Challenges in Treating Low Blood Pressure in Preterm Infants

Insights into Neonatal Cerebral Autoregulation by Blood Pressure Monitoring and Cerebral Tissue Oxygenation: A Qualitative Systematic Review

OBJECTIVE

The aim of this qualitative systematic review was to identify publications on blood pressure monitoring in combination with cerebral tissue oxygenation monitoring during the first week after birth focusing on cerebral autoregulation.

METHODS

A systematic search was performed on PubMed. The following search terms were used: infants/newborn/neonates, blood pressure/systolic/diastolic/mean/MAP/SAP/DAP, near-infrared spectroscopy, oxygenation/saturation/oxygen, and brain/cerebral. Additional studies were identified by a manual search of references in the retrieved studies and reviews. Only human studies were included.

RESULTS

Thirty-one studies focused on preterm neonates, while five included preterm and term neonates. In stable term neonates, intact cerebral autoregulation was shown by combining cerebral tissue oxygenation and blood pressure during immediate transition, while impaired autoregulation was observed in preterm neonates with respiratory support. Within the first 24 h, stable preterm neonates had reduced cerebral tissue oxygenation with intact cerebral autoregulation, while sick neonates showed a higher prevalence of impaired autoregulation. Further cardio-circulatory treatment had a limited effect on cerebral autoregulation. Impaired autoregulation, with dependency on blood pressure and cerebral tissue oxygenation, increased the risk of intraventricular hemorrhage and abnormal neurodevelopmental outcomes.

CONCLUSIONS

Integrating blood pressure monitoring with cerebral tissue oxygenation measurements has the potential to improve treatment decisions and optimizes neurodevelopmental outcomes in high-risk neonates.

Changes in perinatal management and outcomes in infants born at 23 weeks of gestational age during the last decade in Spain

INTRODUCTION

The 2021-updated guidelines of the Spanish Society of Neonatology Guidelines have moved the zone of parental discretion to 23 + 0-23 + 6 weeks. The objective of this study was to describe the changes in perinatal management at this gestational age along the last decade and to determine if a more active perinatal management has contributed to improved outcomes.

METHODS

Retrospective analysis of prospectively collected data from the 23-week infants included in the Spanish SEN 1500 neonatal network during the period 2010-2019. The main study outcomes were survival at discharge and survival without major morbidity of actively managed infants. Two periods were compared: 2010-2014 (Period 1) and 2015-2019 (Period 2). NICUs were classified into low activity NICUs (less than 50 admissions of very low birth weight infants per year) and high activity NICUs (50 or more admissions).

RESULTS

A total of 381 infants were included, 182 in Period 1 and 199 in Period 2. In Period 2 an increase in the use of intrapartum magnesium sulfate (21.5% vs 39.9%, p .002), antenatal steroids (56.6% vs 69.3%, p .011) and active neonatal approach in delivery room (76.9% vs 86.9%, p .011) were observed.The clinical outcomes of the actively managed 313 infants were similar in both periods, except for less arterial hypotension in Period 2. Survival was 27.1% in Period 1 and 25% in Period 2 (p .068) and survival without major morbidity was 2.1% and 2.3% respectively (p .914). No difference was found between low and high activity NICUs.

CONCLUSION

A change to a more active intention to treat infants born at 23 weeks is taking place in Spain. But the survival rate of the actively-managed infants has remained stable around 25-30% during the study period. A multidisciplinary effort is needed to improve outcomes in this population.

Early impact of moderate preterm birth on the structure, function and gene expression of conduit arteries

NEW FINDINGS

What is the central question of this study? What is the immediate impact of moderate preterm birth on the structure and function of major conduit arteries using a pre-clinical sheep model? What is the main finding and its importance? Postnatal changes in conduit arteries, including a significant decrease in collagen within the thoracic aortic wall (predominately males), narrowed carotid arteries, reduced aortic systolic blood flow, and upregulation of the mRNA expression of cell adhesion and inflammatory markers at 2 days of age in preterm lambs compared to controls, may increase the risk of cardiovascular impairment in later life.

ABSTRACT

The aim of this work was to compare the structure and function of the conduit arteries of moderately preterm and term-born lambs and to determine whether vascular injury-associated genes were upregulated. Time-mated ewes were induced to deliver either preterm (132 ± 1 days of gestation; n = 11 females and n = 10 males) or at term (147 ± 1 days of gestation; n = 10 females and n = 5 males). Two days after birth, ultrasound imaging of the proximal ascending aorta, main, right and left pulmonary arteries, and right and left common carotid arteries was conducted in anaesthetized lambs. Lambs were then killed and segments of the thoracic aorta and left common carotid artery were either snap frozen for real-time PCR analyses or immersion-fixed for histological quantification of collagen, smooth muscle and elastin within the medial layer. Overall there were few differences in vascular structure between moderately preterm and term lambs. However, there was a significant decrease in the proportion of collagen within the thoracic aortic wall (predominantly in males), narrowing of the common carotid arteries and a reduction in peak aortic systolic blood flow in preterm lambs. In addition, there was increased mRNA expression of the cell adhesion marker P-selectin in the thoracic aortic wall and the pro-inflammatory marker IL-1β in the left common carotid artery in preterm lambs, suggestive of postnatal vascular injury. Early postnatal differences in the function and structure of conduit arteries and evidence of vascular injury in moderately preterm offspring may place them at greater risk of cardiovascular impairment later in life.

