Preterm Infants off Positive Pressure Respiratory Support Have a Higher Incidence of Occult Cerebral Hypoxia

OBJECTIVE

To use cerebral near-infrared spectroscopy (NIRS) to quantify occult cerebral hypoxia across respiratory support modes in preterm infants.

STUDY DESIGN

In this prospective, longitudinal, observational study, infants ≤32 weeks gestation underwent serial pulse oximetry (oxygen saturation [SpO2]) and cerebral NIRS monitoring (4-6 hours per session) following a standardized recording schedule (daily for 2 weeks, every other day for 2 weeks, then weekly until 35 weeks corrected gestational age). Four calculations were made: median cerebral saturation, median cerebral hypoxia burden (proportion of NIRS samples below the hypoxia threshold [<67%]), median systemic saturation, and median systemic hypoxia burden (proportion of SpO2 samples below the desaturation threshold [<85%]). During each recording session, respiratory support mode was noted (room air, low-flow nasal cannula, high-flow nasal cannula, noninvasive positive pressure ventilation, continuous positive airway pressure, and invasive ventilation).

RESULTS

There were 1013 recording sessions made from 174 infants with a median length of 6.9 hours. Although the systemic (SpO2) hypoxia burden was significantly greater for infants on the highest respiratory support (invasive and noninvasive positive pressure ventilation), the cerebral hypoxia burden was significantly greater during recording sessions made on the lowest respiratory support (8% for room air; 29% for low-flow nasal cannula).

CONCLUSIONS

Premature infants on the highest levels of respiratory support have less cerebral hypoxia than those on lower respiratory support. These results raise concern about unrecognized cerebral hypoxia during lower acuity periods of neonatal intensive care unit hospitalization and adverse outcomes.

The hidden consequence of intraventricular hemorrhage: persistent cerebral desaturation after IVH in preterm infants

BACKGROUND

Previous studies describe a short-term decrease in cerebral oxygen saturation (StO2) after intraventricular hemorrhage (IVH) in premature infants; little is known about long-term implications.

METHODS

Infants born <30 weeks gestational age (GA) were included. Clinical characteristics, hemoglobin measurements, the highest grade of IVH, and white matter injury (WMI) were noted. NIRS monitoring occurred daily or every other day for 4 weeks; weekly through 36 weeks GA. Recordings were error-corrected before calculation of mean StO2 and fractional tissue oxygen extraction (FTOE). Mean StO2 and FTOE were plotted by postnatal age and injury group (IVH/no IVH; WMI/no WMI). Non-linear regression by locally estimated scatterplot smoothing was used to generate the best-fit line and CI.

RESULTS

A total of 1237 recordings from 185 infants were included; mean length = 6.5 h; mean GA = 26.3 w; mean BW = 951 g; overall/severe IVH incidence was 29/8%, WMI incidence was 16%. IVH was independently associated with an acute drop in StO2, which remained lower for 68 d. Severe IVH was associated with lower StO2 values than mild IVH. WMI was associated with early and persistent elevation of FTOE.

CONCLUSION

IVH of any grade is associated with a prolonged cerebral desaturation and WMI is associated with prolonged elevation of FTOE. This finding is exacerbated for infants with severe IVH.

IMPACT

The longitudinal impact of IVH on cerebral oxygenation has not been previously studied. IVH is associated with persistent cerebral desaturation, months in length, and is independent of anemia. More severe IVH is associated with worsened cerebral hypoxia. Infants later diagnosed with white matter injury have an early and persistent elevation of cerebral oxygen extraction (cFTOE). This cerebral desaturation, below previously identified normative ranges, may provide insight into the mechanistic link between IVH and white matter injury.

Racial disparities in calculated risk for bronchopulmonary dysplasia: a dataset

Bronchopulmonary dysplasia (BPD) is a severe pulmonary complication of prematurity and is associated with significant morbidity or death. Early use of systemic corticosteroids may alter the trajectory of the disease and improve outcomes. A BPD Outcomes estimator, developed by the NICHD using a large population dataset, can be used to calculate individual risk. Risk above a certain threshold may indicate that the benefits of corticosteroids outweigh the risks. Empiric analysis of this calculator by systematic entry of synthetic patient information reveals a marked racial disparity; black infants have lower risk of moderate/severe BPD due to a higher risk of death despite equivalent severity of illness. Interpretation and analysis of this finding can be found in "The challenge of risk stratification of preterm infants in the setting of competing and disparate healthcare outcomes" [1]. In this report, we provide the underlying data used in this analysis. Calculator output for 108 example patients, systematically varied by sex, birthweight, race, type of ventilator, and fraction of inspired oxygen (FiO2), is reported.

