Jang Hoon Lee

Background/Objectives: Since the establishment of the Korean Neonatal Network (KNN) in 2013, numerous studies have been conducted using its nationwide registry of very low birth weight infants (VLBWIs). Beyond serving as a clinical database, the KNN has evolved into a national healthcare research infrastructure supporting multicenter collaboration, evidence generation, and quality improvement in neonatal care. This study aimed to evaluate the scientific productivity, collaborative structure, and knowledge-generation capacity of the KNN through bibliometric network analysis and to identify future research directions in Korean neonatal research. Methods: Publications from 1 January 2015 to 5 June 2024 were retrieved from the Web of Science Core Collection. Literature searches were performed using Medical Subject Headings (MeSH), Emtree terms, and related keywords associated with very low birth weight infants, extremely low birth weight infants, and the Korean Neonatal Network. A total of 7060 global publications and 86 KNN-related publications were identified for analysis. Co-authorship and keyword co-occurrence analyses were conducted using VOSviewer to evaluate international collaborations, research themes, and temporal trends in keyword emergence. Scimago Graphica was used to visualize keyword evolution, and burst detection analysis was performed using CiteSpace to identify emerging research topics. Results: Among global publications on VLBWIs, South Korea ranked 13th worldwide with 226 publications and demonstrated substantial international collaboration, particularly with researchers in the United States. Analysis of the 86 KNN-related publications revealed the rapid development of observational and topic-focused research areas within a relatively short period. Keyword clustering and temporal analyses demonstrated a progressive expansion of research interests as the database matured. Burst analysis identified emerging themes related to mortality and morbidity risk factors, neurodevelopmental outcomes, and predictive modeling using machine learning techniques. Conclusions: Bibliometric analysis demonstrated that research based on the KNN has largely followed global trends in neonatal research despite its relatively recent establishment. The KNN has successfully functioned as a nationwide research infrastructure facilitating collaborative knowledge generation and scientific productivity. Nevertheless, several underrepresented research areas and opportunities for broader international collaboration were identified. These findings may help guide future research strategies and maximize the impact of national neonatal registry-based healthcare systems.

Background/Objectives: This study compared the pharmacokinetic (PK)/pharmacodynamic (PD) targets of vancomycin in obese patients using two Bayesian programs to evaluate the accuracy and bias of these estimates. Additionally, population pharmacokinetics in obese patients were compared with those in the general patient population. Methods: Medical records of obese adults [body mass index (BMI) ≥ 30 kg/m²] treated with vancomycin at Ajou University Hospital between 2010 and 2017 were retrospectively reviewed. Patients with peak (C_peak) and trough (C_trough) concentrations were included. Vancomycin area under the plasma concentration-time curve (AUC) and C_trough were estimated using Capcil (ver 6.31) and MwPharm (ver 2.3.1.89) software. Accuracy and bias were analyzed, and population PK parameters were evaluated. Results: A total of 149 cases were analyzed. AUC estimates from one-point sampling using Capcil were significantly lower than the reference values, whereas MwPharm produced estimates closer to the reference with higher accuracy and lower bias. C_trough estimates from one-point sampling showed high accuracy for both programs. Obese patients exhibit lower volume of distribution, higher total body clearance, and shorter elimination half-life than the general patient population. Conclusions: Vancomycin pharmacokinetics differ in obese patients. Bayesian analysis using MwPharm showed AUC and C_trough estimates that were closer to the reference values and exhibited lower bias than those obtained with Capcil in this dataset. These findings may support more informed dosing decisions for vancomycin in obese patients.

