The effects of nitric oxide inhalation on respiratory mechanics and gas exchange during endotoxaemia in the pig

Background : In the adult respiratory distress syndrome, nitric oxide (NO) inhalation improves oxygenation through reducing ventilation-perfusion mismatching, but detailed information on the pulmonary effects of NO inhalation in septic shock is scarce. The present study investigated the effects of inhaled NO on alveolar dead space (Vdalv) and venous admixture as well as on respiratory system compliance (Crs) and respiratory system resistance (Rrs) in a porcine model of septic shock. Protective effects of NO are discussed.
Methods : Thirteen anaesthetised and ventilated pigs were given an infusion of endotoxin for an observation time of 220 min to induce acute lung injury (ALI). In the NO-early group (n=6), an inhalation of 60 ppm NO was started simultaneously with the endotoxin infusion and continued for 190 min. In 7 control/NO-late animals, 60 ppm NO was administered for 30 min following 190 min of endotoxin infusion. Haemodynamics, single-breath CO₂-, pressure-, and flow signals were recorded.
Results : Endotoxin induced haemoconcentration, pulmonary vasoconstriction, and a decrease in Crs, while venous admixture, Vdalv, and Rrs increased. In the NO-early group, the pulmonary vasoconstriction was attenuated, no increase in pulmonary venous admixture or in Vdalv was seen before cessation of NO, and the improvements in oxygenation outlasted the NO inhalation. In the control/NO-late group, the NO inhalation reversed the changes in dead space and venous admixture. NO had no effect on the changes in respiratory mechanics.
Conclusion : In porcine ALI, 60 ppm NO diminishes pulmonary vasoconstriction and improves gas exchange by reducing pulmonary venous admixture and alveolar dead space, but does not prevent a fall in Crs. NO inhalation may help prevent longlasting pulmonary failure.     

Effect of NO donor sodium nitroprusside on lipopolysaccharide induced acute lung injury in rats

Nitric oxide (NO) donor-sodium nitroprusside (SNP) mitigates acute lung injury (ALI), but the mechanism of this protection is incompletely known. We investigated the effect of SNP on lipopolysaccharide (LPS)-induced ALI in rats. Forty-eight male Wistar rats were randomly assigned into six groups: the sham-operation group (S group), the LPS instillation group (LPS group), the haemin, a haeme oxygenase-1 (HO-1) inducer, pretreatment group (HM group), the haemin pretreatment plus LPS instillation group (HM+LPS group), the SNP alone and SNP plus LPS treatment groups. Macroscopic and histopathological examinations and immunohistochemistry analysis were performed for the lung specimens 8h after LPS instillation. Intratracheal administration of LPS induced significant expressions of the inducible isoform of NO synthase (iNOS) and HO-1, while both haemin pretreatment and SNP treatment increased the expression of HO-1 and prevented the expression of iNOS. In the LPS group, the wet-dry weight ratio (W/D), bronchoalveolar lavage fluid (BALF) protein, and lung malondialdehyde (MDA) content were significantly higher than those in the sham-operation group, which were reversed by the pretreatment with haemin or administration of SNP. These results suggest that HO-1 plays a protective role against LPS-induced acute lung injury, which may be achieved at least in part, via inactivating the iNOS/NO system that is involved in the pathophysiological process of LPS-induced acute lung injury. The nitric oxide (NO) donor-SNP ameliorates LPS-induced ALI, which may be related to the induction of HO-1 and the subsequent inhibition of iNOS.     

Effect of Ulinastatin, a human urinary trypsin inhibitor, on the oleic acid-induced acute lung injury in rats via the inhibition of activated leukocytes

