[Long-term lung protection of probiotics in children with sepsis and its mechanism].

To observe the effects of probiotics supplementation on the natural killer T cell (NKT cell) and inflammatory factors in children with sepsis and its protective effect on long-term lung function.A total of 100 children with sepsis admitted to the department of pediatric intensive care unit (PICU) of Henan Provincial People's Hospital from March 2021 to May 2022 were selected as the research objects. The children were randomly divided into placebo group and probiotic group, 50 cases in each group. In addition to the conventional treatment, the probiotic group was given oral or nasal administration of 0.5 g probiotics, three times a day for 30 days, and the placebo group received oral placebo. 40 healthy children were selected as the healthy control group. The levels of interleukins (IL-4, IL-10), interferon-γ (IFN-γ) and immunoglobulin E (IgE), percentages of NKT cell in blood and induced sputum, lung function of the two groups of children with sepsis were measured before treatment, 7 days after treatment, and during follow-up. All these data were compared with those of healthy children. Kaplan-Meier analysis was used to compare the incidence of cough varied cough (CVA) between the two septic groups. Multiple linear regression analysis was used to explore the influence of various factors on the proportion of NKT cells in induced sputum.In the placebo group, 2 cases died and 4 cases were lost to follow-up. In the probiotics group, 3 cases died and 5 cases were lost to follow-up. All the inflammatory factors of two groups decreased slowly after 7 day after treatment. There was no significance in the parameters of the two groups, but the levels of probiotic group declined more evidently. During the follow-up, a further decrease of inflammatory factors in probiotic group could be found, the levels of IL-4 and IL-10 were significantly different from those in the placebo group [IL-4 (ng/L): 20.3±9.3 vs. 27.6±11.9, IL-10 (ng/L): 23.1±6.8 vs. 14.4±4.4, both P < 0.05], with a significant decrease in IgE level (μg/L: 53.0±15.6 vs. 64.2±16.9, P < 0.05]. The results of flow cytometry showed that the percentage of NKT cell in peripheral blood in two septic groups decreased gradually, and the proportion of peripheral blood NKT cells in the probiotics group was significantly lower than that in the placebo group after 7 days of treatment [(4.2±0.9)% vs. (5.3±1.2)%, P < 0.05]. In the follow-up, the level of NKT cell in peripheral blood and induced sputum in probiotic group were lower than the placebo group [peripheral blood: (0.024±0.009)% vs. (0.029±0.008)%, induced sputum: (0.025±0.008)% vs. (0.035±0.01)%, both P < 0.05], which were similar to those in the healthy control group. Meanwhile, the percentage of predicted peak expiratory (PEF%) and ratio of forced expiratory volume in one second/forced vital capacity (FEV1/FVC) of probiotic group were higher than those in the placebo group [PEF%: (91.3±4.8)% vs. (85.8±8.6)%, FEV1/FVC ratio: (91.8±4.7)% vs. (87.2±7.4)%, both P < 0.05]. Although there was no significance in the incidence of CVA between two septic groups according to the Kaplan-Meier curve analysis, multiple linear regression analysis showed mechanical ventilation and allergic history were the risk factors for the increase of NKT cells [β values were 0.584, 0.601, 95% confidence interval (95%CI) were 0.069 to 1.099, 0.011 to 1.192, P = 0.027, 0.046], and probiotics was an independent protective factor for the relieve of increase in NKT cells (β value was -0.984,95%CI was -1.378 to -0.591, P = 0.001).Application of probiotics to septic children early could promote the recovery of NKT cell and inflammatory factors, and alleviate the lung function injury induced by them during follow-up, which is helpful to improve the long-term prognosis of the patients.