Methylprednisolone does not enhance the surfactant effects on oxygenation and histology in paraquat-induced rat lung injury

OBJECTIVE: To investigate whether exogenous surfactant would improve gas exchange and lung histology and methylprednisolone pretreatment would enhance the surfactant effect in a rat model of paraquat-induced lung injury. SETTING: University research facility. SUBJECTS: Thirty-three adult male Sprague-Dawley rats. INTERVENTIONS: All rats received intraperitoneal paraquat injection (35 mg/kg) and were assigned randomly to one of four groups: the control group received no further treatment; the methylprednisolone group received a concomitant intraperitoneal methylprednisolone injection (30 mg/kg); the surfactant group received intratracheal Survanta (100 mg/kg) at the start of ventilation; and the methylprednisolone + surfactant group received both methylprednisolone and surfactant treatments. MEASUREMENTS AND MAIN RESULTS: Three days after paraquat injection, every rat was ventilated for 90 min, a static pressure-volume curve and bronchoalveolar lavage were performed and postmortem histology was examined. Treatment with surfactant and methylprednisolone + surfactant improved oxygenation relative to the control group and produced significantly higher lung volumes than the control and methylprednisolone groups. Treatment with surfactant resulted in a significant decrease in total cell and neutrophil counts relative to the control group. Surfactant with methylprednisolone pretreatment significantly decreased total cell, macrophage and neutrophil counts when compared with the surfactant group. The histological appearance of the lungs was better in the two surfactant-treated groups. CONCLUSION: Intratracheal instillation of surfactant improves gas exchange, ameliorates lung inflammation and results in less lung damage in paraquat-induced rat lung injury. Surfactant with methylprednisolone pretreatment decreases inflammatory cell infiltration, but cannot further improve oxygenation and lung histology.     

Bilateral lavage with diluted surfactant improves lung function after unilateral lung contusion in pigs

OBJECTIVE: This study evaluates the effects of bronchoalveolar lavage with diluted surfactant on unilateral lung contusion-induced lung dysfunction. DESIGN: Randomized prospective animal study. SETTING: An animal laboratory. SUBJECTS: Twenty adult pigs, weighing 25-35 kg. INTERVENTIONS: Animals were randomly assigned to controls and surfactant treatment. Bilateral lavage with surfactant treatment began 30 mins after unilateral lung contusion. Then 25 mg/kg of body weight diluted Curosurf (5 mg/mL) was applied in a volume of 5 mL/kg of body weight. Observation time was 8 hrs postinjury. MEASUREMENTS AND MAIN RESULTS: The Pao2/Fio2 ratio fell from 500 to 250 and then recovered gradually in controls and surfactant-treated pigs. After another 4 hrs, the Pao2/Fio2 ratio deteriorated again in controls, but not in surfactant-treated animals. Total compliance fell by 50% after injury but was completely restored by surfactant treatment. Lung contusion increased the median number of neutrophils in bronchoalveolar lavage fluid from 2% to 30% of total cells and peaked >60% at 480 mins in the contused lungs of control pigs. Surfactant-treated pigs had 40% neutrophils at 480 mins without reaching significant difference to controls. The leukocyte neutral proteinase inhibitor increased to 500 ng/mL at 30 mins postinjury in the contused lungs and increased to 2000 ng/mL after surfactant treatment. CONCLUSIONS: Bilateral bronchoalveolar lavage with diluted surfactant can effectively improve lung function after experimental unilateral lung contusion in pigs.     

Response to exogenous surfactant is different during open lung and conventional ventilation

OBJECTIVE: Previous studies have shown that the efficacy of exogenous surfactant is dose-dependent during conventional positive pressure ventilation (PPVCON). The present study aimed to determine whether this dose-dependent relationship is also present during open lung (OLC) ventilation. We also explored the effect of exogenous surfactant on the ventilation pressures applied during ventilation. DESIGN: Animal study. SETTING: University-affiliated research laboratory. SUBJECTS: Seventy-two newborn piglets. INTERVENTIONS: After repeated whole lung lavage, animals were randomly allocated to two surfactant groups receiving either 100 mg/kg surfactant (S100) or 25 mg/kg surfactant (S25) or to a control group receiving a bolus of air. Within each group, animals were randomly assigned to either PPVCON, open lung PPV (PPVOLC), or open lung high-frequency oscillatory ventilation (HFOVOLC) and ventilated for 5 hrs. MEASUREMENTS AND MAIN RESULTS: The ventilation pressures decreased in a dose-dependent way, showing the largest reduction in the S100 group. In both OLC groups, oxygenation, lung mechanics, and polymorphonuclear neutrophils analyzed in bronchoalveolar lavage were independent of the surfactant dose. In the PPVCON group, however, there was a clear dose-dependency, resulting in a deterioration of oxygenation and lung mechanics and an increase in polymorphonuclear neutrophils as the surfactant dose decreased. Although comparable between the three ventilation groups, bronchoalveolar lavage interleukin-8 concentrations significantly increased in all ventilation groups as the surfactant dose increased. Alveolar protein influx and conversion of large to small aggregate surfactant were higher during PPVCON compared with both OLC groups. There were no differences in the surfactant treatment response between PPVOLC and HFOVOLC. CONCLUSION: Exogenous surfactant enables a reduction in ventilation pressures. Compared with PPVCON, the efficacy of surfactant treatment is less dose-dependent during open lung ventilation. Surfactant conversion during open lung ventilation is reduced compared with PPVCON. Exogenous surfactant seems to up-regulate bronchoalveolar lavage interleukin-8 concentrations, independent of the ventilation strategy.     