Cerebellar hemorrhage: a 10-year evaluation of risk factors

Background: While cerebellar hemorrhage (CH) has been linked with adverse neurodevelopmental outcome in preterm infants, it remains under-recognized and the underlying mechanisms are not fully understood.Objective: To determine risk factors for CH in premature infants.Methods: A retrospective cohort study included all inborn infants ≤ 30 weeks EGA admitted to the NICU from 2007 to 2016. Comprehensive perinatal and clinical factors were collected. CH size, sidedness, and symmetry were noted. Factors associated with CH were evaluated using univariate and multivariate logistic regression.Results: Of the 352 identified infants, 69 (20%) had CH. Those with CH were born at earlier EGA, received less antenatal steroids, more frequently had an admission temperature <36 °C, had more severe lung disease, received more inotropes, and had higher rates of intraventricular hemorrhage (IVH). In the regression model, low admission temperature (OR = 3.5), inotrope exposure (OR = 2.6), chorioamnionitis (OR = 2.3), and increased ventilator days (OR = 1.02) were associated with increased risk, while antenatal steroids (OR = 0.3) and male sex (OR = 0.5) were associated with decreased risk. Imaging modality at first diagnosis was split between ultrasound and MRI (52 versus 48%). Median age at diagnosis was 4 d; 52% of cases were unilateral, and size was punctate, small, and large in 23, 45, and 32% of cases, respectively.Conclusions: CH is common in premature infants and can be diagnosed using ultrasound or MRI. Clinically modifiable risk factors have been identified and should serve as the basis for improved clinical strategies in temperature, ventilator, and blood pressure management.

A Web-Based Calculator for the Prediction of Severe Neurodevelopmental Impairment in Preterm Infants Using Clinical and Imaging Characteristics

Although the most common forms of brain injury in preterm infants have been associated with adverse neurodevelopmental outcomes, existing MRI scoring systems lack specificity, do not incorporate clinical factors, and are technically challenging to perform. The objective of this study was to develop a web-based, clinically-focused prediction system which differentiates severe neurodevelopmental outcomes from normal-moderate outcomes at two years. Infants were retrospectively identified as those who were born ≤30 weeks gestation and who had MRI imaging at term-equivalent age and neurodevelopmental testing at 18–24 months. Each MRI was scored on injury in three domains (intraventricular hemorrhage, white matter injury, and cerebellar hemorrhage) and clinical factors that were strongly predictive of an outcome were investigated. A binary logistic regression model was then generated from the composite of clinical and imaging components. A total of 154 infants were included (mean gestational age = 26.1 ± 1.8 weeks, birth weight = 889.1 ± 226.2 g). The final model (imaging score + ventilator days + delivery mode + antenatal steroids + retinopathy of prematurity requiring surgery) had strong discriminatory power for severe disability (AUC = 0.850), with a PPV (positive predictive value) of 76% and an NPV (negative predictive value) of 90%. Available as a web-based tool, it can be useful for prognostication and targeting early intervention services to infants who may benefit the most from such services.

Anemia of prematurity and cerebral near-infrared spectroscopy: should transfusion thresholds in preterm infants be revised?

OBJECTIVE

To determine the impact of progressive anemia of prematurity on cerebral regional saturation (C-rSO₂) in preterm infants and identify the hemoglobin threshold below which a critical decrease (>2SD below the mean) in C-rSO₂ occurs.

STUDY DESIGN

In a cohort of infants born ≤30 weeks EGA, weekly C-rSO₂ data were prospectively collected from the second week of life through 36 weeks post-menstrual age (PMA). Clinically obtained hemoglobin values were noted at the time of recording. Recordings were excluded if they were of insufficient duration (<1 h) or if the hemoglobin was not measured within 7 days. Statistical analysis was performed using a linear mixed effects-model and ROC analysis. ROC analysis was used to determine the threshold of anemia, where C-rSO₂ critically decreased >2SD below the mean normative value (<55%) in preterm infants.

RESULTS

In total 253 recordings from 68 infants (mean EGA 26.9 ± 2.1 weeks, BW 1025 ± 287 g, 49% male) were included. Approximately 29 out of 68 infants (43%) were transfused during hospitalization. Mixed-model statistical analysis adjusting for EGA, BW, and PMA revealed a significant association between decreasing hemoglobin and C-rSO₂ (p < 0.01) in transfusion-naive infants but not in transfused infants. In the transfusion naive group, using ROC analysis demonstrated a threshold hemoglobin of 9.5 g/dL (AUC 0.81, p < 0.01) for critical cerebral desaturation in preterm infants.

CONCLUSIONS

In transfusion-naive preterm infants, worsening anemia was associated with a progressive decrease in cerebral saturations. Analysis identified a threshold hemoglobin of 9.5 g/dL below which C-rSO₂ dropped >2SD below the mean.