Administration of a synthetic antiprotease reduces smoke-induced lung injury

Effects of Gabexate Mesylate on the Gut Microbiota and Metabolomics in Rats with Sepsis

Background

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. However, there is still no single drug that could reduce septic mortality. Previous studies have reported gabexate mesylate (GM) significantly reduced serum inflammatory factors, alleviated sepsis-induced lung injury and improved clinical outcomes. This study aimed to combine with microbiome sequencing and metabolomics analysis to explore the effects of GM administration in septic rats.

Methods

Sixty SD rats were randomly divided into the sham control (SC), cecal ligation and puncture (CLP), and GM injection (GM) groups. The mortality was measured and colonic feces were collected to examine the gut microbiota and metabolism 24 h after the procedure. The lung tissues were collected for hematoxylin-eosin staining.

Results

We observed the relative abundance of Pygmaiobacter, which contributed to short-chain fatty acids (SCFAs) promotion, Lactobacillus and Erysipelotrichaceae UCG-003 increased in the GM-treated rats, while Escherichia-Shigella and Akkermansia decreased compared to the sepsis-induced lung injury group. Furthermore, these 3 metabolites including Palmitoylethanolamide, Deoxycholic acid and Chenodeoxycholic acid correlated significantly to CLP- and GM-rich genus (P < 0.05). Besides, the lung tissues of CLP group showed more severe inflammatory infiltration and edema, and the mortality rate in the CLP group (10/20) was significantly higher than in the SC group (0/20) (P < 0.001) and GM group (4/20) (P < 0.05).

Conclusion

Our findings showed that GM attenuated sepsis-induced lung injury rats and regulated metabolites related to gut microbiota, which may provide an effective treatment for sepsis patients.

Inhalation Injury in the Burned Patient

Inhalation injury causes a heterogeneous cascade of insults that increase morbidity and mortality among the burn population. Despite major advancements in burn care for the past several decades, there remains a significant burden of disease attributable to inhalation injury. For this reason, effort has been devoted to finding new therapeutic approaches to improve outcomes for patients who sustain inhalation injuries.The three major injury classes are the following: supraglottic, subglottic, and systemic. Treatment options for these three subtypes differ based on the pathophysiologic changes that each one elicits.Currently, no consensus exists for diagnosis or grading of the injury, and there are large variations in treatment worldwide, ranging from observation and conservative management to advanced therapies with nebulization of different pharmacologic agents.The main pathophysiologic change after a subglottic inhalation injury is an increase in the bronchial blood flow. An induced mucosal hyperemia leads to edema, increases mucus secretion and plasma transudation into the airways, disables the mucociliary escalator, and inactivates hypoxic vasocontriction. Collectively, these insults potentiate airway obstruction with casts formed from epithelial debris, fibrin clots, and inspissated mucus, resulting in impaired ventilation. Prompt bronchoscopic diagnosis and multimodal treatment improve outcomes. Despite the lack of globally accepted standard treatments, data exist to support the use of bronchoscopy and suctioning to remove debris, nebulized heparin for fibrin casts, nebulized N-acetylcysteine for mucus casts, and bronchodilators.Systemic effects of inhalation injury occur both indirectly from hypoxia or hypercapnia resulting from loss of pulmonary function and systemic effects of proinflammatory cytokines, as well as directly from metabolic poisons such as carbon monoxide and cyanide. Both present with nonspecific clinical symptoms including cardiovascular collapse. Carbon monoxide intoxication should be treated with oxygen and cyanide with hydroxocobalamin.Inhalation injury remains a great challenge for clinicians and an area of opportunity for scientists. Management of this concomitant injury lags behind other aspects of burn care. More clinical research is required to improve the outcome of inhalation injury.The goal of this review is to comprehensively summarize the diagnoses, treatment options, and current research.

Pathophysiology, research challenges, and clinical management of smoke inhalation injury

Smoke inhalation injury is a serious medical problem that increases morbidity and mortality after severe burns. However, relatively little attention has been paid to this devastating condition, and the bulk of research is limited to preclinical basic science studies. Moreover, no worldwide consensus criteria exist for its diagnosis, severity grading, and prognosis. Therapeutic approaches are highly variable depending on the country and burn centre or hospital. In this Series paper, we discuss understanding of the pathophysiology of smoke inhalation injury, the best evidence-based treatments, and challenges and future directions in diagnostics and management.