Purine in bronchoalveolar lavage fluid as a marker of ventilation-induced lung injury.

OBJECTIVE: To investigate in a rat model of ventilation-induced lung injury whether metabolic changes in the lung are reflected by an increased purine concentration (adenosine, inosine, hypoxanthine, xanthine, and urate; an index of adenosine-triphosphate breakdown) of the bronchoalveolar lavage fluid and whether purine can, thus, indirectly serve as a marker of ventilation-induced lung injury. DESIGN: Prospective, randomized, controlled trial. SETTING: Research laboratory. SUBJECTS: Forty-two male Sprague-Dawley rats. INTERVENTIONS: Five groups of Sprague-Dawley rats were subjected to 6 mins of mechanical ventilation. One group was ventilated at a peak inspiratory pressure of 7 cm H2O and a positive end-expiratory pressure of 0 cm H2O. A second group was ventilated at a peak inspiratory pressure of 45 cm H2O and a positive end-expiratory pressure of 10 cm H2O. Three groups of Sprague-Dawley rats were ventilated at a peak inspiratory pressure of 45 cm H2O without positive end-expiratory pressure. Before mechanical ventilation, two of these groups received intratracheal administration of saline or exogenous surfactant at a dose of 100 mg/kg and one group received no intratracheal administration. A sixth group served as the nonventilated controls. MEASUREMENTS AND MAIN RESULTS: Bronchoalveolar lavage fluid was collected in which both purine concentration (microM; mean +/- SD) and protein concentration (mg/mL; mean +/- SD) were determined. Statistical differences were analyzed using the one-way analysis of variance (ANOVA) with a Student-Newman-Keul's post hoc test. Purine and protein concentrations were different between groups (ANOVA p value for purine and protein, <.0001). Both purine and protein concentrations in bronchoalveolar lavage fluid were increased in Group 45/0 (3.2 +/- 1.9 and 4.2 +/- 1.6, respectively) compared with Group 7/0 (0.4 +/- 0.1 [p < .05] and 0.4 +/- 0.2 [p < .001]) and controls (0.2 +/- 0.2 [p < .01] and 0.2 +/- 0.1 [p < .001]) and in Group 45/Na (5.8 +/- 2.5 and 4.2 +/- 0.5) compared with Group 7/0 (purine and protein, p < .001) and the controls (purine and protein, p < .001). Positive end-expiratory pressure prevented an increase in purine and protein concentrations in bronchoalveolar lavage fluid (0.4 +/- 0.3 and 0.4 +/- 0.2, respectively) compared with Group 45/0 (purine, p < .01; protein, p < .001) and Group 45/Na (purine and protein, p < .001). Surfactant instillation preceding lung overinflation reduced purine and protein concentration in bronchoalveolar lavage fluid (2.1 +/- 1.6 and 2.7 +/- 1.0) compared with Group 45/Na (purine, p < .001; protein (p < .01). Surfactant instillation reduced protein concentration compared with Group 45/0 (p < .01). CONCLUSIONS: This study shows that metabolic changes in the lung as a result of ventilation-induced lung injury are reflected by an increased level of purine in the bronchoalveolar lavage fluid and that purine may, thus, serve as an early marker for ventilation-induced lung injury. Moreover, the study shows that both exogenous surfactant and positive end-expiratory pressure reduce protein infiltration and that positive end-expiratory pressure decreases the purine level in bronchoalveolar lavage fluid after lung overinflation.     

