Role of L-selectin in physiological manifestations after burn and smoke inhalation injury in sheep

Obstructive Tracheal Necrosis in a Dog Secondary to Smoke Inhalation Injury-Case Report

A 4-year-old Siberian Husky mix was referred to the emergency service of the University of California Davis Veterinary Medical Teaching Hospital after being found unconscious in a housefire. Upon arrival, the dog was conscious and panting with normal breathing effort. The dog was initially treated with oxygen therapy to minimize the risk of carbon monoxide toxicosis. Progressive agitation with paroxysmal episodes of increased respiratory effort and increased upper airway sounds were noted ~48 h after presentation. Hypoxemia was then documented. Clinical signs continued to progress despite supportive measures, and five days after initial presentation mechanical ventilation was deemed indicated. Following anesthetic induction, endotracheal intubation was performed. Capnography and peak inspiratory pressures recorded on the mechanical ventilator were consistent with airway obstruction. Diffuse intraluminal tracheal obstruction with grossly necrotic tracheal tissue was confirmed using fiber optic tracheoscopy. The patient was humanely euthanized due to grave prognosis. At necropsy, the tracheal lumen was obstructed by sloughed, necrotic tracheal mucosa. This is the first report describing a severe delayed intrathoracic large airway complication secondary to smoke inhalation in a dog.

Emerging therapies for smoke inhalation injury: a review

Background

Smoke inhalation injury increases overall burn mortality by up to 20 times. Current therapy remains supportive with a failure to identify an optimal or targeted treatment protocol for smoke inhalation injury. The goal of this review is to describe emerging therapies that are being developed to treat the pulmonary pathology induced by smoke inhalation injury with or without concurrent burn injury.

Main body

A comprehensive literature search was performed using PubMed (1995–present) for therapies not approved by the U.S. Food and Drug Administration (FDA) for smoke inhalation injury with or without concurrent burn injury. Therapies were divided based on therapeutic strategy. Models included inhalation alone with or without concurrent burn injury. Specific animal model, mechanism of action of medication, route of administration, therapeutic benefit, safety, mortality benefit, and efficacy were reviewed. Multiple potential therapies for smoke inhalation injury with or without burn injury are currently under investigation. These include stem cell therapy, anticoagulation therapy, selectin inhibition, inflammatory pathway modulation, superoxide and peroxynitrite decomposition, selective nitric oxide synthase inhibition, hydrogen sulfide, HMG-CoA reductase inhibition, proton pump inhibition, and targeted nanotherapies. While each of these approaches shows a potential therapeutic benefit to treating inhalation injury in animal models, further research including mortality benefit is needed to ensure safety and efficacy in humans.

Conclusions

Multiple novel therapies currently under active investigation to treat smoke inhalation injury show promising results. Much research remains to be conducted before these emerging therapies can be translated to the clinical arena.

A model of recovery from inhalation injury and cutaneous burn in ambulatory swine

Inhalation injury commonly accompanies thermal injury, increasing the likelihood of mortality and multiple organ dysfunction (MOD). Large animal models have given important insight into the pathophysiology of this injury; however recapitulating late MOD has remained difficult. The current report describes experiments using a smoke inhalation and burn model, with follow-up of ambulatory swine for 14days with bronchoscopy, CT scanning, and bronchoalveolar lavage fluid (BALF)/blood collection. Clinically, animals cleared airway damage in the first several days after-injury. This was mirrored with erythematous airways on day 2 after-injury, which resolved by the end of the experiment, as did parenchymal damage seen on CT. An initial rise in the protein content of BALF immediately after-injury was followed by a dramatic increase in the concentration of leukocytes. Circulating neutrophils increased while lymphocytes decreased; both correlated with cell counts in BALF. IL8 levels in BALF increased 30-fold and remained elevated throughout the experiment. IL1ra increased circulation immediately after-injury, and afterwards in BALF. Other cytokines (TNFα, IL12) transiently increased in BALF (and decreased in circulation) on day 2. Taken together, these results display a remarkable capability for the lungs to recover in the absence of intubation, with further evidence of the role of cytokines such as IL8 and IL1ra. The possible exacerbating effects of clinical practices such as ventilation and bronchoscopies should be considered.

A rat model of smoke inhalation injury

CONTEXT

Smoke inhalation injury is the leading cause of acute respiratory failure in critical burn victims. Advances in the treatment of smoke inhalation injury have been limited in the past years. To further explore the pathogenesis, stable and practical animal models are necessary.