Purpose: This study aimed to evaluate the association between the calcium-to-phosphorus (Ca/P) ratio and serum phosphate levels in preterm infants receiving total parenteral nutrition (TPN) and to explore Ca/P ratio ranges associated with hypophosphatemia.Methods: We retrospectively reviewed the medical records of preterm infants admitted to the neonatal intensive care unit at Ajou University Hospital between January 2022 and June 2024. The review focused on TPN composition and serum electrolyte changes during the first week of life. Based on the cumulative Ca/P ratio during this period, infants were categorized into two groups: Ca/P-Low (mass ratio ≤1.3) and Ca/P-High (mass ratio >1.3).Results: A total of 117 preterm infants were included in the analysis (Ca/P-Low group, n=46; Ca/P-High group, n=71). During the first week of life, the cumulative phosphorus deficit was significantly greater in the Ca/P-High group (61.4 mg/kg vs. 8.5 mg/kg; P<0.001). By day of life (DOL) 7, both hypophosphatemia and severe hypophosphatemia had increased markedly in the Ca/P-High group compared with DOL 3. In the Ca/P-High group, the incidence of hypophosphatemia increased from 44.4% on DOL 3 to 75.0% on DOL 7, while the incidence of severe hypophosphatemia increased from 4.8% to 23.1%.Conclusion: These findings suggest that parenteral nutrition strategies may benefit from phase-adapted Ca/P ratios rather than a fixed ratio during the first week of life. A higher ratio may be considered during DOL 0–2, whereas a lower ratio may be considered during DOL 3–6, particularly when overall calcium and phosphorus supply is suboptimal.

Purpose: Human parechovirus (HPeV) is one of the major causes of viral meningitis in neonates. Following the COVID‐19 pandemic, a resurgence of HPeV infections was reported worldwide. This exploratory case series is aimed at describing the symptoms of neonatal HPeV meningitis occurring after the lifting of large‐scale quarantine measures. Methods: We retrospectively reviewed eight neonates admitted between June 1, 2023, and September 30, 2023, with fever and HPeV detected in cerebrospinal fluid (CSF) using the FilmArray Meningitis/Encephalitis Panel. Demographic variables, clinical presentation, laboratory data, respiratory support requirements, and treatment courses were analyzed. Results: Fever was the primary presenting symptom. Despite the absence of leukocytosis or pleocytosis, fever duration was prolonged (mean 4.3 days). Four patients (50%) exhibited respiratory symptoms requiring high‐flow nasal cannula support. Hyponatremia occurred in two neonates without neurological manifestations—an observation not commonly described in previous cohorts. No patients required invasive ventilation. Conclusion: This small, single‐center series suggests possible variations in neonatal HPeV presentation after the COVID‐19 pandemic; however, findings are preliminary and hypothesis‐generating. Larger multicenter studies with subtype analysis and long‐term neurodevelopmental follow‐up are essential.

Aim: Allergic diseases, such as asthma, allergic rhinitis (AR), and atopic dermatitis (AD) are prevalent chronic childhood conditions, with a rising incidence globally and in South Korea. Neonatal jaundice is a common perinatal condition. However, its association with the subsequent development of allergic diseases remains unclear. Methods: This retrospective population‐based cohort study used data from the Korean Health Insurance Review and Assessment Service database. Participants were categorised according to the history and severity of neonatal jaundice, defined by treatment status. Logistic regression and Cox proportional hazard models were used to estimate the risk of neonatal jaundice. Results: Children with neonatal jaundice showed a moderately increased risk of asthma and AR, particularly those who received treatment. Neonatal jaundice requiring treatment showed significantly elevated odds ratios for asthma and AR. Conclusion: Neonatal jaundice requiring treatment was associated with an increased risk of asthma and AR in early childhood. This suggests that the severity of neonatal jaundice may influence the later development of allergic diseases and highlights the need for closer follow‐up of this population.

