Clark, Reese H.

Objective We characterize the most recent natural history of necrotizing enterocolitis (NEC), as this is an essential first step in guiding the prevention and treatment of this disease in the present day. Study Design We performed a retrospective cohort study of neonates who were born at 23 to 29 weeks' gestation and birth weight <1,500 g who received care from the Pediatrix Medical Group between 2004 and 2019. We assessed the incidence of medical and surgical NEC and the patterns of initial antibiotic treatment to develop a contemporary cohort for further analysis. Among patients discharged between 2015 and 2019, we characterized the stage-specific risk factors for patients diagnosed with medical or surgical NEC, as well as patterns of disease onset, progression, biomarkers, and outcomes. We used the same approach to characterize patients diagnosed with suspected NEC. Results Among 34,032 patients in the contemporary cohort, 1,150 (3.4%) were diagnosed with medical NEC and 543 (1.6%) were diagnosed with surgical NEC. The temporal pattern of disease onset was different for medical and surgical NEC, with gestational age– and birth weight–specific risk disparities emerging earlier in surgical NEC. Thirty-day mortality was much greater among surgical NEC patients (medical NEC 16.4% vs. surgical NEC 43.0%), as were rates of various in-hospital and long-term outcomes. Suspected NEC was diagnosed in 1,256 (3.7%) patients, among whom risk factors and disease onset, progression, and outcomes closely resembled those of medical NEC. Conclusion Analyzing data from a contemporary cohort enabled us to characterize the current, stage-specific natural history of NEC, including novel insights into suspected NEC. Future studies could leverage this cohort to characterize how specific patient characteristics, care processes, or biomarkers may influence or predict disease outcomes. Key Points

BACKGROUND: Severe intraventricular hemorrhage (IVH) is a leading mortality risk factor among extremely premature neonates. Because other life-threatening conditions also occur in this population, it is unclear whether severe IVH is independently associated with death. The existence and potential implications of regional variation in severe IVH–associated mortality are unknown. METHODS: We performed a retrospective cohort study of mechanically ventilated neonates born at 22 to 29 weeks’ gestation who received care in 242 American NICUs between 2000 and 2014. After building groups composed of propensity score–matched and center-matched pairs, we used the Cox proportional hazards analysis to test our hypothesis that severe IVH would be associated with greater all-cause in-hospital mortality, defined as death before transfer or discharge. We also performed propensity score–matched subgroup analyses, comparing severe IVH–associated mortality among 4 geographic regions of the United States. RESULTS: In our analysis cohort, we identified 4679 patients with severe IVH. Among 2848 matched pairs, those with severe IVH were more likely to die compared with those without severe IVH (hazard ratio 2.79; 95% confidence interval 2.49–3.11). Among 1527 matched pairs still hospitalized at 30 days, severe IVH was associated with greater risk of death (hazard ratio 2.03; 95% confidence interval 1.47–2.80). Mortality associated with severe IVH varied substantially between geographic regions. CONCLUSIONS: The early diagnosis of severe IVH is independently associated with all-cause in-hospital mortality in extremely premature neonates. Regional variation in severe IVH–associated mortality suggests that shared decision-making between parents and neonatologists is strongly influenced by ultrasound-based IVH assessment and classification.

Objective To compare the risk of mortality and morbidity between outborn and propensity score-matched inborn extremely preterm neonates. Setting Multiple neonatal intensive care units (NICU) across the USA. Patients Singleton neonates born at 22–29 weeks’ gestation with no major anomalies who were admitted to a NICU and discharged between 2000 and 2014. Outborn neonates were restricted to those who transferred into a NICU on the day of birth. Methods The association between inborn-outborn status and the time-to-event outcomes of in-hospital mortality and necrotising enterocolitis (NEC) were assessed using Cox proportional hazards regression. Logistic regression was used to assess the remaining secondary outcomes: retinopathy of prematurity requiring treatment (tROP), chronic lung disease (CLD), periventricular leucomalacia (PVL) and severe intraventricular haemorrhage (IVH). Since outborn status was not random, we used 1:1 propensity score matching to reduce the imbalance in illness severity. Results There were 59 942 neonates (7991 outborn) included in the study. Outborn neonates had poorer survival than inborns and higher rates of NEC, severe IVH, tROP and PVL. Inborn-outborn disparities in mortality were reduced over the study period. When analysing the matched cohort (6524 matched pairs), outborns were less likely to die in-hospital compared with inborns (HR 0.84, 95% CI 0.77 to 0.91). However, outborns experienced higher rates of NEC (HR 1.14, 95% CI 1.04 to 1.25), severe IVH (OR 1.52, 95% CI 1.38 to 1.68), tROP (OR 1.45, 95% CI 1.25 to 1.69) and CLD (OR 1.12, 95% CI 1.01 to 1.24). Conclusion Additional research is needed to understand the contributors to increased morbidity for outborn extremely preterm neonates and identify interventions that mitigate this risk.

