TO THE ISSUE OF THE DEVELOPMENT AN ALGORITHM FOR A DIFFERENTIATED APPROACH TO THE MANAGEMENT OF PERSISTENT PULMONARY HYPERTENSION IN PREMATURE INFANTS

correlations between the indices and mPAP and between the indices and the level of 8-OHdG were established. The Schwedel index showed the highest reliability in all cases. Conclusion. On the basis of scienti ﬁ cally established relationships between clinical, laboratory, radiological and gender aspects of premature infants with perinatal pathology and the identi ﬁ ed diagnostic and prognostic values of urinary 8-OHdG, an algorithm for a di ﬀ erentiated approach to the management of PPH was developed. Determination of the degree of OS and mPAP in premature infants allows us to adjust and individualize the tactics of respiratory support in the management of premature infants, thus improving the quality of medical care of premature infants with RDS and perinatal asphyxia. In prematurely born children in perinatal centers, additional determination of the severity of RDS based on the level of 8-OHdG in urine allows to predict the adverse course of PPH and the development of complications: bronchopulmonary dysplasia, intraventricular hemorrhage III-IV grade, retinopathy II-III grade, hearing impairment, hypoxic-ischemic lesions of the central nervous system II-III grade in prematurely born children.


Introduction
Oxidative stress (OS) is a component of the pathophysiology of neonatal lung disease associated with persistent pulmonary hypertension (PPH) [1][2][3][4].The most sensitive OS biomarker in preterm infants is urinary 8-hydroxy-2-deoxyguanosine (8-OHdG) [5][6][7][8], which shows a high correlation with mean pulmonary artery trunk pressure and duration of respiratory support [9].In this article, we add to the body of scientifi c work on the development of a diff erentiated approach to the management of PPH.Previously, we published data on the analysis of modern medical literature with the determination of the need to improve the diagnosis and treatment of PPH in premature infants [10] and the results of the search for the optimal urinary OS biomarker correlating between the levels of OS and mPAP in premature infants with RDS and asphyxia [11,12].Data were also presented on the type and duration of respiratory support and its relationship with the dynamics of OS levels in preterm infants with PPH [13], and the results of the scientifi cally established algorithm for a diff erentiated approach to the management of PPH in preterm infants [9].
Aim of the study -to increase the eff ectiveness of the treatment of premature infants with persistent pulmonary hypertension with asphyxia and respiratory distress syndrome based on the development of an algorithm for a diff erentiated approach to the management of pulmonary hypertension taking into account the level of oxidative stress as determined by urinary 8-hydroxy-2-deoxyguanosine.

Material and methods
The study was conducted in 2020-2023 on the basis of the intensive care unit for premature infants of the Kharkiv Municipal Perinatal Center.Were studied 100 premature infants, divided into groups.The fi rst group consisted of 50 infants with RDS (26 boys and 24 girls), the second group -50 infants with perinatal asphyxia associated with RDS (25 boys and 25 girls).The clinical characteristics of the groups are shown in Table 1.Inclusion criteria of the study: persistent pulmonary hypertension; gestational age 26-34 weeks; neonatal period; respiratory distress syndrome IInd-IIIrd degree; RDS associated with perinatal asphyxia; obtaining voluntary informed consent of the patient's parents/caregivers to participate in the study.Exclusion criteria: gestational age less than 26 weeks or more than 34 weeks; congenital heart disease and patent ductus arteriosus; necrotic enterocolitis, sepsis; refusal of parents/caregivers to participate in the study [14].
Clinical and echocardiographic criteria were used to determine the presence and severity of PPH in all infants during the first and dynamic 3-5 days of life.Among the clinical criteria, the oxygenation index (OI) was the most important.Echocardiographic criteria, according to international recommendations, include: assessment of the rate of tricuspid regurgitation, measurement of systolic pressure in the right ventricle, assessment of the state of the right ventricle and the interventricular septum, blood shunt, ratio of pulmonary artery acceleration time to right ventricular ejection time [15][16][17][18].The mean pressure in the pulmonary artery trunk was determined according to the international standards for the diagnosis of pulmonary hypertension [19].Quantitative determination of urinary 8-OHdG (ng/ml) was performed in 44 infants on day 1 of life and again on days 3-5 by the ELISA method using the DNA Damage ELISA reagent kit, Enzo Life Sciences (USA), according to the manufacturer's instructions.Radiographic assessment of PPH severity was performed according to the criteria of Spuzyak MI et al. (2006) [20].