OBJECTIVE

To develop a rat model of smoke inhalation injury.

MATERIALS AND METHODS

The smoke composition including the particulate matters, irritant gases, chemical carcinogens was measured. The blood gas values, pro-inflammatory and protein concentration in bronchoalveolar lavage fluid and lung wet to dry weight ratio were assayed. Pathological evaluations of pulmonary were performed at 24 h, 96 h, 7 days and 28 days post-injury. Masson-Goldner trichrome staining was performed on day 7 and 28 post-injury, along with the measurement of hydroxyproline and collagen I and III.

RESULTS

In our present animal model, smoke inhalation caused a significant hypoxemia and CO poisoning. A surge of pro-inflammatory response and microvascular hyperpermeability with neutrophils accumulations were also found in our animal model. At 24 h post-smoke inhalation, the hematoxylin and eosin results exhibited that there were inflammatory exudates and diffuse hemorrhage in the lung tissue with significant edema. With the time going, the lung injuries appeared at alveolar collapse and alveolar septum thickening, which indicated that smoke inhalation further induced damage to lung parenchyma. Specially, the markedly collagen deposition appeared at 28 days post-injury indicated that pulmonary fibrosis happened.

DISCUSSION AND CONCLUSION

In conclusion, this rat smoke inhalation injury model induced by our novel self-made smoke generator could be used for acute and chronic lung injury experiments.

Sclerosis therapy of bronchial artery attenuates acute lung injury induced by burn and smoke inhalation injury in ovine model

INTRODUCTION

In burned sheep, we showed more than a 10-fold increase in bronchial blood flow following smoke inhalation. It was previously reported that sclerosis of the bronchial artery prior to smoke exposure reduces the pathophysiology of the inhalation insult. We hypothesized that sclerosis of the bronchial artery after insult attenuates smoke/burn-induced acute lung injury.

METHODS

Through an incision at the 4th intercostal space, a catheter was placed via the esophageal artery into the bronchial artery such that the bronchial blood flow remained intact. Acute lung injury was induced by a 40% total body surface area, 3rd degree cutaneous burn and smoke inhalation. Adult female sheep (n=18, 35.6±1.0 kg) were divided into three groups following the injury: (1) sclerosis group: 1h after injury, 4 mL of 70% ethanol was injected into bronchial artery via bronchial catheter, n=6; (2) control group: 1h after injury, an equal dose of saline was injected into bronchial artery via the bronchial catheter, n=6; (3) sham group: no injury and no treatment, n=6. The experiment was conducted in awake animals for 24 h.

RESULTS

Bronchial blood flow, measured by microspheres, was significantly reduced after ethanol injection in the sclerosis group. Pulmonary function, evaluated by measurement of blood gas analysis, pulmonary mechanics, and pulmonary transvascular fluid flux, was severely impaired in the control group. However, pulmonary function was significantly improved by bronchial artery sclerosis.

CONCLUSION

The results of our study clearly demonstrate a crucial role of enhanced bronchial circulation in thermal injury-related morbidity. Decreasing bronchial circulation using pharmacological agents may be an effective strategy in management of burn patients with concomitant smoke inhalation injury.

Pathophysiology, management and treatment of smoke inhalation injury

Smoke inhalation injury continues to increase morbidity and mortality in burn patients in both the third world and industrialized countries. The lack of uniform criteria for the diagnosis and definition of smoke inhalation injury contributes to the fact that, despite extensive research, mortality rates have changed little in recent decades. The formation of reactive oxygen and nitrogen species, as well as the procoagulant and antifibrinolytic imbalance of alveolar homeostasis, all play a central role in the pathogenesis of smoke inhalation injury. Further hallmarks include massive airway obstruction owing to cast formation, bronchospasm, the increase in bronchial circulation and transvascular fluid flux. Therefore, anticoagulants, antioxidants and bronchodilators, especially when administered as an aerosol, represent the most promising treatment strategies. The purpose of this review article is to provide an overview of the pathophysiological changes, management and treatment options of smoke inhalation injury based on the current literature.