Background Acute kidney injury (AKI) is commonly observed in critically ill neonates; however, early identification of AKI in the first week of life is challenging due to the influence of maternal serum creatinine (SCr). An alternative criterion proposed by Gupta et al. based on SCr decline may identify additional infants at risk beyond the KDIGO definition. Methods We retrospectively reviewed 409 infants with a gestational age < 32 weeks who were admitted to our NICU between 2018 and 2024. AKI was defined according to the KDIGO guidelines or the Gupta threshold for days 3, 5, or 7 SCr. We compared mortality, bronchopulmonary dysplasia (BPD), and length of hospital stay among the No-AKI, Gupta-only AKI, and KDIGO-AKI groups. Results Among 409 infants, 145 (35.5%) had Gupta-only AKI, 9 (2.2%) had KDIGO-only AKI, and 54 (13.2%) had both definitions. The infants with AKI were premature and had lower birth weights than those without AKI. Both AKI groups showed higher rates of composite outcomes (mortality or BPD) than the No-AKI (p < 0.001) group. Gupta-only AKI was associated with prolonged stay (+ 10.1 days, p = 0.01) and increased odds of BPD (adjusted OR 2.12, p = 0.023), while KDIGO-AKI had a stronger association with mortality (27.0%, p < 0.001). Conclusions The Gupta definition identified a substantial subset of highly preterm infants at a higher risk of adverse outcomes who were missed using the KDIGO criteria. Integrating SCr level decline-based methods may improve early AKI detection and enhance outcomes in this vulnerable population. Graphical Abstract A higher resolution version of the Graphical abstract is available as Supplementary information

Introduction: Intravenous lipid emulsions are essential for parenteral nutrition in preterm infants. However, hypertriglyceridemia (HTG) is a common complication that can lead to severe complications if left untreated. This study analyzed factors influencing HTG and the effects of reduced intravenous lipid emulsion dosages.Methods: A retrospective cohort study involving premature infants born at less than 32 weeks of gestation and admitted to Ajou University Hospital between 2017 and 2022 was conducted. Infants with documented triglyceride levels within the first 10 days of life were included. The risk factors for HTG and the time to normalize triglyceride levels after intravenous lipid dose reduction were evaluated.Results: HTG was diagnosed in 104 infants. Significant risk factors included lower birth weight (OR = 0.75; 95% CI, 0.66–0.85; p < 0.001), treated for patent ductus arteriosus (OR = 2.47; 95% CI, 1.30–4.69; p = 0.006), intravenous lipid emulsion intake (OR = 1.79; 95% CI, 1.25–2.55; p = 0.001), and serum glucose level (OR = 1.01; 95% CI, 1.00–1.02; p = 0.023). The average triglyceride level in the HTG group was 287.8 mg/dl, with intravenous lipid doses of 2.7 g/kg/day. Reducing intravenous lipid doses by 0.27 ± 0.46 g/kg/day shortened the triglyceride normalization time to 4.9 ± 5.0 days and reduced the risk of retinopathy of prematurity stage 2 or higher (OR = 0.59; 95% CI, 0.40–0.88; p = 0.011). The fat overload infusion rate, which induces HTG, was 0.332 cc/kg/h (1.6 g/kg/day).Discussion: Lower birth weight, treated patent ductus arteriosus, serum glucose levels, and higher intravenous lipid levels are significant risk factors for HTG. Adjusting the lipid dose aids in triglyceride normalization and reducing severe retinopathy of prematurity risk. Careful monitoring and management of intravenous lipid emulsion infusion rates are crucial to prevent HTG.

Purpose: The COVID-19 (coronavirus disease 2019) pandemic led to significant changes in clinical clerkships, including reduced ward rounds. We aimed to determine how the pandemic–induced changes in the clinical practice environment affect the clinical performance of medical students.Methods: We analyzed objective structured clinical examination scores of third- and fourth-year medical students from 2019–2020 and 2020–2021 across six stations by the Seoul–Gyeonggi Consortium. Clinical, communication, and ability scores were measured and analyzed using repeated-measures multivariate analysis of variance.Results: The interaction between clinical practice progress and pandemic-induced changes significantly affected physical examination and medical history scores, though the differences were not substantial. Patient-physician interaction significance varied by measurement period. Clinical communication ability also showed significant differences based on the measurement period and practical experience.Conclusion: During the pandemic, alternative learning methods, including self–learning, simulation/practice, and peer role–play, helped improve medical competency in areas such as history–taking and physical examination. However, these were less effective in improving patient–physician interactions or clinical communication efficacy. Alternative learning methods have limitations, and they cannot replace direct patient encounters in clinical practice.