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The lack of a clinically relevant animal models for research in facial nerve reconstruction is challenging. In this study, we investigated the surgical anatomy of the ovine sural nerve as a potential candidate for facial nerve reconstruction, and performed its histological quantitative analysis in comparison to the buccal branch (BB) of the facial nerve using cadaver and anesthetized sheep. The ovine sural nerve descended to the lower leg along the short saphenous vein. The length of the sural nerve was 14.3 ± 0.5 cm. The distance from the posterior edge of the lateral malleolus to the sural nerve was 7.8 ± 1.8 mm. The mean number of myelinated fibers in the sural nerve was significantly lower than that of the BB (2,311 ± 381vs. 5,022 ± 433, respectively. p = 0.003). The number of fascicles in the sural nerve was also significantly lower than in the BB (10.5 ± 1.7 vs. 21.3 ± 2.7, respectively. p = 0.007). The sural nerve was grafted to the BB with end-to-end neurorrhaphy under surgical microscopy in cadaver sheep. The surgical anatomy and the number of fascicles of the ovine sural nerve were similar of those reported in humans. The results suggest that the sural nerve can be successfully used for facial nerve reconstruction research in a clinically relevant ovine model.

Smoke inhalation injury promotes exfoliation of the upper airway columnar epithelium. Tracheal tissues from sheep 30 min after smoke exposure show intact epithelial areas, areas of epithelial disruption with loss of columnar cells and areas denuded of columnar cells. In intact areas detaching ciliated cells can be seen raised above the apical surface. This study aims to assess cell-specific toxicity by examining intact epithelium after inhalation injury. The junctional adhesion integrity between columnar and basal cells and the type of cells initially being displaced were also studied using light (LM) and transmission electron microscopy (TEM). TEM assessment of intact areas of sheep tracheal tissue (n=3) 30 min after exposure showed secretory cell toxicity including extrusion of cytoplasmic contents. In cells with severe secretory cell cytoplasmic disruption, loss of desmosomal junctions between the secretory and adjacent ciliated cells was evident. The number of desmosomes visible between columnar cells and basal cells was reduced (2.8 ± 1.8) in smoke-exposed animals compared to those in uninjured animals (5.0 ± 2.7), p=0.008. Serial sections of intact regions found 52 cells being displaced from the epithelium. All detaching cells were identified as ciliated cells. These studies show that the acute effects of inhalation injury include selective secretory cell toxicity which is associated with loss of junctional adhesion mechanisms and displacement of ciliated cells. Improved understanding of acute hypersecretory responses and epithelial integrity after exposure to toxic agents may improve understanding of epithelial fragility in airway disease.

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.

BackgroundHuman bone marrow-derived mesenchymal stem (stromal) cells (hMSCs) improve survival in mouse models of acute respiratory distress syndrome (ARDS) and reduce pulmonary oedema in a perfused human lung preparation injured with Escherichia coli bacteria. We hypothesised that clinical grade hMSCs would reduce the severity of acute lung injury (ALI) and would be safe in a sheep model of ARDS.MethodsAdult sheep (30-40 kg) were surgically prepared. After 5 days of recovery, ALI was induced with cotton smoke insufflation, followed by instillation of live Pseudomonas aeruginosa (2.5×10(11) CFU) into both lungs under isoflurane anaesthesia. Following the injury, sheep were ventilated, resuscitated with lactated Ringer's solution and studied for 24 h. The sheep were randomly allocated to receive one of the following treatments intravenously over 1 h in one of the following groups: (1) control, PlasmaLyte A, n=8; (2) lower dose hMSCs, 5×10(6) hMSCs/kg, n=7; and (3) higher-dose hMSCs, 10×10(6) hMSCs/kg, n=4.ResultsBy 24 h, the PaO2/FiO2 ratio was significantly improved in both hMSC treatment groups compared with the control group (control group: PaO2/FiO2 of 97±15 mm Hg; lower dose: 288±55 mm Hg (p=0.003); higher dose: 327±2 mm Hg (p=0.003)). The median lung water content was lower in the higher-dose hMSC-treated group compared with the control group (higher dose: 5.0 g wet/g dry [IQR 4.9-5.8] vs control: 6.7 g wet/g dry [IQR 6.4-7.5] (p=0.01)). The hMSCs had no adverse effects.ConclusionsHuman MSCs were well tolerated and improved oxygenation and decreased pulmonary oedema in a sheep model of severe ARDS.Trail registration numberNCT01775774 for Phase 1. NCT02097641 for Phase 2.