Effect of ablated bronchial blood flow on survival rate and pulmonary function after burn and smoke inhalation in sheep

The bronchial circulation plays a significant role in the pathophysiological changes of burn and smoke-inhalation injury. Bronchial blood flow markedly increases immediately after inhalational injury. This study examines whether the ablation of the bronchial artery attenuates pathophysiological changes and improves survival after burn and smoke-inhalational injury in an ovine model. Acute lung injury was induced by 40% total body surface-area third-degree cutaneous burn and cotton smoke inhalation (48 breaths of cotton smoke, <40 degrees C) under deep anaesthesia. Twelve adult female sheep were divided into two groups: (1) sham (injured, non-ablated bronchial artery, n=6); (2) ablation (injured, ablated bronchial artery, n=6). Ablation of the bronchial artery was performed 72 h before the injury. The experiment was continued for 96 h. Burn and smoke-inhalation injury significantly increased regional blood flow in the bronchi. Ablation of the bronchial artery significantly reduced acute regional blood flow increases in the proximal and distal bronchi. All animals in the ablation group survived to 96 h. Four of these were successfully weaned off the ventilator. Three animals of the sham group met standardised euthanasia criteria at 60 h, while another met the criteria at 78 h. The lung wet-to-dry weight ratio, histology score and myeloperoxidase (MPO) activity were significantly increased by the insult, but ablation of the bronchial artery attenuated these changes. Burn and smoke-inhalation injury induced a significant increase in bronchial blood flow and accelerated airway obstruction, pulmonary vascular changes, pulmonary oedema and pulmonary dysfunction. Ablated bronchial circulation attenuated these pathophysiological changes.

gamma-Tocopherol nebulization by a lipid aerosolization device improves pulmonary function in sheep with burn and smoke inhalation injury

Fire accident victims who sustain both thermal injury to skin and smoke inhalation have gross evidence of systemic and pulmonary oxidant damage and acute lung injury. We hypothesized that gamma-tocopherol (gT), a reactive O(2) and N(2) scavenger, when delivered into the airway, would attenuate lung injury induced by burn and smoke inhalation. Acute lung injury was induced in chronically prepared, anesthetized sheep by 40% total burn surface area, third-degree skin burn and smoke insufflation (48 breaths of cotton smoke, <40 degrees C). The study groups were: (1) Sham (not injured, flaxseed oil (FO)-nebulized, n=6); (2) SA-neb (injured, saline-nebulized, n=6); (3) FO-neb (injured, FO-nebulized, n=6); and (4) gT+FO-neb (injured, gT and FO-nebulized, n=6). Nebulization was started 1 h postinjury, and 24 ml of FO with or without gT (51 mg/ml) was delivered into airways over 47 h using our newly developed lipid aerosolization device (droplet size: 2.5-5 microm). The burn- and smoke inhalation-induced pathological changes seen in the saline group were attenuated by FO nebulization; gT addition further improved pulmonary function. Pulmonary gT delivery along with a FO source may be a novel effective treatment strategy in management of patients with acute lung injury.

Combined anticoagulants ameliorate acute lung injury in sheep after burn and smoke inhalation

Burn and smoke inhalation-related multiple organ dysfunction is associated with a severe fall in the plasma concentration of antithrombin. Therefore the aim of the present study was to test the hypothesis that intravenous administration of recombinant human antithrombin in combination with aerosolized heparin will ameliorate acute lung injury in sheep exposed to cutaneous burn and smoke inhalation. Sheep were prepared operatively for study and, 7 days post-surgery, sheep were given a cutaneous burn (40% of total body surface area, third-degree burn) and insufflated with cotton smoke (48 breaths, <40 degrees C) under halothane anaesthesia. After injury, sheep were placed on a ventilator and resuscitated with Ringer's lactate solution. The animals were divided into three groups: sham group (non-injured and non-treated; n=6), saline group (injured and received saline; n=6) and rhAT.iv.+Hep group [injured and treated with rhAT (recombinant human antithrombin) and heparin; n=6]. In the rhAT.iv.+Hep group, rhAT was infused continuously for 48 h starting 1 h post-injury with a dose of 0.34 mg.h(-1).kg(-1) of body weight and heparin (10000 units) was aerosolized every 4 h starting at 1 h post-injury. The experiment lasted 48 h. Haemodynamics were stable in sham group, whereas the saline-treated sheep developed multiple signs of acute lung injury, including decreased pulmonary gas exchange, increased inspiratory pressures, extensive airway obstruction and increased pulmonary oedema. These pathological changes were associated with a severe fall in plasma antithrombin concentration, lung tissue accumulation of leucocytes and excessive production of NO. Treatment of injured sheep with anticoagulants attenuated all of the pulmonary pathophysiology observed. In conclusion, the results provide definitive evidence that anticoagulant therapy may be a novel and effective treatment tool in the management of burn patients with concomitant smoke inhalation injury.