At surfactant deficiency, application of "the open lung concept" prevents protein leakage and attenuates changes in lung mechanics

OBJECTIVE: To evaluate whether mechanical ventilation using "the open lung concept" during surfactant depletion can attenuate the deterioration in pulmonary function. DESIGN: Experimental, comparative study. SETTING: Research laboratory of a large university. SUBJECTS: Eighteen adult male Sprague-Dawley rats, weighing 280-340 g. INTERVENTIONS: Twelve rats were anesthetized, mechanically ventilated with 100% oxygen, and randomly divided into two groups (n = 6 each). The open lung group underwent six saline lavages at different ventilator settings that prevented alveolar collapse. The settings (expressed as frequency/peak inspiratory pressure/positive end-expiratory pressure/inspiratory:expiratory ratio) were 30/26/6/1:2 during the first lavage, 100/27/10/1:1 during the next two lavages, and 100/33/15/1:1 during the last three lavages and during the remaining ventilation period. The ventilated control group underwent six saline lavages with settings at 30/26/6/1:2. After the lavages, peak inspiratory pressure and positive end-expiratory pressure were increased in this group by 2 cm H2O each for the remaining study period. An additional group of six animals were killed immediately after induction of anesthesia and served as healthy controls. Blood gases were measured before lavage, immediately after the last lavage, and thereafter hourly. At the end of the 4-hr study period, we constructed pressure-volume curves from which we determined total lung capacity at a distending pressure of 35 cm H2O (TLC35). Subsequently, total lung volume at a distending pressure of 5 cm H2O (V5) was determined, followed by bronchoalveolar lavage. RESULTS: In the ventilated control group, PaO2, V5, and TLC35 were significantly decreased and protein concentration of bronchoalveolar lavage was significantly increased compared with the healthy control group. In the open lung group, PaO2 did not decrease after the lavage procedure, and V5, TLC35, and the protein concentration of bronchoalveolar lavage were comparable with the healthy controls. CONCLUSION: We conclude that application of the open lung concept during surfactant depletion attenuates deterioration in pulmonary function.     

Insulin attenuates endotoxin-induced acute lung injury in conscious rats

OBJECTIVES: To investigate the effects of insulin on the acute lung injury induced by lipopolysaccharide using a conscious rat model. DESIGN: Prospective, randomized, controlled animal study. SETTING: University research laboratory. SUBJECTS: A total of 190 adult male Sprague-Dawley rats weighing 250-300 g. INTERVENTIONS: Endotoxemia was induced by intravenous infusion of lipopolysaccharide. Lipopolysaccharide at various doses (0, 1, 5, 10, 20, and 30 mg/kg, n=10 for each dose) was administered intravenously in 20 mins. Insulin infusion at doses of 0.5, 1, and 5 microU/kg/min was given 5 mins before lipopolysaccharide administration. Plasma glucose was clamped at 90-110 mg/dL by infusion of 10-80% glucose solution. Insulin and glucose infusion (0.01 mL/min) was started 5 mins before lipopolysaccharide and continued for 120 mins. The rats received a total of 60, 120, and 600 microU/kg insulin as well as 0.12, 0.36, and 0.96 g of glucose in respective groups. The animals were then observed for 4 hrs. MEASUREMENTS AND MAIN RESULTS: The extent of acute lung injury was evaluated by lung weight/body weight ratio, lung weight gain, protein concentration in bronchoalveolar lavage, and exhaled nitric oxide. We also measured plasma nitrate/nitrite and methyl guanidine. In addition, histopathologic changes of the lung were examined. Lipopolysaccharide caused systemic hypotension and severe acute lung injury with increases in plasma nitrate/nitrite and methyl guanidine. Pretreatment with insulin infusion at doses of 0.5, 1, and 5 microU/kg/min mitigated or prevented systemic hypotension and the development of acute lung injury, depending on the dose. Insulin also attenuated the lipopolysaccharide-induced increases in nitrate/nitrite and methyl guanidine. CONCLUSIONS: Insulin is effective in reducing or preventing the lipopolysaccharide-induced increases in plasma nitrate/nitrite and methyl guanidine and the occurrence of acute lung injury.     

不同剂量猪肺表面活性物质对大鼠油酸型急性肺损伤疗效的影响

目的 探讨不同剂量猪肺表面活性物质（PPS）混悬液对油酸致大鼠急性肺损伤（ALI）的治疗作用及量-效关系。方法56只SD大鼠按随机数字表法分为假手术组、油酸模型组和5个不同剂量PPS治疗组。静脉注入油酸诱发大鼠ALI，30min后治疗组和模型组经气管分别滴入50、80、100、150和200mg／kg PPS和等量生理盐水。实验过程中计数大鼠呼吸频率，测定动脉血气。4h后处死，计算大鼠存活率，观察肺组织形态学改变，并检测肺系数、支气管肺泡灌洗液（BALF）中总蛋白含量和血浆肿瘤坏死因子-α（TNF-α）的浓度。结果与模型组比较，PPS50mg／kg组有减慢呼吸频率、短时间内提高动脉血氧分压（PaO2）的作用，但是并不能明显改善肺损伤；PPS80～200mg／kg组除改善呼吸功能外，大鼠肺毛细血管通透性、肺出血、肺水肿、血浆TNF-α浓度以及大鼠死亡率也均明显降低（P均〈0．05）。显示高剂量PPS（150～200mg／kg）在减轻炎症反应和肺损伤方面具有更好的效果。结论单独应用PPS能明显改善早期油酸型ALI大鼠的呼吸功能，≥80mg／kg的PPS有明显减轻肺损伤的作用，而各剂量之间无量-效关系。     

