Pulmonary changes in a mouse model of combined burn and smoke inhalation-induced injury.

The morbidity and mortality of burn victims increase when burn injury is combined with smoke inhalation. The goal of the present study was to develop a murine model of burn and smoke inhalation injury to more precisely reveal the mechanistic aspects of these pathological changes. The burn injury mouse group received a 40% total body surface area third-degree burn alone, the smoke inhalation injury mouse group received two 30-s exposures of cotton smoke alone, and the combined burn and smoke inhalation injury mouse group received both the burn and the smoke inhalation injury. Animal survival was monitored for 120 h. Survival rates in the burn injury group, the smoke inhalation injury group, and the combined injury group were 70%, 60%, and 30%, respectively. Mice that received combined burn and smoke injury developed greater lung damage as evidenced by histological changes (septal thickening and interstitial edema) and higher lung water content. These mice also displayed more severely impaired pulmonary gas exchange [arterial PO2 (PaO2)/inspired O2 fraction (FiO2)<200]. Lung myeloperoxidase activity was significantly higher in burn and smoke-injured animals compared with the other three experimental groups. Plasma NO2-/NO3-, lung inducible nitric oxide synthase (iNOS) activity, and iNOS mRNA increased with injury; however, the burn and smoke injury group exhibited a higher response. Severity of burn and smoke inhalation injury was associated with more pronounced production of nitric oxide and accumulation of activated leukocytes in lung tissue. The murine model of burn and smoke inhalation injury allows us to better understand pathophysiological mechanisms underlying cardiopulmonary morbidity secondary to burn and smoke inhalation injury.     

Carboxyhemoglobin formation following smoke inhalation injury in sheep is interrelated with pulmonary shunt fraction

Carboxyhemoglobin (COHb) formation is triggered by the inducible isoform of heme oxygenase (HO-1) catalyzing carbon monoxide (CO) production through breakdown of heme molecules, exposure to CO or both. In the setting of CO poisoning, COHb is regarded as a reliable marker characterizing both severity of injury and efficacy of treatment strategies. This study was designed as a prospective laboratory experiment to elucidate potential interdependencies between COHb generation, oxygenation, and pulmonary shunt fraction (Qs/Qt) in an ovine model of smoke inhalation injury. Chronically instrumented ewes (n=15) were repeatedly subjected to cotton smoke (4 x 12 breaths) according to an established protocol. This approach resulted in a progressive increase in COHb formation that was interrelated with the degree of Qs/Qt (P<0.001) and inversely correlated with both arterial and mixed venous HbO(2) saturation (r=-0.96 and -0.93). Although the arteriovenous COHb gradient successively decreased over time, COHb determined in venous blood underestimated the arterial content.     

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.     

A murine model of sepsis following smoke inhalation injury

Acute lung injury (ALI) by smoke inhalation with subsequent pneumonia and sepsis represents a major cause of morbidity and mortality in burn patients. The aim of the present study was to develop a murine model of ALI and sepsis to enhance the knowledge of mechanistic aspects and pathophysiological changes in patients with these injuries. In deeply anesthetized female C57BL/6 mice, injury was induced by four sets of cotton smoke using an inhalation chamber. Afterward, live Pseudomonas aeruginosa (3.2 × 10⁷ colony-forming units) was administered intranasally. The indicated dose of bacteria was determined based on the results of a dose-response study (n = 47). The following study groups were monitored for survival over 96 h: (1) sham injury group, (2) only smoke inhalation group, (3) only bacteria group, and (4) smoke inhalation plus bacteria group. Each group included 10 mice. The survival rates were 100%, 90%, 30%, and 10%, respectively. The double hit injury was associated with excessive releases of pro-inflammatory cytokines in the plasma, and enhanced neutrophil accumulation, increased lipid peroxidation, and excessive formation of reactive nitrogen species in the lung. In mice receiving only smoke inhalation injury, no systemic cytokine release and increased lung tissue lipid peroxidation were observed. However, smoke alone significantly increased neutrophil accumulation and formation of reactive nitrogen species in lung tissue. In conclusion, bacterial pneumonia is predominantly responsible for mortality and morbidity in this novel murine model of smoke inhalation and pulmonary sepsis. Reactive oxygen and nitrogen species mediate the severity of lung injury.     