BACKGROUND: The acute respiratory distress syndrome (ARDS) is often caused by fat tissue embolism. One of the most common animal models of ARDS is produced by direct administration of oleic acid (OA). Activated leukocytes are critically involved in the pathological mechanism in this model. Human urinary trypsin inhibitor (UTI) is known to inhibit production of tumor necrosis factor (TNF)-alpha, which potently stimulates leukocyte activation. The purpose of this study was to clarify whether UTI improves OA-induced lung injury in rats by inhibiting activated leukocytes via TNF-alpha production. MATERIALS AND METHODS: Rats were subjected to a single intravenous administration of OA into the pedicle vein. Acute lung injury was evaluated by arterial blood gases and histological changes in lungs. Pulmonary vascular permeability, accumulation of neutrophils, and the levels of TNF-alpha in lung tissues were also examined. Rats were divided into four experimental groups: a sham operated, OA, OA + UTI, and OA + nitrogen mustard (NM)-induced leukocytopenia group. UTI was intravenously administered 30 min before OA administration. Leukocytopenia was induced by the administration of NM. RESULTS: UTI significantly improved the OA-induced histological changes for 4 h after OA administration. The OA-induced reduction of PaO2, the increase of pulmonary vascular permeability, and the levels of MPO activity and TNF-alpha in lung tissues were significantly improved in rats administrated UTI. The effects in the leukocytopenia group were similar to those in the UTI-administered group. CONCLUSION: Leukocytes play a critical role in the development of OA-induced lung injury. It was suggested that UTI contributed to the reduction in the OA-induced lung injury by inhibiting TNF-alpha and thereby suppressing leukocyte.     

Factors Influencing the Tracheal Fluctuation of Inhaled Nitric Oxide in Patients with Acute Lung Injury

Background: Inhaled nitric oxide (NO) improves arterial oxygenation in patients with acute lung injury (ALI) by selectively dilating pulmonary vessels perfusing ventilated lung areas. It can be hypothesized that NO uptake from the lung decreases with increasing ventilation perfusion mismatch. This study was undertaken to determine the factors influencing the fluctuation of tracheal NO concentration over the respiratory cycle as an index of NO pulmonary uptake in patients with ALI.

Methods: By using a prototype system (Opti-NO) delivering a constant flow of NO only during the inspiratory phase, 3 and 6 ppm of NO were administered during controlled mechanical ventilation into a lung model and to 11 patients with ALI. All patients had a thoracic computed tomography (CT) scan. Based on an analysis of tomographic densities, lungs were divided into three zones: normally aerated (-1.000 to 500 Hounsfield units [HU]), poorly aerated (-500 to -100 HU), and nonaerated (-100 to +100 HU), and the volume of each zone was computed. Concentrations of NO in the inspiratory limb and trachea were continuously measured by a fast-response chemiluminescence apparatus.

Results: In the lung model, tracheal NO concentration was stable with minor fluctuation. In contrast, in patients, tracheal NO concentration fluctuated widely during the respiratory cycle (55 +/- 10%). Because uptake of NO from the lungs was absent in the lung model but present in the patients, this fluctuation was considered as an index of pulmonary uptake of NO. This was further substantiated by (1) the coincidence of the peak and minimum tracheal NO concentration with the end-inspiratory and end-expiratory phases, respectively, and (2) continued decrease of tracheal NO concentration during prolonged expiratory phase. In patients with ALI, the fluctuation of tracheal NO concentration expressed as the difference between inspiratory and expiratory NO concentrations divided by inspiratory NO concentration was greater at 6 ppm than at 3 ppm (P < 0.01), was linearly correlated with normally aerated lung volume, inversely correlated with alveolar dead space and with poorly aerated lung volume.     

Low-dose phosphodiesterase inhibition improves responsiveness to inhaled nitric oxide in isolated lungs from endotoxemic rats

BACKGROUND: Inhalation of nitric oxide (NO) and inhibition of phosphodiesterase type 5 (PDE5) selectively dilate the pulmonary circulation in patients with acute lung injury (ALI) associated with pulmonary hypertension. PDE5 inhibitors administered at doses that decrease pulmonary artery pressures have been shown to worsen arterial oxygenation. We investigated the efficacy of doses of PDE5 inhibitors that do not reduce pulmonary artery pressure alone (subthreshold doses) to improve the response to inhaled NO in an animal model of ALI. MATERIALS AND METHODS: Adult Sprague-Dawley rats were pre-treated with 0.5 mg/kg Escherichia coli 0111:B4 endotoxin and 16 to 18 h later, their lungs were isolated perfused and ventilated. The thromboxane mimetic U46619 was used to induce pulmonary hypertension. After the determination of subthreshold doses of two different PDE5 inhibitors, either 50 microg zaprinast or 10 ng sildenafil was added to the perfusate and the decrease of pulmonary artery pressure measured in the presence and absence of inhaled NO. RESULTS: In the presence of 4 or 10 ppm NO, zaprinast (-1.6 +/- 0.4 and -2.9 +/- 0.6 mmHg, respectively) and sildenafil (-1.9 +/- 0.4 and -2.4 + 0.3 mmHg, respectively) improved responsiveness to inhaled NO compared to lungs from rats treated with LPS only (0.7 +/- 0.1 and -1.0 +/- 0.1 mmHg, respectively; P<0.05). Neither zaprinast nor sildenafil prolonged the pulmonary vasodilatory response to inhaled NO. CONCLUSIONS: Subthreshold doses of PDE5 inhibitors improved responsiveness to inhaled NO. Combining inhaled NO with subthreshold doses of PDE5 inhibitors may offer a therapeutic strategy with minimal side-effects in ALI associated with pulmonary hypertension.     

