Risk factors associated with prolonged mechanical ventilation after surgical ligation of patent ductus arteriosus in very low birth weight infants in China: a single-center study

Risk factors associated with prolonged mechanical ventilation after surgical ligation of patent ductus arteriosus in very low birth weight infants in China: a single-center study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Risk factors associated with prolonged mechanical ventilation after surgical ligation of patent ductus arteriosus in very low birth weight infants in China: a single-center study Yue Yang, Tianming Yuan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6676905/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background In developing countries, surgical ligation continues to be the primary approach for managing patent ductus arteriosus (PDA) in premature infants, owing to its simplicity, feasibility in resource-constrained environments, and proven effectiveness. The aim of our study is to investigate the risk factors associated with prolonged mechanical ventilation following surgical ligation of PDA in very low birth weight infants (VLBWIs) in China. Methods A retrospective analysis was conducted on the clinical data of VLBWIs who underwent PDA ligation surgery between January 1,2022 and December 30,2024. The infants were divided into two groups based on the duration of mechanical ventilation following ligation: those with mechanical ventilation ≤ 7 days and those with prolonged mechanical ventilation > 7 days. The perioperative clinical characteristics, preoperative echocardiographic changes, postoperative complications, and mortality rates were compared between two groups. Risk factors associated with prolonged mechanical ventilation after ligation were analyzed. Results A total of 47 VLBWIs were enrolled over a three-year period. 34 cases (72%) were successfully extubated within 7 days, while 13 cases (28%) experienced prolonged mechanical ventilation after ligation. Statistically significant differences were observed between the two groups in terms of preoperative left ventricular end-diastolic diameter, peak systolic velocity, proportion of preoperative and postoperative respiratory severity score/weight > 3, proportion of postoperative oxygenation index > 10, inhaled oxygen concentration, inotrope score, oxygen partial pressure, and mortality rate ( p 3 and/or moderate to severe bronchopulmonary dysplasia (BPD)) were more prone to postoperative mechanical ventilator dependency. Conclusion VLBWIs with more severe lung disease before PDA ligation, characterized by RSS/kg > 3 and/or moderate to severe BPD, were more likely to experience postoperative ventilator dependence. Patent ductus arteriosus PDA ligation Very low birth weight infants Prolonged mechanical ventilation Figures Figure 1 Background PDA is a common cardiovascular condition among VLBWIs. The incidence of PDA is inversely related to BW and GA[ 1 ]. The incidence of PDA among VLBWIs ranges from 20–70% [ 2 ], and over 40% of premature infants < 28 weeks of gestational age still have PDA at 4 months of age [ 3 , 4 ]. Additionally, risk factors for persistent PDA include the absence of ACS and the need for invasive mechanical ventilation[ 5 , 6 ]. Hs-PDA leads to excessive pulmonary circulation and insufficient systemic perfusion in premature infants, resulting in adverse clinical outcomes such as ventilator dependency, NEC, renal dysfunction, GM-IVH, PVL, and cerebral palsy. In severe cases, it can even be fatal[ 7 – 9 ]. Therefore, optimizing the management strategy for hs-PDA in premature infants remains a current clinical research priority and challenge. There exist disparities in medical resources and technological levels across different regions of developing countries. With the advancement of medical technology and the deepening understanding of PDA in premature infants, the application of interventional occlusion procedures is on the rise in these countries. However, in China, including our center, besides pharmacological therapy, PDA ligation remains a primary treatment approach in premature infants. PDA ligation serves as a profound therapeutic method especially for those premature infants who do not respond to medical treatment, have severe complications, or are not suitable for transcatheter device intervention[ 10 ]. Early closure of PDA after birth is beneficial for cardiopulmonary stability in VLBWIs. Studies have showed that 60%-70% of extremely low birth weight infants require medical treatment or surgical ligation of PDA after birth[ 11 ]. PDA ligation can reduce pulmonary vascular overload, improve lung compliance, shorten the duration of invasive mechanical ventilation, and can also reduce the risk of BPD, with more prominent effects than medical treatment alone[ 12 , 13 ]. However, some infants do not experience improved respiratory conditions after PDA ligation. Instead, they may require prolonged mechanical ventilation, develop moderate to severe BPD, or even die in severe cases[ 14 ]. For infants whose PDA can close spontaneously or respond to medical treatment, early surgical ligation unnecessarily exposes them to potential post-surgical complications[ 15 ]. Therefore, there has been controversy regarding the indications and optimal timing for PDA ligation. Identifying the optimal timing for surgical PDA ligation in premature infants, which allows for early successful extubation and improved lung function, could benefit more high-risk premature infants[ 16 ]. This study aims to identify risk factors for prolonged mechanical ventilation after surgical PDA ligation in VLBWIs through a retrospective analysis of clinical data from 47 VLBWIs who underwent surgical PDA ligation. 1 Materials and Methos 1.1 Patient selection and ethical considerations VLBWIs (birth weight< 1500g) who underwent transthoracic ligation for PDA in the NICU of Children's Hospital of Zhejiang University School of Medicine from January 1, 2022, to December 30, 2024, were enrolled. To eliminate the influence of different preoperative ventilation modes on the results, our study focused on infants who were dependent on invasive mechanical ventilation＞3 days before ligation. The infants were divided into two groups based on whether they were successfully extubated from mechanical ventilation within 7 days after PDA ligation. Prolonged mechanical ventilation was defined as extubation＞7 days after ligation. Exclusion criteria included: (1) Infants with major congenital malformations; (2) Presence of ductus-dependent congenital heart disease; (3) Preoperative dependence on invasive mechanical ventilation ≤3 days; (4) Incomplete data. This study was approved by the Medical Ethics Committee of Children's Hospital of Zhejiang University School of Medicine (Approval No. 2022-IRB-076). Given the retrospective nature of the study and the use of anonymized clinical data, the committee granted a waiver of informed consent. 1.2 Data collection Clinical data were collected of all subjects, including the following: (1) Basic clinical characteristics of newborns, including gender, GA, BW, mode of delivery, 5-minute Apgar score, SGA, ACS, RDS, use of PS, and treatment with cyclo-oxygenase inhibitors; (2) Preoperative echocardiographic indicators (results taken within 24-48 hours before surgery), including PDA diameter, PSV, LA/AO, and LVDD; (3) Perioperative clinical data (average values taken within 24 hours before and after surgery), including postnatal age at surgery, corrected gestational age at surgery, weight at surgery; ventilator parameters before and after surgery, including MAP and FiO 2 ; OI>10 before and after surgery, RSS>3 before and after surgery, proportion of RSS/kg>3 before and after surgery, arterial blood gas analysis (PH, PaO 2 , PaCO 2 , and ABE) before and after surgery, IS before and after surgery, and blood pressure (SDP, DBP, PP) before and after surgery; (4) In-Hospital complications in premature infants, including NEC, BPD, GM-IVH, ROP, PVL, and in-hospital death; (5) Clinical manifestations and echocardiography staging, including the distribution of clinical manifestations in C4 stage and echocardiography findings in E4 stage, according to hs-PDA staging criteria proposed by MacNamara et al[17]. 1.3 Study-related definitions (1) hs-PDA: When PDA results in clinical or echocardiographic excessive pulmonary circulation volume and insufficient systemic circulation perfusion, it is defined as hs-PDA. Signs of increased pulmonary circulation volume include tachypnea, apnea, carbon dioxide retention, or increased need for respiratory support (including mechanical ventilation). Chest radiographs may show increased pulmonary vascular markings or signs of pulmonary edema. Signs of left ventricular overload include prominent left ventricular pulsation and cardiomegaly on chest radiographs. Manifestations of systemic ischemia include a bounding pulse and widened pulse pressure (>25mmHg), or a difference between systolic and diastolic blood pressure greater than half of the systolic value, with lower diastolic blood pressure. Other clinical manifestations caused by insufficient systemic perfusion include acidosis, oliguria, and abdominal distension[18]. (2) For the diagnosis of RDS, BPD, NEC, and PVL, we referred to the criteria outlined in Practical Neonatology (fifth edition)[19]. The diagnostic criteria and grading system for IVH were based on Volpe's Neurology of the Newborn [20]. 1.4 Surgical PDA ligation (1) Indications for surgical ligation：Surgical ligation was indicated for premature infants with hs-PDA who fail to respond 2-3 courses of cyclo-oxygenase inhibitors (indomethacin or ibuprofen) or those who could not undergo medical treatment due to contraindications ( including gastrointestinal bleeding, intracranial hemorrhage, oliguria, elevated creatinine, elevated urea, DIC, thrombocytopenia, etc.). Significant hemodynamic changes and/or ventilator dependency were also considered indications for surgical intervention[21]. (2) Surgical Method: PDA ligation was performed at bedside in NICU by an experienced pediatric cardiothoracic surgery team. A small incision was made under the axilla, and the chest cavity was entered through the third intercostal space. The ductus arteriosus was isolated and ligated using two 7-0 silk sutures. The chest cavity was then closed in layers after confirming the absence of internal bleeding. 1.5 Statistical analysis Statistical analysis was performed using SPSS 26.0 software. Measurement data that conformed to normal distribution and homogeneity of variance were expressed as mean ± standard deviation (±s), and comparisons between groups were conducted using the independent samples t-test. Measurement data with a skewed distribution were expressed as median [Q1, Q3], and comparisons between groups were made using the Mann-Whitney U test. Count data were expressed as percentages (%), and comparisons between groups were performed using the chi-square test or Fisher's exact test. Univariate analysis was conducted on the included influencing factors, and the significant factors identified were further subjected to binary logistic regression analysis. A p -value less than 0.05 was considered statistically significant. 2 Result Over a three-year period, 76 cases of VLBWIs underwent surgical PDA ligation. After excluding 23 cases with preoperative invasive mechanical ventilation≤3 days, 3 cases with severe congenital malformations, and 3 cases with incomplete data, a total of 47 cases met the criteria and were included in our study (Figure 1). Among these, 34 infants were successfully extubated from mechanical ventilation within 7 days (≤7 days) after PDA ligation, while 13 infants required mechanical ventilation for >7 days after ligation. The study cohort included 25 males and 22 females, with a male-to-female ratio of 1.14:1. The mean gestational age at birth was 26.7±1.3 weeks, and the mean birth weight was 894.2±205.2g. The mean postnatal age at surgery was 31.3±14.6 days, the mean corrected gestational age at surgery was 31.2±2.3 weeks, and the mean weight at surgery was 1355.1±409.5g. The distribution of gestational age and birth weight at birth was as follows: 13 infants were born at< 26 weeks, 23 were born between 26-27 +6 weeks, and 11 were born between 28-31 +6 weeks; 11 infants had a birth weight of < 750g, 23 had a birth weight between 750-999g, and 13 had a birth weight between 1000-1500g. The mean duration of mechanical ventilation before PDA ligation was 23.7±15.1 days, and the mean duration of mechanical ventilation after ligation was 10.7±12.7 days. The overall mortality rate was 6.4% (3/47). There were no statistically significant differences between two groups in terms of gender, gestational age, birth weight, proportion of cesarean deliveries, 5-minute Apgar score, SGA, ACS, RDS, use of PS, and use of cyclo-oxygenase inhibitors ( p > 0.05) (Table 1). Compared with VLBWIs in mechanical ventilation≤7 days after ligation group, those in mechanical ventilation>7 days after ligation group had a significantly higher proportion of preoperative RSS/kg >3 ( p <0.05). There were no statistically significant differences between two groups in terms of corrected gestational age at surgery, postnatal age at surgery, weight at surgery, proportion of C4 stage of hs-PDA, or preoperative mechanical ventilation time. Additionally, there were no significant differences