Beneficial pulmonary effects of a metalloporphyrinic peroxynitrite decomposition catalyst in burn and smoke inhalation injury

During acute lung injury, nitric oxide (NO) exerts cytotoxic effects by reacting with superoxide radicals, yielding the reactive nitrogen species peroxynitrite (ONOO(-)). ONOO(-) exerts cytotoxic effects, among others, by nitrating/nitrosating proteins and lipids, by activating the nuclear repair enzyme poly(ADP-ribose) polymerase and inducing VEGF. Here we tested the effect of the ONOO(-) decomposition catalyst INO-4885 on the development of lung injury in chronically instrumented sheep with combined burn and smoke inhalation injury. The animals were randomized to a sham-injured group (n = 7), an injured control group [48 breaths of cotton smoke, 3rd-degree burn of 40% total body surface area (n = 7)], or an injured group treated with INO-4885 (n = 6). All sheep were mechanically ventilated and fluid-resuscitated according to the Parkland formula. The injury-related increases in the abundance of 3-nitrotyrosine, a marker of protein nitration by ONOO(-), were prevented by INO-4885, providing evidence for the neutralization of ONOO(-) action by the compound. Burn and smoke injury induced a significant drop in arterial Po(2)-to-inspired O(2) fraction ratio and significant increases in pulmonary shunt fraction, lung lymph flow, lung wet-to-dry weight ratio, and ventilatory pressures; all these changes were significantly attenuated by INO-4885 treatment. In addition, the increases in IL-8, VEGF, and poly(ADP-ribose) in lung tissue were significantly attenuated by the ONOO(-) decomposition catalyst. In conclusion, the current study suggests that ONOO(-) plays a crucial role in the pathogenesis of pulmonary microvascular hyperpermeability and pulmonary dysfunction following burn and smoke inhalation injury in sheep. Administration of an ONOO(-) decomposition catalyst may represent a potential treatment option for this injury.     

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.     

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.     

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

The effects of a monoclonal antibody against L-selectin [leukocyte adhesion molecule (LAM)1-3] on microvascular fluid flux were determined in conscious sheep subjected to a combined injury of 40% third-degree burn and smoke inhalation. This combined injury induced a rapid increase in systemic prefemoral lymph flow (sQlymph) from the burned area and a delayed-onset increase in lung lymph flow. The initial increase in sQlymph was associated with an elevation of the lymph-to-plasma oncotic pressure ratio; consequently, it leads to a predominant increase in the systemic soft tissue permeability index (sPI). In an untreated control group, the increased sPI was sustained beyond 24 h after injury. Pretreatment with LAM1-3 resulted in earlier recovery from the increased sPI, although the initial responses in sQlymph and sPI were identical to those in the nontreatment group. The delayed-onset lung permeability changes were significantly attenuated by pretreatment with LAM1-3. These findings indicate that both leukocyte-dependent and -independent mechanisms are involved in the pathogenesis that occurs after combined injury with burn and smoke inhalation.     

Vitamin E attenuates acute lung injury in sheep with burn and smoke inhalation injury

Abstract

Introduction: A decrease in α-tocopherol (vitamin E) plasma levels in burn patients is typically associated with increased mortality. We hypothesized that vitamin E supplementation (α-tocopherol) would attenuate acute lung injury induced by burn and smoke inhalation injury.