The algorithm of the diff erentiated approach was based on the study of clinical and anamnestic data of the studied groups of children, the ultrasound criteria of PPH, the dynamics of OS levels, the determined prognostic threshold value of 8-OHdG, and comparison with the indicators of comprehensive radiographic evaluation of pulmonary hypertension in premature infants with RDS and perinatal asphyxia.
The A heterogeneous sequential Wald procedure [21] was used to determine the diagnostic coeffi cients (DC) and informativeness (I) of the studied features.The prognostic threshold for quantitative indicators was determined using ROC analysis with the construction of a curve between the sensitivity and specifi city of the diagnostic method.

Results and discussion
At the first stage of research there was presented a characteristics of indicators of PPH and factors that determine the occurrence of PPH; were determined their diagnostic and prognostic significance in prematurely born children in the gestational age of 26-34 weeks with asphyxia and RDS.Against the background of treatment and selection of the most optimal tactics of respiratory support (traditional mechanical ventilation with PEEP of at least 6 cm H2O, high-frequency mechanical ventilation, non-invasive mechanical ventilation, CPAP), the average mPAP, mm Hg, was measured by the Echo CG method as an indicator of PPH in both groups in the fi rst and in dynamics on the 3rd-5th day of life.On the fi rst day of life, the average value of mPAP in group I was signifi cantly lower than in group II.In the dynamics of observation on the 3rd-5th day of life, the average mPAP signifi cantly decreased in the group of infants with RDS, and increased in the group with perinatal asphyxia (Table 2).
The above evidence supports the aggravating eff ect of perinatal asphyxia on the course of PPH and defi nes asphyxia as a factor determining the development of PPH in premature infants, which is confi rmed by modern scientifi c and medical literature [22,23].We evaluated the diagnostic signifi cance and power of the main clinical and anamnestic data of premature infants, the course of pregnancy, the method of delivery, and analyzed their infl uence as factors determining the development of persistent pulmonary hypertension of various degrees (Table 3).The following clinical and diagnostic factors are of high diagnostic signifi cance for an unfavorable course of PPH: mean pulmonary artery pressure on day 3-5 of life > 31.9 mm Hg (I=7.0),oxygenation index on day 3-5 of life > 8 (I=4.35),body weight at birth <1500 g (I=4.30).(I=7.0),oxygenation index on day 3-5 of life > 8 (I=4.35),birth weight <1500 g (I=4.30),perinatal asphyxia (I=4.22), Apgar score at 5 minutes of life < 7 points (I=3.49),gestational age < 30 weeks (I=3.24),mean pulmonary artery pressure on day 1 of life > 34 mm Hg. (I=1.98),natural childbirth (I=1.68),small for gestational age (I=1.13),male sex (I=1.04),placental dysfunction during pregnancy (I=1.11),mater nal hypertension during pregnancy (I=0.60)[14].The obtained results are consistent with modern literature data [24,25,26].
The second stage was to study the value of urinary 8-OHdG in premature infants with asphyxia and RDS in the early neonatal period and to determine the clinical signifi cance of its levels at diff erent degrees of PPH (Table 4).The obtained data indicate that on the first day of life there is almost no signifi cant diff erence between the studied groups of children.On the 3rd-5th day of life, in the fi rst group of children there is a signifi cant decrease in the studied urinary OS biomarker (p<0.05), in the second group -a signifi cant increase by 1.8 times (p<0.05).Our results indicate that perinatal asphyxia has a detrimental eff ect on the degree of oxidative stress, reduced adaptability and reactivity to OS in premature infants.