between the two groups in preoperative MAP, FiO 2 , preoperative blood gas analysis indicators (PH, PaO 2 , PaCO 2 , and ABE), preoperative IS, preoperative blood pressure changes (SBP, DBP, PP), proportion of preoperative RSS>3, or proportion of preoperative OI>10 (Table 2). Echocardiography results showed a significant decrease in systolic PSV and a significant reduction in LVDD in the mechanical ventilation>7 days after ligation group ( p <0.05). However, there were no statistically significant differences between two groups in PDA diameter, LA/AO ratio, or proportion of E4 stage of hs-PDA (Table 3). Compared with VLBWIs in mechanical ventilation≤ 7 days after ligation group, those in the mechanical ventilation>7 days after ligation group had significantly higher proportions of postoperative RSS/kg> 3 and OI> 10, as well as higher postoperative FiO 2 and IS ( p 7 days after ligation group ( p 3, postoperative blood gas analysis indicators (PH, PaO 2 , PaCO2, and ABE), or postoperative blood pressure changes (SBP, DBP, PP) (Table 4). There were no statistically significant differences in the incidence of in-hospital complications between two groups, including NEC stage 2 or higher, GM-IVH grade III-IV, ROP stage 3 or higher, and PVL ( p > 0.05). The incidence of moderate to severe BPD showed an upward trend in group of VLBWIs who required mechanical ventilation for＞7 days after ligation ( χ 2 = 3.072, p = 0.080). The mortality rate in mechanical ventilation＞7 days after ligation group (23.1%) was higher than that in mechanical ventilation ≤ 7 days after ligation group, with a statistically significant difference ( χ 2 = 0.964, p = 0.026) (Table 5). Factors with p <0.1 identified in the univariate analysis were included in the binary logistic regression analysis. Since moderate to severe BPD can affect lung ventilation and gas exchange in premature infants, leading to increased respiratory support requirements before PDA ligation and influencing the need for invasive mechanical ventilation after PDA ligation, our study incorporated moderate to severe BPD into the model analysis. The results showed that a preoperative RSS/kg> 3 was an independent risk factor for mechanical ventilation> 7 days after PDA ligation in VLBWIs. When preoperative RSS/kg >3, the likelihood of mechanical ventilation> 7 days after ligation increased by approximately 10 times (OR=10.04). Elevated postoperative PaO 2 was identified as an independent protective factor for mechanical ventilation> 7 days after PDA ligation in VLBIWs, increasing the likelihood of successful extubation within 7 days after ligation by 16.4%. Additionally, there was a trend suggesting that moderate to severe BPD influenced extubation time after ligation ( p =0.09) (Table 6). 3 Discussion Our study identified several key factors influencing the duration of mechanical ventilation after surgical ligation of PDA in VLBWIs. We emphasize the importance of a comprehensive preoperative evaluation of lung disease severity and respiratory status in VLBWIs before proceeding with surgical PDA ligation. PDA is the most common clinical cardiovascular issue in premature infants, particularly in developing countries where access to advanced medical technologies may be limited. Despite the increasing adoption of transcatheter device closure in more developed regions, surgical ligation persists as a necessary option in many parts of the world. This is largely due to the availability and relative simplicity of the surgical procedure compared to the more technologically demanding transcatheter device closure. In addition, the cost of transcatheter devices and the need for specialized equipment and expertise can be prohibitive in developing countries, further reinforcing the reliance on surgical ligation. Surgical ligation has been a traditional method for managing PDA, especially in VLBWIs, due to its effectiveness in ensuring ductal closure and its feasibility in resource-limited environments[ 10 ]. Early treatment for premature infants with hs-PDA can improve their clinical outcomes and reduce mortality rates. The main pathophysiological change in hs-PDA is pulmonary over-circulation caused by excessive left-to-right shunting, which is associated with an increased need for respiratory support and mechanical ventilation[ 7 , 22 ]. Zong et al.[ 23 ] found that lung water content is much higher in PDA surgery infants among premature infants with a gestational age of ≤ 25 weeks. Qian et al.[ 8 ] analyzed clinical data from CHNN and found that extremely premature infants receiving invasive mechanical ventilation were the primary beneficiaries of PDA treatment. Although surgical ligation carries potential risks, persistent hs-PDA and long-term dependence on mechanical ventilation in premature infants with contraindications to pharmacological therapy or those who have failed medical treatment are common indications for PDA ligation[ 24 ]. However, Seo et al. [ 22 ] showed that premature infants with poor respiratory conditions were more prone to prolonged mechanical ventilation dependence after PDA ligation. Therefore, finding the most suitable time for PDA ligation to improve postoperative clinical outcomes has become an urgent problem for clinicians. Our study aims to identify risk factors for prolonged mechanical ventilation after PDA ligation and optimize perioperative management strategies for surgical PDA ligation. The magnitude of duct shunt flow and echocardiographic indicators reflecting excessive pulmonary circulation volume can represent the degree of pulmonary insufficiency caused by PDA. Studies have shown that lung compliance, tidal volume, and minute ventilation of premature infants with hs-PDA improved rapidly after ligation[ 25 ]. A lower PSV was associated with delayed extubation after PDA ligation[ 26 ]. In a retrospective study of ventilator-dependent extremely premature infants who underwent PDA ligation, Krishnappa et al. [ 16 ] found that a large PDA diameter (greater than 2.5 mm) and left ventricular dilation were associated with earlier extubation after ligation. Our study also found that higher PSV and relatively dilated left ventricle (higher LVDD) were associated with early extubation (mechanical ventilation ≤ 7 days) after PDA ligation in VLBWIs. However, this association was no longer significant after adjusting for confounding factors, which may be related to the limited sample size in our study, and PDA diameter in both groups of VLBWIs were greater than 2.5mm. PaO 2 reflects the oxygen status of the pulmonary capillaries and serves as an indicator for evaluating extrapulmonary respiratory function, as well as representing the lung's ventilation function. Our study showed a significant increase in postoperative FiO 2 , postoperative IS, and the proportion of OI > 10, while postoperative PaO 2 decreased significantly in mechanical ventilation>7days after ligation group of VLBWIs. This suggests that VLBWIs with prolonged mechanical ventilation after PDA ligation have a higher demand for respiratory and circulatory support. Elevated postoperative PaO 2 was identified as an independent protective factor for mechanical ventilation > 7 days after ligation in VLBWIs, increasing the likelihood of successful extubation within 7 days after ligation by 16.4%. Additionally, there was a trend indicating that moderate to severe BPD influences on extubation time after ligation, meaning that VLBWIs with moderate to severe BPD are more likely to fail extubating within 7 days after PDA ligation. Meanwhile, the in-hospital mortality rate of VLBWIs in the mechanical ventilation>7 days after ligation group was significantly higher, suggesting that prolonged mechanical ventilation after PDA ligation is associated with elevated in-hospital mortality rate. OI is commonly used to quantify the severity of respiratory failure in premature infants. However, continuous OI monitoring for real-time PaO 2 data requires indwelling arterial catheters and frequent arterial blood sampling, which may lead to complications such as thromboembolism, ischemic injury, and iatrogenic anemia in VLBWIs[ 27 ]. Clinicians have recognized the value of using non-invasive measures to assess the severity of respiratory failure and lung condition. RSS is a non-invasive, continuously monitorable clinical indicator. It is a simplified severity score calculated as the product of MAP and FiO 2 [ 28 ]. When target oxygen saturation of mechanically ventilated premature infants was maintained between 88% and 94%, there is a strong correlation between RSS and OI. Therefore, RSS can be used as a surrogate for OI when premature infants are kept within target oxygen saturation range[ 29 ]. Studies have shown that RSS can predict the occurrence and progression of neonatal respiratory diseases. An elevated RSS (> 4) of newborns is associated with increased demand for respiratory support within 24 hours after birth[ 30 ]. In VLBWIs receiving invasive mechanical ventilation, elevated RSS is correlated with extubation failure[ 31 ]. RSS can also predict neonatal clinical outcomes. In extremely premature infants, RSS ≥ 3 on day 14 and RSS ≥ 3.6 on day 21 after birth are reliable indicators for predicting severe BPD or death[ 32 ]. Shah et al.[ 33 ] found that in premature infants with birth weight ≤ 1250g, those with RSS ≥ 2 within 24 hours after birth had an increased risk of death and morbidity, and those with elevated RSS had a higher proportion of receiving PDA treatment. Bhattacharjee et al.[ 34 ] obtained similar results in a study focusing on extremely low birth weight infants. In neonates receiving mechanical ventilation, the required pressure support during ventilation is correlated with the severity of lung pathology. In clinical settings, a MAP of 10 cmH 2 O in a premature infant weighing 500 grams is considered to notably differ from the same magnitude of pressure in an infant weighing 1000 grams. This suggests that pressure demand for respiratory support during ventilation in neonates appeared to correlate with body weight, leading to the introduction of a newer concept known as RSS/kg in the literature[ 22 , 35 ]. Studies have shown that RSS/kg is a potential marker associated with occurrence and progression of PH in premature infants, and an elevated RSS is correlated with an increased risk of BPD-PH[ 35 , 36 ]. In our study, there was no significant difference in RSS > 3 between the two groups of VLBWIs, while the proportion of preoperative RSS/kg > 3 was significantly higher in the prolonged mechanical ventilation (> 7 days) after ligation group. Further binary logistic regression analysis revealed that preoperative RSS/kg > 3 was an independent risk factor for prolonged mechanical ventilation (> 7 days) after PDA ligation in VLBWIs (OR = 10.04). This means that when RSS/kg > 3 before PDA ligation, the risk of prolonged mechanical ventilation (> 7 days) after ligation in VLBWIs increased by approximately 10 times, further validating previous research findings[ 35 ]. We hypothesize that a higher RSS/kg before PDA ligation in VLBWIs may be associated with persistent hs-PDA-induced pulmonary congestion, pulmonary edema, and subsequent irreversible exacerbation of lung pathology. There were several limitations in our study: (1) This study only included data from a single center with a limited sample size. Further validation with a larger sample size is needed in the next step. (2) As a retrospective study, there were certain limitations in PDA assessment timing and treatment decisions, and echocardiography data was difficult to replicate. (3) Since the focus of this study was on infants who underwent surgical PDA ligation, the results cannot be used to infer the effectiveness of medical treatment. In conclusion, our study found that VLBWIs with more severe lung disease before PDA ligation, characterized by RSS/kg > 3 and/or moderate to severe BPD, were more likely to experience postoperative ventilator dependence. This approach can help minimize the risk of prolonged mechanical ventilation after ligation and its associated adverse outcomes, including death. Abbreviations ABE: Actual Base Surplus ACS: Antenatal Corticosteroid BPD: Bronchopulmonary Dysplasia BW: Birth Weight CHNN: Chinese Neonatal Network DBP: Diastolic Blood Pressure DIC: Disseminated Intravascular Coagulation FiO 2 : Inhaled Oxygen Concentration GA: Gestational Age GM-IVH: Germinal Matrix-Intraventricular Hemorrhage hs-PDA: Hemodynamically Significant Patent Ductus Arteriosus IS: Inotrope Score IVH: Intraventricular Hemorrhage LA/AO: Left Atrium-to-Aortic Root Diameter Ratio LVDD: Left Ventricular End-diastolic Diameter MAP: Mean Airway Pressure NEC: Necrotizing Enterocolitis NICU: Neonatal Intensive Care Unit OI: Oxygen Index PaO 2 : Oxygen Partial Pressure PaCO 2 : Arterial Partial Pressure of Carbon Dioxide PDA: Patent Ductus Arteriosus PH: Pulmonary Hypertension PP: Pulse Pressure Difference PS: Pulmonary Surfactant PSV: Peak Systolic Velocity PVL: Periventricular Leukomalacia RDS: Respiratory Distress Syndrome ROP: Retinopathy of Prematurity RSS: Respiratory Severity Score SBP: Systolic Blood Pressure SGA: Small for Gestational Age VLBWIs: Very Low Birth Weight Infants Declarations Ethics approval and consent to participate This study was approved by the Medical Ethics Committee of Children's Hospital of Zhejiang University School of Medicine (Approval No. 2022-IRB-076). Given the retrospective nature of the study and the use of anonymized clinical data, the committee granted a waiver of informed consent. Consent for publication Not applicable. Availability of data and materials The datasets used and/or analyzed during this study are available from the corresponding author on reasonable request. Competing interests All authors declare that there is no conflict of interest in this study. Funding This work is supported by Shanghai Children’s Hospital Clinical Research Project [2022YLYM010]. Author contributions YY and TM contributed to the conception and design of this study. YY and TM drafted the manuscript and revised it critically. YY contributed to acquisition, analysis and interpretation of data. All authors read the manuscript and gave the permission to be published. Acknowledgements The authors want to thank all the participants in this study. Clinical trial number Not applicable. 