The role of the bronchial circulation in the acute lung injury resulting from burn and smoke inhalation

Smoke inhalation in burn patients is a serious medical problem around the world. Inhalation injury increases mortality in addition to increasing infections, ventilator-days, and hospital stays. There are also large numbers of patients subjected to smoke inhalation without burns from cooking fires, burning crops and forest fires. The injury results in a fall in arterial oxygenation as a result of airway blockade, increased pulmonary transvascular fluid flux and loss of hypoxic pulmonary vasoconstriction. The changes in cardiopulmonary function are mediated at least in part by reactive oxygen and nitrogen species. Nitric oxide (NO) is generated by both inducible and constitutive isoforms of nitric oxide synthase (NOS). NO combines with superoxide to form reactive nitrogen species such as peroxynitrite. These reactive nitrogen species can be detected by measuring their reaction products such as 3-nitrotyrosine. The latter is elevated in the airway following smoke/burn injury. The control of NO formation involves poly (ADP ribose) polymerase (PARP) and its ability to up-regulate the activity of nuclear transcription factors through ribosylation. Present data also support a major role for the bronchial circulation in the injury since blockade of bronchial blood flow will also minimize the pulmonary injury. The data suggest that cytotoxins or activated cells are formed in the airway and carried to the parenchyma. These materials cause the formation of oedema and a reduction of PaO(2).

Effect of inhaled nitric oxide on pulmonary vascular hyperpermeability in sheep following smoke inhalation

Smoke inhalation increases mortality and morbidity in burn patients. We have reported that smoke inhalation increases lung lymph flow, an index of pulmonary transvascular fluid flux and decreases reflection coefficient, an index of microvascular permeability to protein. Nitric oxide has been reported to decrease microvascular permeability to protein. We hypothesize that inhaled nitric oxide decreases pulmonary microvascular hyperpermeability following smoke inhalation. Sheep were prepared for study with a chronic lung lymph fistula, Swan-Ganz, left atrial, and femoral arterial catheters. Occluders were placed on pulmonary veins to measure reflection coefficient. All animals were insufflated with 4 x 12 breaths of cotton smoke. Sheep were randomly divided into two groups: NO (injured, treated with nitric oxide (40 ppm) inhalation, n=6) and control (injured, not treated, n=6). Nitric oxide inhalation was started 22 h after the insult. Control animals showed an increase in lung lymph flow, and lung water content. These changes were associated with marked increase in pulmonary microvascular resistance, pulmonary artery pressure, and decrease in reflection coefficient. Nitric oxide inhalation ameliorated the above-mentioned pathological changes. The results suggest that nitric oxide inhalation has potential for beneficial effect in the treatment of patients suffering from smoke inhalation.

Assessment of oxidative stress in lungs from sheep after inhalation of wood smoke

To elucidate potential dose-dependent mechanisms associated with wood smoke inhalation injury, the present study evaluated antioxidant status and the extent of pulmonary injury in sheep after graded exposure to smoke. Adult, male sheep (n=4-5 per group) were anesthetized and received 0, 5, 10 or 16 units of cooled western pine bark smoke, corresponding to 0, 175, 350 and 560 s, respectively, of smoke dwell time in the airways and lung. Smoke was mixed at a 1:1 ratio with 100% O2 to minimize hypoxia. Plasma and expired breath samples were collected pre-smoke, and 6, 12, 18, 24, 36 and 48 h after smoke exposure. Sheep were euthanatized 48 h after smoke exposure and lung and airway sections were evaluated histologically for injury and biochemically for indices of oxidative stress. Plasma thiobarbituric acid reactive substances (TBARS) were 66 and 69% higher than controls after moderate and severe smoke exposure at 48 h, whereas total antioxidant potential was not statistically different among groups at any time after exposure. Lung TBARS showed a dose-dependent response to smoke inhalation and were approximately 2-, 3- and 4-fold higher, respectively, than controls after exposure to 5, 10 and 16 units of smoke. Lung myeloperoxidase (MPO) activity was also higher in smoke-exposed animals than controls, and MPO activity was markedly elevated (19- and 22-fold higher than controls in right apical and medial lobes) in response to severe smoke exposure. Smoke exposure also induced a dose-dependent injury to tracheobronchial epithelium and lung parenchyma. Taken together these data show that few indices of oxidative stress responded in a dose-dependent manner to graded doses of smoke inhalation, although most of the indices measured in lung were affected by the highest dose of smoke. Additional time course studies are necessary to determine whether these oxidants are a cause or a consequence of the airway and lung injury associated with exposure to wood smoke.