Materials and Methods: Under deep anesthesia, sheep (33 ± 5 kg) were subjected to a flame burn (40% total body surface area, third degree) and inhalation injury (48 breaths of cotton smoke, < 40°C). Half of the injured group received α-tocopherol (1000 IU vitamin E) orally, 24 h prior to injury. The sham group was neither injured nor given vitamin E. All three groups (n = 5 per group) were resuscitated with Ringer's lactate solution (4 ml/kg/%burn/24 h), and placed on a ventilator (PEEP = 5 cmH₂O; tidal volume = 15 ml/kg) for 48 h.

Results: Plasma α-tocopherol per lipids doubled in the vitamin E treated sheep. Vitamin E treatment prior to injury largely prevented the increase in pulmonary permeability index and moderated the increase in lung lymph flow (52.6 ± 6.2 ml/min, compared with 27.3 ± 6.0 ml/min, respectively), increased the PaO₂/FiO₂ ratio, ameliorated both peak and pause airway pressure increases, and decreased plasma conjugated dienes and nitrotyrosine.

Conclusions: Pretreatment with vitamin E ameliorated the acute lung injury caused by burn and smoke inhalation exposure.     

Oxidants and the pathophysiology of burn and smoke inhalation injury.

A skin burn is a common traumatic injury that results in both local tissue damage and a systemic mediator-induced response. There is evidence of both local and systemic oxidant changes manifested by lipid peroxidation in animal burn models and also in burned man. Both increased xanthine oxidase and neutrophil activation appear to be the oxidant sources. Animal studies have also demonstrated decreased burn edema, and also decreased distant organ dysfunction with the use of antioxidants, suggesting a cause-and-effect relationship, which needs to be tested in man. Smoke inhalation injury, a chemical injury to the airways caused by incomplete products of combustion, is frequently seen in conjunction with a body burn. Lipid peroxidation, both in lung and in distant organs, is also seen with this injury. The combined body burn and smoke inhalation injury lead to a marked increase in mortality rate and also an increase in the degree of generalized oxidant release and lipid peroxidation. Although data in man are limited, the available information, along with that from animal research on burns and smoke inhalation, indicates oxidants may well play a key role, and antioxidants may be of clinical therapeutic use.     

Inhibition of JNK activation prolongs survival after smoke inhalation from fires

Initial injury from smoke inhalation is mainly to the trachea and bronchi and is characterized by mucosal hyperemia and increased microvascular permeability, exfoliation of epithelial lining, mucous secretion, mucous plugging, and an acute inflammatory cell influx. In this study, we explore the role of the c-Jun N-terminal protein kinase (JNK) pathway in smoke inhalation lung injury using a rat model of exposure to smoke from burning cotton. Male Sprague-Dawley rats were exposed to smoke from burning cotton for 15 min, and 1 h after injury a JNK inhibitor (SP-600125) or vehicle was injected. We measured neutrophil influx, cytokine release, percent of apoptotic cells, airway plugging, and survival. Administration of a JNK inhibitor 1 h after smoke inhalation decreased airway apoptosis, mucous plugging, influx of inflammatory cells, and the release of cytokines and significantly prolonged animal survival (P < 0.05). These in vivo data show that the JNK pathway plays a critical role in smoke-induced lung injury and offer an attractive therapeutic approach for this injury.     

Effect of smoke inhalation on viscoelastic properties and ventilation distribution in sheep.