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J Matern Fetal Neonatal Med. 2022;35(23):4620-7. Seo YM, Yum SK, Sung IK. Respiratory Severity Score with Regard to Birthweight during the Early Days of Life for Predicting Pulmonary Hypertension in Preterm Infants. J Trop Pediatr. 2020;66(6):561-8. Beer L, Rivera BK, Jama W, Slaughter JL, Backes CH, Conroy S, et al. Association of the respiratory severity score with bronchopulmonary dysplasia-associated pulmonary hypertension in infants born extremely preterm. J Perinatol. 2024;44(2):294-300. Tables Table 1 Comparison of basic clinical characteristics Mechanical ventilation ≤7d after ligation（n=34） Mechanical ventilation＞7d after ligation（n=13） χ 2 /Z/t p -value Male, n (%) 18（52.9） 7（53.8） 0.003 0.956 GA a (w) 26.5[24.7,30.0] 26.7[25.3,28.1] -0.393 0.694 BW (g) 920.3±188.8 825.8±237.3 1.429 0.160 Cesarean deliveries, n (%) 12（35.3） 5（38.5） 0.000 1.000 5min Apgar score a 8[2,10] 8.5[2,10] -0.651 0.515 SGA, n (%) 0（0） 2（15.4） 2.34 0.126 ACS, n (%) 5（14.7） 3（23.1） 0.062 0.803 RDS, n (%) 33（97.1） 12（92.3） 0.521 0.470 PS, n (%) 31（91.2） 12（92.3） 0.000 1.000 cyclo-oxygenase inhibitors, n (%) 29（85.3） 11（84.6） 0.000 1.000 Data are presented as n (%), mean ± standard deviation (±s), and median [P25, P75] for a . GA, gestational age; BW, birth weight; SGA, small for gestational age; ACS, antenatal corticosteroids; RDS, respiratory distress syndrome in newborns; PS, pulmonary surfactant. A p -value less than 0.05 was considered statistically significant. Table 2 Comparison of preoperative characteristics Mechanical ventilation ≤7d after ligation（n=34） Mechanical ventilation＞7d after ligation（n=13） χ 2 /Z/t p -value Age at surgery a (d) 30[4-66] 28[8-70] -1.286 0.199 Corrected gestational age at surgery (w) 31.5±2.4 30.5±2.0 1.307 0.198 Weight at surgery (g) 1403.2±408.0 1229.2±401.7 1.313 0.196 Preoperative C4 hs-PDA, n (%) 10（29.4%） 5（38.5%） 0.060 0.906 Preoperative mechanical ventilation time a (d) 23[4-66] 18[3-70] -1.095 0.274 Preoperative MAP a (cmH 2 O) 11[8-16] 12[9-23] -1.700 0.089 Preoperative FiO 2 a 0.33[0.21-0.80] 0.40[0.21-1.00] -1.646 0.100 Preoperative RSS>3, n (%) 24（70.6） 11（84.6） 0.375 0.540 Preoperative RSS/kg>3, n (%) 11（32.4） 10（79.6） 7.558 0.006* Preoperative PaO 2 (mmHg) 59.8±7.2 50.2±10.8 1.899 0.077 Preoperative OI>10, n (%) 2（5.9） 3（23.1） 1.396 0.237 Preoperative PH a 7.30[7.20-7.53] 7.30[7.10-7.40] -0.061 0.952 Preoperative PaCO 2 (mmHg) 54.0±11.4 50.2±10.8 1.035 0.306 Preoperative ABE (mmol/l) 2.15[0.2-9.2] 3.7[0.4-19.1] -1.785 0.074 Preoperative IS a 0[0-40] 5[0-50] -1.886 0.059 Preoperative SBP a (mmHg) 62.0±13.0 60.9±8.8 0.228 0.774 Preoperative DBP a (mmHg) 32.9±7.7 32.7±6.5 0.476 0.947 Preoperative PP a (mmHg) 30[5-51] 30[7-37] -0.107 0.915 Data are presented as n (%), mean ± standard deviation (±s), and median [P25, P75] for a . PDA, patent ductus arteriosus; MAP, mean airway pressure; FiO 2 , inhaled oxygen concentration; RSS, respiratory severity score; PaO 2 , arterial oxygen partial pressure; OI, oxygen index; PaCO 2 , arterial partial pressure of carbon dioxide; ABE, actual base surplus; IS, inotrope score; SBP, systolic blood pressure; DBP, diastolic blood pressure; PP, pulse pressure difference; C4 hs-PDA, conducted to clinical manifestations in C4 stage proposed by MacNamara. A p -value* less than 0.05 was considered statistically significant. Table 3 Comparison of preoperative echocardiographic indicators Mechanical ventilation ≤7d after ligation（n=34） Mechanical ventilation＞7d after ligation（n=13） χ 2 /Z/t p -value PDA diameter a (mm) 2.7[1.6-4.0] 3.0[2.0-4.6] -0.798 0.425 PSV (m/s) 2.3±0.7 1.7±0.5 2.584 0.013* LA/AO a 1.2[1.0-1.5] 1.1[1.0-1.7] -0.384 0.701 LVDD (mm) 16.5±2.5 14.0±1.9 3.249 0.001* E4 hs-PDA, n (%) 11（32.4%） 6（42.6%） 0.293 0.588 Data are presented as n (%), mean ± standard deviation (±s), and median [P25, P75] for a . PSV, peak systolic velocity; LA/AO, left atrium-to-aortic root diameter ratio; LVDD, left ventricular end-diastolic diameter; E4 hs-PDA, conducted to echocardiography in E4 stage proposed by MacNamara. A p -value* less than 0.05 was considered statistically significant. Table 4 Comparison of postoperative characteristics Mechanical ventilation ≤7d after ligation（n=34） Mechanical ventilation＞7d after ligation（n=13） χ 2 /Z/t p -value Mechanical ventilation time after ligation a (d) 4[1-7] 20[8-48] -5.267 0.000* Postoperative MAP a (cmH 2 O) 11[7,15] 11[9,17] -1.553 0.121 Postoperative FiO 2 a 0.30[0.21,0.45] 0.35[0.21,0.63] -2.106 0.035* Postoperative RSS>3, n (%) 20（58.8） 11（84.6） 1.756 0.185 Postoperative RSS/kg>3, n(%) 7（20.6） 8（61.5） 5.495 0.019* Postoperative PaO 2 a (mmHg) 64.6[52.1,85] 59[41.8,68.5] -3.052 0.002* Postoperative OI>10, n (%) 0（0） 4（30.8） 7.824 0.005* Postoperative PH a 7.4[7.1,7.5] 7.3[7.1,7.5] -1.128 0.259 Postoperative PaCO 2 a (mmHg) 42.3[27.4,63.0] 47.2[26.9,80.0] -0.868 0.385 Postoperative ABE a (mmol/l) 1.9[0.1,8.1] 2.4[0.4,9.7] -1.452 0.146 Postoperative IS a 5.0[0.0,60.0] 20.0[0.0,60.0] -2.719 0.029* Postoperative SBP (mmHg) 65.7±9.3 62.1±8.7 1.204 0.235 Postoperative DBP a (mmHg) 39.0[21.0,52.0] 33.0[20.0,51.0] -0.988 0.323 Postoperative PP a （mmHg） 29.0[6.0,47.0] 28.0[12.0,37.0] -0.619 0.536 Data are presented as n (%), mean ± standard deviation (±s), and median [P25, P75] for a . PDA, patent ductus arteriosus; MAP, mean airway pressure; FiO 2 , inhaled oxygen concentration; RSS, respiratory severity score; PaO 2 , arterial oxygen partial pressure; OI, oxygen index; PaCO 2 , arterial partial pressure of carbon dioxide; ABE, actual base surplus; IS, inotrope score; SBP, systolic blood pressure; DBP, diastolic blood pressure; PP, pulse pressure difference. A p -value less than 0.05 was considered statistically significant. Table 5 Comparison of in-hospital complications and death Mechanical ventilation ≤7d after ligation（n=34） Mechanical ventilation＞7d after ligation （n=13） χ 2 /Z/t p -value NEC ≥ stage 2, n (%) 1（2.9） 0（0） 0.000 1.000 Moderate to severe BPD, n (%) 7（20.6） 6（46.2） 3.072 0.080 GM-IVH grade III-IV, n (%) 11（32.4） 2（15.4） 0.638 0.424 ROP ≥ stage 3, n (%) 9（26.5） 3（23.1） 0.000 1.000 PVL, n (%) 3（8.8） 4（30.8） 2.052 0.152 In-hospital death, n (%) 0（0） 3（23.1） 0.964 0.026* Data are presented as n (%). NEC, necrotizing enterocolitis; BPD, bronchopulmonary dysplasia; GM-IVH, germinal matrix-intraventricular hemorrhage; ROP, retinopathy of prematurity; PVL, periventricular leukomalacia. A p -value less than 0.05 was considered statistically significant. Table 6 Binary logistic regression analysis of factors influencing prolonged mechanical ventilation time after PDA ligation Factors β Wald-value OR-value 95%CI p -value Preoperative RSS/kg>3 2.306 4.781 10.04 1.27-79.33 0.029* Postoperative PaO 2 -0.179 4.159 0.836 0.70-0.99 0.041* Moderate to severe BPD 1.825 2.836 6.203 0.741-51.89 0.092 RSS, respiratory severity score; PaO2, arterial oxygen partial pressure; BPD, bronchopulmonary dysplasia. A p -value less than 0.05 was considered statistically significant. Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6676905","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":469937093,"identity":"0c1069b0-3a8e-4c2f-9458-fa2de634b21e","order_by":0,"name":"Yue Yang","email":"","orcid":"","institution":"Shanghai Jiao Tong University","correspondingAuthor":false,"prefix":"","firstName":"Yue","middleName":"","lastName":"Yang","suffix":""},{"id":469937095,"identity":"73760356-5280-438d-9c9c-f153e68e24f7","order_by":1,"name":"Tianming Yuan","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9klEQVRIiWNgGAWjYNACAyBmBuIPDGwwLgFwAKqFcQbxWqA0Mw/CUjxOupH87PGHArs83Xbew69t/vAlNrA3b5NgqLmDR0uaucEBg+Ris8N8adY5PGyJDTzHyiQYjj3DoyXBTOKAAXPitsM8ZsY5EkAtEjlmEowNh/FoSf8G1FIP0WJhANQi/4aQlhyQLYdBWowfMySAbOHBr0XyzJsyiTMGx8G2MPYcYDNu40krtkg4hlsL3/H0bRIVf6oTt50/Y/zhx59jsv3shzfe+FCDW4vCAQSbTYKB4RgkMhNwamBgkG9AsJk/MDDU4FE7CkbBKBgFIxUAAMXCVZvoQtLEAAAAAElFTkSuQmCC","orcid":"","institution":"Zhejiang University School of Medicine","correspondingAuthor":true,"prefix":"","firstName":"Tianming","middleName":"","lastName":"Yuan","suffix":""}],"badges":[],"createdAt":"2025-05-16 04:08:05","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6676905/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6676905/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":84776061,"identity":"f10e81d8-6070-4995-9dd9-5d634d59c1ef","added_by":"auto","created_at":"2025-06-17 08:57:17","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":172640,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEnrollment flowchart\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eVLBWIs, very low birth weight infants\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6676905/v1/05b66d8d9a639f4ac1e774d3.jpeg"},{"id":95524581,"identity":"6bf45f7c-3e37-4abf-bdec-cf4eeeab0b88","added_by":"auto","created_at":"2025-11-10 10:02:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1149960,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6676905/v1/3b77b472-e063-4271-a76f-725c224cdb1c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eRisk factors associated with prolonged mechanical ventilation after surgical ligation of patent ductus arteriosus in very low birth weight infants in China: a single-center study\u003c/p\u003e","fulltext":[{"header":"Background","content":"\u003cp\u003ePDA is a common cardiovascular condition among VLBWIs. The incidence of PDA is inversely related to BW and GA[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The incidence of PDA among VLBWIs ranges from 20\u0026ndash;70% [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], and over 40% of premature infants\u0026thinsp;\u0026lt;\u0026thinsp;28 weeks of gestational age still have PDA at 4 months of age [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Additionally, risk factors for persistent PDA include the absence of ACS and the need for invasive mechanical ventilation[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Hs-PDA leads to excessive pulmonary circulation and insufficient systemic perfusion in premature infants, resulting in adverse clinical outcomes such as ventilator dependency, NEC, renal dysfunction, GM-IVH, PVL, and cerebral palsy. In severe cases, it can even be fatal[\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Therefore, optimizing the management strategy for hs-PDA in premature infants remains a current clinical research priority and challenge.\u003c/p\u003e \u003cp\u003eThere exist disparities in medical resources and technological levels across different regions of developing countries. With the advancement of medical technology and the deepening understanding of PDA in premature infants, the application of interventional occlusion procedures is on the rise in these countries. However, in China, including our center, besides pharmacological therapy, PDA ligation remains a primary treatment approach in premature infants. PDA ligation serves as a profound therapeutic method especially for those premature infants who do not respond to medical treatment, have severe complications, or are not suitable for transcatheter device intervention[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eEarly closure of PDA after birth is beneficial for cardiopulmonary stability in VLBWIs. Studies have showed that 60%-70% of extremely low birth weight infants require medical treatment or surgical ligation of PDA after birth[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. PDA ligation can reduce pulmonary vascular overload, improve lung compliance, shorten the duration of invasive mechanical ventilation, and can also reduce the risk of BPD, with more prominent effects than medical treatment alone[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. However, some infants do not experience improved respiratory conditions after PDA ligation. Instead, they may require prolonged mechanical ventilation, develop moderate to severe BPD, or even die in severe cases[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. For infants whose PDA can close spontaneously or respond to medical treatment, early surgical ligation unnecessarily exposes them to potential post-surgical complications[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Therefore, there has been controversy regarding the indications and optimal timing for PDA ligation. Identifying the optimal timing for surgical PDA ligation in premature infants, which allows for early successful extubation and improved lung function, could benefit more high-risk premature infants[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. This study aims to identify risk factors for prolonged mechanical ventilation after surgical PDA ligation in VLBWIs through a retrospective analysis of clinical data from 47 VLBWIs who underwent surgical PDA ligation.