Effect of poly(ADP ribose) synthetase inhibition on burn and smoke inhalation injury in sheep

We investigated the role of the nuclear enzyme poly (ADP ribose) synthetase (PARS) in the pathogenesis of combined burn and smoke inhalation (burn/smoke) injury in an ovine model. Eighteen sheep were operatively prepared for chronic study. PARS inhibition was achieved by treatment with a novel and selective PARS inhibitor INO-1001. The PARS inhibitor attenuated 1) lung edema formation, 2) deterioration of gas exchange, 3) changes in airway blood flow, 4) changes in airway pressure, 5) lung histological injury, and 6) systemic vascular leakage. Lipid oxidation and plasma nitrite/nitrate (stable breakdown products of nitric oxide) levels were suppressed with the use of INO-1001. We conclude that PARS inhibition attenuates various aspects of the pathophysiological response in a clinically relevant experimental model of burn/smoke inhalation injury.

Combined Smoke Inhalation and Scald Burn in the Rat

The combination of burn injury with smoke inhalation from fires significantly increases mortality. The mechanism of increased mortality is poorly understood but has been associated with multiple organ dysfunction syndrome, including cardiac dysfunction. Impaired cardiac function correlates with decreased survival in burn patients. We investigated smoke inhalation from burning cotton combined with a 40% body surface area, third-degree burn during the first 4 hours after injury in rats. In the early phase after injury, burn caused a significant rise in lung neutrophil infiltration but no increase in lung water. Smoke led to a rise in lung water but only a mild increase in neutrophil infiltration. Combined smoke and burn did not increase neutrophil accumulation or lung water above that which occurred with either injury alone. Only in combined smoke and burn was there a drop in cardiac output and stroke volume with pulmonary edema and lung neutrophil influx.

Effects of rolling inhibition on smoke inhalation injury

Inhalation of chemical and particulate products of smoke is one of the principal determinant of mortality following burn injury. Inflammatory responses have been implicated in the pathogenesis of lung injury after smoke inhalation. In the current study, we tested the inhibitory effect of Fucoidin on the neutrophil rolling stage of inflammatory response and determined the degree of pulmonary injury. Fifteen rats were divided into three groups: sham group (N: 5) of rats inhaled room air; control group (N: 5) inhaled smoke, and experimental group inhaled smoke and received Fucoidin. All the rats were sacrificed 24h after smoke inhalation. The trachea and lungs were removed totally; samples for histopathological and biochemical (myeloperoxidase (MPO)) analysis were taken from each lung and trachea. Morphologic studies using light and electron microscopes showed a decrease in lung parenchymal and tracheoepithelial injury in the experiment group of rats. Also, biochemical analysis of tissue MPO was significantly lower in test group than in control group. These results suggest that the inhibition of neutrophil rolling leads to a reduction of neutrophil invasion to pulmonary parenchyma and trachea, which may be beneficial for attenuating neutrophil mediated inhalation injury.

Role of anti-L-selectin antibody in burn and smoke inhalation injury in sheep

We hypothesized that the antibody neutralization of L-selectin would decrease the pulmonary abnormalities characteristic of burn and smoke inhalation injury. Three groups of sheep (n = 18) were prepared and randomized: the LAM-(1-3) group (n = 6) was injected intravenously with 1 mg/kg of leukocyte adhesion molecule (LAM)-(1-3) (mouse monoclonal antibody against L-selectin) 1 h after the injury, the control group (n = 6) was not injured or treated, and the nontreatment group (n = 6) was injured but not treated. All animals were mechanically ventilated during the 48-h experimental period. The ratio of arterial PO2 to inspired O2 fraction decreased in the LAM-(1-3) and nontreatment groups. Lung lymph flow and pulmonary microvascular permeability were elevated after injury. This elevation was significantly reduced when LAM-(1-3) was administered 1 h after injury. Nitrate/nitrite (NO(x)) amounts in plasma and lung lymph increased significantly after the combined injury. These changes were attenuated by posttreatment with LAM-(1-3). These results suggest that the changes in pulmonary transvascular fluid flux result from injury of lung endothelium by polymorphonuclear leukocytes. In conclusion, posttreatment with the antibody for L-selectin improved lung lymph flow and permeability index. L-selectin appears to be principally involved in the increased pulmonary transvascular fluid flux observed with burn/smoke insult. L-selectin may be a useful target in the treatment of acute lung injury after burn and smoke inhalation.

