Comparative Assessment of Morphological Changes in the Pleura and Lung Tissue after Pleurodesis with Various Solutions in the Experiment

Introduction. Currently, spontaneous pneumothorax occurs in 6,2-7,1% of patients with nonspecific lung diseases. There has been a steady increase in prevalence of this disease. The relevance of preventing recurrence of spontaneous pneumothorax is still beyond doubt. Most authors recommend performing chemical pleurodesis when nonspecific spontaneous pneumothorax occurs, especially if it is recurrent. At the present time, the issue of choosing the optimal chemical agent for performing pleurodesis remains important.
The aim of the study was to analyse the nature and severity of the inflammatory reaction from the lungs, pleura and adjacent subpleural tissues of the chest wall in experimental animals during chemical pleurodesis with 4% sodium bicarbonate, 6% hydrogen peroxide and 5-fluorouracil solutions.
Materials and methods. The experiment was conducted at the experimental laboratory of Voronezh Regional Clinical Hospital № 1. The study involved 200 experimental rats (WISTAR type) with simulated spontaneous pneumothorax; after a fixed time, one of the preparations was sprayed into the pleural cavity. All animals were divided into 3 groups depending on the method of pleurodesis (5-fluorouracil solution, 4% sodium bicarbonate solution and 6% hydrogen peroxide solution) and control (0,9% sodium chloride solution). Groups of animals were withdrawn from the experiment in accordance with the rules of humane treatment of animals in 3, 5, 7, 10, 30 days with sampling of organs and tissues of the chest for histological examination to compare severity of inflammatory reactions in the pleura and adjacent areas of the lungs depending on the drug used for pleurodesis. The main criterion for assessing the comparative effectiveness of chemical agents was the morphological picture of inflammation presented by counting free cell populations (lymphocytes, macrophages, neutrophils, histiocytes) in the pleura and adjacent areas of the lung tissue of the studied animals.
Quantitative results were statistically processed using parametric and nonparametric methods with STATISTICA 10. The main statistical parameters of the studied data were estimated by the methods of descriptive statistics. Comparison of the studied samples was conducted with the Kruskal-Wallis test. Differences between the compared samples were considered significant at p≤0,05.
Results. The morphology of the inflammatory reaction in the pleura and adjacent lung tissue in all the studied groups of animals was characterized by the predominance of neutrophils over other cells in the first days of the experiment; the fact supporting acute aseptic inflammation in response to drug administration. Further, the content of lymphocytes, macrophages and their inactive forms (histiocytes) increased, and the content of neutrophils decreased, which was typical for the transition of acute inflammation to chronic. Compared dynamics in the number of analyzed immunocompetent cells evidenced that the number of lymphocytes, macrophages and histiocytes increased faster. After pleurodesis with a 6% hydrogen peroxide solution, the lowest content of immunocompetent cells in the studied tissue samples was noted if compared with the samples obtained from other groups in the same period. In all cases, pleurodesis with 6% hydrogen peroxide resulted in the minimal number of neutrophils, and the dynamics of their decrease was the most pronounced. In the control group, the number of studied cells fluctuated within the average value for this group.
Conclusion. The dynamics in the number of studied cell populations in all comparison groups was assessed as common. The method of pleurodesis significantly affects the number of cellular elements involved in the inflammatory response. Clinical outcomes of pleurodesis performed with a 6% hydrogen peroxide solution are characterized by a shorter duration and severity of the inflammatory response from the pleura and adjacent parts of the chest wall, compared with 5-fluorouracil and 4% sodium bicarbonate solutions.