To evaluate the possibility of using the biomarker of oxidative stress in clinical practice in the management of premature infants, we analyzed the diagnostic and prognostic significance of the dynamics of 8-OHdG levels in the first and 3-5 days of life.The DC values (Table 5) indicate that a decrease in urinary 8-OHdG in premature infants is associated with a favorable course of PPH, and the absence of a decrease in the studied indicator indicates the probable development of severe PPH.The above is also confirmed by our correlation analysis between mPAP and the level of urinary 8-OHdG, ng/ml in premature infants [14].
Urinary 8-OHdG as a biomarker of OS in preterm infants with RDS correlates with mean pulmonary artery pressure on day 1 (r=0.85,p<0.001) and day 3-5 (r=0.84,p<0.001).A correlation was found between the level of urinary 8-OHDG in preterm infants with RDS associated with perinatal asphyxia and mPAP on the fi rst (r=0.82,p<0.05) and on the third to fifth days of life (r=0.80,p<0.05).The gender characteristics of the dynamics of 8-OHdG levels in premature infants with RDS and asphyxia with perinatal pathology confi rm the reduced adaptability and reactivity of boys to oxidative stress in the early neonatal period: on the fi rst day of life in both groups of studied newborns there is no significant difference (p>0.05) in the levels of 8-OHdG in urine between boys and girls.On the 3-5th day of life, a signifi cant increase in urinary 8-OHdG levels was observed in boys in both groups (p<0.05)compared with girls.It was found that the level of urinary 8-OHdG on the 3rd -5th day of life has a high diagnostic signifi cance for determining the risk of developing severe PPH (I=6.39): a decrease in the level of urinary 8-OHdG indicates a favorable course of PPH, and an increase -about the risk of developing severe PPH.The prognostic signifi cance of decreased levels of urinary 8-OHdG on the 3rd -5th day of life indicates a decrease in the probability of developing complications in the neonatal period (I=3.25).
Clinical and laboratory correlations between mean pulmonary artery pressure, 8-OHdG levels and the need for respiratory support in premature infants revealed that the more intensive the dynamics of 8-OHdG reduction, the shorter the duration of respiratory support required by the infants to establish spontaneous breathing (r=0.80,p<0.001).The high diagnostic value of the duration and type of respiratory support for the prognosis of the course of PPH in premature infants was established: the risk of developing severe PPH is indicated by: duration of HFOV > 48 hours (I=3.03),duration of traditional mechanical ventilation > 72 hours (I=2.49), when nIV/CPAP is not the only type of respiratory support (I=1.56).The prognostic signifi cance of the duration and type of respiratory support for predicting the course of PPH in preterm infants was determined: the following factors indicate the risk of complications in the neonatal period: duration of traditional mechanical ventilation > 72 hours (I=2.65),duration of HFOV > 48 hours (I=1.46), when nIV/CPAP is not the only type of respiratory support (I=1.08).
Perinatal asphyxia worsens the course of RDS in preterm infants with higher levels of mPAP (p<0.05),3.5 times more cases of severe pulmonary hypertension (p<0.05),higher levels of OS (p<0.05), and longer duration of ventilatory support (p<0.05).
In the third stage we determined the diagnostic and informative value of predictors of PPH formation in premature infants with asphyxia and RDS.According to the results of the ROC analysis, the signs indicating the development of an unfavorable course of PPH are: the level of urinary 8-OHdG on the 3rd-5th day of life > 2.5 ng/ml; mPAP level on the fi rst day of life > 34 mm Hg; mPAP level on the 3rd-5th day of life > 31.9 mm Hg; Moore's index on the fi rst day of life > 42 %; Moore's index on the 3rd-5th days of life > 43 %, Schwedel's index on the fi rst day of life > 0.4 cm, Schwedel's index on the 3rd-5th days of life > 0.5 cm, CTI on the fi rst day of life > 60 %; CTI on the 3rd-5th days of life > 60 %, oxygenation index on the fi rst day of life > 16, oxygenation index on the 3rd-5th days of life > 8. High specifi city was demonstrated by ROC curves for urinary 8-OHdG levels and radiologic indices on days 3-5 of life.High sensitivity was demonstrated by ROC curves for mean pulmonary artery pressure on days 1 and 3-5 of life, Moore's index on day 1, oxygenation index on days 3-5 of life.