Effects of N-acetylcysteine plus deferoxamine in lipopolysaccharide-induced acute lung injury in the rat

OBJECTIVES: Interventions that reduce the generation or the effects of reactive oxygen species exert controversial effects in animal models of lung injury, and these could be secondary to the pro-oxidant effects of antioxidants generally by their interaction with iron. We here describe the effects of N-acetylcysteine, deferoxamine, or both in the treatment of acute lung injury induced by intratracheal lipopolysaccharide injection. DESIGN: Prospective, randomized, controlled experiment. SETTING: Animal basic science laboratory. SUBJECTS: Male Wistar rats, weighing 200-250 g. INTERVENTIONS: Rats exposed intratracheally to lipopolysaccharide were treated with N-acetylcysteine (20 mg/kg subcutaneously 3, 6, and 12 hrs after lipopolysaccharide instillation), deferoxamine (20 mg/kg subcutaneously 3 hrs after lipopolysaccharide instillation), N-acetylcysteine (20 mg/kg, 3, 6, and 12 hrs after lipopolysaccharide instillation) plus deferoxamine (20 mg/kg 3 hrs after lipopolysaccharide instillation), or vehicle. MEASUREMENTS AND MAIN RESULTS: Acute lung injury was induced by intratracheal instillation of lipopolysaccharide in Wistar rats. The animals were randomly divided into five groups: group 1, control with instillation of isotonic saline; group 2, lipopolysaccharide treated with saline; group 3, lipopolysaccharide treated with N-acetylcysteine; group 4, lipopolysaccharide treated with deferoxamine; and group 5, lipopolysaccharide treated with N-acetylcysteine plus deferoxamine. Several times after lipopolysaccharide instillation, the rats were killed and a bronchoalveolar lavage was performed to determine thiobarbituric acid reactive species, protein carbonyls, superoxide dismutase and catalase activities, mitochondrial superoxide production (oxidative stress variables), the degree of the alveolar-capillary membrane compromise, and inflammatory infiltration. Samples from the lung were isolated and assayed for oxidative stress variables or histopathologic analyses. N-acetylcysteine plus deferoxamine decreased bronchoalveolar lavage fluid protein, inflammatory cells, oxidative damage variables, and proinflammatory cytokines. N-acetylcysteine plus deferoxamine treatment significantly attenuated lung oxidative damage, mitochondrial superoxide production, and histopathologic alterations after lipopolysaccharide instillation. CONCLUSIONS: Our data provide the first experimental demonstration that N-acetylcysteine plus deferoxamine decreases oxidative stress and mitochondrial dysfunction and limits inflammatory response and alveolar pathology induced by lipopolysaccharide in the rat.     

肺表面活性物质稀释剂延迟肺灌洗治疗烟雾吸入性损伤

目的 探讨外源性肺表面活性物质(PS)稀释剂延迟肺灌洗对大鼠严重烟雾吸入伤后内源性PS功能障碍和急性呼吸衰竭的治疗效果.方法 90只Wistar大鼠随机分为5组:Ⅰ组,正常对照(n=14);Ⅱ组,烟雾吸入(n=27);Ⅲ组,烟雾+PS灌洗+机械通气(MV),n=21;Ⅳ组,烟雾+盐水灌洗+MV,n=10;V组,烟雾+MV,n=18.伤后2 h经气管插管注入含PS(100ms/ks)的等渗盐水30 ml/kg或等量盐水行肺灌洗,MV 4 h,观察24 h;检测动脉血气、肺水量、静态肺顺应性(Cst)、支气管肺泡灌洗液(BAIF)蛋白含量、BALF表面张力特性和24 h病死率等.结果 致伤动物伤后立即出现严重缺氧和一氧化碳中毒;Ⅱ组发生急性呼吸衰竭、高通透性肺水肿和PS功能障碍;Ⅲ组Cst和BALF表面张力特性显著改善(P<0.05),但氧合能力、肺水量和BALF蛋白含量无明显好转(P>0.05).Ⅳ、V组疗效不佳.结论 外源性PS稀释剂延迟肺灌洗可一定程度恢复烟雾吸入所致内源性PS功能抑制,改善肺功能,但不能显著减轻高通透性肺水肿和呼吸衰竭,不能降低早期病死率.     