\u003c/p\u003e"},{"header":"1 Materials and Methos","content":"\u003cp\u003e\u003cstrong\u003e1.1\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003ePatient selection and ethical considerations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eVLBWIs (birth weight\u0026lt; 1500g) who underwent transthoracic ligation for PDA in the NICU of Children\u0026apos;s Hospital of Zhejiang University School of Medicine from January 1, 2022, to December 30, 2024, were enrolled. To eliminate the influence of different preoperative ventilation modes on the results, our study focused on infants who were dependent on invasive mechanical ventilation＞3 days before ligation.\u0026nbsp;The infants were divided into two groups based on whether\u0026nbsp;they were successfully\u0026nbsp;extubated from mechanical ventilation within 7 days after PDA ligation.\u0026nbsp;Prolonged mechanical ventilation was defined as extubation＞7 days after ligation.\u0026nbsp;Exclusion criteria included: (1) Infants with major congenital malformations; (2) Presence of ductus-dependent congenital heart disease; (3) Preoperative dependence on invasive mechanical ventilation\u0026nbsp;\u0026le;3 days; (4) Incomplete data.\u003c/p\u003e\n\u003cp id=\"_Toc8190\"\u003eThis study was approved by the Medical Ethics Committee of Children\u0026apos;s Hospital of Zhejiang University School of Medicine (Approval No. 2022-IRB-076). Given the retrospective nature of the study and the use of anonymized clinical data, the committee granted a waiver of informed consent.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e1.2\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eData collection\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eClinical data were collected of all subjects, including the following:\u0026nbsp;(1) Basic clinical characteristics of newborns, including\u0026nbsp;gender, GA, BW,\u0026nbsp;mode of\u0026nbsp;delivery, 5-minute Apgar score,\u0026nbsp;SGA,\u0026nbsp;ACS,\u0026nbsp;RDS, use of PS, and treatment with cyclo-oxygenase inhibitors;\u0026nbsp;(2) Preoperative echocardiographic indicators (results taken within 24-48 hours before surgery), including PDA diameter, PSV, LA/AO, and LVDD;\u0026nbsp;(3) Perioperative clinical data (average values taken within 24 hours before and after surgery), including\u0026nbsp;postnatal\u0026nbsp;age at surgery, corrected gestational age at surgery, weight at surgery;\u0026nbsp;ventilator parameters before and after surgery, including\u0026nbsp;MAP and FiO\u003csub\u003e2\u003c/sub\u003e; OI\u0026gt;10 before and after surgery, RSS\u0026gt;3 before and after surgery,\u0026nbsp;proportion of\u0026nbsp;RSS/kg\u0026gt;3 before and after surgery, arterial blood gas analysis (PH, PaO\u003csub\u003e2\u003c/sub\u003e, PaCO\u003csub\u003e2\u003c/sub\u003e, and ABE) before and after surgery, IS before and after surgery, and blood pressure (SDP, DBP, PP) before and after surgery; (4) In-Hospital complications in premature infants, including NEC, BPD, GM-IVH, ROP, PVL, and in-hospital death; (5) \u003cstrong\u003eClinical manifestations and echocardiography staging, including\u0026nbsp;\u003c/strong\u003ethe distribution of clinical manifestations in C4 stage and echocardiography findings in E4 stage, according to hs-PDA staging criteria proposed by MacNamara et al[17].\u003c/p\u003e\n\u003cp id=\"_Toc4305\"\u003e\u003cstrong\u003e1.3\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;Study-related definitions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(1) hs-PDA: When PDA results in clinical or echocardiographic excessive pulmonary circulation volume and insufficient systemic circulation perfusion, it is defined as hs-PDA. Signs of increased pulmonary circulation volume include tachypnea, apnea, carbon dioxide retention, or increased need for respiratory support (including mechanical ventilation). Chest radiographs may show increased pulmonary vascular markings or signs of pulmonary edema. Signs of left ventricular overload include prominent left ventricular pulsation and cardiomegaly on chest radiographs. Manifestations of systemic ischemia include a bounding pulse and widened pulse pressure (\u0026gt;25mmHg), or a difference between systolic and diastolic blood pressure greater than half of the systolic value, with lower diastolic blood pressure. Other clinical manifestations caused by insufficient systemic perfusion include acidosis, oliguria, and abdominal distension[18].\u003c/p\u003e\n\u003cp\u003e(2) For the diagnosis of RDS, BPD, NEC, and PVL, we referred to the criteria outlined in \u003cem\u003ePractical Neonatology\u0026nbsp;\u003c/em\u003e(fifth edition)[19]. The diagnostic criteria and grading system for IVH were based on \u003cem\u003eVolpe\u0026apos;s Neurology of the Newborn\u003c/em\u003e[20].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e1.4 Surgical PDA ligation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(1) Indications for surgical ligation：Surgical ligation was indicated for premature infants with hs-PDA who fail to respond 2-3 courses of cyclo-oxygenase inhibitors (indomethacin or ibuprofen) or those who could not undergo medical treatment due to contraindications ( including gastrointestinal bleeding, intracranial hemorrhage, oliguria, elevated creatinine, elevated urea, DIC, thrombocytopenia, etc.). Significant hemodynamic changes and/or ventilator dependency were also considered indications for surgical intervention[21].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e(2) Surgical Method: PDA ligation was performed at bedside in NICU by an experienced pediatric cardiothoracic surgery team. A small incision was made under the axilla, and the chest cavity was entered through the third intercostal space. The ductus arteriosus was isolated and ligated using two 7-0 silk sutures. The chest cavity was then closed in layers after confirming the absence of internal bleeding.\u003c/p\u003e\n\u003cp id=\"_Toc11759\"\u003e\u003cstrong\u003e1.5\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;Statistical analysis\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eStatistical analysis was performed using SPSS 26.0 software. Measurement data that conformed to normal distribution and homogeneity of variance were expressed as mean \u0026plusmn; standard deviation (\u0026plusmn;s), and comparisons between groups were conducted using the independent samples t-test. Measurement data with a skewed distribution were expressed as median [Q1, Q3], and comparisons between groups were made using the Mann-Whitney U test. Count data were expressed as percentages (%), and comparisons between groups were performed using the chi-square test or Fisher\u0026apos;s exact test. Univariate analysis was conducted on the included influencing factors, and the significant factors identified were further subjected to binary logistic regression analysis. A \u003cem\u003ep\u003c/em\u003e-value less than 0.05 was considered statistically significant.\u003c/p\u003e"},{"header":"2 Result","content":"\u003cp\u003eOver a three-year period, 76 cases of VLBWIs underwent surgical PDA ligation. After excluding 23 cases with preoperative invasive mechanical ventilation\u0026le;3 days, 3 cases with severe congenital malformations, and 3 cases with incomplete data, a total of 47 cases met the criteria and were included in our study (Figure 1). Among these, 34 infants were successfully extubated from mechanical ventilation within 7 days (\u0026le;7 days) after PDA ligation, while 13 infants required mechanical ventilation for \u0026gt;7 days after ligation. The study cohort included 25 males and 22 females, with a male-to-female ratio of 1.14:1. The mean gestational age at birth was 26.7\u0026plusmn;1.3 weeks, and the mean birth weight was 894.2\u0026plusmn;205.2g. The mean postnatal age at surgery was 31.3\u0026plusmn;14.6 days, the mean corrected gestational age at surgery was 31.2\u0026plusmn;2.3 weeks, and the mean weight at surgery was 1355.1\u0026plusmn;409.5g.\u0026nbsp;The distribution of gestational age and birth weight at birth was as follows:\u0026nbsp;13 infants were born at\u0026lt; 26 weeks, 23 were born between 26-27\u003csup\u003e+6\u0026nbsp;\u003c/sup\u003eweeks, and 11 were born between 28-31\u003csup\u003e+6\u003c/sup\u003e weeks; 11 infants had a birth weight of \u0026lt; 750g, 23 had a birth weight between 750-999g, and 13 had a birth weight between 1000-1500g. The mean duration of mechanical ventilation before PDA ligation was 23.7\u0026plusmn;15.1 days, and the mean duration of mechanical ventilation after ligation was 10.7\u0026plusmn;12.7 days. The overall mortality rate was 6.4% (3/47).\u003c/p\u003e\n\u003cp\u003eThere were no statistically significant differences between two groups in terms of gender, gestational age, birth weight, proportion of cesarean deliveries, 5-minute Apgar score, SGA,\u0026nbsp;ACS,\u0026nbsp;RDS, use of\u0026nbsp;PS, and use of cyclo-oxygenase inhibitors (\u003cem\u003ep\u003c/em\u003e\u0026gt; 0.05) (Table 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eCompared with VLBWIs in mechanical ventilation\u0026le;7 days after ligation group, those in mechanical ventilation\u0026gt;7 days after ligation group had a significantly higher proportion of preoperative RSS/kg \u0026gt;3 (\u003cem\u003ep\u003c/em\u003e\u0026lt;0.05). There were no statistically significant differences between two groups in terms of corrected gestational age at surgery,\u003c/p\u003e\n\u003cp\u003epostnatal age at surgery, weight at surgery, proportion of C4 stage of hs-PDA, or preoperative mechanical ventilation time.\u0026nbsp;Additionally,\u0026nbsp;there were no significant differences between the two groups in preoperative MAP, FiO\u003csub\u003e2\u003c/sub\u003e, preoperative blood gas analysis indicators (PH, PaO\u003csub\u003e2\u003c/sub\u003e, PaCO\u003csub\u003e2\u003c/sub\u003e, and ABE), preoperative IS, preoperative blood pressure changes (SBP, DBP, PP), proportion of preoperative RSS\u0026gt;3, or proportion of preoperative OI\u0026gt;10 (Table 2).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEchocardiography results showed a significant decrease in systolic PSV and a significant reduction in LVDD in the mechanical ventilation\u0026gt;7 days after ligation group (\u003cem\u003ep\u003c/em\u003e\u0026lt;0.05). However, there were no statistically significant differences between two groups in PDA diameter, LA/AO ratio, or proportion of E4 stage of hs-PDA (Table 3).\u003c/p\u003e\n\u003cp\u003eCompared with VLBWIs in mechanical ventilation\u0026le; 7 days after ligation group,\u0026nbsp;those in the mechanical ventilation\u0026gt;7 days after ligation group had significantly higher proportions of postoperative RSS/kg\u0026gt; 3 and OI\u0026gt; 10, as well as higher postoperative FiO\u003csub\u003e2\u003c/sub\u003e and IS (\u003cem\u003ep\u003c/em\u003e\u0026lt; 0.05).\u0026nbsp;Conversely,\u0026nbsp;postoperative PaO\u003csub\u003e2\u003c/sub\u003e was significantly lower in mechanical ventilation\u0026gt; 7 days after ligation group (\u003cem\u003ep\u003c/em\u003e\u0026lt; 0.05). There were no statistically significant differences between two groups in postoperative MAP, proportion of postoperative RSS\u0026gt; 3, postoperative blood gas analysis indicators (PH, PaO\u003csub\u003e2\u003c/sub\u003e, PaCO2, and ABE), or postoperative blood pressure changes (SBP, DBP, PP) (Table 4).\u003c/p\u003e\n\u003cp\u003eThere were no statistically significant differences in the incidence of in-hospital complications between two groups, including NEC stage 2 or higher, GM-IVH grade III-IV, ROP stage 3 or higher, and PVL (\u003cem\u003ep\u003c/em\u003e\u0026gt; 0.05). The incidence of moderate to severe BPD showed an upward trend in group of VLBWIs who required mechanical ventilation for＞7 days after ligation (\u003cem\u003e\u0026chi;\u003csup\u003e2\u003c/sup\u003e\u0026nbsp;\u003c/em\u003e= 3.072, \u003cem\u003ep\u003c/em\u003e= 0.080). The mortality rate in mechanical ventilation＞7\u0026nbsp;days after ligation group (23.1%) was higher than that in mechanical ventilation \u0026le; 7 days after ligation group, with a statistically significant difference (\u003cem\u003e\u0026chi;\u003csup\u003e2\u003c/sup\u003e\u0026nbsp;\u003c/em\u003e= 0.964, \u003cem\u003ep\u003c/em\u003e= 0.026) (Table 5).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFactors with \u003cem\u003ep\u003c/em\u003e\u0026lt;0.1 identified in the univariate analysis were included in the binary logistic regression analysis. Since moderate to severe BPD can affect lung ventilation and gas exchange in premature infants, leading to increased respiratory support requirements before PDA ligation and influencing the need for invasive mechanical ventilation after PDA ligation, our study incorporated moderate to severe BPD into the model analysis. The results showed that a preoperative RSS/kg\u0026gt; 3 was an independent risk factor for mechanical ventilation\u0026gt; 7 days after PDA ligation in VLBWIs. When preoperative RSS/kg \u0026gt;3, the likelihood of mechanical ventilation\u0026gt; 7 days after ligation increased by approximately 10 times (OR=10.04). Elevated postoperative PaO\u003csub\u003e2\u003c/sub\u003e was identified as an independent protective factor for mechanical ventilation\u0026gt; 7 days after PDA ligation in VLBIWs,\u0026nbsp;increasing the likelihood of successful extubation\u0026nbsp;within 7 days after ligation by 16.4%. Additionally, there was a trend\u0026nbsp;suggesting that\u0026nbsp;moderate to severe BPD influenced extubation time after ligation (\u003cem\u003ep\u003c/em\u003e=0.09) (Table 6).