The effects of tiotropium bromide on ERK 1/2, SMAD 2/3 and NFκB signaling in bronchial submucosal gland (SMG) cells of sheep after smoke inhalation and burn injury (S + B) were studied. We hypothesized that tiotropium would modify intracellular signaling processes within SMG cells after injury. Bronchial tissues were obtained from uninjured (sham, n = 6), S + B injured sheep 48 h after injury ( n = 6), and injured sheep nebulized with tiotropium ( n = 6). The percentage (mean ± SD) of cells showing nuclear localization of phosphorylated ERK 1/2, pSMAD 2/3, and NFκB (p65) was determined by immunohistochemistry. Nuclear pERK 1/2 staining was increased in injured animals as compared to sham, (66 ± 20 versus 14 ± 9), p = 0.0022, as was nuclear pSMAD, 84 ± 10 versus 20 ± 10, p = 0.0022. There was a significant decrease in pERK 1/2 labeling in the tiotropium group compared to the injured group (31 ± 20 versus 66 ± 20, p = 0.013), and also a decrease in pSMAD labeling, 62 ± 17 versus 84 ± 10, p = 0.04. A significant increase for NFκB (p65) was noted in injured animals as compared to sham (73 ± 16 versus 7 ± 6, p = 0.0022). Tiotropium-treated animals showed decreased p65 labeling as compared to injured (35 ± 17 versus 74 ± 16, p = 0.02). The decrease in nuclear expression of pERK, pSMAD and NFκB molecules in SMG cells with tiotropium treatment is suggestive that their activation after injury is mediated in part through muscarinic receptors. [ABSTRACT FROM AUTHOR]

Background and Purpose: The present study investigated whether the pathophysiological changes induced by burn and smoke inhalation are modulated by parenteral administration of Na(2)S, a H(2)S donor.Experimental Approach: The study used a total of 16 chronically instrumented, adult female sheep. Na(2)S was administered 1 h post injury, as a bolus injection at a dose of 0.5 mg.kg(-1) and subsequently, as a continuous infusion at a rate of 0.2 mg.kg(-1).h(-1) for 24 h. Cardiopulmonary variables (mean arterial and pulmonary arterial blood pressure, cardiac output, ventricular stroke work index, vascular resistance) and arterial and mixed venous blood gases were measured. Lung wet-to-dry ratio and myeloperoxidase content and protein oxidation and nitration were also measured. In addition, lung inducible nitric oxide synthase expression and cytochrome c were measured in lung homogenates via Western blotting and enzyme-linked immunosorbent assay (elisa) respectively.Key Results: The H(2)S donor decreased mortality during the 96 h experimental period, improved pulmonary gas exchange and lowered further increase in inspiratory pressure and fluid accumulation associated with burn- and smoke-induced acute lung injury. Further, the H(2)S donor treatment reduced the presence of protein oxidation and 3-nitrotyrosine formation following burn and smoke inhalation injury.Conclusions and Implications: Parenteral administration of the H(2)S donor ameliorated the pulmonary pathophysiological changes associated with burn- and smoke-induced acute lung injury. Based on the effect of H(2)S observed in this clinically relevant model of disease, we propose that treatment with H(2)S or its donors may represent a potential therapeutic strategy in managing patients with acute lung injury. [ABSTRACT FROM AUTHOR]