Current concepts in the pathophysiology and treatment of inhalation injury

The opinions or assertions contained herein are the private views of the author, and are not to be construed as official or as reflecting the official views of the Department of the Army or Department of Defense. Smoke inhalation injury occurs in about 10% of patients admitted to burn centres, and increases the mortality of burn patients by up to 20% over predictions based on age and burn size alone. The primary lesion in smoke inhalation injury is localized to the small airways, with alveolar injury and pulmonary oedema exercising a less prominent role during the initial phases. Injury incites a cascade of events that include ventilation-perfusion mismatch, secondary lung injury, systemic inflammation, impaired immune function, and pneumonia. The most important recent developments in the treatment of inhalation injury have included improved methods of pulmonary care targeted at the pathophysiology of the injury, such as high-frequency percussive ventilation and gentle mechanical ventilation.

Effects of a synthetic protease inhibitor (gabexate mesilate) and a neutrophil elastase inhibitor (sivelestat sodium) on acid-induced lung injury in rats

The present study was designed to examine the combined effects of a synthetic protease inhibitor, gabexate mesilate, with a specific neutrophil elastase inhibitor, sivelestat sodium, on acid-induced lung injury. Adult male Sprague-Dawley rats weighing 300-350 g were anaesthetised intraperitoneally with pentobarbitone sodium and the right jugular vein was cannulated. Following tracheostomy, rats were ventilated mechanically and underwent intratracheal instillation of hydrochloric acid (HCl, 0.1N 1.5 ml/kg) or normal saline. Gabexate mesilate (10mg/kg, i.p.) and/or sivelestat sodium (10mg/kg/h, i.v.) were administered 30 min before HCl instillation. Bronchoalveolar lavage fluid samples were obtained 5h after HCl instillation. In bronchoalveolar lavage fluid, the HCl-induced increases in total nucleated cell counts, neutrophil counts, optical density at 412 nm as an index of pulmonary haemorrhage, concentrations of albumin and cytokine-induced neutrophil chemoattractant (CINC) were significantly attenuated by either gabexate mesilate or sivelestat sodium treatment. Gabexate mesilate or sivelestat sodium treatment also significantly attenuated the wet to dry weight ratio induced by HCl. However, combined treatment with both gabexate mesilate and sivelestat sodium did not show additive effects on HCl-induced lung injury, compared with single treatments. These findings suggested that gabexate mesilate and sivelestat sodium each exhibited protective effects on acid-induced lung injury, but that synergistic effects of both agents are limited in this acid-induced lung injury model.

Tracheobronchial protease inhibitors, body surface area burns, and mortality in smoke inhalation

The objective of this study was to assess tracheobronchial protease inhibitor concentrations longitudinally and determine whether initial concentrations predict subsequent lung injury and mortality in intubated burn victims. Tracheobronchial suction fluid was collected every 2 hours for 36 hours. Alpha-1-antitrypsin (AAT), secretory leukocyte peptidase inhibitor (SLPI), alpha-2-macroglobulin (A2M), and cell and differential counts were assayed. Partial pressure of oxygen in arterial blood/fraction of inspired oxygen (PaO2/FIO2) and peak airway pressure (PAP) were recorded for 72 hours. Standard statistics were used to evaluate cross-sectional relationships; random coefficient (mixed) models were used to evaluate temporal trends in marker concentrations and relation to clinical outcomes. Among 29 patients, 24 (83%) developed hypoxemia (PaO2/FIO2 <200); six died within 2 weeks. When adjusted for gender, age, %TBSA burn, and positive end-expiratory pressure setting, A2M (P = .007) and neutrophils (P = .032) increased linearly during 36 hours, and SLPI decreased (P = .038). Initial SLPI concentration was a negative predictor of maximum PAP (P = .009). None of the markers predicted longitudinal change in PaO2/FIO2. Mean levels of AAT and A2M in initial samples were significantly lower in patients with >35% TBSA burn (P = .010 and .033, respectively), when compared with patients with less severe burns. However, patients with increased A2M in combination with >35% TBSA burn had a 6-fold (95% CI: 1.8-20) increased relative risk of death. Tracheobronchial AAT and A2M levels were significantly lower in patients with more severe burns and increased over time. Initial SLPI levels predicted subsequent PAP. Increased early A2M in combination with extensive burn predicted early mortality.