ONO-1714, a nitric oxide synthase inhibitor, attenuates endotoxin-induced acute lung injury in rabbits

Overproduction of nitric oxide by inducible nitric oxide synthase (iNOS) expressed in the lung is thought to play a crucial role in the pathogenesis of endotoxin-induced acute lung injury (ALI). In this two-part study, we determined whether ONO-1714, a new selective iNOS inhibitor, attenuates endotoxin-induced ALI in rabbits. For Part I of the study, a control group received IV saline and ALI was induced by IV infusion of endotoxin 5 mg/kg over 30 min in 4 groups. Three groups received either 0.1, 0.03, or 0.01 mg/kg of ONO-1714 10 min before the start of endotoxin and the fourth group received saline. For Part II of the study, ALI was induced by endotoxin infusion in all 6 groups. One group was treated with saline. The other 5 groups received ONO-1714 0.1 mg/kg at various timings (10 min before or 1, 2, 3, or 4 h after ALI induction). The lungs were mechanically ventilated with 40% oxygen for 6 h after induction of ALI. In Part I, pretreatment with 0.1 mg/kg ONO-1714 mitigated endotoxin-induced ALI. In Part II, early posttreatment (within 2 h after the insult) with ONO-1714 was as effective as pretreatment in improving oxygenation, lung mechanics, lung leukosequestration, pulmonary edema, and histological change. However, lung damage was not improved in rabbits receiving the drug 3 or 4 h after endotoxin. These data suggest that the current study is a basis for future clinical trials to elucidate whether ONO-1714 can be a promising therapeutic approach in patients with acute respiratory distress syndrome induced by endotoxin/sepsis. IMPLICATIONS: An excess of nitric oxide is thought to play a crucial role in the pathogenesis of acute organ injury in endotoxemia. Early posttreatment with ONO-1714, a nitric oxide synthase inhibitor, attenuated physiological, biochemical, and pathological changes in endotoxin-induced acute lung injury in rabbits.     

Inhaled NO and prostacyclin during porcine single lung transplantation

Background. Increased pulmonary vascular resistance (PVR) and decreased arterial oxygenation frequently complicate lung transplantation. Inhaled nitric oxide (NO) and aerosolized prostacyclin (PGI₂) both dilate the pulmonary vasculature and improve oxygenation in adult respiratory distress syndrome. We investigated whether similar effects would occur during early reperfusion of a lung graft.

Methods. Eighteen pigs underwent left lung transplantation. We measured blood flow distribution, mean pulmonary artery pressure, PVR, and gas exchange in each lung separately. Animals were randomized into three groups to receive NO (10 ppm/30 minutes, 40 ppm/30 minutes), nebulized PGI₂ (25 μg/mL/30 minutes, 50 μg/mL/30 minutes), or no drugs (control).

Results. In the transplanted lung, PVR was significantly higher than in the native lung. Pulmonary vascular resistance of the transplanted lung was lower in the NO and PGI₂ groups in comparison with the control group. During the first hour of inhalation, NO decreased PVR more than PGI₂. Neither drug improved oxygenation in the graft.

Conclusions. Nitric oxide and PGI₂ decreased PVR of the transplanted lung slightly, but the effect did not produce a normal pressure in pulmonary vasculature.     

Triolein increases microvascular permeability in isolated perfused rabbit lungs: role of neutrophils

BACKGROUND: Pathophysiologic mechanisms of the fat embolism syndrome are poorly understood. Neutrophils are thought to play a role in the development of many forms of acute lung injury. The objective of this study was to examine the role of intrapulmonary neutrophils in lung injury resulting from fat infusion. METHODS: Triolein (0.08 mL/kg) was infused into isolated rabbit lungs perfused with Krebs-Henseleit buffer. Pulmonary arterial pressure was monitored, and pulmonary vascular resistance and microvascular permeability (Kf) were measured at baseline and 60 minutes after triolein infusion. RESULTS: Triolein produced increases in pulmonary arterial pressure, pulmonary vascular resistance, and Kf. Neutrophil depletion or inhibition of neutrophil elastase prevented the increase in Kf after triolein, and catalase partially blocked this Kf increase. CONCLUSION: These results suggest that activated intrapulmonary neutrophils play a major role in developing triolein-induced lung injury, intrapulmonary neutrophils act chiefly via neutrophil elastase release, and reactive oxygen species are involved in the lung injury.     