Cell adhesion molecules, leukocyte trafficking, and strategies to reduce leukocyte infiltration

Leukocyte-endothelial cell interactions are mediated by various cell adhesion molecules. These interactions are important for leukocyte extravasation and trafficking in all domestic animal species. An initial slowing of leukocytes on the vascular endothelium is mediated by selectins. This event is followed by (1) activation of beta2 integrins after leukocyte exposure to cytokines and pro-inflammatory mediators, (2) adherence of leukocyte beta2 integrins to vascular endothelial ligands (eg, intercellular adhesion molecule-1 [ICAM-1]), (3) extravasation of leukocytes into tissues through tight junctions of endothelial cells mediated by platelet and endothelial cell adhesion molecule-1 (PECAM-1), and (4) perivascular migration through the extracellular matrix via beta1 integrins. Inhibiting excessive leukocyte egress and subsequent free radical-mediated damage caused by leukocyte components may attenuate or eliminate tissue damage. Several methods have been used to modify leukocyte infiltration in various animal models. These methods include nonspecific inhibition of pro-inflammatory mediators and adhesion molecules by nonsteroidal anti-inflammatory drugs (NSAIDs) and glucocorticoids, inhibition of cytokines and cytokine receptors, and inhibition of specific types of cell adhesion molecules, with inhibitors such as peptides and antibodies to beta2 integrins, and inhibitors of selectins, ICAMs, and vascular cell adhesion molecule-1 (VCAM-1). By understanding the cellular and molecular events in leukocyte-endothelial cell interactions, therapeutic strategies are being developed in several animal models and diseases in domestic animal species. Such therapies may have clinical benefit in the future to overcome tissue damage induced by excessive leukocyte infiltration.

[Initial shock from burns. Physiopathology: therapeutic principles]

Widespread destruction of the skin induces a large necrotic mass and a break of the skin barrier. It also leads to an intense inflammatory reaction. This activates keratinocytes, endothelial cells and neutrophils. Certain mediators (e.g. endothelin, histamine, bradykinin, serotonin, catecholamines, vasopressin, prostaglandins, cytokines and nitrogen monoxide) are thus released in large quantities and act both at the site of the burns and at a distance. The abnormally high level of albumin in the capillary wall and the increased capacity of absorption of the interstitial areas around the burns are the main abnormalities observed. This results in a hypovolemia associated with a hemoconcentration, hyponatremia, hypoalbuminemia, systemic vasoconstriction and myocardial malfunction, which is difficult to evidence. During the initial phase, the major risk is the appearance of hypovolemic shock, which is rapidly irreversible if early treatment is not administered. Vascular filling with iso- or hyper-osmolar sodium crystalloids, associated with buffer solutions, is the first line. There is still debate regarding the best moment at which to give albumin. A hyperkinetic shock may occur after several hours and despite the filling. The symptoms are tachycardia, increased heart rate and a dramatic decrease in systemic vascular resistance. This may lead to metabolic acidosis and multi-organ failure. Study of the hemodynamic profile of the patient allows the rational use of pressor amines and haemodialysis.

Role of nitric oxide in myocardial dysfunction after combined burn and smoke inhalation injury

This study tested the hypothesis that nitric oxide (NO) synthesized from inducible NO synthase (iNOS) is responsible for the cardiac dysfunction observed after burn and smoke inhalation injury. Twelve sheep received 40% third-degree burn and smoke inhalation under halothane anesthesia. The animals were divided into two groups: a MEG group [iNOS was inhibited with mercaptoethylguanidine (MEG), a selective inhibitor of iNOS, n=6] and a control group (n=6). The control group showed a significant increase in NO(2)(-)/NO(3)(-) (NO(x)) concentration, metabolite of NO, in plasma after 24 h, whereas the MEG group did not. In the control group, cardiac depression was observed immediately after injury associated with hemoconcentration. Cardiac function returned to a normal level within 6 h following injury. In the control group cardiac dysfunction was observed again after 24 h although the hemoconcentration peaked at 24 h after injury and then began to resolve. In the MEG group, cardiac depression and hemoconcentration were not observed. The present data suggest that cardiac depression seen with this combination injury consists of two phases and that the later phase is mediated by iNOS-NO.