Lung injury from smoke inhalation

Significant morbidity and mortality from smoke inhalation occurs in victims of fire. Lung injury can be caused by chemical and thermal insults. A variety of noxious gases, irritants and asphyxiants are generated depending on the material burnt. Carbon monoxide is the predominant cause of death among fire victims. Treatment should be directed at reversing hypoxaemia as a result of asphyxia or carbon monoxide poisoning. There is no evidence that the routine use of corticosteroids or prophylactic antibiotics is beneficial. Through a better understanding of the pathophysiology of smoke-induced lung injury, the effects of exogenous surfactant, leukotriene inhibitors, antioxidants, nitric oxide synthase inhibitors and fibrinolytics suggest that these compounds may have a future therapeutic role in smoke-induced injury. Studies are needed to evaluate the safety and efficacy of these potential therapies before they are used clinically.

Effects of gabexate mesilate on ischemia-reperfusion-induced testicular injury in rats

The aim of this study was to determine the effects of a synthetic serine protease inhibitor, gabexate mesilate (GM), in rats with ischemia-reperfusion (I-R) damage due to unilateral testicular torsion. Thirty male Sprague-Dawley rats were separated into three groups, each containing ten rats. A sham operation was performed in group 1 (control). In group 2 (I-R/untreated), 1 h detorsion of the testis was performed after 6 h of unilateral testicular torsion. In group 3 (I-R/GM), after performing the same surgical procedures as in group II, gabexate mesilate was given intravenously. In all experimental rats, ipsilateral orchiectomies were performed for histological examination and measuring the tissue levels of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px). MDA values and the testicular injury score decreased and SOD, CAT and GSH-Px values increased in the GM-treated group compared to the I-R/untreated group. The Tc-99m pertechnetate uptake ratio and the perfusion index were significantly decreased in the group 2 compared to the group 1 and 3 rats. In group 3, these values were significantly increased compared to group 2. Most of the specimens in the GM-treated group showed grade-I testicular injury. However, the injuries in the I-R/untreated rats varied between grade-III and grade-IV. The results of this study show that GM may play a role in reducing the injury caused by I-R.

In vivo effect of wood smoke on the expression of two mucin genes in rat airways

A short-term, time-dependent smoke exposure of rats in a nose-only chamber to burning wood and 24-h recovery time revealed inflammation of the airways with varying degrees of injury from loss of cilia, degeneration of epithelium, and squamous metaplasia to submucosal edema. These histological changes were reflected in variable expression of the secretory Muc5AC and low expression of membrane-associated Muc4 mucin genes. 20-min smoke exposure in extended recovery experiments showed marked disorder of tracheal epithelium for up to 72 h of recovery with a return to normal by 7 days. Gene expressions were elevated at 24 and 48 h of recovery. 30-min smoke exposure showed a more severe degeneration of the epithelium and a longer recovery time. Muc5AC expression decreased after 72 h of recovery, while there was upregulation of Muc4 gene from 48 through 96 h. Because Muc4 upregulation and histological results correlate and it has reportedly been associated with epithelium renewal, Muc4 gene may be a useful marker for the regeneration of tracheal epithelium.