猪肺表面活性物质治疗兔油酸型急性呼吸窘迫综合征

目的：探讨肺表面活性物质（PS）对实验性急性呼吸窘迫综合征（ARDS）的治疗作用。方法：油酸诱发新西兰兔ARDS模型后分组（n＝9）治疗4h：1）对照组；2）气管内滴入PS100mg／kg（PS组）。测定动态肺顺应性（Cdyn）、动脉血气和灌洗液的总磷脂（TPL）、总蛋白（TP）、饱和卵磷脂（DSPC）、最小表面张力（STmin）、肺湿干重比（W／D）。结果：治疗后PS组各时点Cdyn和PaO2／FiO2较治疗前和同时点的对照组显著升高，TPL、DSPC／TPL和DSPC／TP较对照组显著增加，STmin和肺W／D明显降低。结论：PS对油酸型ARDS有效，可作为ARDS综合治疗的重要措施之一。     

Protective effect of lipophilic antioxidants on phorbol-induced acute lung injury in rats

OBJECTIVE: To determine whether the lipophilic antioxidant U-74389G can ameliorate the acute lung injury induced by phorbol myristate acetate (PMA) in our isolated lung model in rats, and to compare its activity with the intracellular enzymes superoxide dismutase (SOD) or catalase. DESIGN: Randomized, controlled study. SETTING: Animal-care facility procedure room. SUBJECTS: Forty-two adult male Sprague-Dawley rats each weighing 250-350 g. INTERVENTIONS: Typical acute lung injury was induced successfully by PMA during 60 mins of observation. PMA (2 microg/kg) elicited a significant increase in microvascular permeability (measured by using the capillary filtration coefficient Kfc), lung weight gain, the lung weight/body weight ratio, pulmonary arterial pressure, and the protein concentration of the bronchoalveolar lavage fluid. MEASUREMENTS AND MAIN RESULTS: Pretreatment with 1 mg of U-74389G significantly attenuated the acute lung injury induced by PMA, all parameters having decreased significantly (p <.001). The protective effect of U-74389G was dose dependent, but SOD (6,000 U/kg) or catalase (50,000 U/kg) exhibited no protective effect. CONCLUSIONS: U-74389G significantly ameliorates acute lung injury induced by PMA in rats.     

Bronchoalveolar lavage with a diluted surfactant suspension prior to surfactant instillation improves the effectiveness of surfactant therapy in experimental acute respiratory distress syndrome (ARDS)

Objective: To assess whether bronchoalveolar lavage (BAL) with a diluted surfactant suspension prior to surfactant instillation prevents the only transient improvement in lung function as reported after surfactant instillation in severe acute respiratory distress syndrome (ARDS). Design: Randomized, prospective, experimental study. Setting: Laboratory and animal facility of a large university. Materials: Adult male Sprague-Dawley rats (280 ± 30 g). Interventions: All animals underwent repetitive whole lung saline lavage to induce acute lung injury. Then, animals were randomly divided into seven study groups: the first group received surfactant (150 mg/kg) within 10 min after the last lavage (early treatment), whereas in the other six groups mechanical ventilation was continued for 3 h before treatment (late treatment). Treatment consisted of: surfactant instillation at a dose of 150 mg/kg; at a dose of 250 mg/kg; BAL with saline; BAL with a diluted surfactant suspension (2.5 mg/ml); BAL with saline, immediately followed by surfactant instillation (150 mg/kg) and BAL with a diluted surfactant suspension (2.5 mg/kg), immediately followed by surfactant instillation (150 mg/kg). Measurements and results: Blood gases were measured for 6 h and then BAL was performed to measure the protein concentration and surface tension properties. Mean PaO₂ values increased immediately after surfactant instillation to pre-lavage values but remained stable only in the group that received surfactant immediately after the lavage procedure and the group that underwent BAL with a diluted surfactant suspension prior to surfactant instillation. Conclusion: BAL with a diluted surfactant suspension prior to surfactant instillation at a later time point in lung injury resulted in a stable improvement of lung function. This improvement is comparable with the results seen after surfactant instillation immediately after lung lavage.     

Open lung ventilation preserves the response to delayed surfactant treatment in surfactant-deficient newborn piglets

OBJECTIVE: Delayed surfactant treatment (>2 hrs after birth) is less effective than early treatment in conventionally ventilated preterm infants with respiratory distress syndrome. The objective of this study was to evaluate if this time-dependent efficacy of surfactant treatment is also present during open lung ventilation. DESIGN: Prospective, randomized controlled animal study. SETTING: University-affiliated research laboratory. SUBJECTS: Thirty-eight newborn piglets. INTERVENTIONS: Following repeated whole-lung lavage, animals were randomly allocated to conventional positive pressure ventilation (PPVCON) using a positive end-expiratory pressure (PEEP) of 5 cm H2O and a tidal volume of 7 mL/kg or open lung positive pressure ventilation (PPVOLV). During PPVOLV, collapsed alveoli were actively recruited and thereafter stabilized with sufficient PEEP. Within each ventilation group, animals received surfactant (25 mg/kg) either after 2 hrs (PPVCON-2 and PPVOLV-2) or after 4 hrs (PPVCON-4 and PPVOLV-4) of ventilation. A control group received surfactant immediately after lung lavage. Following surfactant administration, all animals were conventionally ventilated for an additional 2 hrs. MEASUREMENTS AND MAIN RESULTS: Two hours after surfactant treatment, both oxygenation and lung mechanics showed a clear deterioration in the PPVCON-4 group compared with PPVCON-2 and the control group. However, this deterioration of the surfactant response over time was not observed during PPVOLV. Analysis of the bronchoalveolar lavage fluid obtained at the end of the experiment showed that the protein concentration and the conversion of large to small aggregate surfactant was significantly higher in the PPVCON-4 group compared with the PPVCON-2 group while comparable in both PPVOLV groups. In addition, interleukin-8 and myeloperoxidase levels tended to be higher in the PPVCON-4 group compared with the PPVOLV-4 group. CONCLUSIONS: In contrast to conventional ventilation, open lung ventilation preserves the response to delayed surfactant treatment in surfactant-deficient newborn piglets. This sustained response is accompanied by an attenuation of secondary lung injury.     