\u0026nbsp;\u003c/p\u003e"},{"header":"3 Discussion","content":"\u003cp\u003eOur study identified several key factors influencing the duration of mechanical ventilation after surgical ligation of PDA in VLBWIs. We emphasize the importance of a comprehensive preoperative evaluation of lung disease severity and respiratory status in VLBWIs before proceeding with surgical PDA ligation.\u003c/p\u003e \u003cp\u003ePDA is the most common clinical cardiovascular issue in premature infants, particularly in developing countries where access to advanced medical technologies may be limited. Despite the increasing adoption of transcatheter device closure in more developed regions, surgical ligation persists as a necessary option in many parts of the world. This is largely due to the availability and relative simplicity of the surgical procedure compared to the more technologically demanding transcatheter device closure. In addition, the cost of transcatheter devices and the need for specialized equipment and expertise can be prohibitive in developing countries, further reinforcing the reliance on surgical ligation. Surgical ligation has been a traditional method for managing PDA, especially in VLBWIs, due to its effectiveness in ensuring ductal closure and its feasibility in resource-limited environments[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eEarly treatment for premature infants with hs-PDA can improve their clinical outcomes and reduce mortality rates. The main pathophysiological change in hs-PDA is pulmonary over-circulation caused by excessive left-to-right shunting, which is associated with an increased need for respiratory support and mechanical ventilation[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Zong et al.[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] found that lung water content is much higher in PDA surgery infants among premature infants with a gestational age of \u0026le;\u0026thinsp;25 weeks. Qian et al.[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] analyzed clinical data from CHNN and found that extremely premature infants receiving invasive mechanical ventilation were the primary beneficiaries of PDA treatment. Although surgical ligation carries potential risks, persistent hs-PDA and long-term dependence on mechanical ventilation in premature infants with contraindications to pharmacological therapy or those who have failed medical treatment are common indications for PDA ligation[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. However, Seo et al. [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] showed that premature infants with poor respiratory conditions were more prone to prolonged mechanical ventilation dependence after PDA ligation. Therefore, finding the most suitable time for PDA ligation to improve postoperative clinical outcomes has become an urgent problem for clinicians. Our study aims to identify risk factors for prolonged mechanical ventilation after PDA ligation and optimize perioperative management strategies for surgical PDA ligation.\u003c/p\u003e \u003cp\u003eThe magnitude of duct shunt flow and echocardiographic indicators reflecting excessive pulmonary circulation volume can represent the degree of pulmonary insufficiency caused by PDA. Studies have shown that lung compliance, tidal volume, and minute ventilation of premature infants with hs-PDA improved rapidly after ligation[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. A lower PSV was associated with delayed extubation after PDA ligation[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. In a retrospective study of ventilator-dependent extremely premature infants who underwent PDA ligation, Krishnappa et al. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] found that a large PDA diameter (greater than 2.5 mm) and left ventricular dilation were associated with earlier extubation after ligation. Our study also found that higher PSV and relatively dilated left ventricle (higher LVDD) were associated with early extubation (mechanical ventilation\u0026thinsp;\u0026le;\u0026thinsp;7 days) after PDA ligation in VLBWIs. However, this association was no longer significant after adjusting for confounding factors, which may be related to the limited sample size in our study, and PDA diameter in both groups of VLBWIs were greater than 2.5mm.\u003c/p\u003e \u003cp\u003ePaO\u003csub\u003e2\u003c/sub\u003e reflects the oxygen status of the pulmonary capillaries and serves as an indicator for evaluating extrapulmonary respiratory function, as well as representing the lung's ventilation function. Our study showed a significant increase in postoperative FiO\u003csub\u003e2\u003c/sub\u003e, postoperative IS, and the proportion of OI\u0026thinsp;\u0026gt;\u0026thinsp;10, while postoperative PaO\u003csub\u003e2\u003c/sub\u003e decreased significantly in mechanical ventilation\u0026gt;7days after ligation group of VLBWIs. This suggests that VLBWIs with prolonged mechanical ventilation after PDA ligation have a higher demand for respiratory and circulatory support. Elevated postoperative PaO\u003csub\u003e2\u003c/sub\u003e was identified as an independent protective factor for mechanical ventilation\u0026thinsp;\u0026gt;\u0026thinsp;7 days after ligation in VLBWIs, increasing the likelihood of successful extubation within 7 days after ligation by 16.4%. Additionally, there was a trend indicating that moderate to severe BPD influences on extubation time after ligation, meaning that VLBWIs with moderate to severe BPD are more likely to fail extubating within 7 days after PDA ligation. Meanwhile, the in-hospital mortality rate of VLBWIs in the mechanical ventilation\u0026gt;7 days after ligation group was significantly higher, suggesting that prolonged mechanical ventilation after PDA ligation is associated with elevated in-hospital mortality rate.\u003c/p\u003e \u003cp\u003eOI is commonly used to quantify the severity of respiratory failure in premature infants. However, continuous OI monitoring for real-time PaO\u003csub\u003e2\u003c/sub\u003e data requires indwelling arterial catheters and frequent arterial blood sampling, which may lead to complications such as thromboembolism, ischemic injury, and iatrogenic anemia in VLBWIs[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Clinicians have recognized the value of using non-invasive measures to assess the severity of respiratory failure and lung condition. RSS is a non-invasive, continuously monitorable clinical indicator. It is a simplified severity score calculated as the product of MAP and FiO\u003csub\u003e2\u003c/sub\u003e [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. When target oxygen saturation of mechanically ventilated premature infants was maintained between 88% and 94%, there is a strong correlation between RSS and OI. Therefore, RSS can be used as a surrogate for OI when premature infants are kept within target oxygen saturation range[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Studies have shown that RSS can predict the occurrence and progression of neonatal respiratory diseases. An elevated RSS (\u0026gt;\u0026thinsp;4) of newborns is associated with increased demand for respiratory support within 24 hours after birth[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. In VLBWIs receiving invasive mechanical ventilation, elevated RSS is correlated with extubation failure[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. RSS can also predict neonatal clinical outcomes. In extremely premature infants, RSS\u0026thinsp;\u0026ge;\u0026thinsp;3 on day 14 and RSS\u0026thinsp;\u0026ge;\u0026thinsp;3.6 on day 21 after birth are reliable indicators for predicting severe BPD or death[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Shah et al.[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e] found that in premature infants with birth weight\u0026thinsp;\u0026le;\u0026thinsp;1250g, those with RSS\u0026thinsp;\u0026ge;\u0026thinsp;2 within 24 hours after birth had an increased risk of death and morbidity, and those with elevated RSS had a higher proportion of receiving PDA treatment. Bhattacharjee et al.[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] obtained similar results in a study focusing on extremely low birth weight infants.\u003c/p\u003e \u003cp\u003eIn neonates receiving mechanical ventilation, the required pressure support during ventilation is correlated with the severity of lung pathology. In clinical settings, a MAP of 10 cmH\u003csub\u003e2\u003c/sub\u003eO in a premature infant weighing 500 grams is considered to notably differ from the same magnitude of pressure in an infant weighing 1000 grams. This suggests that pressure demand for respiratory support during ventilation in neonates appeared to correlate with body weight, leading to the introduction of a newer concept known as RSS/kg in the literature[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Studies have shown that RSS/kg is a potential marker associated with occurrence and progression of PH in premature infants, and an elevated RSS is correlated with an increased risk of BPD-PH[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. In our study, there was no significant difference in RSS\u0026thinsp;\u0026gt;\u0026thinsp;3 between the two groups of VLBWIs, while the proportion of preoperative RSS/kg\u0026thinsp;\u0026gt;\u0026thinsp;3 was significantly higher in the prolonged mechanical ventilation (\u0026gt;\u0026thinsp;7 days) after ligation group. Further binary logistic regression analysis revealed that preoperative RSS/kg\u0026thinsp;\u0026gt;\u0026thinsp;3 was an independent risk factor for prolonged mechanical ventilation (\u0026gt;\u0026thinsp;7 days) after PDA ligation in VLBWIs (OR\u0026thinsp;=\u0026thinsp;10.04). This means that when RSS/kg\u0026thinsp;\u0026gt;\u0026thinsp;3 before PDA ligation, the risk of prolonged mechanical ventilation (\u0026gt;\u0026thinsp;7 days) after ligation in VLBWIs increased by approximately 10 times, further validating previous research findings[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. We hypothesize that a higher RSS/kg before PDA ligation in VLBWIs may be associated with persistent hs-PDA-induced pulmonary congestion, pulmonary edema, and subsequent irreversible exacerbation of lung pathology.\u003c/p\u003e \u003cp\u003eThere were several limitations in our study: (1) This study only included data from a single center with a limited sample size. Further validation with a larger sample size is needed in the next step. (2) As a retrospective study, there were certain limitations in PDA assessment timing and treatment decisions, and echocardiography data was difficult to replicate. (3) Since the focus of this study was on infants who underwent surgical PDA ligation, the results cannot be used to infer the effectiveness of medical treatment.\u003c/p\u003e \u003cp\u003eIn conclusion, our study found that VLBWIs with more severe lung disease before PDA ligation, characterized by RSS/kg\u0026thinsp;\u0026gt;\u0026thinsp;3 and/or moderate to severe BPD, were more likely to experience postoperative ventilator dependence. This approach can help minimize the risk of prolonged mechanical ventilation after ligation and its associated adverse outcomes, including death.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eABE: Actual Base Surplus\u003c/p\u003e\n\u003cp\u003eACS:\u0026nbsp;Antenatal Corticosteroid\u003c/p\u003e\n\u003cp\u003eBPD:\u0026nbsp;Bronchopulmonary Dysplasia\u003c/p\u003e\n\u003cp\u003eBW: Birth Weight\u003c/p\u003e\n\u003cp\u003eCHNN:\u0026nbsp;Chinese Neonatal Network\u003c/p\u003e\n\u003cp\u003eDBP:\u0026nbsp;Diastolic Blood Pressure\u003c/p\u003e\n\u003cp\u003eDIC:\u0026nbsp;Disseminated Intravascular Coagulation\u003c/p\u003e\n\u003cp\u003eFiO\u003csub\u003e2\u003c/sub\u003e: Inhaled Oxygen Concentration\u003c/p\u003e\n\u003cp\u003eGA:\u0026nbsp;Gestational Age\u003c/p\u003e\n\u003cp\u003eGM-IVH:\u0026nbsp;Germinal Matrix-Intraventricular Hemorrhage\u003c/p\u003e\n\u003cp\u003ehs-PDA:\u0026nbsp;Hemodynamically Significant Patent Ductus Arteriosus\u003c/p\u003e\n\u003cp\u003eIS:\u0026nbsp;Inotrope Score\u003c/p\u003e\n\u003cp\u003eIVH: Intraventricular Hemorrhage\u003c/p\u003e\n\u003cp\u003eLA/AO:\u0026nbsp;Left Atrium-to-Aortic Root Diameter Ratio\u003c/p\u003e\n\u003cp\u003eLVDD:\u0026nbsp;Left Ventricular End-diastolic Diameter\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMAP: Mean Airway Pressure\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eNEC: Necrotizing Enterocolitis\u003c/p\u003e\n\u003cp\u003eNICU:\u0026nbsp;Neonatal Intensive Care Unit\u003c/p\u003e\n\u003cp\u003eOI: Oxygen Index\u003c/p\u003e\n\u003cp\u003ePaO\u003csub\u003e2\u003c/sub\u003e: Oxygen Partial Pressure\u003c/p\u003e\n\u003cp\u003ePaCO\u003csub\u003e2\u003c/sub\u003e:\u0026nbsp;Arterial Partial Pressure of Carbon Dioxide\u003c/p\u003e\n\u003cp\u003ePDA:\u0026nbsp;Patent Ductus Arteriosus\u003c/p\u003e\n\u003cp\u003ePH:\u0026nbsp;Pulmonary Hypertension\u003c/p\u003e\n\u003cp\u003ePP:\u0026nbsp;Pulse Pressure Difference\u003c/p\u003e\n\u003cp\u003ePS:\u0026nbsp;Pulmonary Surfactant\u003c/p\u003e\n\u003cp\u003ePSV:\u0026nbsp;Peak Systolic Velocity\u003c/p\u003e\n\u003cp\u003ePVL:\u0026nbsp;Periventricular Leukomalacia\u003c/p\u003e\n\u003cp\u003eRDS: Respiratory Distress Syndrome\u003c/p\u003e\n\u003cp\u003eROP:\u0026nbsp;Retinopathy of Prematurity\u003c/p\u003e\n\u003cp\u003eRSS:\u0026nbsp;Respiratory Severity Score\u003c/p\u003e\n\u003cp\u003eSBP:\u0026nbsp;Systolic Blood Pressure\u003c/p\u003e\n\u003cp\u003eSGA:\u0026nbsp;Small for Gestational Age\u003c/p\u003e\n\u003cp\u003eVLBWIs: Very Low Birth Weight Infants\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Medical Ethics Committee of Children\u0026apos;s Hospital of Zhejiang University School of Medicine (Approval No. 2022-IRB-076). Given the retrospective nature of the study and the use of anonymized clinical data, the committee granted a waiver of informed consent.