EFFECTS OF MANGANESE SUPEROXIDE DISMUTASE NEBULIZATION ON PULMONARY FUNCTION IN AN OVINE MODEL OF ACUTE LUNG INJURY

Smoke inhalation injury is a major cause of morbidity and mortality in thermally injured individuals. There is evidence of increased oxygen free radical activity, e.g., superoxide, in association with smoke inhalation injury. Because superoxide dismutase converts the reactive superoxide radical to peroxide, we hypothesized that nebulization of manganese superoxide dismutase (Mn-SOD) into the airway might attenuate pulmonary dysfunction secondary to smoke inhalation injury. The present study was designed as a prospective, controlled, and randomized laboratory experiment to determine the effects of aerosolized Mn-SOD on lung fluid balance, as indexed by changes in pulmonary microvascular permeability, lung lymph flow (Q(L)), and gas exchange in an established and clinically relevant ovine model of smoke inhalation injury. Fifteen female Merino sheep were chronically instrumented with a femoral arterial, a Swan-Ganz, and a left atrial catheter. In addition, the right caudal mediastinal lymph node was cannulated to measure Q(L) (mL.h(-1)). Pneumatic occluders were placed around the right pulmonary veins for the determination of the reflection coefficient (sigma). After 7 days of recovery, sheep were randomly allocated to (a) an untreated control group (4 groups of 12 breaths of cotton smoke), (b) an injured group treated with nebulized Mn-SOD (5 mg/kg), and (c) an injured group that received only the vehicle (nebulized saline). Nebulization was performed 1 h and 12 h after smoke inhalation. Mn-SOD nebulization attenuated the increase in both filtration coefficient and sigma and significantly decreased lung tissue conjugated dienes. However, there were no differences in Q(L), PaO2/FiO2 ratio, and bloodless lung wet/dry weight ratio between groups. Although Mn-SOD nebulization attenuated the loss of protein, it failed to improve lung edema and pulmonary gas exchange, thereby limiting its clinical use.

Pathophysiological basis of smoke inhalation injury

Smoke inhalation injury results in serious respiratory failure. When smoke inhalation injury is combined with burn injury or pneumonia, the physiological responses are different and more severe than those of smoke inhalation injury alone. Treatment strategies should be planned based on these pathophysiological aspects.

Effects of heparin and lisofylline on pulmonary function after smoke inhalation injury in an ovine model

OBJECTIVE

This study evaluates the effects of heparin alone and in combination with lisofylline, 1-(5-R-hydroxyhexyl)3,7-dimethylxanthine, on severe smoke injury.

DESIGN

Prospective animal study with concurrent controls.

SETTING

An animal laboratory.

SUBJECTS

Eighteen 1-yr-old female sheep, weighing 24-32 kg.

INTERVENTIONS

After smoke exposure and tracheostomy, animals were divided into three groups. Group S (n = 6) received nebulized saline through an endotracheal tube every 4 hrs for 48 hrs. Group H (n = 6) received 10,000 units of nebulized heparin every 4 hrs. Group LH (n = 6) was treated with nebulized heparin and intravenous infusion of lisofylline (10 mg x kg(-1) x hr(-1)) for 48 hrs after a bolus injection (20 mg/kg). Animals initially breathed room air spontaneously. If PaO2 was <50 torr and PaCO2 >60 torr, animals were mechanically ventilated. Sheep were killed 48 hrs postinjury.

MEASUREMENTS AND MAIN RESULTS

Blood gases were measured serially. At 48 hrs, ventilation perfusion distribution mismatching was analyzed by using the multiple inert gas elimination technique. Lung malondialdehyde was determined. The postinjury increase in alveolar-arterial oxygen tension gradient (LH, 36.7 +/- 3.5 vs. S, 89.0 +/- 24.6 torr at 48 hrs) was significantly attenuated in those animals receiving LH. The percentage of pulmonary shunt, Qs/Qt (LH, 20.8 +/- 4.9 vs. S, 36.6 +/- 4.6%), and the percentage of animals that required ventilation (LH, 0 vs. S, 67%) were significantly reduced in LH. Multiple inert gas elimination technique study showed that the true shunt fraction was decreased in LH. Lung malondialdehyde was significantly less in LH (LH, 0.33 +/- 0.06 vs. S, 0.56 +/- 0.09 nmol/mg protein). There was no significant difference in any of these variables between H and S.

CONCLUSION

Treatment with heparin alone did not attenuate pulmonary dysfunction after severe smoke injury. Combined treatment with nebulized heparin and systemic lisofylline had beneficial effects on pulmonary function in association with a decrease in blood flow to poorly ventilated areas and less lipid peroxidation.

Protective effects of inhaled nitric oxide and gabexate mesilate in lung reperfusion injury after transplantation from non-heart-beat donors

BACKGROUND

The use of lung grafts from non-heart-beat donors (NHBDs) is one way of solving the critical donor organ shortage. Inhaled nitric oxide (NO) and gabexate mesilate (FOY), a protease inhibitor, can attenuate some types of neutrophil-mediated tissue injury. Using an isolated lung ventilation and perfusion model, we studied the effects of these agents on reperfusion injury following lung transplantation from NHBDs.

