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Along with the rapid development of global modernization, the general incidence of trauma sees a significant increase, and death caused by trauma has ranked first among people under 40 years of age. Hemorrhagic shock is one of the common complications in severe trauma, with a high incidence of 25%-80%, being the main cause of traumatic death. Prevention and treatment of hemorrhagic shock is therefore of primary importance in emergency medicine. Recently it was reported that nitric oxide (NO) and free radicals played an important role in the process of haemorrhagic shock. Delivery of medicine which could inhibit excessive production of NO and free radicals or block the functioning path of NO might be useful for shock reversion. Methylene blue (ML) was reported to have anti-septic shock effect, by mean of increasing mean arterial pressure (MAP) and systemic vascular resistance (SVR), it could reverse low blood pressure status resulted from septic shock. However, the effects of ML on haemorrhagic shock have not been reported so far, our experimental study was designed to build hemorrhagic shock model of rabbit, observe the function of ML in hemorrhagic shock and investigate its possible mechanism.Materials and Methods1. Animals and groupingTwenty-eight healthy rabbits, all male, provided by Experimental Animal Center of the Medical School. They were randomized into 2 groups: Methylene blue group (ML), 15; Natural saline group (NS): 13.2. Reproduction of hemorrhagic shock model of rabbitThe criteria of shock is 40% blood loss of the total blood capacity. When the blood pressure declines by 40% of the basal blood pressure, the hemorrhagic shock animal model is considered to be ready, and record the time and total amount of bleeding. Ten minutes after shock, ML group were given ML 7.5mg/kg, diluted with NS up to 5 ml, injected intravenously within 20 minutes. While NS group were given mere NS 5ml in the same way. From the onset of shock, record heart rate, blood pressure once every 5 minutes. The observation period was 180 minutes. Timing of blood sampling: start of intravenous injection (10’), end of intravenous injection (30’) ,15 min after injection (45’), 30 min after injection (60’) , 60 min after injection (90’). 3 ml blood for every sampling. Record the survival time of animals. Blood samples were stored in 4癈 refrigerator immediately after harvesting. After every experiment, the blood samples were centrifuged and supernate was ready in hypothermal refrigerator for examination.3. Examination of NONO assay kit were provided by Jingmei Biotech (Beijing) Co Ltd.4. Examination Lipid hydroperoxide (LPO)LPO assay kit was provided by Cayman Chemical Company (Ann Arbor, MI, USA).5. Statistical AnalysisAll data were expressed as mean ?standard deviation ( x+s), SPSS 10.0 (Chicago, IL)was used for student / test, ANOVA, A P value of<0.05 was considered to be statistically significant.Results1. There were no significant differences in body weight, total blood loss, bleeding time, basal blood pressure and initial blood pressure at shock between ML and NS group (/>>0.05), and all rabbits were male, the two groups were therefore comparable on aforementioned items.2. In comparison with the systolic blood pressure (SBP) at 0’ check point, SBP increased prominently at 20’ and 30’ point in ML group (/><0.01). While SBP didn’t increase in NS group, and even decreased significantly at 60’ point comparing SBP at 0’ point (P< 0.01). Between two groups, SBP increased significantly in ML group at 20’, 30’, 45’, 60’ point CP<0.01), which showed that SBP increased immediately 10 minutes after ML injection (7.5mg/kg), and the effect lasted up to 60’ point.3. Comparing with the diastolic blood pressure (DBP) at 0’ check point, DBP increased prominently at 20’ point in ML group (P<0.05), and didn’t decrease until at 75’ point (P <0.05). While DBP didn’t increase in NS group, and even decreased significantly at 60’ point comparing DBP at 0’ point (/><0.01). Between two groups, DBP i
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