不同时间给予猪肺表面活性物质对大鼠油酸型急性肺损伤疗效的影响

目的 探讨不同时间给予猪肺表面活性物质(PPS)混悬液对油酸致大鼠急性肺损伤(ALI)的治疗作用.方法 将48只SD大鼠随机分为假手术组、模型组、0.5 h PPS治疗组和2 h PPS治疗组.假手术组仅行气管和颈动脉插管手术操作,其余各组大鼠静脉注入油酸诱发ALI;0.5 h PPS治疗组和2 h PPS治疗组分别于油酸注入后0.5 h和2 h经气道均滴入100 mg/kg和150 mg/kg两个剂量的PPS,实验过程中计数大鼠呼吸频率,测定动脉血气指标;于实验4 h计算大鼠存活率后处死动物,观察肺组织病理学改变,并检测肺系数及支气管肺泡灌洗液(BALF)中总蛋白(TP)含量和血浆中肿瘤坏死因子-α(TNF-α)浓度.结果 与模型组比较,0.5 h给予PPS 100 mg/kg和150 mg/kg以及2 h给予PPS 150 mg/kg治疗都能显著降低大鼠的呼吸频率,提高动脉血氧分压(PaO2)及大鼠存活率,降低肺毛细血管通透性及肺出血、肺水肿发生率,降低血浆中TNF-α和BALF中TP含量(P均＜0.05).而2 h给予100 mg/kg PPS的治疗作用不明显.结论 早期气道内滴入≥100 mg/kg的PPS,能明显改善油酸型ALI大鼠的呼吸功能、减轻肺损伤;晚期较大剂量的PPS(150 mg/kg)才有治疗作用.     

地塞米松对大鼠光气急性肺损伤血管生成素-1、2的影响

目的 探讨地塞米松对大鼠光气急性肺损伤(ALI)血管生成素-1、2(Ang-1,2)表达的影响.方法 采用大鼠光气吸入性肺损伤动物模型.36只SD大鼠随机(随机数字法)分为3组:正常对照组(吸入与光气染毒组同等流量的空气)、光气染毒组(吸入8.33 mg/L纯度为100％的光气5min)、地塞米松处理组(尾静脉注入2.5 mg/kg地塞米松1h后,吸入同等剂量的光气).染毒2h后收集支气管肺泡灌洗液(BALF)测定中性粒细胞细胞数、蛋白含量和肺湿/干质量比(W/D).采用双抗体夹心酶标免疫分析法(ELISA法)测定各组血清和BALF中Ang-1,2水平.RT-PCR法对肺脏组织中Ang-1,2和Tie-2mRNA的水平进行半定量研究.Western blot技术检测肺脏组织中Ang-1,2和Tie-2蛋白含量.结果 与正常对照组比较,光气染毒组肺W/D、BALF中中性粒细胞数和蛋白含量明显升高,差异具有统计学意义(P＜0.01);与光气染毒组比较,地塞米松处理组的肺W/D、BALF中中性粒细胞数和蛋白含量明显降低,差异具有统计学意义(P＜0.01).与正常对照组比较,光气染毒组血清、BALF及肺组织中Ang-1和Tie-2表达明显下降,差异具有统计学意义(P＜0.01);与光气染毒组比较,地塞米松处理组Ang-1和Tie-2表达明显升高,差异具有统计学意义(P＜0.01).与正常对照组比较,光气染毒组血清、BALF及肺组织中Ang-2表达明显升高,差异具有统计学意义(P＜0.01);与光气染毒组比较,地塞米松处理组Ang-2表达明显下降,差异具有统计学意义(P ＜0.05,P＜0.01).结论 地塞米松可能通过抑制Ang-2表达并促进Ang-1和Tie-2表达来有效地保护大鼠光气吸入性急性肺损伤.     