Effects of intravenous Zaprinast and inhaled nitric oxide on pulmonary hemodynamics and gas exchange in an ovine model of acute respiratory distress syndrome

BACKGROUND: Inhaled nitric oxide (No) selectively dilates the pulmonary vasculature and improves gas exchange in acute respiratory distress syndrome. Because of the very short half-life of NO, inhaled NO is administered continuously. Intravenous Zaprinast (2-o-propoxyphenyl-8-azapurin-6-one), a cyclic guanosine monophosphate phosphodiesterase inhibitor, increases the efficacy and prolongs the duration of action of inhaled NO in models of acute pulmonary hypertension. Its efficacy in lung injury models is uncertain. The authors hypothesized that the use of intravenous Zaprinast would have similar beneficial effects when used in combination with inhaled NO to improve oxygenation and dilate the pulmonary vasculature in a diffuse model of acute lung injury. METHODS: The authors studied two groups of sheep with lung injury produced by saline lavage. In the first group, 0, 5, 10, and 20 ppm of inhaled NO were administered in a random order before and after an intravenous Zaprinast infusion (2 mg/kg bolus followed by 0.1 mg. kg-1. min-1). In the second group, inhaled NO was administered at the same concentrations before and after an intravenous infusion of Zaprinast solvent (0.05 m NaOH). RESULTS: After lavage, inhaled NO decreased pulmonary arterial pressure and resistance with no systemic hemodynamic effects, increased arterial oxygen partial pressure, and decreased venous admixture (all P < 0.05). The intravenous administration of Zaprinast alone decreased pulmonary artery pressure but worsened gas exchange (P < 0.05). Zaprinast infusion abolished the beneficial ability of inhaled NO to improve pulmonary gas exchange and reduce pulmonary artery pressure (P < 0. 05 vs. control). CONCLUSIONS: This study suggests that nonselective vasodilation induced by intravenously administered Zaprinast at the dose used in our study not only worsens gas exchange, but also abolishes the beneficial effects of inhaled NO.     

Inhaled nitric oxide lowers pulmonary capillary pressure and changes longitudinal distribution of pulmonary vascular resistance in patients with acute lung injury

In acute lung injury (ALI), where pulmonary microvascular permeability is increased, transvascular fluid filtration depends mainly on the hydrostatic capillary pressure. In the presence of intrapulmonary vasoconstriction pulmonary capillary pressure (PCP) may increase thereby promoting transvascular fluid filtration and lung oedema formation. We studied the effect of 40 ppm inhaled nitric oxide (NO) on PCP and longitudinal distribution of pulmonary vascular resistance (PVR) in 18 patients with ALI.
PCP was estimated by visual analysis of the pressure decay profile following pulmonary artery balloon inflation. Contribution of venous pulmonary resistance to total PVR was calculated as the percentage of the pressure gradient in the pulmonary venous system to the total pressure gradient across the lung.
Inhalation of 40 ppm NO produced a prompt decrease in mean pulmonary artery pressure (PAP) from 34.1 6.8 to 29.65.7 (s.d.) mmHg; ( P < 0.0001). PCP declined from 24.86.2 to 21.65.2 mmHg; ( P < 0.0001) while pulmonary artery wedge pressure (PAWP) did not change. PVR decreased from 16673 to 12850 dyn sec cm^-5; ( P < 0.0001). Pulmonary venous resistance (PVRven) decreased to a greater extent (from 7641 to 5028 dyn. sec. cm^-5; ( P < 0.001) than pulmonary arterial resistance (PVRart) (from 9036 to 7929 dyn sec cm^-5; ( P < 0.01). The contribution of PVRven to PVR feU from 44.310.8 to 37.811.9%; ( P < 0.01). Cardiac output (CO) remained constant. The findings demonstrate that NO has a predominant vasodilating effect on pulmonary venous vasculature thereby lowering PCP in patients with ALI.     

