目的：探讨早期低分子肝素联合地塞米松对油酸及脂多糖（OA-LPS）双重打击诱导的急性呼吸窘迫综合征（ARDS）大鼠凝血/纤溶的影响。方法将40只成年健康雄性SD大鼠按随机数字表法分为假手术组、ARDS模型组、地塞米松组、低分子肝素组和联合治疗组，每组8只。采用经尾静脉注射OA 0.2 mL/kg联合腹腔注射LPS 5 mg/kg序贯双重打击制备大鼠ARDS模型。地塞米松组制模后腹腔注射地塞米松10 mg/kg，低分子肝素组静脉注射低分子肝素200 U/kg，联合治疗组制模后腹腔注射地塞米松10 mg/kg并静脉注射低分子肝素200 U/kg；假手术组经尾静脉注射生理盐水（NS）0.4 mL/kg及腹腔注射NS 2 mL/kg，4 h后腹腔注射NS 1 mL/kg，其余同模型组。以制模后6 h作为实验终点。光镜下观察肺组织病理改变；测定大鼠动脉血氧分压（PaO2）并计算氧合指数（PaO2/FiO2）；测定肺组织湿/干质量（W/D）比值；采用凝固法检测大鼠凝血指标；酶联免疫吸附试验（ELISA）测定血清纤溶酶原激活物抑制剂-1（PAI-1）和Ⅲ型前胶原（PC-Ⅲ）含量。结果光镜下模型组大鼠可见肺间质和肺泡内有红细胞渗出及纤维素沉积，肺泡壁有透明膜形成，肺间质有炎性细胞浸润，肺毛细血管或肺小动脉内可见纤维素性血栓形成；地塞米松组、低分子肝素组和联合治疗组肺间质和肺泡内红细胞渗出及纤维素沉积减少，肺间质炎性细胞浸润减轻，肺毛细血管或肺小动脉内纤维素性血栓减少，以联合治疗组改善最明显。与假手术组比较，模型组PaO2/FiO2明显降低〔mmHg（1 mmHg＝0.133 kPa）：272.02±28.28比420.24±35.52，P＜0.01〕，肺W/D比值显著升高（5.59±0.40比3.82±0.28，P＜0.01），凝血酶原时间（PT）、凝血酶时间（TT）明显延长〔PT（s）：18.78±1.57比16.36±0.97，TT（s）：39.02±5.03比29.22±8.83，均P＜0.05〕，纤维蛋白原（Fib）含量明显降低（g/L：1.82±0.26比2.69±0.40，P＜0.01），血清PAI-1、PC-Ⅲ含量明显升高〔PAI-1（ng/L）：719.04±103.74比517.25±119.18，PC-Ⅲ（μg/L）：29.93±3.24比22.97±6.26，均P＜0.01〕。与模型组比较，地塞米松组、低分子肝素组及联合治疗组3组PaO2/FiO2明显升高，肺W/D比值明显降低，以联合治疗组变化最为明显〔PaO2/FiO2（mmHg）：376.78±25.25比272.02±28.28，肺W/D比值：4.14±0.42比5.59±0.40，均P＜0.01〕，低分子肝素组TT延长最为显著（s：52.00±4.24比39.02±5.03，P＜0.05），3组Fib含量均明显增加（g/L：2.37±0.38、2.59±0.51、2.59±0.24比1.82±0.26，P＜0.05或P＜0.01），而联合治疗组PAI-1含量降低最为显著（ng/L：546.02±93.94比719.04±103.74，P＜0.01）。联合治疗组除PT较地塞米松组及低分子肝素组明显延长（s：19.98±1.61比17.20±1.48、17.02±2.34，均P＜0.05）外，其余指标3组间差异均无统计学意义。结论由OA-LPS双重打击诱导的ARDS大鼠存在凝血功能障碍和纤溶抑制；早期低分子肝素治疗可改善ARDS大鼠凝血及纤溶状况，且联合地塞米松的效果优于单独用药。%Objective To observe the effects of low molecular weight heparin (LMWH) combined with dexamethasone (Dex) on coagulation and fibrinolysis at the early stage in rats with acute respiratory distress syndrome (ARDS) induced by two-hit of oleic acid (OA) and lipopolysaccharide (LPS).Methods Forty healthy adult male Sprague-Dawley (SD) rats were randomly divided into sham operation, ARDS model, Dex, LMWH and combining therapy groups (8 rats in each group). The rat ARDS model was established by sequential two-hit with intravenous injection of OA 0.2 mL/kg in a tail vein and intra-peritoneal injection of LPS 5 mg/kg. After model establishment, the rats in Dex group were intra-peritoneally injected with 10 mg/kg Dex, and those in LMWH group were intravenously injected with 200 U/kg LMWH, while the rats in combining therapy group were given Dex and LMWH simultaneously with the same dosages and methods as above mentioned respectively. In sham operation group, however, the rats were intravenously injected with 0.4 mL of normal saline (NS) and were given 2 mL/kg of intra-peritoneal NS injection, and they accepted another 1 mL/kg NS intra-peritoneal injection 4 hours later, the other procedures being the same as those in the model group. The experiment was ended at 6 hours after the establishment of ARDS model. A light microscope was used to observe the pathological changes in lung tissues, partial pressure of arterial blood oxygen (PaO2) was measured, and the oxygenation index (PaO2/FiO2) was calculated. Wet to dry weight (W/D) ratio of