The Study Of Protective Effects Of Ischemic Preconditioning On Porcine Myocardium

Background and objectiveIschemic preconditioning is defined as an increased tolerance to ischaemia and reperfusion induced by a previous sublethal period of ischaemia. In 1986, Murry and colleagues described the phenomenon of ischemic preconditioning(IP) which proved to be one of the most powerful methods of minimizing ischaemia/reperfusion(I/R) injury. Murry et al. demonstrated in the canine heart that four cumulative 5 min ischemic period, rather than worsening ATP depletion and myocardial necrosis, instead conferred protection from a further prolonged 40 min ischemic insult. The zone of infracted myocardium in preconditioning dogs was reduced by 75% compared to controls subjected only to the 40 min coronary occlusion. Preconditioning obtained has been shown to reduce reperfusion arrhythmias, slow energy metabolism during the early stages of ischaemia, improve post-ischemic recovery of function, protect the coronary endothelium, increases the resistance of isolated myocytes to hypoxic injury . Since this is the most powerful mechanism for limiting infract size, other than timely reperfusion, an overwhelming number of studies have addressed the way in which this form of protection occurs.Nowadays most of these models are built by coronary or use isolated hearts which perfused in the Langendorff mode and randomized to control or preconditioning groups. Through these models to demonstrate the functions of ischemic preconditioning. We can hardly see the global ischemia preconditioning in vivo. Now more and more patients die of cardiac arrest in clinic. Perhapse 2 times of short VF can induce ischemia preconditioning(IP). It can protect the heart to endure a long period of ischemia. This experiment does not use isolated heart. Preconditioned hearts received 2 periods of global ischaemia by fibrillating heart. This study confirms that global ischemic preconditioning can protect the heart to endure a long period of ischaemia. Through studying the resuscitation rate, ROSC rate arterial blood gas, SaO₂, we can evaluate the function of IP.Materials and methordsSixteen Swedish domestic pigs of either sex with a weight of 25.00±0.88 kg (23.60kg-26.2kg) were used for investigation. A blood flow probe was placed on the left internal carotid artery. Catheters(Secalon-t-over-needle central venous catheter, 16G/1.70.130mm)for blood pressure measurements were introduced via a direct puncture of the right carotid artery and right internal jugular vein, in order to avoid ligation of the vessels. First ventricular fibillation(VF) was induced with 5-20mA,6Hz and 30V alternating current delivered to the epicardial surface via a needle electrode. After 3 min of VF, LUCAS-CPR started. Defibrillation was attempt during CPR. After ROSC, in one hour, fibillate the heart again. After 3min of VF, LUCAS-CPR started. Defibrillation was attempt during CPR. When it returns of spontaneous circulation, waits for an hour fibillated again. After 20 min of VF, LUCAS-CPR started. For controls defibrillated the heart directly. After 20 min, LUCAS-CPR started. During CPR, ventricular fibrillation(VF) was attempted.Result1. Compared with control group, the resuscitation rate was 50%. There were significant difference between two group(P<0.05).2. In ischemic group, there was no difference about arterial blood gas(P>0.05).3. Compared with control group, there was no difference about the basic blood gas(P>0.05). 4. In ischemic group, there were significant difference mean blood pressure, carotid blood flood and base blood pressure, base carotid blood flow.Conclusion1. This is a new model of ischemia preconditioning through short periods of ventrical fibrillation in vivo.2. After two times of VF, it can induce protective effect of ischemic preconditioning which can protect the heart for a long periods of global ischemia.