Attenuation of acute lung injury with propofol in endotoxemia

Endotoxin causes acute lung injury (ALI) through many mediators of inflammatory and immune responses. Propofol is an antiinflammatory and immunosuppressive drug. We conducted this study to evaluate whether propofol attenuates ALI associated with endotoxemia. Thirty-two anesthetized rabbits were randomly divided into four groups (n = 8 each). ALI was induced by IV endotoxin 5 mg/kg over 30 min in 3 groups. In 2 of the ALI groups, IV administration of propofol (2 or 5 mg/kg as a bolus followed by continuous infusion at 4 or 15 mg x kg(-1) x h(-1)) was started 15 min before endotoxin. The other ALI group received soybean-oil emulsion. The nonlung injury control group received infusion of both vehicles. The lungs were mechanically ventilated with 40% oxygen for 6 h after endotoxin. Hemodynamics did not differ among groups. The large dose of propofol attenuated lung leukosequestration, pulmonary edema (as assessed by lung wet/dry weight ratio), and pulmonary hyperpermeability (as assessed by albumin levels in bronchoalveolar lavage fluid) and resulted in better oxygenation, lung mechanics, and histological change. The small dose of propofol failed to do so. Our findings suggest that a large dose of propofol successfully mitigates physiological, biochemical, and histological deterioration in ALI in endotoxemia.     

Neutrophils mediate acute lung injury in rabbits: role of neutrophil elastase

We investigated the roles of neutrophil and neutrophil elastase in acute lung injury (ALI) to elucidate the mechanism of ALI. We designed two protocols. Protocol I: Experimental ALI was induced by endotoxin (0.02 mg/kg) and platelet-activating factor (8 microg/kg/4 h) in untreated rabbits (control group I), in neutropenic rabbits pretreated with nitrogen-N-oxide hydrochloride, and in untreated rabbits infused with a neutrophil elastase inhibitor (ONO-5046; 20 mg/kg/4 h). Protocol II: ALI was induced by smaller doses of endotoxin (0.015 mg/kg) and platelet-activating factor (7 microg/kg/4 h) than those used in protocol I in untreated rabbits (control group II), in neutrophilic rabbits pretreated with human recombinant granulocyte colony-stimulating factor, and in neutrophilic rabbits infused with ONO-5046 (as in protocol I). The severity of ALI was assessed by the protein concentration, the elastase activity in the bronchoalveolar lavage fluid, and the histologic pulmonary edema ratio. The degree of pulmonary neutrophil accumulation was assessed by pulmonary myeloperoxidase activity and histological findings. Both ALI and pulmonary neutrophil accumulation were suppressed by neutropenia (protocol I), while they were exacerbated by neutrophilia (protocol II). The neutrophil elastase inhibitor could suppress ALI, but it could not suppress pulmonary neutrophil accumulation in both untreated and neutrophilic rabbits (protocols I and II). These findings indicate that neutrophils play an important role in the pathogenesis of ALI via neutrophil elastase.     

Hyperbaric oxygen as a chemotherapy adjuvant in the treatment of metastatic lung tumors in a rat model

OBJECTIVES: The objectives of the study were to test the hypothesis that hyperbaric levels of oxygen enhance the sensitivity of a sarcoma cell line to doxorubicin (Adriamycin) both in vitro and in vivo in a rat model of pulmonary metastases and to test the feasibility of arterialization of mixed venous blood by direct injection of aqueous oxygen into the pulmonary artery in a rat model. METHODS: Rat sarcoma (MCA-2) cells were incubated in the presence of increasing concentrations of doxorubicin (0.1-2.0 micromol/L). A dose-dependent toxicity relationship at 12 hours of treatment was examined with and without pretreatment with hyperbaric oxygen (3.7 atm absolute for 1.5-3.5 hours). In vivo, Sprague-Dawley rats (n = 24) were injected intravenously with 10(6) MCA-2 cells, and the lung tumors were allowed to mature for 14 days. At that time the animals were divided into four groups: control (no treatment), doxorubicin at 2 mg/kg, hyperbaric oxygen (oxygen at 2 atm absolute for 30 minutes), and hyperbaric oxygen plus doxorubicin. Seven days after treatment, the numbers of lung nodules were counted and the lung weights were determined. In additional rats (n = 7), aqueous oxygen (1 mL oxygen/g saline solution) was infused into the pulmonary artery to determine whether arterialization of mixed venous blood was comparable to pulmonary artery oxygenation with a hyperbaric chamber (n = 7). RESULTS: Hyperbaric oxygen plus doxorubicin produced significantly greater cytolysis of MCA-2 cells (P <.01) than did doxorubicin alone. Hyperbaric oxygen plus doxorubicin also significantly decreased the number of lung metastases and the lung weight relative to doxorubicin alone (P <.01 and P <.01, respectively). The feasibility of arterialization of mixed venous blood (>100 mm Hg) with aqueous oxygen infusion was demonstrated. CONCLUSIONS: Hyperbaric oxygen enhanced the chemotherapeutic effect of doxorubicin both in cell culture and in the rat model. Aqueous oxygen infusion can be used to oxygenate mixed venous blood at levels similar to those obtained with the use of a hyperbaric chamber.     

