimental design is clearly inconsistent with the clinical practice. However, this experimental design was not intended to improve the success rate of CPR, but to compare drugs in the CPR the net effect, from the perspective of academic research to explore these two drugs may exist in the CPR, but the role has not been found mechanism. The results can be a reasonable explanation for epinephrine and vasopressin in CPR different effect provide one new ideas .
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