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during this study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors declare that there is no conflict of interest in this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work is supported by Shanghai Children\u0026rsquo;s Hospital Clinical Research Project [2022YLYM010].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eYY and TM contributed to the conception and design of this study. YY and TM drafted the manuscript and revised it critically. YY contributed to acquisition, analysis and interpretation of data. All authors read the manuscript and gave the permission to be published.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors want to thank all the participants in this study. \u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eGupta S, Subhedar N, Bell J, Field D, Bowler U, Hutchison E, et al. Trial of Selective Early Treatment of Patent Ductus Arteriosus with Ibuprofen. N Engl J Med. 2024;390(4):314-25.\u003c/li\u003e\n\u003cli\u003eOgnean ML, Boantă O, Kovacs S, Zg\u0026acirc;rcea C, Dumitra R, Olariu E, et al. Persistent Ductus Arteriosus in Critically Ill Preterm Infants. 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Front Pediatr. 2020;8:573627.\u003c/li\u003e\n\u003cli\u003eHamrick SEG, Sallmon H, Rose AT, Porras D, Shelton EL, Reese J, et al. Patent Ductus Arteriosus of the Preterm Infant. Pediatrics. 2020;146(5).\u003c/li\u003e\n\u003cli\u003eQian A, Jiang S, Gu X, Li S, Lei X, Shi W, et al. Treatment of patent ductus arteriosus and short-term outcomes among extremely preterm infants: a multicentre cohort study. EClinicalMedicine. 2024;67:102356.\u003c/li\u003e\n\u003cli\u003eBackes CH, Hill KD, Shelton EL, Slaughter JL, Lewis TR, Weisz DE, et al. Patent Ductus Arteriosus: A Contemporary Perspective for the Pediatric and Adult Cardiac Care Provider. J Am Heart Assoc. 2022;11(17):e025784.\u003c/li\u003e\n\u003cli\u003eHoffmann JK, Khazal Z, Apers W, Sharma P, Weismann CG, Kaganov K, et al. Who Still Gets Ligated? Reasons for Persistence of Surgical Ligation of the Patent Ductus Arteriosus Following Availability of Transcatheter Device Occlusion for Premature Neonates. J Cardiovasc Dev Dis. 2024;11(5).\u003c/li\u003e\n\u003cli\u003eKoch J, Hensley G, Roy L, Brown S, Ramaciotti C, Rosenfeld CR. Prevalence of spontaneous closure of the ductus arteriosus in neonates at a birth weight of 1000 grams or less. Pediatrics. 2006;117(4):1113-21.\u003c/li\u003e\n\u003cli\u003eWeisz DE, More K, McNamara PJ, Shah PS. PDA ligation and health outcomes: a meta-analysis. Pediatrics. 2014;133(4):e1024-e46.\u003c/li\u003e\n\u003cli\u003eSzymankiewicz M, Hodgman JE, Siassi B, Gadzinowski J. Mechanics of breathing after surgical ligation of patent ductus arteriosus in newborns with respiratory distress syndrome. Biol Neonate. 2004;85(1):32-6.\u003c/li\u003e\n\u003cli\u003eMitra S, Florez ID, Tamayo ME, Mbuagbaw L, Vanniyasingam T, Veroniki AA, et al. Association of Placebo, Indomethacin, Ibuprofen, and Acetaminophen With Closure of Hemodynamically Significant Patent Ductus Arteriosus in Preterm Infants: A Systematic Review and Meta-analysis. Jama. 2018;319(12):1221-38.\u003c/li\u003e\n\u003cli\u003eWeisz DE, Mirea L, Resende MHF, Ly L, Church PT, Kelly E, et al. Outcomes of Surgical Ligation after Unsuccessful Pharmacotherapy for Patent Ductus Arteriosus in Neonates Born Extremely Preterm. J Pediatr. 2018;195:292-6.e3.\u003c/li\u003e\n\u003cli\u003eKrishnappa S, Shah PS, Jain A, Resende MHF, McNamara PJ, Weisz DE. Predictors of Early Extubation after Patent Ductus Arteriosus Ligation among Infants Born Extremely Preterm Dependent on Mechanical Ventilation. J Pediatr. 2019;214.\u003c/li\u003e\n\u003cli\u003eMcNamara PJ, Sehgal A. Towards rational management of the patent ductus arteriosus: the need for disease staging. Arch Dis Child Fetal Neonatal Ed. 2007;92(6):F424-F7.\u003c/li\u003e\n\u003cli\u003eMcNamara PJ, Sehgal A. Towards rational management of the patent ductus arteriosus: the need for disease staging. Arch Dis Child Fetal Neonatal Ed. 2007;92(6):F424-7.\u003c/li\u003e\n\u003cli\u003eQiu X, Ye H, Shao X. Practice of Neonatology. 5th ed. Beijing: People\u0026rsquo;s Medical Publishing House; 2018. 577,96,634,861 p.\u003c/li\u003e\n\u003cli\u003eInder TE, Perlman JM, Volpe JJ. Chapter 24 - Preterm Intraventricular Hemorrhage/Posthemorrhagic Hydrocephalus. In: Volpe JJ, Inder TE, Darras BT, de Vries LS, du Plessis AJ, Neil JJ, et al., editors. Volpe\u0026apos;s Neurology of the Newborn (Sixth Edition): Elsevier; 2018. p. 637-98.e21.\u003c/li\u003e\n\u003cli\u003eEl-Khuffash AF, Jain A, McNamara PJ. Ligation of the patent ductus arteriosus in preterm infants: understanding the physiology. J Pediatr. 2013;162(6):1100-6.\u003c/li\u003e\n\u003cli\u003eSeo YM, Sung IK, Yum SK. Risk factors associated with prolonged mechanical ventilation after surgical patent ductus arteriosus ligation in preterm infants. J Matern Fetal Neonatal Med. 2020:1-8.\u003c/li\u003e\n\u003cli\u003eZong H, Huang Y, Huang Z, Zhao J, Lin B, Fu Y, et al. Lung ultrasound score predicts patent ductus arteriosus ligation among neonates \u0026lt;/=25 weeks. Pediatr Pulmonol. 2023;58(9):2487-94.\u003c/li\u003e\n\u003cli\u003eWeisz DE, Giesinger RE. Surgical management of a patent ductus arteriosus: Is this still an option? Semin Fetal Neonatal Med. 2018;23(4):255-66.\u003c/li\u003e\n\u003cli\u003eSu BH, Lin HY, Chiu HY, Tsai ML, Chen YT, Lu IC. Therapeutic strategy of patent ductus arteriosus in extremely preterm infants. Pediatr Neonatol. 2020;61(2):133-41.\u003c/li\u003e\n\u003cli\u003eNaik-Mathuria B, Chang S, Fitch ME, Westhoff J, Brandt ML, Ayres NA, et al. Patent ductus arteriosus ligation in neonates: preoperative predictors of poor postoperative outcomes. J Pediatr Surg. 2008;43(6):1100-5.\u003c/li\u003e\n\u003cli\u003eAboalqez A, Deindl P, Ebenebe CU, Singer D, Blohm ME. Iatrogenic Blood Loss in Very Low Birth Weight Infants and Transfusion of Packed Red Blood Cells in a Tertiary Care Neonatal Intensive Care Unit. Children (Basel). 2021;8(10).\u003c/li\u003e\n\u003cli\u003eMerrill JD, Ballard RA, Cnaan A, Hibbs AM, Godinez RI, Godinez MH, et al. Dysfunction of pulmonary surfactant in chronically ventilated premature infants. Pediatr Res. 2004;56(6):918-26.\u003c/li\u003e\n\u003cli\u003eIyer NP, Mhanna MJ. Non-invasively derived respiratory severity score and oxygenation index in ventilated newborn infants. Pediatr Pulmonol. 2013;48(4):364-9.\u003c/li\u003e\n\u003cli\u003eHedstrom AB, Gove NE, Mayock DE, Batra M. Performance of the Silverman Andersen Respiratory Severity Score in predicting PCO(2) and respiratory support in newborns: a prospective cohort study. J Perinatol. 2018;38(5):505-11.\u003c/li\u003e\n\u003cli\u003eMhanna MJ, Iyer NP, Piraino S, Jain M. Respiratory severity score and extubation readiness in very low birth weight infants. Pediatr Neonatol. 2017;58(6):523-8.\u003c/li\u003e\n\u003cli\u003eJung YH, Jang J, Kim HS, Shin SH, Choi CW, Kim EK, et al. Respiratory severity score as a predictive factor for severe bronchopulmonary dysplasia or death in extremely preterm infants. BMC Pediatr. 2019;19(1):121.\u003c/li\u003e\n\u003cli\u003eShah SI, Aboudi D, La Gamma EF, Brumberg HL. Respiratory Severity Score greater than or equal to 2 at birth is associated with an increased risk of mortality in infants with birth weights less than or equal to 1250\u0026thinsp;g. Pediatr Pulmonol. 2020;55(12):3304-11.\u003c/li\u003e\n\u003cli\u003eBhattacharjee I, Das A, Collin M, Aly H. Predicting outcomes of mechanically ventilated premature infants using respiratory severity score. J Matern Fetal Neonatal Med. 2022;35(23):4620-7.\u003c/li\u003e\n\u003cli\u003eSeo YM, Yum SK, Sung IK. Respiratory Severity Score with Regard to Birthweight during the Early Days of Life for Predicting Pulmonary Hypertension in Preterm Infants. J Trop Pediatr. 2020;66(6):561-8.\u003c/li\u003e\n\u003cli\u003eBeer L, Rivera BK, Jama W, Slaughter JL, Backes CH, Conroy S, et al. Association of the respiratory severity score with bronchopulmonary dysplasia-associated pulmonary hypertension in infants born extremely preterm. J Perinatol. 2024;44(2):294-300.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003e\u003cstrong\u003eTable 1 Comparison of basic clinical characteristics\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"602\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 189px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 151px;\"\u003e\n \u003cp\u003eMechanical ventilation \u0026le;7d\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eafter ligation（n=34）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003eMechanical ventilation＞7d after ligation（n=13）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 61px;\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026chi;\u003csup\u003e2\u003c/sup\u003e\u003c/em\u003e/Z/t\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eMale, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e18（52.9）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 141px;\"\u003e\n \u003cp\u003e7（53.8）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e0.956\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eGA \u003csup\u003ea\u0026nbsp;\u003c/sup\u003e(w)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e26.5[24.7,30.0]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 141px;\"\u003e\n \u003cp\u003e26.7[25.3,28.1]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e-0.393\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e0.694\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eBW (g)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e920.3\u0026plusmn;188.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 141px;\"\u003e\n \u003cp\u003e825.8\u0026plusmn;237.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e1.429\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e0.160\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eCesarean deliveries, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e12（35.3）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 141px;\"\u003e\n \u003cp\u003e5（38.5）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e0.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003e5min Apgar score \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e8[2,10]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 141px;\"\u003e\n \u003cp\u003e8.5[2,10]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e-0.651\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e0.515\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eSGA, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e0（0）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 141px;\"\u003e\n \u003cp\u003e2（15.4）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e2.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e0.126\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eACS, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e5（14.7）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 141px;\"\u003e\n \u003cp\u003e3（23.1）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e0.062\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e0.803\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eRDS, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e33（97.1）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 141px;\"\u003e\n \u003cp\u003e12（92.3）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e0.521\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e0.470\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003ePS, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e31（91.2）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 141px;\"\u003e\n \u003cp\u003e12（92.3）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e0.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003ecyclo-oxygenase inhibitors, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e29（85.3）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 141px;\"\u003e\n \u003cp\u003e11（84.6）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 61px;\"\u003e\n \u003cp\u003e0.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 60px;\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eData are presented as n (%), mean \u0026plusmn; standard deviation (\u0026plusmn;s), and median [P25, P75] for \u003csup\u003ea\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eGA, gestational age; BW, birth weight; SGA, small for gestational age; ACS, antenatal corticosteroids; RDS, respiratory distress syndrome in newborns; PS, pulmonary surfactant.