Smoke inhalation injuries are the leading cause of mortality from burn injury. Airway obstruction due to mucus plugging and bronchoconstriction can cause severe ventilation inhomogeneity and worsen hypoxia. Studies describing changes of viscoelastic characteristics of the lung after smoke inhalation are missing. We present results of a new smoke inhalation device in sheep and describe pathophysiological changes after smoke exposure. Fifteen female Merino ewes were anesthetized and intubated. Baseline data using electrical impedance tomography and multiple-breath inert-gas washout were obtained by measuring ventilation distribution, functional residual capacity, lung clearance index, dynamic compliance, and stress index. Ten sheep were exposed to standardized cotton smoke insufflations and five sheep to sham smoke insufflations. Measured carboxyhemoglobin before inhalation was 3.87 +/- 0.28% and 5 min after smoke was 61.5 +/- 2.1%, range 50-69.4% (P < 0.001). Two hours after smoke functional residual capacity decreased from 1,773 +/- 226 to 1,006 +/- 129 ml and lung clearance index increased from 10.4 +/- 0.4 to 14.2 +/- 0.9. Dynamic compliance decreased from 56.6 +/- 5.5 to 32.8 +/- 3.2 ml/cmH(2)O. Stress index increased from 0.994 +/- 0.009 to 1.081 +/- 0.011 (P < 0.01) (all means +/- SE, P < 0.05). Electrical impedance tomography showed a shift of ventilation from the dependent to the independent lung after smoke exposure. No significant change was seen in the sham group. Smoke inhalation caused immediate onset in pulmonary dysfunction and significant ventilation inhomogeneity. The smoke inhalation device as presented may be useful for interventional studies.     

Inducible nitric oxide synthase dimerization inhibitor prevents cardiovascular and renal morbidity in sheep with combined burn and smoke inhalation injury

Inducible nitric oxide synthase (iNOS) is implicated in the pathogenesis of acute respiratory distress syndrome (ARDS). ARDS treatment is frequently complicated by significant extrapulmonary comorbidity. This study was designed to clarify the role of iNOS in mediating extrapulmonary comorbidity in sheep after combined burn and smoke inhalation injuries using a potent and highly selective iNOS dimerization inhibitor, BBS-2. Twenty-two female sheep were operatively prepared. After 5 days of recovery, tracheostomy was performed under ketamine-halothane anesthesia. Sheep were given a 40% total body surface third-degree burns and insufflated with cotton smoke (48 breaths, <40 degrees C). Sheep were divided into four groups: noninjured and nontreated (sham group; n = 6), noninjured but treated with BBS-2 (sham/BBS-2 group; n = 4), injured but nontreated (control group, n = 6), and injured but treated with 100 microg.kg-1.h-1 BBS-2 (BBS-2 group; n = 6). Evaluation was in a laboratory intensive care unit setting for 48 h. The sham group had stable cardiopulmonary and systemic hemodynamics. Control animals showed multiple signs of morbidity. Decreased left ventricular stroke work index and stroke volume index with elevated left atrial pressure indicated myocardial depression. Systemic vascular leak was evidenced by robust hemoconcentration, decreased plasma oncotic pressure, and increased transvascular fluid flux into the lymphatic system. Finally, severely impaired renal function (urinary output) was associated with adverse net fluid balance. Treatment with BBS-2 prevented all these morbidities without adversely effecting cardiovascular hemodynamics such as cardiac index and mean arterial pressure. The results identify a major role for iNOS in mediating extrapulmonary comorbidity in a clinically relevant and severe trauma model and support the use of highly selective iNOS inhibitors as novel treatments in critical care medicine.     

Administration of a synthetic antiprotease reduces smoke-induced lung injury.

Our previous studies suggest that a neutrophil-mediated inflammatory injury causes a major fraction of the pulmonary edema that occurs after smoke inhalation. Because activated neutrophils extrude cytotoxic proteases, the current study was conducted to evaluate the role of proteases in the pulmonary microvascular injury. Twelve sheep, instrumented for collection of lung lymph, were insufflated with cotton smoke. The sheep were treated 30 min after smoke inhalation with either gabexate mesilate (an inhibitor of serine proteases) or vehicle. Smoke inhalation resulted in an increased protease activity in the lung interstitium, as evidenced by decreases in both antiprotease activity and immunoreactive alpha 2-macroglobulin. Intravenous infusion of gabexate mesilate prevented the decrease in antiprotease activity. The protease inhibitor significantly attenuated the smoke-induced increase in transvascular fluid and protein flux, with untreated animals exhibiting 460% increases in flux compared with 180% in the inhibitor treated sheep. The protease inhibitor also eliminated the functional degradation in gas exchange that was observed in the untreated sheep. These studies strongly suggest that an increase in pulmonary proteolytic enzyme activity is responsible for a significant fraction of the degradation in microvascular integrity and gas exchange that is associated with smoke inhalation injury.     

