| Backgroud Rats are one of the most commonly used small animals for research. However, due to the small size, endotracheal intubation has been a challenge because of the narrow oral cavity and the difficulty in visualizing vocal cords. There are many methods described in the literature for endotracheal intubations in rats. These methods include tracheostomy, blind intubation, and intubation under direct visualization. Each of these methods has its own limitation, such as a high failure and complication rate. Therefore, it is necessary to develop a safe and accurate endotracheal intubation in rats. We described a novel method with an optical fiber (0.9mm in diameter) laying in the tracheal catheter as a source of light for visualization and as a guide for endotracheal intubation in rats.Post-resuscitation myocardial dysfunction, including arterial hypotension, shock, ventricular arrhythmias, and recurrent cardiac arrest, has recently been recognized as a leading cause of early death after initially successful resuscitation. Approximately 60～70% of successfully resuscitated victims of cardiac arrest die due to hypotension, shock, ventricular arrhythmias, and recurrent cardiac arrest within the first 24 hours, and only 4.5% are ultimately discharged from the hospital. This myocardial dysfunction has been attributed both to global myocardial ischemia during the cardiac arrest and the adverse effects of reperfusion.Erythropoietin (Epo) is a 30.4-kDa glycoprotein best known for its action on erythroid progenitor cells and regulation of circulating red cell mass. Yet, within the past few years, Epo has been found to provide protective effects during ischemia and reperfusion in a broad array of tissues, including the heart, brain, retina, kidney, liver, and skin. In various experimental ischemia/reperfusion studies, Epo can attenuate the extent of myocardial infarction and ameliorate the cardiac ischemia/reperfusion injuries, thereby improving the cardiac function.Because ischemia/reperfusion injury is central pathophysiological processes to cardiac arrest and resuscitation, we hypothesized that administration of erythropoietin during cardiac resuscitation could be beneficial for cardiac resuscitation, hence promoting the post resuscitation myocardial function.Part 1 A new method of endotracheal intubation in rats1.ObjectivesTo develop a new method of orotracheal intubation in rats by using an optical fiber of 0.9mm in diameter-laying in the tracheal catheter as a source of light.2.MethodsSprague-Dawley rats were radomnly received two methods of orotracheal intubation.ⅰ) A comprehensive rodent model of orotracheal intubation was developed, which called conventional group.ⅱ) Whereas in the improved method, a optical fiber was utilized as a light to visualized the trachea and vocal cords, which called optical fiber group, The intubation time and intubation frequency, the success rate of the first operate were compared between the optical fiber group and the conventional group. After intubation the rats were mechanically ventilated for 60min, with the tidal volume at 0.65 ml/100g and respiratory frequency at 60/min. And then the endotracheal tube was removed, the survival rate was compared between two groups after 1 week.3.Results3.1 The time and frequency of intubation were significantly less in the optical fiber group than those in the conventional group [(36.00±16.43s vs 86.20±56.48s , 1.05±0.22 vs 1.75±1.02), P<0.01].3.2 The success rate of the first intubation in the optical fiber group was obviously higher than that of the optical fiber group [(95 % vs 60 %), P<0.05].3.3 The survival rate of the optical fiber group was lower than that of the conventional group after extubation in 1 week [(100%vs80%), P>0.05].4.Brief summaryThe Improved orotracheal intubation technique with optical fiber was a method of innovation, which was superior to traditional method and deserved to apply.Part 2 The effects of erythropoietin on myocardium after cardiopulmonary resuscitation1.ObjectivesTo investigate the post-resuscitation myocardial dysfunction and the myocardial injury, followwing asphyxia -induced cardiac arrest in the rats. To investigate the effects of erythropoietin for the management of myocardial dysfunction and myocardial injury after cardiopulmonary resuscitation.2.Methods2.1 Sprague Dawley rats were used for the prospective controlled animal study. Asphyxia-induced cardiac arrest was performed by turning-off the ventilator and clamping the endotracheal tube. Chest compression and mechanical ventilation were then started with an intravenous injection of 0.02 mg/kg epinephrine after 8 minutes of asphyxia.2.2 Rats were randomly divided into 3 groups:ⅰ) the sham group(n=8): right carotid artery and vein, left femoral artery and vein were surgically exposed, with endocheal intubationin for ventrilaton, without any treatment for cardiac arrest and cardiopulmonary resuscitation.ⅱ) the CPR group(n=8): cardiac arrest and cardiopulmonary resuscitation were started, with a volume of 0.9% saline 0.5 ml through the left femoral vein after 3 minutes of restoration of spontaneous circulation(ROSC).ⅲ) the Epo group (n=8): with erythropoietin (5000U/kg) intravenously instead of 0.9% saline after 3 minutes of ROSC.2.3 Myocardial function was assessed from measurements of HR, MAP, LVSP, LVEDP, and±dp/dt. ECG was Continiously measured. A heat lamp was used to maintain body temperature at 36.5±0.5°C throughout the experiment.2.4 Myocardial injury was assessed by measurement of serum level of CTnI and microscopic examination of the myocardUm at 120min after ROSC. 3.Results3.1 The baseline hemodynamic parameters, including HR, MAP, LVSP, LVEDP, and±dp/dt, were not different among three groups before cardiac arrest.3.2 HR, MAP, LVSP, and±dp/dt were obviously decreased (p<0.01), while LVEDP rised in the Epo group and CPR group after ROSC (p<0.01).3.3 It revealed that myocardium pathologic lesions were happenned in the CPR group at 120min after ROSC. With light and electronic microscopic observation, myocardium was characterized by necrosis and some neutrophilic infiltration, in addition to the mitochondrial swollen and vacuolated.The serum level of CTnI was significantly higher (p<0.01).3.4 Compared to the CPR group, the Epo group yielded a significantly higher LVSP,±dP/dt (p<0.01), and lower LVEDP, while the HR and MAP were no obviously difference between groups (p>0.05).3.5 The Epo group showed a reduction of serum level of CTnI (p>0.05), and much less myocardial injury comparing with the CPR group.4.Brief summary4.1 Post- resuscitation myocardial dysfunction and myocardial injury happened in rats of asphyxia-induced cardiac arrest model.4.2 Epo can rapidly induce myocardial protection in rats after cardiopulmonary resuscitation.Conclusions1. The Improved orotracheal intubation technique with optical fiber was a method of innovation, which can obtained a quick, effective and accurate intubation, and deserved to apply.2. Post- resuscitation myocardial dysfunction and myocardial injury happened in the rats after cardiopulmonary resuscitation.3. Epo can rapidly induce myocardial protection in the rats after cardiopulmonary resuscitation.
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