Role of nitric oxide in treatment of acute lung injury after surgery with extracorporeal circulation

Postoperative acute lung injury (ALI) compromises oxygen transfer across alveolar-capillary membrane with consecutive hypoxia, one of its indicators being reduction of oxygenation index PaO2/FiO2 below 40 kPa (300 mm Hg). Management of ALI includes different procedures like mechanical lung ventilation (MLV), drugs and others. One of the new possibilities for treatment of ALI is nitric oxide (NO) inhalation. The aim of this prospective study was to examine the role of NO inhalation in treatment of ALI. 14 patients with ALI developed immediately after operation with extracorporeal circulation (ECC) were included in the study. Group A (n = 8) inhaled NO and group B (n = 6) did not inhale NO during treatment of ALI. All other therapeutic measures were the same in both groups. The groups were similar in relation to demographic data, type of surgery and duration of ECC. PaO2/FiO2 was calculated before operation (T1), immediately after surgery (T2) and after lung recovery, when the need for MLV stopped (T3). The duration of MLV was also registered. PaO2/FiO2 (kPa) in referent times was in group A 54.9 +/- 1.6, 33.8 +/- 1.2 and 46.2 +/- 0.8 and in group B 52.2 +/- 1.1, 33.5 +/- 1.5 and 47.3 +/- 0.9, respectively. There was a statistically significant decrease of PaO2/FiO2 in T2 and T3 vs T1 in both groups (p < 0.05), while the difference between the groups was not statistically significant. The duration of MLV (h) in group B (28.5 +/- 1.6) was statistically significantly shorter than in group A (63.1 +/- 8.7) (p < 0.01). According to the results of this study we conclude that NO inhalation during ALI after surgery with ECC significantly reduces the duration of MVL and improves pulmonary recovery.     

Radiographic lung density assessed by computed tomography is associated with extravascular lung water content

Background: We hypothesized that in acute lung injury (ALI), the volume of pulmonary tissue with aqueous density, as determined by spiral computed tomography (CT), is associated with extravascular lung water content. Our aim was to compare tissue volume index, as assessed by CT, before and after oleic acid‐induced ALI, with extravascular lung water indexes (EVLWI), determined with single transpulmonary thermodilution (EVLWI_STD), thermal‐dye dilution (EVLWI_TDD), and postmortem gravimetry (EVLWI_G). Methods: Seven instrumented sheep received an intravenous infusion of oleic acid 0.08 ml/kg (OA group) and four animals had vehicle only (Control group). The day before, and immediately after the experiment, sheep were anesthetized to undergo quantitative CT examinations during a short breath hold. Hemodynamics, oxygenation, EVLWI_STD, and EVLW_TDD were registered. Linear regression analysis was used to assess the relationships between EVLWI_STD, EVLW_TDD, EVLWI_G, and lung tissue volume index (TVI_CT) determined with CT. Results: In the OA group, total lung volume increased compared with Controls. Poorly and non‐aerated lung volumes increased a 3.6‐ and 4.9‐fold, respectively, and TVI_CT almost doubled. EVLWI_STD, EVLWI_TDD, and TVI_CT were associated significantly with EVLWI_G (r=0.85, 0.90, and 0.88, respectively; P<0.001). TVI_CT deviated from the reference EVLWI_G values to the greatest extent with a mean bias ± 2SD of 4.0 ± 6.0 ml/kg. Conclusions: In ovine oleic acid‐induced ALI, lung tissue volume, as assessed by quantitative CT, is in close agreement with EVLWI, as determined by indicator dilution methods and postmortem gravimetry, but overestimates lung fluid content.     