Effects of allopurinol on smoke inhalation in the ovine model

We hypothesized that the pulmonary damage induced by smoke inhalation is the result of ischemic reperfusion injury. We determined the effect of allopurinol (xanthine oxidase inhibitor) on the pulmonary microvascular fluid flux in an ovine model after inhalation of cotton smoke (n = 13) and compared these data with those from untreated similarly smoke-injured (n = 7), as well as sham- (air, n = 9) smoked, animals and sheep given an equivalent dose of CO (n = 7). Smoke injury resulted in an increased lung lymph flow, lymph-to-plasma protein ratio, lung content of polymorphonuclear cells, and extravascular lung water (gravametric), in addition to histological evidence of tissue (pulmonary) edema and destruction. No significant difference was found in these variables between the sheep that were injured with smoke whether or not they were pretreated with allopurinol. The sham-smoked and CO-insufflated animals showed no significant changes in cardiopulmonary function or morphology. We conclude that there are few data to support a role of ischemic reperfusion injury in the pulmonary damage seen after smoke inhalation.     

Inhibition of neuronal nitric oxide synthase by 7-nitroindazole attenuates acute lung injury in an ovine model

Nitric oxide (NO) has been shown to play a major role in acute lung injury (ALI) after smoke inhalation. In the present study, we developed an ovine sepsis model, created by exposing sheep to smoke inhalation followed by instillation of bacteria into the airway, that mimics human sepsis and pneumonia. We hypothesized that the inhibition of neuronal NO synthase (nNOS) might be beneficial in treating ALI associated with this model. Female sheep (n = 26) were surgically prepared for the study and given a tracheostomy. This was followed by insufflation of 48 breaths of cotton smoke (40 degrees C) into the airway of each animal and subsequent instillation of live Pseudomonas aeruginosa [5 x 10(11) colony forming units (CFU)] into each sheep's lung. All sheep were mechanically ventilated using 100% O2. Continuous infusion of 7-nitroindazole (7-NI), an nNOS inhibitor, NG-monomethyl-l-arginine (l-NMMA), a nonspecific NOS inhibitor, or aminoguanidine (AG), an inducible NOS inhibitor, was started 1 h after insult. The administration of 7-NI improved pulmonary gas exchange (PaO2/FiO2; where PaO2 is arterial PO2 and FiO2 is fractional inspired oxygen concentration) and pulmonary shunt fraction and attenuated the increase in lung wet-to-dry weight ratio seen in the nontreated sheep. Histologically, 7-NI prevented airway obstruction. The increase in airway blood flow after injury in the nontreated group was significantly inhibited by 7-NI. The increase in plasma concentration of nitrate and nitrite (NOx) was inhibited by 7-NI as well. Posttreatment with l-NMMA improved the pulmonary gas exchange, but AG did not. The results of the present study show that nNOS may be involved in the pathogenesis of ALI after smoke inhalation injury followed by bacterial instillation in the airway.     

JNK activation is responsible for mucus overproduction in smoke inhalation injury

Background

Increased mucus secretion is one of the important characteristics of the response to smoke inhalation injuries. We hypothesized that gel-forming mucins may contribute to the increased mucus production in a smoke inhalation injury. We investigated the role of c-Jun N-terminal kinase (JNK) in modulating smoke-induced mucus secretion.

Methods

We intubated mice and exposed them to smoke from burning cotton for 15 min. Their lungs were then isolated 4 and 24 h after inhalation injury. Three groups of mice were subjected to the smoke inhalation injury: (1) wild-type (WT) mice, (2) mice lacking JNK1 (JNK1-/- mice), and (3) WT mice administered a JNK inhibitor. The JNK inhibitor (SP-600125) was injected into the mice 1 h after injury.

