Objective To investigate the effect of dexamethasone for acute lung injury ( ALI ) following open chest trauma and sea water immersion in dogs and its mechanism .Methods Sixteen healthy adult dogs were used to make the ALI models by seawater immersed thoracic cavity after open chest trauma .Then the ALI models were randomly assigned in-to the control group ( CG) and the dexamethasone treatment group ( DG) , 8 in each group .Dogs in the DG group were in-travenously injected with 1 mg/kg dexamethasone ( DG) 30 min after open chest trauma and sea water immersion , and dogs in the CG group were treated with equal normal saline .Arterial blood gas indexes (PaO2 and PaO2/FiO2) and expression changes of alveolar surfactant protein-A ( SP-A) and alveolar surfactant protein-B ( SP-B) in the lung bronchoalveolar lav-age fluid ( BALF) and serum as well as the EVL-WI and ELI were observed .Results At 4 h after treatment , the PaO2 and PaO2/FiO2 in the DG group was significantly higher than that of the control group (P<0.05), the EVL-WI and ELI in the DG group was lower than that of the control group (P<0.05), and the SP-A and SP-B in the DG group in the BALF was higher than that of the CG group but lower than in the blood serum .Conclusion Dexamethasone can relieve hypoxia and pulmonary edema after open chest trauma and sea water immersion in dogs and its mechanism may be associated with the increase of the SP-A and SP-B contents in lungs .%目的：探讨地塞米松对海水浸泡胸部开放伤所致致急性肺损伤（ ALI）的治疗作用及其机制。方法取健康成年杂交犬16只制备海水浸泡胸部开放伤ALI模型，随机分为对照组及治疗组各8只。治疗组于海水浸泡30 min后静脉注射地塞米松1 mg/kg，对照组静脉注射等量生理盐水。动态观察伤后动脉血气指标（ PaO2、PaO2/FiO2），支气管肺泡灌洗液（ BALF）、血清中体内肺表面活性蛋白A和B（ SP-A、SP-B）含量变化及血管外肺水含量指数（ EVL-WI）、肺微血管通透性（ ELI ）变化。结果伤后4 h治疗组PaO2、PaO2/FiO2显著高于对照组（ P均＜0．05），EVL-WI、ELI均低于对照组（P均＜0．05），SP-A、SP-B含量在BALF中高于对照组而在血清中低于对照组（ P均＜0．05）。结论地塞米松能改善胸部开放伤后海水浸泡致ALI犬的缺氧及减轻肺水肿，其机制可能为提高肺内SP-A、SP-B含量。
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