Response to dopamine in prematurity: a biomarker for brain injury?

Blood pressure values and hypotension management in extremely preterm infants: a multi-center study

OBJECTIVE

To describe high/low daily blood pressures (BP) and variability in BP management with vasoactive infusions (VI) and/or hydrocortisone (HC) in extremely preterm infants.

STUDY DESIGN

Analysis of data from 24-27 weeks' gestation infants in the Preterm Erythropoietin Neuroprotection (PENUT) Trial. Daily high/low BPs, the use of VI and/or HC, and adverse outcomes were compared descriptively and using regression models.

RESULTS

936 infants were included; 64% untreated, 20% VI, 3% HC, and 13% VI + HC. BP ranges are described for the 602 untreated infants. Considerable inter- and intra-center variability was demonstrated in the rate of VI and/or HC use and the lowest BP on the day of VI or HC initiation.

CONCLUSIONS

Despite published expert opinion guidance regarding BP management in extremely preterm infants, our results suggest a continued lack of consensus result in both inter- and intra-center variability in practice. Well-designed studies in the field are urgently needed.

Low Variability of Blood Pressure Predicts Abnormal Electroencephalogram in Infants with Hypoxic Ischemic Encephalopathy

OBJECTIVE

This study aimed to evaluate the role of an objective physiologic biomarker, arterial blood pressure variability, for the early identification of adverse short-term electroencephalogram (EEG) outcomes in infants with hypoxic-ischemic encephalopathy (HIE).

STUDY DESIGN

In this multicenter observational study, we analyzed blood pressure of infants meeting these criteria: (1) neonatal encephalopathy determined by modified Sarnat exam, (2) continuous mean arterial blood pressure (MABP) data between 18 and 27 hours after birth, and (3) continuous EEG performed for at least 48 hours. Adverse outcome was defined as moderate-severe grade EEG at 48 hours. Standardized signal preprocessing was used; the power spectral density was computed without interpolation. Multivariate binary logistic regression was used to identify which MABP time and frequency domain metrics provided improved predictive power for adverse outcomes compared with standard clinical predictors (5-minute Apgar score and cord pH) using receiver operator characteristic analysis.

RESULTS

Ninety-one infants met inclusion criteria. The mean gestational age was 38.4 ± 1.8 weeks, the mean birth weight was 3,260 ± 591 g, 52/91 (57%) of infants were males, the mean cord pH was 6.95 ± 0.21, and 10/91 (11%) of infants died. At 48 hours, 58% of infants had normal or mildly abnormal EEG background and 42% had moderate or severe EEG backgrounds. Clinical predictor variables (10-minute Apgar score, Sarnat stage, and cord pH) were modestly predictive of 48 hours EEG outcome with area under curve (AUC) of 0.66 to 0.68. A composite model of clinical and optimal time- and frequency-domain blood pressure variability had a substantially improved AUC of 0.86.

CONCLUSION

Time- and frequency-domain blood pressure variability biomarkers offer a substantial improvement in prediction of later adverse EEG outcomes over perinatal clinical variables in a two-center cohort of infants with HIE.

KEY POINTS

· Early outcome prediction in HIE is suboptimal.. · Patterns in blood pressure physiology may be predictive of short-term outcomes.. · Early time- and frequency-domain measures of blood pressure variability predict short-term EEG outcomes in HIE infants better than perinatal factors alone..

Preterm brain injury: Germinal matrix-intraventricular hemorrhage and post-hemorrhagic ventricular dilatation

Germinal matrix hemorrhage and intraventricular hemorrhages (GMH-IVH) remain a common and clinically significant problem in preterm infants, particularly extremely preterm infants. A large GMH-IVH is often complicated by posthemorrhagic ventricular dilation (PHVD) or parenchymal hemorrhagic infarction and is associated with an increased risk of adverse neurologic sequelae. The widespread use of cranial ultrasonography since the early 1980s has shown a gradual decrease in the incidence of GMH-IVH and has helped with the identification of antenatal and perinatal risk factors and timing of the lesion. The increased use of magnetic resonance imaging (MRI) has contributed to more detailed visualization of the site and extent of the GMH-IVH. In addition, MRI has contributed to the awareness of associated white matter changes as well as associated cerebellar hemorrhages. Although GMH-IVH and PHVD still cannot be prevented, cerebrospinal fluid drainage initiated in the early stage of PHVD development seems to be associated with a better neurodevelopmental outcome. Further studies are underway to improve treatment strategies for PHVD and to potentially prevent and repair GMH-IVH and PHVD and associated brain injury. This chapter discusses the pathogenesis, incidence, risk factors, and management, including preventive measures, of GHM-IVH and PHVD.