\u003c/p\u003e\n\u003cp\u003eA \u003cem\u003ep\u003c/em\u003e-value less than 0.05 was considered statistically significant.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2 Comparison of preoperative characteristics\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"615\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 142px;\"\u003e\n \u003cp\u003eMechanical ventilation \u0026le;7d\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eafter ligation（n=34）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003eMechanical ventilation＞7d after ligation（n=13）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 67px;\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026chi;\u003csup\u003e2\u003c/sup\u003e\u003c/em\u003e/Z/t\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eAge at surgery \u003csup\u003ea\u0026nbsp;\u003c/sup\u003e(d)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e30[4-66]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e28[8-70]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-1.286\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.199\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eCorrected gestational age at surgery (w)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e31.5\u0026plusmn;2.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e30.5\u0026plusmn;2.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e1.307\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.198\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003eWeight at surgery (g)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e1403.2\u0026plusmn;408.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e1229.2\u0026plusmn;401.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e1.313\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.196\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative C4 hs-PDA, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e10（29.4%）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e5（38.5%）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e0.060\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.906\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative mechanical\u003c/p\u003e\n \u003cp\u003eventilation time\u003csup\u003e\u0026nbsp;a\u0026nbsp;\u003c/sup\u003e(d)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e23[4-66]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e18[3-70]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-1.095\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.274\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative MAP\u003csup\u003e\u0026nbsp;a\u003c/sup\u003e (cmH\u003csub\u003e2\u003c/sub\u003eO)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e11[8-16]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e12[9-23]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-1.700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.089\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative FiO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026nbsp;a\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e0.33[0.21-0.80]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e0.40[0.21-1.00]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-1.646\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.100\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative RSS\u0026gt;3, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e24（70.6）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e11（84.6）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e0.375\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.540\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative RSS/kg\u0026gt;3, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e11（32.4）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e10（79.6）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e7.558\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.006*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative PaO\u003csub\u003e2\u003c/sub\u003e (mmHg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e59.8\u0026plusmn;7.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e50.2\u0026plusmn;10.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e1.899\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative OI\u0026gt;10, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e2（5.9）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e3（23.1）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e1.396\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.237\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative PH\u003csup\u003e\u0026nbsp;a\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e7.30[7.20-7.53]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e7.30[7.10-7.40]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-0.061\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.952\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative PaCO\u003csub\u003e2\u003c/sub\u003e (mmHg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e54.0\u0026plusmn;11.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e50.2\u0026plusmn;10.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e1.035\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.306\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative ABE (mmol/l)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e2.15[0.2-9.2]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e3.7[0.4-19.1]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-1.785\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.074\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative IS\u003csup\u003e\u0026nbsp;a\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e0[0-40]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e5[0-50]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-1.886\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.059\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative SBP\u003csup\u003e\u0026nbsp;a\u003c/sup\u003e (mmHg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e62.0\u0026plusmn;13.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e60.9\u0026plusmn;8.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e0.228\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.774\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative DBP\u003csup\u003e\u0026nbsp;a\u003c/sup\u003e (mmHg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e32.9\u0026plusmn;7.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e32.7\u0026plusmn;6.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e0.476\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.947\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 208px;\"\u003e\n \u003cp\u003ePreoperative PP\u003csup\u003e\u0026nbsp;a\u003c/sup\u003e (mmHg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 142px;\"\u003e\n \u003cp\u003e30[5-51]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e30[7-37]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-0.107\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.915\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eData are presented as n (%), mean \u0026plusmn; standard deviation (\u0026plusmn;s), and median [P25, P75] for \u003csup\u003ea\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003ePDA, patent ductus arteriosus; MAP, mean airway pressure; FiO\u003csub\u003e2\u003c/sub\u003e, inhaled oxygen concentration; RSS, respiratory severity score; PaO\u003csub\u003e2\u003c/sub\u003e, arterial oxygen partial pressure; OI, oxygen index; PaCO\u003csub\u003e2\u003c/sub\u003e, arterial partial pressure of carbon dioxide; ABE, actual base surplus; IS, inotrope score; SBP, systolic blood pressure; DBP, diastolic blood pressure; PP, pulse pressure difference; C4 hs-PDA, conducted to clinical manifestations\u0026nbsp;in C4 stage proposed by MacNamara.\u003c/p\u003e\n\u003cp\u003eA \u003cem\u003ep\u003c/em\u003e-value* less than 0.05 was considered statistically significant.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3 Comparison of preoperative echocardiographic indicators\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"615\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 166px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 132px;\"\u003e\n \u003cp\u003eMechanical ventilation \u0026le;7d\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eafter ligation（n=34）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 161px;\"\u003e\n \u003cp\u003eMechanical ventilation＞7d after ligation（n=13）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026chi;\u003csup\u003e2\u003c/sup\u003e\u003c/em\u003e/Z/t\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 90px;\"\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003ePDA diameter \u003csup\u003ea\u0026nbsp;\u003c/sup\u003e(mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e2.7[1.6-4.0]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e3.0[2.0-4.6]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e-0.798\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.425\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003ePSV (m/s)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e2.3\u0026plusmn;0.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e1.7\u0026plusmn;0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e2.584\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.013*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003eLA/AO\u003csup\u003e\u0026nbsp;a\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e1.2[1.0-1.5]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e1.1[1.0-1.7]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e-0.384\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.701\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003eLVDD (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e16.5\u0026plusmn;2.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e14.0\u0026plusmn;1.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e3.249\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003eE4 hs-PDA, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e11（32.4%）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 156px;\"\u003e\n \u003cp\u003e6（42.6%）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.293\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.588\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 24px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eData are presented as n (%), mean \u0026plusmn; standard deviation (\u0026plusmn;s), and median [P25, P75] for \u003csup\u003ea\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003ePSV, peak systolic velocity; LA/AO, left atrium-to-aortic root diameter ratio; LVDD, left ventricular end-diastolic diameter; E4 hs-PDA, conducted to echocardiography\u0026nbsp;in E4 stage proposed by MacNamara.\u003c/p\u003e\n\u003cp\u003eA \u003cem\u003ep\u003c/em\u003e-value* less than 0.05 was considered statistically significant.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 4 Comparison of postoperative characteristics\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"615\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 194px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 156px;\"\u003e\n \u003cp\u003eMechanical ventilation \u0026le;7d\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eafter ligation（n=34）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003eMechanical ventilation＞7d after ligation（n=13）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 67px;\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026chi;\u003csup\u003e2\u003c/sup\u003e\u003c/em\u003e/Z/t\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 198px;\"\u003e\n \u003cp\u003eMechanical ventilation\u0026nbsp;\u003c/p\u003e\n \u003cp\u003etime after ligation \u003csup\u003ea\u003c/sup\u003e (d)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e4[1-7]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e20[8-48]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-5.267\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.000*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 198px;\"\u003e\n \u003cp\u003ePostoperative MAP \u003csup\u003ea\u0026nbsp;\u003c/sup\u003e(cmH\u003csub\u003e2\u003c/sub\u003eO)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e11[7,15]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e11[9,17]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-1.553\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.121\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 198px;\"\u003e\n \u003cp\u003ePostoperative FiO\u003csub\u003e2\u003c/sub\u003e \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e0.30[0.21,0.45]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e0.35[0.21,0.63]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-2.106\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.035*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 198px;\"\u003e\n \u003cp\u003ePostoperative RSS\u0026gt;3, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e20（58.8）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e11（84.6）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e1.756\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.185\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 198px;\"\u003e\n \u003cp\u003ePostoperative