Shed L-selectin (sCD62L) load in trauma patients

BACKGROUND

Low circulating plasma concentrations of the leukocyte adhesion molecule L-selectin (sCD62L) were found to be associated with an increased risk for subsequent lung failure and case fatality after severe trauma. The objective of this study was to determine the robustness of soluble L-selectin, correcting for a broad spectrum of physiological variables.

METHODS

Patients with suspected multiple and/or trunk injuries were enrolled into this study over a 1-year period. Plasma samples were obtained on hospital presentation, and circulating soluble L-selectin was measured with a commercially available ELISA kit. Study records comprised all relevant clinical and laboratory data. Thirty-day survival rate, subsequent acute lung failure, and nosocomial pneumonia were defined as study endpoints. Statistical analysis was performed using multivariate logistic regression models.

RESULTS

Seventy patients with a mean age of 35.51 years (range, 10-87 years) and a mean ISS score of 36.61 (95% CI, 31.08-42.14) entered the study. Eleven patients died, leading to an attributable mortality of 15.70%. L-Selectin levels did not differ between survivors and nonsurvivors. Five patients progressed to acute lung injury, whereas 11 patients developed hospital-acquired pneumonia. Lower L-selectin levels indicated patients at risk for lung injury with a relative odds estimated at 4.43 (P = 0.017). Statistical significance diminished in the multivariate model. In contrast, plasma concentrations of circulating sCD62L were significantly decreased in patients developing nosocomial pneumonia (P = 0.023), with a twofold increased relative odds (OR, 1.96; 95% CI, 0.51-7.50). No effect modification was observed by the included covariables.

CONCLUSIONS

The results of this study highlight the independent predictive value of initially decreased soluble L-selectin levels for the identification of patients susceptible to subsequent respiratory complications after severe trauma.

Pathophysiological analysis of combined burn and smoke inhalation injuries in sheep

We investigated the pathophysiological alterations seen with combined burn and smoke inhalation injuries by focusing on pulmonary vascular permeability and cardiopulmonary function compared with those seen with either burn or smoke inhalation injury alone. To estimate the effect of factors other than injury, the experiments were also performed with no injury in the same experimental setting. Lung edema was most severe in the combined injury group. Our study revealed that burn injury does not affect protein leakage from the pulmonary microvasculature, even when burn is associated with smoke inhalation injury. The severity of lung edema seen with the combined injury is mainly due to augmentation of pulmonary microvascular permeability to fluid, not to protein. Cardiac dysfunction after the combined injury consisted of at least two phases. An initial depression was mostly related to hypovolemia due to burn injury. It was improved by a large amount of fluid resuscitation. The later phase, which was indicated to be a myocardial contractile dysfunction independent of the Starling equation, seemed to be correlated with smoke inhalation injury.

Effects of selectin-sialyl Lewis blockade on mesenteric microvascular permeability associated with cardiopulmonary bypass

OBJECTIVES

Cardiopulmonary bypass is associated with an inflammatory response that is associated with a neutrophil-mediated microvascular barrier injury. We studied the effects of blocking neutrophil-endothelial tethering on microvascular permeability and edema formation during cardiopulmonary bypass. Using a selectin antagonist that prevents interactions with their ligands, we hypothesized that there would be less neutrophil infiltration into the tissue and a reduction in microvascular permeability and edema formation.

METHODS

A canine mesenteric lymphatic fistula was created to measure Starling forces and to determine microvascular permeability. Normothermic, atrial-femoral cardiopulmonary bypass was initiated (70-90 mL. kg(-1). min(-1)). Intestinal tissue water was determined with microgravimetry. Ileal tissue myeloperoxidase was measured as an index of neutrophil tissue infiltration. One experimental group received the selectin antagonist TBC 1269 before the initiation of bypass, and the control group received saline solution.

RESULTS

There was a modest increase in microvascular permeability in both groups, as evidenced by significantly increased transvascular protein clearance and a trend toward a decrease in reflection coefficient. There were no differences in the experimental group compared with the control group. Ileal tissue myeloperoxidase levels were lower in the experimental group than in the control group.

CONCLUSIONS

The selectin antagonist TBC 1269 reduces neutrophil infiltration into the ileum without altering ileal microvascular permeability or edema associated with cardiopulmonary bypass.