Divergent risk factors for cerebellar and intraventricular hemorrhage

OBJECTIVE

To identify whether intraventricular hemorrhage (IVH) and cerebellar hemorrhage (CH) have common or divergent risk factors.

STUDY DESIGN

This is a retrospective cross-sectional cohort of infants including all infants born <30 weeks from 2007 to 2016. Comprehensive perinatal and clinical factors were extracted from the medical record. Outborn infants, infants with major congenital anomaly, those transferred prior to discharge, and those with mixed or no brain injury were excluded. The remaining infants were divided into two groups: IVH only and CH only. Continuous variables were evaluated with the Wilcoxon-Mann-Whitney test, and categorical variables were evaluated with Fisher's exact test. Multinomial logistic regression was used to identify factors which predispose infants towards injury type more than another, holding other factors constant.

RESULTS

In total, 127 infants were included (CH n = 27, IVH n = 100). Compared to those with IVH, infants with CH were of lower EGA (p = 0.03), lower birth weight (p = 0.01), more often of multiple gestation (p = 0.03), more frequently born emergently (p = 0.03), had a greater number of ventilator days (p = 0.03), received postnatal steroids more often (p = 0.02), had a greater incidence of hemodynamically significant patent ductus arteriosus (PDA), and less frequently had pulmonary hemorrhage (p = 0.04). In multinomial regression analysis, three factors were identified which favored CH over IVH: multiple gestation (RR 4.70, 95% CI 1.56-14.21, p < 0.01), chorioamnionitis (RR 3.18, 95% CI 1.13-8.92, p = 0.03), and emergent delivery (RR 4.14, 95% CI 1.48-11.55, p < 0.01). Only advancing gestational favored IVH over CH (RR 0.74, 95% CI 0.65-0.85, p < 0.01).

CONCLUSIONS

IVH and CH have unique risk factors. These results highlight the need to tailor neuroimaging surveillance to specific patient risk factors.

Low-frequency blood pressure oscillations and inotrope treatment failure in premature infants

The underlying mechanism as to why some hypotensive preterm infants do not respond to inotropic medications remains unclear. For these infants, we hypothesize that impaired vasomotor function is a significant factor and is manifested through a decrease in low-frequency blood pressure variability across regulatory components of vascular tone. Infants born ≤28 wk estimated gestational age underwent prospective recording of mean arterial blood pressure for 72 h after birth. After error correction, root-mean-square spectral power was calculated for each valid 10-min data frame across each of four frequency bands (B1, 0.005-0.0095 Hz; B2, 0.0095-0.02 Hz; B3, 0.02-0.06 Hz; and B4, 0.06-0.16) corresponding to different components of vasomotion control. Forty infants (twenty-nine normotensive control and eleven inotrope-exposed) were included with a mean ± SD estimated gestational age of 25.2 ± 1.6 wk and birth weight 790 ± 211 g. 9.7/11.8 Million (82%) data points were error-free and used for analysis. Spectral power across all frequency bands increased with time, although the magnitude was 20% less in the inotrope-exposed infants. A statistically significant increase in spectral power in response to inotrope initiation was noted across all frequency bands. Infants with robust blood pressure response to inotropes had a greater increase compared with those who had limited or no blood pressure response. In this study, hypotensive infants who require inotropes have decreased low-frequency variability at baseline compared with normotensive infants, which increases after inotrope initiation. Low-frequency spectral power does not change for those with inotrope treatment failure, suggesting dysfunctional regulation of vascular tone as a potential mechanism of treatment failure.NEW & NOTEWORTHY In this study, we examine patterns of low-frequency oscillations in blood pressure variability across regulatory components of vascular tone in normotensive and hypotensive infants exposed to inotropic medications. We found that hypotensive infants who require inotropes have decreased low-frequency variability at baseline, which increases after inotrope initiation. Low-frequency spectral power does not change for those with inotrope treatment failure, suggesting dysfunctional regulation of vascular tone as a potential mechanism of treatment failure.