lung tissues was also checked. Coagulation indexes were measured by solidification method, and the serum level of plasminogen activator inhibitor-1 (PAI-1) as well as the content of procollagen type Ⅲ (PC-Ⅲ) was determined by enzyme linked immunosorbent assay (ELISA).Results Under the light microscope, effusion of red blood cells, fibrin deposit in the lung interstitium and alveoli, formation of transparent membrane at alveolar wall, inflammatory cells infiltration in pulmonary interstitial tissue, and fibrinous thrombi in lung capillaries or lung arterioles were seen in the model group. Compared with model group, the red blood cells effusion and fibrin deposition in the lung interstitium and alveoli were less, inflammatory cells infiltration in pulmonary interstitium was alleviated and the fibrinous blood emboli in the lung capillaries or lung small arterioles were also decreased in Dex, LMWH and combining therapy groups, among the three groups, the best results being in the combining therapy group. Compared with sham operation group, the PaO2/FiO2 was significantly lowered [mmHg (1 mmHg = 0.133 kPa): 272.02±28.28 vs. 420.24±35.52,P < 0.01], the lung W/D ratio was obviously higher (5.59±0.40 vs. 3.82±0.28,P < 0.01), prothrombin time (PT) as well as thrombin time (TT) were markedly longer [PT (s): 18.78±1.57 vs. 16.36±0.97, TT (s): 39.02±5.03 vs. 29.22±8.83, bothP < 0.05], fibrinogen (Fib) content was significantly decreased (g/L: 1.82±0.26 vs. 2.69±0.40,P < 0.01), but both the serum contents of PAI-1 and PC-Ⅲ were remarkably elevated in model rats [PAI-1 (ng/L): 719.04±103.74 vs. 517.25±119.18, PC-Ⅲ (μg/L): 29.93±3.24 vs. 22.97±6.26, bothP < 0.01); Compared with model group, the level of PaO2/FiO2 was significantly elevated, and the lung W/D ratio was obviously decreased in Dex, LMWH and combining therapy groups respectively, the most significant changes being in combining therapy group [PaO2/FiO2 (mmHg): 376.78±25.25 vs. 272.02±28.28, lung W/D ratio: 4.14±0.42 vs. 5.59±0.4, bothP < 0.01] , in LMWH group, the prolongation of TT was the longest (s: 52.00±4.24 vs. 39.02±5.03,P < 0.05), while Fib contents in the three treatment groups were all obviously increased (g/L: 2.37±0.38, 2.59±0.51, 2.59±0.24 vs. 1.82±0.26,P < 0.05 orP < 0.01); meanwhile, the decrease of PAI-1 in combining therapy group was the greatest (ng/L: 546.02±93.94 vs. 719.04±103.74,P < 0.01). The indexes showed no statistically significant differences among the three treatment groups, except that PT in combining therapy group which was significantly longer than that in Dex and LMWH groups (s: 19.98±1.61 vs. 17.20±1.48, 17.02±2.34, bothP < 0.05). Conclusions The rats with ARDS induced by two-hit of OA combined with LPS have coagulation dysfunction and fibrinolytic inhibition. Using LMWH early can improve coagulation and fibrinolytic status in the rats with ARDS, and the therapeutic effects of LMWH plus Dex for treatment of ARDS are better than those of using each of them alone.
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