Meconium Aspiration Syndrome (MAS) affects newborns that have eliminated meconium due to fetal hypoxia. It can lead to respiratory failure. Despite advances made regarding therapeutics, it is still associated with high mortality rates. Meconium impregnates the lungs and inactivates the pulmonary surfactant, causing atelectasia. MAS also activates inflammatory responses associated with important tissue damage, stimulating the release of mediators such as IL-8, which is somewhat responsible to the decrease of the pulmonary function. One of the treatments for MAS is the replacement with animal surfactant. Although clinical trials have demonstrated controversial results, experimental studies have shown positive aspects of this therapy, such as control over the inflammatory response, reducing cytokines e chemokynes such as IL-8. The hypothesis of this study is that the surfactant reduces IL-8 lung levels in newborn rabbits with MAS, consequently decreasing tissue damage. Objectives: to determine IL-8 levels in pulmonary tissue of newborn rabbits with MAS, which ongo mechanical ventilation, with and without bovine surfactant treatment. Material and Methods: Term newborn rabbits will be sedated and undergo tracheostomy, then divided randomly in two study groups: "MEC" - animals that receive meconium but not treatment; "SURVA" - animals that receive meconium such as "MEC" and undergo treatment. After randomization, all animals will receive standard mechanical ventilation (ventilatory pressure needed to maintain a tidal volume of 8 ml/kg) for 20 minutes, with acquirement of pulmonary mechanics data, at 5, 10, 15 and 20 minutes of the process, through a pneumotachograph, connected to a computer software, specially designed for the study. After ventilation, the animals will be properly sacrificed and their lungs will be dissected for posterior IL-8 dosage from macerated lung. The measurement will be done according to the method of ELISA, using a IL-8 kit for rabbits, produced by UCNLIFE.The study will happen in the Experimental Laboratory of the Pediatrics Department at Botucatu Medical School - UNESP. In 2011, a Laboratory of Neonatal Respiratory Diseases established, with FAPESP financing (process number 2010/1151-1). For this experiment, the laboratory will use remaining resources from previous projects. The comparison of means will be calculated using Student t test adopting a significance level of 5%. When data does not show normal distribution and variance requisitions Mann-Whitney test will be applied. Expected Results: It is expected that the lungs of animals with MAS that received surfactant replacement treatment demonstrate smaller IL-8 concentration. Consequently, they will show less inflammatory lung damage when compared to the group of animals that have the disease but receive no treatment.
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