METHODS

Five groups of minipigs were studied. In group 1(n = 6), the lungs were flushed and harvested after cardiac arrest, and were reperfused for 2 hours after 2 hours of cold ischemia. In group 2 (n = 6), the lungs were harvested after 2 hours of in situ warm ischemia, followed by 2 hours of cold ischemia and 2 hours of reperfusion. In groups 3 (n = 7), 4 (n = 7), and 5 (n = 6), the procedure was the same as in group 2, except in group 3, NO was inhaled before and after ischemia, in group 4, FOY was given intravenously, and in group 5, a combination of inhaled NO and intravenous FOY were administered.

RESULTS

Compared with group 1, group 2 had higher mean pulmonary arterial pressure, vascular resistance, and lower arterial blood oxygen tension. Furthermore, these negative effects of warm ischemia were also reflected in the contents of bronchoalveolar lavage fluid, tissue myeloperoxidase (MPO) activity, histology, and permeability change. Either FOY or NO administration (groups 3 or 4) ameliorated the associated injury. A combination of FOY and NO use (group5) decreased the parameters of lung reperfusion injury measurement to a larger degree than either agent individually.

CONCLUSIONS

The inhaled NO and FOY can protect NHBD lung grafts at an early reperfusion period. Their use in combination has an additive protective effect that might be applied to the protection of NHBD grafts from preservation and reperfusion injury.

The effects of inhaled nitric oxide, gabexate mesilate, and retrograde flush in the lung graft from non-heart beating minipig donors

BACKGROUND

The use of lung grafts from non-heart-beating donors (NHBD) is one way of solving the donor organ shortage problem. In this experiment, we studied the effect of retrograde flush (RF) from the left atrium before harvest, inhaled nitric oxide (NO), and gabexate mesilate (FOY), a protease inhibitor, in the lung grafts from NHBD.

METHODS

Forty-eight Lee-Sung, small-ear, miniature pigs (15-20 kg) were divided into 24 pairs (donor and recipient) and four groups. The donor lungs were flushed and harvested 90 min after cardiac arrest. No i.v. heparin was administered until the time before flush and harvest. Left single lung transplantation was undertaken, and the recipients were observed for 18 hr. The grafts warm and cold ischemia times were 90 (controlled) and 183+/-23.4 min. Group 1 (untreated control, UC, n=6) had core perfusion through a Swan-Ganz catheter followed by a single, antegrade flush with modified Euro-Collin's solution containing heparin, urokinase, and PGE1. Group 2 (RF group, n=6) had the same as group 1, except that one additive retrograde flush through the left atrium was administered. Group 3 (NO group, n=6) had the same as group 1, except that 20 parts per million (ppm) inhaled NO was administered for the cadaver donors before the graft harvest, and for the recipients after the grafts reperfusion. Group 4 (FOY group, n=6) had the same as group 1, except that the recipients received FOY i.v. infusion from the beginning of the recipient's operation and continuously throughout the experiments.

RESULTS

Compared with the group 1 (control), group 2 (RF) had significantly (P<0.05) lower mean pulmonary artery pressure, pulmonary vascular resistance (PVR), lung wet/dry ratio, histological lung injury score, and higher PaO2/FiO2 and pulmonary dynamic compliance. Group 3 (NO) had significantly lower mean pulmonary arterial pressure, PVR, lung injury score, degree of tissue neutrophils infiltration (histological and myeloperoxidase assay), bronchoalveolar lavage fluid protein content and neutrophils (PMNs) percentage, and higher PaO2/FiO2 and pulmonary dynamic compliance. Group 4 (FOY) had significantly lower PMNs infiltration, lung injury score, wet/dry ratio, bronchoalveolar lavage fluid protein and PMNs percentage, and higher PaO2/FiO2. Group 2 (RF) revealed better gas exchange (PaO2/FiO2) than the control (group 1) at earlier reperfusion periods (1st and 5th hr). On the contrary, group 4 (FOY) had higher PaO2/FiO2 than group 1 only at later period (18th hr). Pathologically, retrograde flush (group 2, RF) inhibited the intravascular thrombi formation more effectively than the NO or FOY treatment. However, the NO or FOY treatment inhibited the neutrophil infiltration more effectively than did the retrograde flush.