Thus, reliable predictors of the progressive course of persistent pulmonary hypertension in premature infants with RDS and perinatal asphyxia are: the level of the urinary 8-OHdG > 2.5 ng/ml on the 3 rd -5 th day of life, the Schwedel index on the 3 rd -5 th day of life > 0.5 cm.Favorable course of PPH in premature infants is evidenced by: mPAP on the fi rst day of life ≤ 34 mm Hg, mPAP on the 3-5th day of life ≤ 31.9 mm Hg, Moore's index on the fi rst day life ≤ 42 %, oxygenation index on the 3rd-5 th day of life ≤ 8 [14].
On the basis of the obtained informative indicators of complex radiological assessment of the degree of PPH and dynamics of OS levels, the fi nal stage of the work was carried out -a diff erentiated approach to the diagnosis and treatment of PPH in premature infants with asphyxia and RDS was developed.The developed algorithm (Table 6) is used by algebraic summation of DC until the diagnostic threshold is reached, which for the 95 % level of confi dence is ≥ -13.0, and for the 99 % level -DC ≥ -20.If there is a «-» sign next to the sum of DC of all indicators, there is a risk of developing severe PPH, which requires correction of ventilator parameters and increased treatment, and a «+» sign indicates a favorable course of PPH.If the diagnostic threshold was not reached when adding the DC of all algorithm indicators, the diagnosis is considered uncertain.Conclusions 1.In our research, the development of an algorithm for a diff erentiated approach to the management of PPH, taking into account the complex radiological assessment of pulmonary hypertension, OS levels as determined by urinary 8-OHdG in premature infants at gestational age of 26-34 weeks with respiratory distress syndrome and perinatal asphyxia is scientifi cally based.
2. The pathogenetic signifi cance of urinary 8-OHdG in the development of PPH was determined and substantiated by the ELISA method, and a direct strong correlation was established between the OS indicator and the mPAP level in premature infants with RDS and with RDS associated with perinatal asphyxia in the early neonatal period.Perinatal asphyxia has been shown to exacerbate the degree and course of pulmonary hypertension in premature infants with RDS.
3. Diagnostic and prognostic determinants of the development and course of pulmonary hypertension in premature infants with RDS and perinatal asphyxia were determined.It was found that a decrease in urinary 8-OHdG levels on the 3rd to 5th day of life is a prognostic sign of a favorable course of PPH (I=6.39).
4. On the basis of scientifically substantiated correlations between clinical, laboratory, radiological, gender aspects of premature infants with perinatal pathology and the identifi ed diagnostic and prognostic values of the informative value of urinary 8-OHdG levels, an algorithm for a diff erentiated approach to the management of PPH was developed.
5. Determination of the degree of OS and mPAP in premature infants allows to optimize the tactics of respiratory support in the management of premature infants, thus improving the quality of medical care of premature infants with RDS and perinatal asphyxia.
6.In premature infants in perinatal centers, additional determination of the severity of PPH on the basis of urinary 8-OHdG level allows to predict the adverse course of PPH and development of complications: bronchopulmonary dysplasia, intraventricular hemorrhage of III-IV degree, retinopathy of II-III degree, hearing impairment, hypoxicischemic lesions of the central nervous system of II-III degree in premature infants.
Prospects for further research.Prospects for further research are to carry out a catamnestic observation of premature infants in order to study the infl uence of OS on the development of complications.

Table 6 Algorithm of a diff erentiated approach to management of persistent pulmonary hypertension in premature infants [9, 14]
Note:The sign (+) indicates about favorable course of PPH, and the sign (-) indicates about the development of signifi cant/severe PPH on the 3-5th day of life.