Causes of acute pneumonia in children

Risk factors for acute pneumonia. Intrauterine infections and ZVUR, perinatal pathology, congenital malformations of the lungs and heart, prematurity, immunodeficiency, rickets and dystrophy, polyhypovitaminosis, the presence of chronic foci of infection, allergic and lymphatic-hypoplastic diathesis, unfavorable social conditions, contacts when visiting pre-school institutions, especially in children under 3 years of age.

Etiology of acute pneumonia . Typical bacterial pathogens of out-of-hospital pneumonia in children are Streptococcus pneumoniae, Haemophilus influenzae, less often Staphylococcus aureus; so-called atypical pathogens - Mycoplasma pneumoniae, Legionella pneumophila - play a certain role. In children in the first months of life, pneumonia is caused more often by Haemophilus influenzae, Staphylococcus, Proteus and less often by Streptococcus pneumoniae. Viral pneumonia is much less common, respiratory syncytial viruses, influenza and adenoviruses can play a role from viruses in the etiology. The respiratory virus causes destruction of cilia and ciliated epithelium, violation of mucociliary clearance, edema of interstitium and interalveolar septa, dilatation of alveoli, disorders of hemodynamics and lymphocirculation, impaired vascular permeability, that is, it has a "dressing" effect on the mucous of the lower respiratory tract. It is also known immunosuppressive effect of viruses. In such cases, microbial colonization of the lower respiratory tract and the respiratory department occurs due to autoflora. The danger of endogenous infection in children with acute respiratory infections, with unreasonable use of antibiotics, increases significantly, as antibiotics, without affecting the viruses, suppress the saprophytic autoflora of the rotosynopharynx, which plays an important role in the natural resistance of the respiratory apparatus to opportunistic microbes.

In children of the first half of life, 50% of all pneumonias are nosocomial, in the bacterial flora, gram-negative microbes predominate. Since the second half of life and up to 4-5 years in the etiology of community-acquired pneumonia, pneumococci predominate, hemophilic rod, less often - staphylococcus. At an older age, along with pneumococci, a significant proportion of mycoplasmal infection is due (most often in the autumn-winter period). In recent years, the role of Chlamydia infection as a causative agent of pneumonia in schoolchildren in whom pneumonia often occurs with concomitant lymphadenitis increases.

The pathogenesis of acute pneumonia .

The main way of penetration of the infection into the lungs is bronchogenic with the spread of the infection along the course of the respiratory tract to the respiratory department. The hematogenous pathway is possible with septic (metastatic) and intrauterine pneumonia. The lymphogenous path is a rarity, but on the lymphatic pathways the process passes from the pulmonary focus to the pleura.

SARS play an important role in the pathogenesis of bacterial pneumonia. Viral infection increases the production of mucus in the upper respiratory tract and reduces its bactericidal activity; violates the mucociliary apparatus, destroys epithelial cells, reduces local immunological defense, facilitates the penetration of bacterial flora into the lower respiratory tract and promotes the development of inflammatory changes in the lungs.

Intruding into the respiratory tract, the infectious agent with its toxins, metabolic products, irritating the interoceptors leads to reflex reactions of both local character and general, causing; disturbances in the function of external respiration, functions of the central nervous system and other organs and systems. In the clinic, this is manifested by symptoms of intoxication and breathing disorders.

With bronchogenic pathways of infection, inflammatory changes are found in the respiratory bronchioles and in the lung parenchyma. The resulting inflammation leads to a decrease in the respiratory surface of the lungs, to a violation of the permeability of the pulmonary membranes, to a decrease in the partial pressure and diffusion of oxygen, which causes hypoxemia. Oxygen starvation is the central link in the pathogenesis of pneumonia. The body includes compensatory reactions from the cardiovascular system and hematopoiesis. There is an increase in the pulse, an increase in the shock and minute volume of blood. An increase in cardiac output, aimed at reducing hypoxia, ultimately does not give an effect, since with the embolism of the lungs, the intensity of the forced exhalation decreases and the circulatory disorders deepen . In addition, as a result of hypoxia and enzyme shifts, depletion of energetically active substances (decrease in the level of glycogen, ATP, creatine phosphate, etc.) is observed, which leads to the inadequacy of this compensatory link and the circulatory attachment to respiratory hypoxemia . One of the compensatory links is the release of erythrocytes, but their function as oxygen carriers is changed due to enzymatic and histotoxic disorders, and hypoxic hypoxia is attached. There is an intensification of processes of lipid peroxidation and violation of antioxidant protection.

Oxygen deficiency has an effect on the metabolism, oppression of oxidative processes occurs, undo-oxidized metabolic products accumulate in the blood and acid-base balance shifts toward acidosis. Acidosis is also an important link in the pathogenesis of pneumonia, which plays a role in impairing the functions of various organs and systems, especially the liver. Violation of the function of the liver, in turn, aggravates metabolic disturbances, especially the exchange of vitamins, which leads to clinical manifestations of polyhypovitaminosis. In addition, trophic disorders increase, especially in young children, posing a threat of development of malnutrition.

In children with pneumonia, metabolic processes are naturally disturbed:

• acid-base state - metabolic or respiratory-metabolic acidosis with a decrease in the capacity of buffer bases, the accumulation of under-oxidized products;
• water-salt - fluid retention, chlorides, hypokalemia; Dehydration is possible in newborns and infants;
• protein - dysproteinemia with a decrease in the level of albumins, an increase in a1- and y-globulins, an increase in the content of ammonia, amino acids, urea, etc .;
• carbohydrate - pathological sugar curves, with severe pneumonia - hypoglycemia;
• lipid - hypocholesterolemia, increase in the level of total lipids against the background of a decrease in the content of phospholipids.

Respiratory failure is a condition in which either the lungs do not provide maintenance of the normal gas composition of the blood, or the latter is achieved due to abnormal operation of the external respiration apparatus, leading to a decrease in the functional capacity of the body.

On morphological forms distinguish focal, segmental, focal-drainage, croupous and interstitial pneumonia. Interstitial pneumonia in children is a rare form in pneumocystis, sepsis and some other diseases. The morphological form of pneumonia is determined by the clinical picture and radiographic data. Isolation of morphological forms has a certain prognostic significance and can influence the choice of starting therapy.

[1], [2], [3], [4], [5]