CONCLUSION

The retrograde flush, inhaled NO and FOY infusion are beneficial to the protection of the NHBD lung grafts at an early reperfusion period, through different mechanisms. The use of these treatments in combination might help us to find a better way to protect the NHBD grafts against the preservation and reperfusion injury.

New clinically relevant sheep model of severe respiratory failure secondary to combined smoke inhalation/cutaneous flame burn injury

OBJECTIVES

To develop a predictable, dose-dependent, clinically relevant model of severe respiratory failure associated with a 40% total body surface area, full-thickness (third-degree) cutaneous flame burn and smoke inhalation injury in adult sheep.

DESIGN

Model development.

SETTING

Research laboratory.

SUBJECTS

Adult female sheep (n = 22).

INTERVENTIONS

Animals were divided into three groups, determined by the number of smoke breaths administered (24, 36, 48) for a graded inhalation injury. The smoke was insufflated into a tracheostomy with a modified bee smoker at airway temperatures <40 degrees C. All animals concurrently received a 40% total body surface area (third-degree) cutaneous flame burn to the body (flanks). After injury, the animals were placed on volume-controlled ventilation to achieve PaO2 >60 mm Hg and PaCO2 <40 mm Hg. Arterial blood gases and ventilator settings were monitored every 6 hrs postinjury for up to 7 days.

MEASUREMENTS AND MAIN RESULTS

All animals survived the induction of injury. In the 24 smoke breath/40% total body surface area burn (24/40) group, PaO2/F(IO2) never decreased below 300, and peak inspiratory pressure was consistently <14 cm H2O with normal arterial blood gases throughout the observation period. With 36 smoke breaths/40% total body surface area burn (36/40) (n = 7), all animals had PaO2/F(IO2) of <200 and peak inspiratory pressure of 26 cm H2O within 40-48 hrs, as 30% died during the study period. With 48 smoke breaths/40% total body surface area burn (48/40) (n = 12), all animals developed respiratory distress syndrome (RDS) in 24-30 hrs, but none survived the experimental period.

CONCLUSIONS

Development of RDS by smoke and cutaneous flame bum injury depends on smoke inhalation dose. A combination of 36 breaths of smoke and a 40% total body surface area (third-degree) cutaneous flame burn injury can induce severe RDS (PaO2/F(IO2) <200) within 40-48 hrs to allow evaluation of various treatment modalities of RDS.

Effects of gabexate mesilate (FOY) on ischemia-reperfusion-induced acute lung injury in dogs

BACKGROUND

To assess the effects of gabexate mesilate (FOY), a protease inhibitor, on a canine model of pulmonary ischemia-reperfusion injury. FOY has been applied clinically to treat acute pancreatitis and disseminated intravascular coagulation (DIC) and has been found to suppress some leukocyte-mediated tissue injuries in both in vitro and in vivo studies.

MATERIALS AND METHODS

DESIGN

Comparison of four experimental groups: group 1 (untreated control, n = 8), unilateral (left) pulmonary ischemia due to perfusion and ventilation obstruction followed by reperfusion, without receiving any specific treatment; group 2 (negative control, sham operation, n = 8), left pulmonary hilar dissection without ischemia; group 3 (FOY posttreatment, n = 8), FOY treatment during the reperfusion stage only; and group 4 (FOY pretreatment, n = 8), FOY treatment before ischemia and then continued during reperfusion.

SETTING

University animal laboratory.

SUBJECTS

Heart-worm-free mongrel dogs (12 to 15 kg body wt) were anesthetized with pentobarbital and mechanically ventilated.

INVESTIGATIONS

Lung ischemia was made by snaring the left pulmonary artery and veins and clamping the bronchus with peribronchial tissue for 90 min followed by reperfusion for 18 h. Animals of the two treatment groups received a 1 mg/kg bolus of FOY at the beginning of reperfusion, with infusion of 2 mg/kg/h of FOY continuously starting 30 min before ischemia (group 4) or after reperfusion (group 3). During this study the following were measured: hemodynamics and aerodynamics, blood gas, bronchoalveolar lavage (BAL) fluid neutrophil percentage and protein concentration, lung wet to dry weight ratio (W/D ratio), myeloperoxidase (MPO) activity of the lung tissue, alveolar neutrophil infiltration, and degree of injury.

