Persistent pulmonary hypertension in neonates with perinatal asphyxia and therapeutic hypothermia: a frequent and perilous combination

Necrotizing enterocolitis in monochorionic twins: Insights from an identical twin model

Necrotizing enterocolitis (NEC) is a major cause of neonatal morbidity and mortality in preterm neonates, yet its pathophysiology remains unclear. The aim of this study is to evaluate risk factors for NEC using an identical twin model. In this case-control study, all monochorionic twin pairs born in our center in 2002-2020 were retrospectively reviewed for NEC. Potential risk factors for NEC were studied. For within-pair comparison, outcomes were compared between affected and unaffected twins. Within-pair analyses showed that the twin with NEC had a lower birth weight compared to its unaffected co-twin (1100 (913-1364) vs. 1339 (1093-1755) grams). Median gestational age at birth and birth weight were lower in twin pairs in the NEC-group compared to the no-NEC group, 29.1 weeks (27.8-30.8) versus 33.6 (30.7-36.0) and 1221 g (1010-1488) versus 1865 (1356-2355) respectively. Twin pregnancies in the NEC-group were more often complicated by twin-to-twin transfusion syndrome compared to the no-NEC-group (70 % (14/20) vs. 49 % (472/962)), particularly when treated with amnioreduction. This unique population of identical twins confirms that preterm neonates with a relatively lower birth weight are more prone to develop NEC compared to their co-twin, regardless of other genetic, maternal and obstetrical factors.

Meconium Aspiration Syndrome, Hypoxic-Ischemic Encephalopathy and Therapeutic Hypothermia-A Recipe for Severe Pulmonary Hypertension?

Hypoxic-ischemic encephalopathy (HIE) is the leading cause of mortality among term newborns globally. Infants born through meconium-stained amniotic fluid are at risk of developing meconium aspiration syndrome (MAS) and HIE. Simultaneous occurrence of MAS and HIE is a perilous combination for newborns due to the risk of persistent pulmonary hypertension of the newborn (PPHN). Moreover, therapeutic hypothermia (TH), which is the current standard of care for the management of HIE, may increase pulmonary vascular resistance (PVR) and worsen PPHN. Infants with MAS and HIE require close cardiorespiratory and hemodynamic monitoring for PPHN. Therapeutic strategies, including oxygen supplementation, ventilation, use of surfactant, inhaled nitric oxide and other pulmonary vasodilators, and systemic vasopressors, play a critical role in the management of PPHN in MAS, HIE, and TH. While TH reduces death or disability in infants with HIE, infants with MAS and HIE undergoing TH need close hemodynamic monitoring for PPHN.

Impact of persistent pulmonary hypertension and oxygenation on brain injury in neonates with neonatal encephalopathy treated with therapeutic hypothermia

OBJECTIVE

To investigate the effects of persistent pulmonary hypertension (PPHN) and oxygenation on outcome of neonates with neonatal encephalopathy (NE) treated with therapeutic hypothermia (TH).

STUDY DESIGN

We compared the outcome of neonates with NE treated with TH with or without PPHN.

RESULTS

384 neonates with NE were treated with TH; 24% had PPHN. The fraction of inspired oxygen was higher in the first 4 days of life (p < 0.001) in neonates with PPHN. They had a significantly lower arterial partial pressure of oxygen in the first 4 days of life (p = 0.005) and higher on days 3-4 of life (p < 0.001). They were more often intubated (p < 0.001) and more often had concomitant hypotension (p < 0.001). They had higher mortality (p = 0.009) and more often developed brain injury (p = 0.02).

CONCLUSION

PPHN occurred frequently in neonates with NE treated with TH and was associated with a higher incidence of adverse outcome.

Comorbidities and Late Outcomes in Neonatal Pulmonary Hypertension

Long-term outcomes of persistent pulmonary hypertension of newborn (PPHN) depend on disease severity, duration of ventilation, and associated anomalies. Congenital diaphragmatic hernia survivors may have respiratory morbidities and developmental delay. The presence of PPHN is associated with increased mortality in hypoxic-ischemic encephalopathy, though the effects on neurodevelopment are less clear. Preterm infants can develop pulmonary hypertension (PH) early in the postnatal course or later in the setting of bronchopulmonary dysplasia (BPD). BPD-PH is associated with higher mortality, particularly within the first year. Evidence suggests that both early and late PH in preterm infants are associated with neurodevelopmental impairment.

Asphyxia, Therapeutic Hypothermia, and Pulmonary Hypertension

Neonates with a perinatal hypoxic insult and subsequent neonatal encephalopathy are at risk of acute pulmonary hypertension (aPH) in the transitional period. The phenotypic contributors to aPH following perinatal asphyxia include a combination of hypoxic vasoconstriction of the pulmonary vascular bed, right heart dysfunction, and left heart dysfunction. Therapeutic hypothermia is the standard of care for neonates with moderate-to-severe hypoxic ischemic encephalopathy. This review summarizes the underlying risk factors, causes of aPH in neonates with perinatal asphyxia, discusses the unique phenotypical contributors to disease, and explores the impact of the initial insult and subsequent therapeutic hypothermia on aPH.

Growth and developmental outcomes of infants with hypoxic ischemic encephalopathy

Despite advances in obstetric care, hypoxic ischemic encephalopathy (HIE) remains a significant disease burden. We determined the national trends of HIE prevalence, therapeutic hypothermia (TH) use, mortality, and outcomes from 2012 to 2019. This study included term infants diagnosed with HIE between 2012 and 2019 from the National Health Insurance Service database. The prevalence of HIE was 2.4 per 1000 births without significant change during the period. TH was performed in approximately 6.7% of infants with HIE, and the annual variation ranged from 2.4 to 12.5%. The mortality among all term infants with HIE was 4.6%. The mortality rate among infants with HIE and TH significantly declined from 40 to 16.9% during the eight years. Infants with TH had higher mortality, increased use of inhaled nitric oxide, and more invasive ventilator use, indicating greater disease severity in the TH group. Infants with TH also showed significantly poorer outcomes, including delayed development, cerebral palsy, sensorineural hearing loss, and seizure, compared to infants without TH (p < 0.0001). With the increasing application of TH, mortality and developmental outcomes among infants with HIE have been improving in the past eight years in Korea. Further efforts to improve outcomes should be needed.