Hypercapnic acidosis does not modulate the severity of bacterial pneumonia-induced lung injury

OBJECTIVE: Deliberate induction of hypercapnic acidosis protects against lung injury after ischemia-reperfusion, endotoxin-induced, and ventilation-induced lung injury. The efficacy of hypercapnic acidosis in bacterial lung infection, a common cause of acute respiratory distress syndrome, is not known. Furthermore, its effect may differ depending on the presence or absence of antibiotic therapy. We investigated whether hypercapnic acidosis-induced by adding CO2 to inspired gas-would protect against acute lung injury induced by pulmonary Escherichia coli instillation in an in vivo model in the presence and absence of effective antibiotic therapy. DESIGN: Prospective randomized animal study. SETTING: University research laboratory. SUBJECTS: Adult male Wistar-Kyoto rats. INTERVENTIONS: The animals were anesthetized and ventilated. In series 1, rats were administered intravenous ceftriaxone (100 mg x kg) and randomized to normocapnia (Normocapnia-ABx; Fico2 0.00, n = 10) or hypercapnia (Hypercapnia-ABx; Fico2 0.05, n = 10) groups. E. coli (8.4 x 10 colony forming units) was instilled intratracheally. Series 2 animals did not receive antibiotics. They were randomized to normocapnia (Normocapnia, n = 10) or hypercapnia (Hypercapnia, n = 10) groups, and intratracheal E. coli was administered. All animals were ventilated for 6 hrs. MEASUREMENTS AND MAIN RESULTS: In series 1, there were no differences between Hypercapnia-ABx and Normocapnia-ABx groups with regard to: (a-a)o2 gradient (mean +/- sem; 215 +/- 13 vs. 252 +/- 22 mm Hg), Pao2, bronchoalveolar lavage neutrophil count, static lung compliance, or histologic injury. Lung bacterial yield was not different between the groups. In series 2, in the absence of antibiotic therapy, there were no differences between Hypercapnia and Normocapnia groups in: (a-a)o2 gradient (mean +/- sem, 345 +/- 25 vs. 332 +/- 23 mm Hg), systemic Pao2, bronchoalveolar lavage neutrophil count, or static lung compliance. Lung bacterial yield was not altered by hypercapnia in either series 1 or 2. CONCLUSIONS: We conclude that hypercapnic acidosis did not alter the magnitude of the lung injury induced by intratracheal E. coli instillation in the presence or absence of antibiotics.     

Hypothermia protects against endotoxin-induced acute lung injury in rats

OBJECTIVE: Hypothermia in humans and animals is known to decrease the number and function of circulating neutrophils. Because an activation of circulating neutrophils and their sequestration into the lung are important pathogenetic phenomena in endotoxin-associated lung injury, we conjectured that hypothermia could prevent this type of lung injury. DESIGN AND SETTING: Animal study at a university-affiliated research institute. SUBJECTS: Thirty-six Sprague-Dawley rats. INTERVENTIONS: After anesthesia, the rats were randomly assigned to normothermia (37 degrees C, rectal temperature) or hypothermia (27 degrees C), which was induced by surface cooling. After 1 h of stable temperature, the rats were administered intratracheal doses of lipopolysaccharide (LPS; 3 mg/kg) (normothermia-LPS; hypothermia-LPS) or an equivalent volume of normal saline (normothermia-saline; hypothermia-saline). The rectal temperature was maintained within +/-1 degrees C of the target temperature for 6 h after the intratracheal treatment. MEASUREMENTS AND RESULTS: Compared with the normothermia-LPS group, the neutrophil count in bronchoalveolar lavage (BAL) fluid (p=0.002) and the myeloperoxidase activity of lung tissues (p=0.002) of the hypothermia-LPS group were both lower. Compared with the normothermia-LPS group, the BAL interleukin-1beta level of the hypothermia-LPS group was lower (p<0.001), whereas the BAL interleukin-10 level of the hypothermia-LPS group was higher (p=0.026). Compared with the normothermia-LPS group, the histologic scores for acute lung injury of the hypothermia-LPS group were lower (p=0.007). CONCLUSIONS: Hypothermia pretreatment decreased the pulmonary sequestration of neutrophils, induced a favorable balance between pro- and anti-inflammatory cytokines, and attenuated histologic injury in endotoxin-challenged rats.     