Net fluid leakage (LN) in experimental pulmonary oedema in the dog

Net fluid leakage (LN) from the intravascular to the extravascular pulmonary space was estimated in anaesthetised dogs after injection of oleic acid (OA) (n = 8), or after hydrostatic pressure elevation by inflation of a left atrial balloon (n = 5). LN was calculated as the sum of: (i) rate of change in extravascular lung water (delta EVLW), (ii) thoracic lymph flow, and (iii) pleural fluid formation per time unit. Pleural fluid formation was measured in five dogs with hydrostatic or OA induced pulmonary oedema and was 1.8 +/- 0.9 ml/kg/h. In OA-induced pulmonary oedema, LN increased to a peak of 9.2 ml/kg/h within 2 h after OA injection. Thereafter LN fell and was 2-4 ml/kg/h during the succeeding 2-4 h. During hydrostatic pulmonary oedema LN was increased to as much as 13 ml/kg/h, but it became negative, -5 to -8 ml/kg/h (reabsorption of extravascular fluid) as soon as pulmonary vascular pressures returned to normal following deflation of the left atrial balloon. We conclude that in both forms of oedema there is an initial rapid leakage. In OA-induced oedema this leakage continues, although at a slower rate, whereas in hydrostatic oedema there is a considerable net fluid absorption from the pulmonary extravascular to the intravascular space as soon as vascular pressures are brought to normal levels.     

Carbon monoxide can prevent acute lung injury observed after ischemia reperfusion of the lower extremities

BACKGROUND: Pulmonary expression of heme oxygenase has been observed in multiple studies. This expression has been found beneficial in decreasing the severity of acute lung injury (ALI) post ischemia-reperfusion (I/R). The aim of this study was to assess the role of exogenous administration of the end-products of heme oxygenase reaction, carbon monoxide, and bilirubin, in the severity of ALI. STUDY DESIGN: We compared five groups of rats (n = 7/group) including a sham group and four I/R of the lower extremities by clamping the abdominal aorta for 2 h followed by reperfusion for 2 h. The four I/R groups included a control group, one pretreated with bilirubin (50 micromol/kg IV), another with inhaled carbon monoxide (CO) (250 ppm), and the last pretreated with both. The severity of ALI has been evaluated by a histological assay grading neutrophilic infiltration, as well as a study of the microvascular permeability using the Evans blue. RESULTS: The administration of CO prevented pulmonary microvascular permeability alteration noted after I/R of the lower limbs (pulmonary content of Evans blue: 141 +/- 23 microg/g of tissue in the isolated I/R group versus 68 +/- 34 microg/g of tissue in CO group; P < 0.001). Histologically CO administration inhibited neutrophilic sequestration observed after I/R. On the other hand, treatment by bilirubin alone (50 micromol/kg IV) did not modify the extent of pulmonary injury. CONCLUSION: Exogenous administration of carbon monoxide by inhalation at low doses prevented ALI post-I/R in this model.     

Hemodynamic and oxygenation changes of combined therapy with inhaled nitric oxide and inhaled aerosolized prostacyclin

OBJECTIVE: To evaluate hemodynamic and oxygenation changes of combined therapy with inhaled nitric oxide (iNO) and inhaled aerosolized prostcyclin (IAP) during lung transplantation. DESIGN: Prospective study. SETTING: University hospital. PARTICIPANTS: Ten patients scheduled for lung transplantation. INTERVENTIONS: Ten patients, with a mean age of 38 years (range, 24 to 56 years), were scheduled for lung transplantation (2 single-lung transplantations and 8 double-lung transplantations). During first lung implantation with single-lung perfusion and ventilation, hemodynamic and oxygenation data were analyzed in 3 phases: (1) baseline, 5 minutes after pulmonary artery clamping; (2) inhaled NO phase, 15 minutes after inhaled NO administration (20 ppm) in 100% oxygen; and (3) IAP-inhaled NO phase, 15 minutes after combined administration of inhaled NO (20 ppm) and IAP (10 ng/kg/min) in 100% oxygen. MEASUREMENTS AND MAIN RESULTS: During the inhaled NO phase, reductions of mean pulmonary arterial pressure (p < 0.05) and intrapulmonary shunt (p < 0.05) were noted. After the start of prostacyclin inhalation, a further decrease in mean pulmonary arterial pressure (p < 0.05) was observed. PaO2/FIO2 increased during the IAP-inhaled NO phase (p < 0.05), whereas intrapulmonary shunt decreased (p < 0.05). CONCLUSION: This study confirms the action of inhaled NO as a selective pulmonary vasodilator during lung transplantation. Combined therapy with IAP and inhaled NO increases the effects on pulmonary arterial pressure and oxygenation compared with inhaled NO administered alone without any systemic changes.     