Concomitant smoke inhalation trauma in burn patients is a serious medical problem. Previous investigations in our sheep model revealed that these injuries lead to significant airway hyperemia, enhanced pulmonary fluid extravasation, and severely impaired pulmonary function. However, the pathophysiological mechanisms are still not fully understood. The lung is innervated by sensory nerves containing peptides such as substance P and calcitonin gene-related peptide. Noxious stimuli in the airways can induce a neurogenic inflammatory response, which has previously been implicated in several airway diseases. Calcitonin gene-related peptide is known to be a potent vasodilator. We hypothesized that calcitonin gene-related peptide is also a mediator of the pulnionary reaction to toxic smoke and planned experiments to evaluate its role in this model. We tested the effects of pretreatment with a specific antagonist of the major receptor for calcitonin gene-related peptide (BIBN4096BS; 32 μg/kg, followed by continuous infusion of 6.4 μg·kg-1·h-1) until the animal was killed 48 h after injury in an established ovine model of burn (40% total body surface, third degree) and smoke inhalation (48 breaths, <40°C) injury. In treated animals (n = 7), the injury-related increases in tracheal blood flow and lung lymph flow were significantly attenuated compared with untreated controls (n = 5). Furthermore, the treatment significantly attenuated abnormalities in respiratory gas exchange. The data suggest that calcitonin gene-related peptide contributes to early airway hyperemia, transvascular fluid flux, and respiratory malfunction following ovine burn and smoke inhalation injury. Future studies will be needed to clarify the potential therapeutic benefit for patients with this injury. [ABSTRACT FROM AUTHOR]

Previous studies have indicated increased plasma levels of inducible nitric oxide synthase in lung. This study further examines the pulmonary expression of nitric oxide synthase (NOS) isoforms in an ovine model of acute lung injury induced by smoke inhalation and burn injury (S+B injury). Female range bred sheep (4 per group) were sacrificed at 4, 8, 12, 24, and 48 hours after injury and immunohistochemistry was performed in tissues for various NOS isoforms. The study indicates that in uninjured sheep lung, endothelial (eNOS) is constitutively expressed in the endothelial cells associated with the airways and parenchyma, and in macrophages. Similarly, neuronal (nNOS) is constitutively present in the mucous cells of the epithelium and in neurons of airway ganglia. In uninjured lung, inducible (iNOS) was present in bronchial secretory cells and macrophages. In tissue after S+B injury, new expression of iNOS was evident in bronchial ciliated cells, basal cells, and mucus gland cells. In the parenchyma, a slight increase in iNOS immunostaining was seen in type I cells at 12 and 24 hours after injury only. Virtually no change in eNOS or nNOS was seen after injury. [ABSTRACT FROM AUTHOR]

Objective: To investigate ceftazidime in acute lung injury (ALI) and sepsis.Design and Setting: Prospective, randomized, controlled animal study in an investigational ICU at a university hospital.Interventions: Eighteen female Merino sheep were prepared for chronic study and subjected to smoke inhalation and septic challenge according to an established protocol.Measurements and Results: Whereas global hemodynamics and oxygenation remained stable in sham animals (no injury, no treatment), the injury contributed to a hypotensive-hyperdynamic circulation in the control group (smoke inhalation and sepsis, no treatment), as indicated by a significant increase in cardiac index) and heart rate and a drop in mean arterial pressure. Treatment with ceftazidime (smoke inhalation and sepsis, treatment group) stabilized cardiac index and heart rate and attenuated the decrease in mean arterial pressure. The deterioration in PaO2/FiO2 ratio and pulmonary shunt fraction (Qs/Qt) was significantly delayed and blunted by ceftazidime. At 24 h after injury a significant increase in airway obstruction scores of bronchi and bronchioles in both injured groups was observed. Ceftazidime significantly reduced airway obstruction vs. control animals. Whereas plasma nitrate/nitrite levels increased similarly in the two injured groups, lung 3-nitrotyrosine content remained at the baseline level in the ceftazidime group.Conclusions: In ovine lung injury ceftazidime improves global hemodynamics and oxygenation not only by bacterial clearance but also via reduction in toxic nitrogen species such as 3-nitrotyrosine. Therefore ceftazidime appears as a clinically relevant adjunct in the common setting of sepsis-associated lung injury. [ABSTRACT FROM AUTHOR]