RESULTS

This model of lung ischemia-reperfusion induced significant pulmonary hypertension, increased pulmonary vascular resistance, decreased pulmonary dynamic compliance and arterial hypoxemia, increased BAL fluid total protein amount and neutrophil percentage, and increased alveolar neutrophil infiltration, histological injury score, and lung tissue MPO assay (group 1). Animals of the sham operation (negative control, group 2) showed only minimal changes in the above parameters. Treatment with FOY significantly attenuated the injury by decreasing the lung W/D ratio, alveolar neutrophil infiltration, histological injury score, lung tissue MPO assay, BAL fluid neutrophil percentage, and protein amount. Pretreatment with FOY (group 4) attenuated the injury to a significantly greater degree than it did when administered at the reperfusion stage only (group 3), which was reflected by the above-mentioned parameters, and as well significantly improved gas exchange function. FOY treatment was found to have little effect in altering hemodynamics and aerodynamics at most time points in this model of lung injury.

CONCLUSIONS

FOY can attenuate the ischemia-reperfusion-induced acute lung injury in dogs by ameliorating the degree of alveolar membrane permeability change, neutrophil aggregation, and activation. FOY treatment starting before ischemia attenuated this injury to a significantly higher degree than its use after ischemia. However, the effect of FOY may be partial because it cannot alter the hemodynamics or aerodynamics as prominently as other parameters in this type of lung injury. Concomitant use of FOY with other agents will have additive or synergic effects in preventing lung ischemia-reperfusion injury.

Interleukin-8 mediates injury from smoke inhalation to both the lung endothelial and the alveolar epithelial barriers in rabbits

Although prior studies have shown that smoke inhalation causes lung endothelial injury and formation of pulmonary edema, there is no information about the effect of smoke inhalation on the function of the alveolar epithelial barrier. Therefore, the primary objective of this study was to determine the effect of smoke-induced lung injury on the alveolar epithelial barrier in a rabbit experimental model. The second objective was to investigate whether pretreatment with a monoclonal anti-interleukin (IL)-8 antibody prevented alveolar epithelial barrier injury after smoke inhalation. Anesthetized rabbits were tracheotomized and were insufflated with cooled smoke generated from burning cotton cloth (75 breaths). In some experiments, anti-IL-8 antibody or an irrelevant antibody (2 mg/¿g) was given intravenously 5 min before insufflation of cotton smoke. Smoke inhalation caused a significant increase in the alveolar epithelial permeability to protein and a 40% reduction in the fluid transport capacity of the alveolar epithelium. Pretreatment with anti-IL-8 antibody, but not with an irrelevant-isotype antibody, significantly reduced the smoke-mediated increase in bidirectional transport of protein across the alveolar epithelium, and restored alveolar liquid clearance to a normal level. The results of the study show that smoke inhalation causes injury to both the alveolar epithelial barrier and the lung endothelium, and that IL-8 is an important mediator of this injury.

Effect of Sulfo Lewis C on smoke inhalation injury in an ovine model

OBJECTIVE

To evaluate the effect of Sulfo Lewis C (SO3-3âGal1-3GlcNAc-O(CH2)8-COOMe), a putative ligand of selectins, on smoke inhalation injury.

DESIGN

Prospective animal study with concurrent controls.

SETTING

An animal laboratory.

SUBJECTS

Twelve 1-yr-old female sheep, weighing 24 to 33 kg.

INTERVENTIONS

Twelve sheep received nine exposure units of smoke generated by thermolysis of pine woodchips (80 g). Group 1 (n = 6) was untreated. Group 2 (n = 6) was treated with an intravenous infusion of Sulfo Lewis C after smoke exposure. Animals were killed 48 hrs after injury.

MEASUREMENTS AND MAIN RESULTS

Cardiopulmonary variables and blood gases were measured serially. Granulocyte free-radical production was measured before smoke exposure and at 4 and 48 hrs after injury. Ventilation/perfusion distribution (VA/Q) was analyzed using the multiple inert gas elimination technique. Granulocyte free-radical production was increased after smoke exposure in both groups. Oxygenation was significantly improved by the administration of Sulfo Lewis C. VA/Q analysis demonstrated significantly less blood flow to low VA/Q lung segments in treated animals.