Results

Smoke exposure caused an increase in the production of mucus in the airway epithelium of the mice along with an increase in MUC5AC gene and protein expression, while the expression of MUC5B was not increased compared with control. We found increased MUC5AC protein expression in the airway epithelium of the WT mice groups both 4 and 24 h after smoke inhalation injury. However, overproduction of mucus and increased MUC5AC protein expression induced by smoke inhalation was suppressed in the JNK inhibitor-treated mice and the JNK1 knockout mice. Smoke exposure did not alter the expression of MUC1 and MUC4 proteins in all 3 groups compared with control.

Conclusion

An increase in epithelial MUC5AC protein expression is associated with the overproduction of mucus in smoke inhalation injury, and that its expression is related on JNK1 signaling.     

Macrophage migration inhibitory factor mediates late cardiac dysfunction after burn injury

We have recently demonstrated that macrophage migration inhibitory factor (MIF) is a myocardial depressant protein and that MIF mediates late, prolonged cardiac dysfunction after endotoxin challenge in mice. Because many factors, including endotoxin, have been implicated in the pathogenesis of cardiac dysfunction after burn injury, we tested the hypothesis that MIF might also be the mediator of prolonged cardiac dysfunction in this model. At 4 h after 40% total body surface area burn in anesthetized mice, serum MIF levels increased significantly compared with baseline (2.2-fold). This increase was accompanied by a significant decrease in cardiac tissue MIF levels (2.1-fold decrease compared with controls). This pattern was consistent with MIF release from preformed cytoplasmic stores in the heart and other organs. To determine whether MIF mediates cardiac dysfunction after burn injury, mice were pretreated with anti-MIF neutralizing monoclonal antibodies or isotype control antibodies. Beginning 4 h after burn injury (and continuing through 48 h), burned mice demonstrated a significantly depressed left ventricular shortening fraction of 38.6 +/- 1.8%, compared with the normal controls (56.0 +/- 2.6%). Mice treated with anti-MIF displayed an initial depression of cardiac function similar to nontreated animals but then showed rapid restoration of cardiac function with complete recovery by 24 h, which persisted for the duration of the protocol. This study is the first to demonstrate that MIF mediates late, prolonged cardiac dysfunction after burn injury and suggests that MIF blockade should be considered a therapeutic target for the treatment of burn injury.     

Pulmonary edema with smoke inhalation, undetected by indicator-dilution technique

Despite experimental evidence for an increase in extravascular lung water (EVLW) after inhalation injury, thermal-dye estimations of EVLW, extravascular thermal volume (EVTV), have repeatedly failed to demonstrate its presence in patients. This situation was evaluated in a sheep model. Under halothane anesthesia one lung was insufflated with cotton smoke and the other with air. EVTV values were 8.4 +/- 0.48 ml/kg at base line and were not elevated at 24 h after smoke inhalation (8.3 +/- 0.45 ml/kg; means +/- SE). Gravimetric analysis 24 h after smoke inhalation showed the development of edema in smoke-exposed lungs. The blood-free wet weight-to-dry weight ratio of the smoke-exposed lungs (5.4 +/- 0.32) was significantly higher compared with the contralateral unsmoked lungs (4.3 +/- 0.15; P less than or equal to 0.05). The thermal-dye technique thus underestimates EVLW. Poor perfusion of the smoke-exposed lungs 24 h after injury was demonstrated indirectly by killing a group of sheep with T-61, an agent that causes a dark red coloration of well-perfused lung areas, as well as directly by measurement of blood flow utilizing a radiolabeled microsphere technique. Thus the inability of the thermal-dye technique to detect the lung edema may be the result of poor perfusion of the injured lung.     

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.