Genetic background of high blood pressure is associated with reduced mortality in premature neonates

OBJECTIVE

The aim of our study was to determine if a genetic background of high blood pressure is a survival factor in preterm infants.

DESIGN

Prospective cohort study.

SETTING

Patients were enrolled in 53 neonatal intensive care units.

PATIENTS

Preterm infants with a birth weight below 1500 g.

EXPOSURES

Genetic score blood pressure estimates were calculated based on adult data. We compared infants with high genetic blood pressure estimates (>75th percentile of the genetic score) to infants with low genetic blood pressure estimates (<25th percentile of the genetic score).

MAIN OUTCOME MEASURES

Lowest blood pressure on the first day of life and mortality.

RESULTS

5580 preterm infants with a mean gestational age of 28.1±2.2 weeks and a mean birth weight of 1022±299 g were genotyped and analysed. Infants with low genetic blood pressure estimates had significantly lower blood pressure if compared with infants with high genetic blood pressure estimates (27.3±6.2vs 27.9±6.4, p=0.009, t-test). Other risk factors for low blood pressure included low gestational age (-1.26 mm Hg/week) and mechanical ventilation (-2.24 mm Hg, p<0.001 for both variables, linear regression analysis). Mortality was significantly reduced in infants with high genetic blood pressure estimates (28-day mortality: 21/1395, 1.5% vs 44/1395, 3.2%, p=0.005, Fisher's exact test). This survival advantage was independent of treatment with catecholamines.

CONCLUSIONS

Our study provides first evidence that a genetic background of high blood pressure may be beneficial with regard to survival of preterm infants.

Complications associated with the current sequential pharmacological management of early postnatal hypotension in extremely premature infants

Early postnatal hypotension in premature infants is treated with escalating doses of vasopressor-inotropes (VI), followed by hydrocortisone if VI therapy fails. The adverse effects of this standard clinical practice have not been well reported. In a retrospective case-control study, we compared the complications associated with VI and hydrocortisone (HCVI) treatments in extremely low-birth-weight infants (≤1000 g) with contemporaneous normotensive medication-naïve controls via standard univariate and multivariate analyses. Birth weight, gestational age, and receipt of antenatal steroids did not differ between VI (n = 74) and control (n = 124) groups, while the occurrence of gestational diabetes mellitus and risks for patent ductus arteriosus, intraventricular-periventricular hemorrhage, spontaneous intestinal perforation, ventriculomegaly, and bronchopulmonary dsyplasia were higher in VI. Infants in the HCVI group (n = 69) had lower birth weight, gestational age, and receipt of antenatal steroids and higher risks for intraventricular-periventricular hemorrhage, bronchopulmonary dysplasia, air leaks, and patent ductus arteriosus than controls. Whereas the occurrences of spontaneous intestinal perforation, ventriculomegaly, and maternal diabetes mellitus did not differ, that of maternal hypertension trended to be lower in HCVI recipients (P = 0.06). In conclusion, hypotensive extremely low-birth-weight infants treated with VI or with HCVI are susceptible to intraventricular-periventricular hemorrhage, bronchopulmonary dysplasia, and patent ductus arteriosus. Furthermore, those who receive inotropes are at risk for spontaneous intestinal perforation and ventriculomegaly. Maternal diabetes mellitus increases the occurrence of hypotension, which responds to VI. Maternal hypertension does not contribute to VI responsive and tends to decrease the occurrence of VI-refractory hypotension.

Dobutamine treatment reduces inflammation in the preterm fetal sheep brain exposed to acute hypoxia

BACKGROUND

Impaired cerebral autoregulation in preterm infants makes circulatory management important to avoid cerebral hypoxic-ischemic injury. Dobutamine is frequently used as inotropic treatment in preterm neonates, but its effects on the brain exposed to cerebral hypoxia are unknown. We hypothesized that dobutamine would protect the immature brain from cerebral hypoxic injury.

METHODS

In preterm (0.6 gestation) fetal sheep, dobutamine (Dob, 10 μg/kg/min) or saline (Sal) was infused intravenously for 74 h. Two hours after the beginning of the infusion, umbilical cord occlusion (UCO) was performed to produce fetal asphyxia (Sal+UCO: n = 9, Dob+UCO: n = 7), or sham occlusion (Sal+sham: n = 7, Dob+sham: n = 6) was performed. Brains were collected 72 h later for neuropathology.

RESULTS

Dobutamine did not induce cerebral changes in the sham UCO group. UCO increased apoptosis and microglia density in white matter, hippocampus, and caudate nucleus, and astrocyte density in the caudate nucleus. Dobutamine commenced before UCO reduced microglia infiltration in the white matter, and microglial and astrocyte density in the caudate.

CONCLUSION

In preterm hypoxia-induced brain injury, dobutamine decreases neuroinflammation in the white matter and caudate, and reduces astrogliosis in the caudate. Early administration of dobutamine in preterm infants for cardiovascular stabilization appears safe and may be neuroprotective against unforeseeable cerebral hypoxic injury.