CONCLUSIONS

Selectin blockade attenuated lung injury after smoke exposure. These data support the hypothesis that neutrophils play a pivotal role in smoke inhalation injury.

Smoke-induced inhalation injury: effects of retinoic acid and antisense oligodeoxynucleotide on stability and differentiated state of the mucociliary epithelium

Rabbit tracheal explants, exposed to burning pine wood smoke, were cultured in a chemically defined medium with and without retinoic acid (+/- RA). Exposures of 15-20 minute led to RA-independent degeneration of the mucociliary epithelial sheath. In 10 minute exposures tissue integrity was retained, but epithelial morphology changed from normal pseudostratified columnar to the flattened appearance typical of the squamous phenotype. Despite the dramatic shift in morphology, explants exhibited normal RA-dependent mucin gene expression characteristic of the mucociliary phenotype. Furthermore, electron micrographs showed continued presence of both secretory granules and cilia. RA(+) cultures also showed a normal pattern of adherent epithelial cells. In RA(-) cultures, however, there were prominent intercellular spaces indicating an RA dependence for maintaining adhesive contacts following smoke exposure. An 18-mer mucin antisense oligomer that suppressed mucin gene expression also unexpectedly blocked the smoke induced metaplasia in RA(+) cultures, but the sense oligomer had no effect.

Current treatment of severely burned patients

OBJECTIVE

The authors provide an update on a multidisciplinary approach to the treatment of severely burned patients. A review of studies and clinical trials from the past to the present include fluid resuscitation, sepsis, immune function, hypermetabolism, early excision, wound healing, scar formation, and inhalation injury.

SUMMARY BACKGROUND DATA

Advances in treating initial burn shock, infection control, early wound closure, and modulation of the hypermetabolic response have decreased morbidity and mortality in the last two decades. Specialized burn care centers, using a multidisciplinary approach, not only successfully treat large burns and their complications, but provide the necessary rehabilitation and psychological support required for readjustment back into society.

CONCLUSIONS

Thermal injury results in a number of physiologic alterations that can be minimized by adequate fluid resuscitation to maintain tissue perfusion, early excision of burn wounds, and rapid wound coverage. These measures, in combination with antibiotic coverage and nutritional support in the form of early enteral tube feedings, will decrease the hypermetabolic response and the incidence of sepsis that can lead to hemodynamic instability and organ failure. Ongoing clinical trials using anabolic agents (e.g., recombinant human growth hormone) and pharmacologic agents that modulate inflammatory and endocrine mediators (e.g., ibuprofen and propranolol) show promise in the treatment of severe burn injuries.

Diagnosis and treatment of smoke inhalation

Inhalation remains the most frequent and serious comorbid event that occurs in thermally injured patients. A thorough understanding of the pathophysiology enables individualization of therapy and appropriate triage of patients. We summarize our current knowledge of the pathophysiology, diagnosis, and treatment of inhalation injury, with a focus on newer treatment strategies that are evolving secondary to laboratory research.

Lymph and blood flow responses in central airways

The lymphatic drainage of the lung has been used as a quantitation of pulmonary microvascular fluid flux in normal animals and after various forms of injury. This review supports the importance of the bronchial microvasculature in the formation of lung lymph. Proof that the lymph drainage of the lung comes from the pulmonary circuit has been based on the finding of an elevation of lymph flow when the pulmonary venous pressure is elevated. This proof is wanting since recent work demonstrates that the venous drainage of the intrapulmonary bronchi flows into the pulmonary vascular system at the precapillary level. The administration of endotoxin induces an elevation of lung lymph. The bronchial circuit may play a role in this response since it is likewise exposed to the high pulmonary pressures induced by endotoxin, and there is evidence that ischemia/reperfusion injury to the airway occurs with endotoxin administration. After acute lung injury from smoke inhalation, lung lymph flow is markedly elevated. The lymph drainage from the airway may play an important role in this response. Bronchial blood flow is markedly increased after inhalation injury and there is airway edema. The increases in lung lymph flow and extravascular lung water are markedly reduced by occlusion of the bronchial artery. These data support the need for additional study of the role of the bronchial circulation in the formation of lung lymph.