Objective Among neonates of 22 to 29 weeks' gestational age (GA) who required mechanical ventilation for the treatment of respiratory distress syndrome (RDS) and clinically diagnosed pulmonary hypertension (PH), we tested our hypothesis that the association between early treatment with inhaled nitric oxide (iNO) and survival would vary according to birth size and GA. Study Design Because iNO was not randomly prescribed to patients in this cohort, we used propensity score matching to pair a neonate who received iNO at a chronological age of ≤7 days with an unexposed neonate with similar baseline characteristics. The primary outcome was inhospital mortality, which we evaluated based on size for GA and GA strata using the Cox proportional hazards regression model. Results Among 1,531 neonates who met study criteria, we created a propensity score matched cohort of 615 pairs of neonates (iNO-exposed and unexposed). The risk of inhospital mortality for iNO-exposed neonates was observed only in the minority (<10%) who were large for GA, though this finding did not persist when matching for illness severity. Conclusion Early treatment with iNO is not associated with survival in most extremely premature neonates with RDS and clinically diagnosed PH when stratified for birth size or GA.

BACKGROUND: Inhaled nitric oxide (iNO) is increasingly prescribed to extremely premature neonates with respiratory distress syndrome (RDS). Most of this off-label use occurs during the first week of life. We studied this practice, hypothesizing that it would not be associated with improved survival. METHODS: We queried the Pediatrix Medical Group Clinical Data Warehouse to identify all neonates born at 22 to 29 weeks’ gestation from 2004 to 2014. In our study sample, we included singletons who required mechanical ventilation for treatment of RDS and excluded those with anomalies. The primary outcome was death before discharge. Through a sequential risk set approach, each patient who received iNO during the first 7 days of life (“case patient”) was matched by using propensity scores to a patient who had not received iNO at a chronological age before the case patient’s iNO initiation age (defined as the index age for the matched pair). The association between iNO status and in-hospital mortality was evaluated in a Cox proportional hazards regression model by using age as the time scale with patients entering the risk set at their respective index age. RESULTS: Among 37 909 neonates in our study sample, we identified 993 (2.6%) who received iNO. The 2 matched cohorts each contained 971 patients. We did not observe a significant association between iNO exposure and mortality (hazard ratio, 1.08; 95% confidence interval, 0.94–1.25; P = .29). CONCLUSIONS: Off-label prescription of iNO is not associated with reduced in-hospital mortality among extremely premature neonates with RDS.

BACKGROUND:Inhaled nitric oxide (iNO) therapy is an off-label medication in infants &lt;34 weeks’ gestational age. In 2011, the National Institutes of Health released a statement discouraging routine iNO use in premature infants. The objective of this study was to describe utilization patterns of iNO in American NICUs in the years surrounding the release of the National Institutes of Health statement. We hypothesized that iNO prescription rates in premature infants have remained unchanged since 2011.METHODS:The Pediatrix Medical Group Clinical Data Warehouse was queried for the years 2009–2013 to describe first exposure iNO use among all admitted neonates stratified by gestational age.RESULTS:Between 2009 and 2013, the rate of iNO utilization in 23- to 29-week neonates increased from 5.03% to 6.19%, a relative increase of 23% (confidence interval: 8%–40%; P = .003). Of all neonates who received iNO therapy in 2013, nearly half were &lt;34 weeks’ gestation, with these infants accounting for more than half of all first exposure iNO days each year of the study period.CONCLUSIONS:The rates of off-label iNO use in preterm infants continue to rise despite evidence revealing no clear benefit in this population. This pattern of iNO prescription is not benign and comes with economic consequences.