Objectives: To test the hypothesis that nebulized epinephrine ameliorates pulmonary dysfunction by dual action-bronchodilation (β2-adrenergic receptor agonism) and attenuation of airway hyperemia (α1-adrenergic receptor agonism) with minimal systemic effects.Design: Randomized, controlled, prospective, and large animal translational studies.Setting: University large animal ICU.Subjects: Twelve chronically instrumented sheep.Interventions: The animals were exposed to 40% total body surface area third degree skin flame burn and 48 breaths of cooled cotton smoke inhalation under deep anesthesia and analgesia. The animals were then placed on a mechanical ventilator, fluid resuscitated, and monitored for 48 hours in a conscious state. After the injury, sheep were randomized into two groups: 1) epinephrine, nebulized with 4 mg of epinephrine every 4 hours starting 1 hour post injury, n = 6; or 2) saline, nebulized with saline in the same manner, n = 6.Measurements and Main Results: Treatment with epinephrine had a significant reduction of the pulmonary transvascular fluid flux to water (p < 0.001) and protein (p < 0.05) when compared with saline treatment from 12 to 48 hours and 36 to 48 hours, respectively. Treatment with epinephrine also reduced the systemic accumulation of body fluids (p < 0.001) with a mean of 1,410 ± 560 mL at 48 hours compared with 3,284 ± 422 mL of the saline group. Hemoglobin levels were comparable between the groups. Changes in respiratory system dynamic compliance, mean airway pressure, PaO2/FiO2 ratio, and oxygenation index were also attenuated with epinephrine treatment. No considerable systemic effects were observed with epinephrine treatment.Conclusions: Nebulized epinephrine should be considered for use in future clinical studies of patients with burns and smoke inhalation injury. [ABSTRACT FROM AUTHOR]

Abstract: We previously reported bronchial circulation contributes to pulmonary edema and increases shunt fraction following smoke inhalation, and bronchial blood flow significantly increases in inhalation injury. We hypothesized reduction of bronchial blood flow reduces exudation to the airway and ameliorates lung injury from combined burn and smoke insults (B&S injury). Method: Merino ewes (n =28) randomly divided into three groups: (1) bronchial artery ligated and injured (injury+ligation group); (2) bronchial artery left intact and injured (injury+no ligation group); (3) bronchial artery ligated but not injured (no injury+ligation group) were subjected to a flame burn and inhalation injury under halothane anesthesia. Parameters were analyzed using Scheffe''s post hoc test (P <0.05). All Groups were resuscitated with Ringer lactate solution and placed on a ventilator for 48h. Results: Pulmonary gas exchange (PaO2/FiO2) improved in injury+ligation group. Further, obstruction score, an index of airway cast formation, significantly changed between injury+no ligation group compared to both ligation groups. Conclusion: Bronchial circulation plays a significant role in lung injury after B&S injury, and reduction of bronchial blood flow by bronchial artery ligation reduces bronchial exudates, resulting in improved gas exchange. [Copyright &y& Elsevier]

The article presents a randomized study which determined whether muscarinic receptor antagonist therapy with tiotropium bromide, an M1 and M3 muscarinic receptor antagonist, will reduce the airway constrictive response and acute bronchial obstruction in sheep after injury from smoke inhalation. It was found that pretreatment with tiotropium bromide substantially decreased ventilatory pressures, upper airway obstruction and pulmonary dysfunction. Post-injury treatment was also found to be as effective as pretreatment.

The article studies the effects of selective neuronal nitric oxide synthase (NOS) inhibition on cardiopulmonary functions and cellular injury in sheep with acute respiratory distress syndrome secondary to combined burn and smoke inhalation injury. The authors report that the study provided evidence that neuronal NOS-derived nitric oxide plays a pivotal role in the pathogenesis of acute respiratory distress syndrome resulting from combined burn and smoke inhalation injury.

Advances in local wound management with early excisional therapy have decreased morbidity and mortality of massive third-degree burn patients. Although blood redistribution within burned tissue is of clinical interest, few studies have longitudinally determined the regional blood flow of various layers of the burn wound. We used a conscious ovine model in which animals were subjected to 40% third degree burn. Burned tissue was divided into the four layers (i.e. skin, panniculus carnosus, adipose tissue, and skeletal muscle), and regional blood flow was determined separately, with fluorescent microspheres, while measuring systemic hemodynamics and total burned tissue microvascular fluid flux. The subburn adipose tissue exhibited a remarkable biphasic alteration in regional blood flow, whereas the skin layer showed only decreased blood flow during the whole experimental period. The increase in blood flow to the adipose tissue seems to be related to a sustained fluid filtrate in the postresuscitation period, resulting in edema formation mainly located in the adipose tissue at the endpoint. [Copyright &y& Elsevier]