RSS/kg\u0026gt;3, n(%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e7（20.6）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e8（61.5）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e5.495\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.019*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 198px;\"\u003e\n \u003cp\u003ePostoperative PaO\u003csub\u003e2\u003c/sub\u003e \u003csup\u003ea\u0026nbsp;\u003c/sup\u003e(mmHg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e64.6[52.1,85]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e59[41.8,68.5]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-3.052\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.002*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 198px;\"\u003e\n \u003cp\u003ePostoperative OI\u0026gt;10, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e0（0）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e4（30.8）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e7.824\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.005*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 198px;\"\u003e\n \u003cp\u003ePostoperative PH \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e7.4[7.1,7.5]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e7.3[7.1,7.5]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-1.128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.259\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 198px;\"\u003e\n \u003cp\u003ePostoperative PaCO\u003csub\u003e2\u003c/sub\u003e \u003csup\u003ea\u0026nbsp;\u003c/sup\u003e(mmHg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e42.3[27.4,63.0]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e47.2[26.9,80.0]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-0.868\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.385\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 198px;\"\u003e\n \u003cp\u003ePostoperative ABE \u003csup\u003ea\u0026nbsp;\u003c/sup\u003e(mmol/l)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e1.9[0.1,8.1]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e2.4[0.4,9.7]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-1.452\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.146\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 198px;\"\u003e\n \u003cp\u003ePostoperative IS \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e5.0[0.0,60.0]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e20.0[0.0,60.0]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-2.719\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.029*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 198px;\"\u003e\n \u003cp\u003ePostoperative SBP (mmHg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e65.7\u0026plusmn;9.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e62.1\u0026plusmn;8.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e1.204\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.235\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 198px;\"\u003e\n \u003cp\u003ePostoperative DBP \u003csup\u003ea\u0026nbsp;\u003c/sup\u003e(mmHg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e39.0[21.0,52.0]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e33.0[20.0,51.0]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-0.988\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.323\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 198px;\"\u003e\n \u003cp\u003ePostoperative PP \u003csup\u003ea\u003c/sup\u003e（mmHg）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e29.0[6.0,47.0]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e28.0[12.0,37.0]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e-0.619\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e0.536\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eData are presented as n (%), mean \u0026plusmn; standard deviation (\u0026plusmn;s), and median [P25, P75] for \u003csup\u003ea\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003ePDA, patent ductus arteriosus; MAP, mean airway pressure; FiO\u003csub\u003e2\u003c/sub\u003e, inhaled oxygen concentration; RSS, respiratory severity score; PaO\u003csub\u003e2\u003c/sub\u003e, arterial oxygen partial pressure; OI, oxygen index; PaCO\u003csub\u003e2\u003c/sub\u003e, arterial partial pressure of carbon dioxide; ABE, actual base surplus; IS, inotrope score; SBP, systolic blood pressure; DBP, diastolic blood pressure; PP, pulse pressure difference.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eA \u003cem\u003ep\u003c/em\u003e-value less than 0.05 was considered statistically significant.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 5 Comparison of in-hospital complications and death\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"568\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 209px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eMechanical ventilation \u0026le;7d after ligation（n=34）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eMechanical ventilation＞7d after ligation\u003c/p\u003e\n \u003cp\u003e（n=13）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026chi;\u003csup\u003e2\u003c/sup\u003e\u003c/em\u003e/Z/t\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 209px;\"\u003e\n \u003cp\u003eNEC \u0026ge; stage 2, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e1（2.9）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e0（0）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e0.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 209px;\"\u003e\n \u003cp\u003eModerate to severe BPD, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e7（20.6）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e6（46.2）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e3.072\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e0.080\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 209px;\"\u003e\n \u003cp\u003eGM-IVH grade III-IV, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e11（32.4）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e2（15.4）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e0.638\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e0.424\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 209px;\"\u003e\n \u003cp\u003eROP \u0026ge; stage 3, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e9（26.5）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e3（23.1）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e0.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e1.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 209px;\"\u003e\n \u003cp\u003ePVL, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e3（8.8）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e4（30.8）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e2.052\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e0.152\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 209px;\"\u003e\n \u003cp\u003eIn-hospital death, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e0（0）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e3（23.1）\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e0.964\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e0.026*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eData are presented as n (%).\u003c/p\u003e\n\u003cp\u003eNEC, necrotizing enterocolitis; BPD, bronchopulmonary dysplasia; GM-IVH, germinal matrix-intraventricular hemorrhage; ROP, retinopathy of prematurity; PVL, periventricular leukomalacia.\u003c/p\u003e\n\u003cp\u003eA \u003cem\u003ep\u003c/em\u003e-value less than 0.05 was considered statistically significant.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 6 Binary logistic regression analysis of factors influencing prolonged mechanical ventilation time after PDA ligation\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"568\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eFactors\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 57px;\"\u003e\n \u003cp\u003e\u0026beta;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 95px;\"\u003e\n \u003cp\u003eWald-value\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 85px;\"\u003e\n \u003cp\u003eOR-value\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e95%CI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 67px;\"\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003ePreoperative RSS/kg\u0026gt;3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e2.306\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e4.781\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e10.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e1.27-79.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e0.029*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003ePostoperative PaO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e-0.179\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e4.159\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e0.836\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e0.70-0.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e0.041*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003eModerate to severe BPD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 57px;\"\u003e\n \u003cp\u003e1.825\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e2.836\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e6.203\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e0.741-51.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e0.092\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eRSS, respiratory severity score; PaO2, arterial oxygen partial pressure;\u0026nbsp;BPD, bronchopulmonary dysplasia.\u003c/p\u003e\n\u003cp\u003eA \u003cem\u003ep\u003c/em\u003e-value less than 0.05 was considered statistically significant.\u0026nbsp;\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Patent ductus arteriosus, PDA ligation, Very low birth weight infants, Prolonged mechanical ventilation","lastPublishedDoi":"10.21203/rs.3.rs-6676905/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6676905/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cb\u003eBackground\u003c/b\u003e\u003c/p\u003e \u003cp\u003eIn developing countries, surgical ligation continues to be the primary approach for managing patent ductus arteriosus (PDA) in premature infants, owing to its simplicity, feasibility in resource-constrained environments, and proven effectiveness. The aim of our study is to investigate the risk factors associated with prolonged mechanical ventilation following surgical ligation of PDA in very low birth weight infants (VLBWIs) in China.\u003c/p\u003e\u003cp\u003e\u003cb\u003eMethods\u003c/b\u003e\u003c/p\u003e \u003cp\u003eA retrospective analysis was conducted on the clinical data of VLBWIs who underwent PDA ligation surgery between January 1,2022 and December 30,2024. The infants were divided into two groups based on the duration of mechanical ventilation following ligation: those with mechanical ventilation\u0026thinsp;\u0026le;\u0026thinsp;7 days and those with prolonged mechanical ventilation\u0026thinsp;\u0026gt;\u0026thinsp;7 days. The perioperative clinical characteristics, preoperative echocardiographic changes, postoperative complications, and mortality rates were compared between two groups. Risk factors associated with prolonged mechanical ventilation after ligation were analyzed.\u003c/p\u003e\u003cp\u003e\u003cb\u003eResults\u003c/b\u003e\u003c/p\u003e \u003cp\u003eA total of 47 VLBWIs were enrolled over a three-year period. 34 cases (72%) were successfully extubated within 7 days, while 13 cases (28%) experienced prolonged mechanical ventilation after ligation. Statistically significant differences were observed between the two groups in terms of preoperative left ventricular end-diastolic diameter, peak systolic velocity, proportion of preoperative and postoperative respiratory severity score/weight\u0026thinsp;\u0026gt;\u0026thinsp;3, proportion of postoperative oxygenation index\u0026thinsp;\u0026gt;\u0026thinsp;10, inhaled oxygen concentration, inotrope score, oxygen partial pressure, and mortality rate (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Binary logistic regression analysis showed that patients with more severe preoperative lung disease (RSS/kg\u0026thinsp;\u0026gt;\u0026thinsp;3 and/or moderate to severe bronchopulmonary dysplasia (BPD)) were more prone to postoperative mechanical ventilator dependency.\u003c/p\u003e\u003cp\u003e\u003cb\u003eConclusion\u003c/b\u003e\u003c/p\u003e \u003cp\u003eVLBWIs with more severe lung disease before PDA ligation, characterized by RSS/kg\u0026thinsp;\u0026gt;\u0026thinsp;3 and/or moderate to severe BPD, were more likely to experience postoperative ventilator dependence.\u003c/p\u003e","manuscriptTitle":"Risk factors associated with prolonged mechanical ventilation after surgical ligation of patent ductus arteriosus in very low birth weight infants in China: a single-center study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-17 08:57:11","doi":"10.21203/rs.3.rs-6676905/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"ceedfca6-df0e-41c5-9689-e63a4fe151f6","owner":[],"postedDate":"June 17th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-07T04:08:50+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-17 08:57:11","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6676905","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6676905","identity":"rs-6676905","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}