Activated protein C attenuates intestinal reperfusion-induced acute lung injury: an experimental study in a rat model

BACKGROUND: Activated protein C (APC) is a serine protease with anticoagulant and anti-inflammatory activities. APC has been shown to attenuate local deleterious effects of ischemia/reperfusion (I/R) injury in many organs. We aimed to investigate the effects of APC on lung reperfusion injury induced by superior mesenteric occlusion. METHODS: Male Wistar-Albino rats were allocated into 4 groups: (1) sham-operated group, laparotomy without I/R injury (n = 12); (2) sham + APC group, identical to group 1 except for APC treatment (n = 12); (3) intestinal I/R group, 60 minutes of ischemia followed by 3 hours of reperfusion (n = 12); and (4) I/R + APC-treated group, 100 microg/kg injection of APC intravenously, 15 minutes before reperfusion (n = 12). Evans blue dye was injected into half of the rats in all groups. We assessed the degree of pulmonary tissue injury by measuring activities of oxidative and antioxidative enzymes, as well as nitrate (NO(3)(-))/nitrite (NO(2)(-)) levels, biochemically. We evaluated acute lung injury (ALI) by establishing pulmonary neutrophil sequestration and ALI scoring histopathologically. Pulmonary edema was estimated by using Evans blue dye extravasation and wet/dry ratios. The plasma levels of proinflammatory cytokines and D-dimer were measured. RESULTS: APC treatment significantly reduced activities of oxidative enzymes and nitrate/nitrite levels in the lung tissues, and plasma levels of proinflammatory cytokines and D-dimer, and also significantly increased activities of antioxidative enzymes (P < .05). Pulmonary neutrophil sequestration and ALI scores were decreased significantly with APC administration (P < .05). In addition, APC treatment significantly alleviated pulmonary edema (P < .05). CONCLUSIONS: This study clearly showed that APC treatment significantly attenuated the lung reperfusion injury. Further clinical studies are required to clarify whether APC has a useful role in the reperfusion injury during particular surgeries in which I/R-induced organ injury occurs.     

人胎盘MSCs移植对急性肺损伤小鼠肺血管内皮通透性及肺组织损伤修复的影响

目的探讨人胎盘MSCs(human placental MSCs,hPMSCs)移植对脂多糖诱导的急性肺损伤(acute lung injury,ALI)小鼠肺血管内皮通透性及肺组织损伤修复的影响。方法取人胎盘组织采用酶消化法分离培养hPMSCs并传至第3代,流式细胞仪检测细胞表型。将24只6周龄雄性C57BL/6小鼠随机分成3组(n=8)。其中,ALI模型组及h PMSCs治疗组采用气道滴注脂多糖方法制备ALI模型,对照组滴注生理盐水;滴注脂多糖12 h后hPMSCs治疗组尾静脉注射第3代hPMSCs,ALI模型组与对照组注射生理盐水。注射24 h后取各组小鼠肺组织,HE染色观察肺组织病理改变,测量肺组织湿/干质量比(wet/dry mass ratio,W/D),伊文思蓝渗漏实验检测小鼠肺血管内皮通透性,Western blot检测肺组织通透性相关蛋白血管内皮钙黏蛋白(VE-cadherin)的表达。结果流式细胞仪检测显示,分离培养的细胞具有典型MSCs表型特征。各组小鼠均存活。ALI模型组肺泡结构明显塌陷、大量炎性细胞浸润、局部肺泡出血;hPMSCs治疗组肺泡塌陷明显改善,炎性细胞浸润明显减少,肺间质有少许红细胞。ALI模型组肺组织W/D、伊文思蓝染液含量明显高于对照组及hPMSCs治疗组,hPMSCs治疗组高于对照组,差异均有统计学意义(P<0.05)。ALI模型组VE-cadherin蛋白相对表达量明显低于对照组及hPMSCs治疗组,hPMSCs治疗组低于对照组,差异均有统计学意义(P<0.05)。结论静脉注射hPMSCs可有效降低脂多糖介导的肺血管内皮通透性增加,减轻肺组织损伤程度,对小鼠ALI具有治疗作用。