Short-term outcome and complications of therapeutic hypothermia in neonates with moderate-to-severe hypoxic ischaemic encephalopathy: a single-centre retrospective observational study in a hospital in Mumbai, India

BACKGROUND

Although shown to reduce death or disability in moderate-to-severe hypoxic ischaemic encephalopathy (HIE), therapeutic hypothermia (TH) has recently been associated with an increase in adverse events in low- and middle-income countries (LMIC).

AIM

To determine the clinical characteristics, complications and short-term outcome in neonates receiving TH in King Edward Memorial Hospital, Mumbai, India.

METHODS

A retrospective single-centre study of neonates with moderate-to-severe HIE who received TH from 1 January 2018 to 31 December 2021 was undertaken. TH was provided as per the unit's protocol using either a servo-controlled device or a phase-changing material (PCM).

RESULTS

One hundred and fifty-five neonates were included with 94.2% intramural births. Mean gestation and birthweight were 38.6 (1.5) weeks and 2776.7 (431) g, respectively. HIE staging was moderate in 87.1% and severe in 12.9%, with a mean cord pH of 6.93 (0.14) and seizures in 38.7%. Adverse events included shock (50.3%), clinically significant bleeding (16%), acute kidney injury (6.7%), culture-positive sepsis (11.6%), persistent pulmonary hypertension (9%), bradycardia (9%), food intolerance (14.9%) and premature termination (7.1%). A servo-controlled device (15.5%) or PCM (84.5%) was used, with comparable adverse events. 84.5% of the neonates were discharged, 7.1% discharged against medical advice and 8.4% died. Detailed neurological assessment at discharge/discharge against medical advice suggested neurological impairment in 128 (87.1%) neonates.

CONCLUSION

Adverse events during TH range from asymptomatic laboratory abnormalities to life-threatening complications, which are manageable in well equipped units. Neurological impairment at discharge in neonates who received cooling mandates strict neurological follow-up.Abbreviations: aEEG: amplitude-integrated EEG; AKI: acute kidney injury; BW: birthweight; EEG: electro-encephalogram; GA: gestational age; HELIX: hypothermia for encephalopathy in low- and middle-income countries; HIE: hypoxic ischaemic encephalopathy; IVH: intraventricular haemorrhage; LMIC: low- and middle-income countries; NICHD: National Institute of Child Health and Human Development; NICU: neonatal intensive care unit; PPHN: persistent pulmonary hypertension of newborn; PCM: phase-changing material; SGA: small-for-gestational age; TH: therapeutic hypothermia.

Posttreatment Strategy Against Hypoxia and Ischemia Based on Selective Targeting of Nonnuclear Estrogen Receptors with PaPE-1

Newly synthesized Pathway Preferential Estrogen-1 (PaPE-1) selectively activates membrane estrogen receptors (mERs), namely, mERα and mERβ, and has been shown to evoke neuroprotection; however, its effectiveness in protecting brain tissue against hypoxia and ischemia has not been verified in a posttreatment paradigm. This is the first study showing that a 6-h delayed posttreatment with PaPE-1 inhibited hypoxia/ischemia-induced neuronal death, as indicated by neutral red uptake in mouse primary cell cultures in vitro. The effect was accompanied by substantial decreases in neurotoxicity and neurodegeneration in terms of LDH release and Fluoro-Jade C staining of damaged cells, respectively. The mechanisms of the neuroprotective action of PaPE-1 also involved apoptosis inhibition demonstrated by normalization of both mitochondrial membrane potential and expression levels of apoptosis-related genes and proteins such as Fas, Fasl, Bcl2, FAS, FASL, BCL2, BAX, and GSK3β. Furthermore, PaPE-1-evoked neuroprotection was mediated through a reduction in ROS formation and restoration of cellular metabolic activity that had become dysregulated due to hypoxia and ischemia. These data provide evidence that targeting membrane non-GPER estrogen receptors with PaPE-1 is an effective therapy that protects brain neurons from hypoxic/ischemic damage, even when applied with a 6-h delay from injury onset.

Pediatric Hypothermia: An Ambiguous Issue

Hypothermia in pediatrics is mainly about small body size. The key thermal factor here is the large surface-to-volume ratio. Although small mammals, including human infants and children, are adapted to higher heat losses through their elevated metabolic rate and thermogenic capacity, they are still at risk of hypothermia because of a small regulatory range and an impending metabolic exhaustion. However, some small mammalian species (hibernators) use reduced metabolic rates and lowered body temperatures as adaptations to impaired energy supply. Similar to nature, hypothermia has contradictory effects in clinical pediatrics as well: In neonates, it is a serious risk factor affecting respiratory adaptation in term and developmental outcome in preterm infants. On the other hand, it is an important self-protective response to neonatal hypoxia and an evidence-based treatment option for asphyxiated babies. In children, hypothermia first enabled the surgical repair of congenital heart defects and promotes favorable outcome after ice water drowning. Yet, it is also a major threat in various prehospital and clinical settings and has no proven therapeutic benefit in pediatric critical care. All in all, pediatric hypothermia is an ambiguous issue whose harmful or beneficial effects strongly depend on the particular circumstances.