Methods
This is a retrospective case control study of preterm newborns with MAS admitted to the NICU of Children’s Hospital of Chongqing Medical University, between Jan 1, 2010 and Jan 1, 2020. Preterm infants born through MSAF grade Ⅲ and need mechanical ventilation support due to respiratory distress onset within first 24 hours of life were included. Preterm neonates with no need of ventilator support or/and with incomplete data were excluded.
Data from electronic medical records were procured, and were recorded using a standardized form: 1)maternal information (gestational age, delivery mode, disorders complicating pregnancy, antenatal steroid therapy); 2)neonatal data (weight, gender, 1-min and 5-min Apgar score, required resuscitation, duration of hospitalization, outcome); 3)treatment and complications (mechanical ventilation, persistent pulmonary hypertension, neonatal sepsis, shock, necrotizing enterocolitis, pneumothorax, pulmonary hemorrhage, intracranial hemorrhage, myocardial injury, renal dysfunction, anemia, hypoglycemia).
MAS was defined as respiratory distress in an infant born through MSAF whose symptoms cannot be otherwise explained [1]. Persistent pulmonary hypertension of the newborn (PPHN) was defined as elevated pulmonary vascular resistance and right-to-left shunting at the ductus arteriosus based on echocardiography[11]. Pulmonary hemorrhage was defined as a nontraumatic gush of bloody secretion from the endotracheal tube associated with clinical deterioration as well as requiring increased ventilatory support[12]. Intracranial hemorrhage was depended on imaging manifestations, including intraventricular hemorrhage and intraparenchymal hemorrhage. Arterial blood gas analysis was done at the time of admission to the NICU. This study was approved by the Ethics Committee of the Children’s Hospital of Chongqing Medical University (No: 2020-09).
Data analysis was performed using SPSS version 26 (IBM Corp., Armonk, NY, USA). Chi-square test or Fisher’s exact test were used to analyze categorical variables, as appropriate, and T- Student test or Mann–Whitney U test were used to analyze continuous variables, as appropriate. Categorical variables were expressed as number of cases and percentages while continuous variables were expressed as mean ± standard deviation (SD) or median (range). A p value below 0.05 was considered as statistically significant. Variables that were statistically significant in the univariate analysis were entered into the logistic regression analysis to identify risk factors for mortality of MAS in preterm infants.