Treatment of ventilation-induced lung injury with exogenous surfactant

OBJECTIVE: It has been demonstrated that pulmonary surfactant plays a role in the pathophysiology of ventilation-induced lung injury (VILI). Therefore, we investigated whether exogenous surfactant might restore lung function and lung mechanics in an established model of VILI. DESIGN: Prospective, randomized, animal study. SETTING: Experimental laboratory of a university. SUBJECTS: Twenty-four adult male Sprague-Dawley rats. INTERVENTIONS: First, a group of six animals were killed immediately after induction of anesthesia and used as healthy controls. Then, in 18 rats, VILI was induced by increasing peak inspiratory pressure (PIP) to 45 cmH2O without positive end-expiratory pressure (PEEP) for 20 min. Thereafter, animals were randomly divided into three groups of six animals each: one group was killed immediately after VILI and served as VILI-control. In the other two groups, ventilator settings were changed to a PIP of 30 cmH2O and a PEEP of 10 cmH2O, and a respiratory rate of 40 bpm. One group received a bolus of surfactant and the other group received no treatment. MEASUREMENTS AND RESULTS: Blood gas tension and arterial blood pressures were recorded every 30 min for 2 h. After the study period, a pressure-volume curve was recorded. Then, a broncho-alveolar lavage (BAL) was performed to determine protein content, minimal surface tension, and surfactant composition in the BAL fluid. Oxygenation, lung mechanics, surfactant function and composition were significantly improved in the surfactant-treated group compared to the ventilated and non-ventilated control groups. CONCLUSION: We conclude that exogenous surfactant can be used to treat VILI.     

Pulmonary surfactant is altered during mechanical ventilation of isolated rat lung

OBJECTIVE: To test the hypothesis that the lung injury induced by certain mechanical ventilation strategies is associated with changes in the pulmonary surfactant system. DESIGN: Analysis of the pulmonary surfactant system from isolated rat lungs after one of four different ventilatory strategies. SETTING: A research laboratory at a university. SUBJECTS: A total of 45 Sprague-Dawley rats. INTERVENTIONS: Isolated lungs were randomized to either no ventilation (0-TIME) or to ventilation at 40 breaths/min in a humidified 37 degrees C chamber for either 30 mins or 120 mins with one of the following four strategies: a) control (CON, 7 mL/kg, 3 cm H2O positive end-expiratory pressure); b) medium volume, zero end-expiratory pressure (MVZP, 15 mL/kg, 0 cm H2O end-expiratory pressure); c) medium volume, high positive end-expiratory pressure (MVHP, 15 mL/kg, 9 cm H2O positive end-expiratory pressure); and d) high volume, zero end-expiratory pressure (HVZP, 40 mL/kg, 0 cm H2O end-expiratory pressure). MEASUREMENTS: Pressure-volume curves were determined before and after the ventilation period, after which the lungs were lavaged for surfactant analysis. MAIN RESULTS: Compared with 0-TIME, 30 mins of ventilation with the HVZP strategy or 120 mins of ventilation with CON and MVZP strategies caused a significant decrease in compliance. Groups showing a decreased compliance had significant increases in the amount of surfactant, surfactant large aggregates, and total lavage protein compared with 0-TIME. CONCLUSIONS: A short period of injurious mechanical ventilation can cause a decrease in lung compliance that is associated with a large influx of proteins into the alveolar space and with alterations of the pulmonary surfactant system. The changes of surfactant in these experiments are different from those seen in acute lung injury, indicating that they may represent an initial response to mechanical ventilation.     

Effect of hyperbaric oxygen on endotoxin-induced lung injury in rats

Oxygen therapy remains the main component of the ventilation strategy for treatment of patients with acute lung injury. Hyperbaric oxygen therapy (HBO(2)) is the intermittent administration of 100% oxygen at pressure greater than sea level and has been applied widely to alleviate a variety of hypoxia-related tissue injuries. The purpose of this study was to evaluate the effect of hyperbaric oxygen on acute lung injury induced by intratracheal spraying of lipopolysaccharide (LPS) in rats. Male Sprague-Dawley rats underwent implantation of a carotid artery catheter under general anesthesia. Aerosolized LPS was delivered twice into the lungs via intratracheal puncture. Animals were either breathing room air (n = 27) or subjected to hyperbaric oxygen (HBO(2)) exposure (n = 27) 1 h after LPS spraying. Acute lung injury was evaluated 5 h and 24 h later. Compared with the control group, intratracheal spraying of LPS caused profound hypoxemia, greater wet/dry weight ratio (W/D) of the lung (5.67 +/- 0.22 vs. 4.98 +/- 0.19), and higher protein concentration (1706 +/- 168 vs. 200 +/- 90 mg/L) and LDH activity (129 +/- 30 vs. 46 +/- 15, mAbs/min) in bronchoalveolar lavage (BAL) fluid. Intratracheal spraying of LPS also caused significant WBC sequestration in the lung tissue. HBO2 treatment significantly reverted hypoxemia, reduced lung injury measures evaluated at 5 and 24 h, and enhanced 24-h animal survival rate (chi = 5.08, P = 0.024). The malondialdehyde (MDA) concentrations in lung tissue and serum were both increased after LPS spraying. Neither single HBO(2) therapy nor five sequential daily treatments enhanced MDA production in lung tissue or serum. Our results suggested that hyperbaric oxygen might reduce acute lung injury caused by intratracheal spraying of LPS in rats. This treatment modality is not associated with enhancement of oxidative stress to the lung.