The Changing Landscape in Supporting Preterm Infants at Birth

Extended period of ventilation before delayed cord clamping augments left-to-right shunting and decreases systemic perfusion at birth in preterm lambs

Previous studies have suggested that an extended period of ventilation before delayed cord clamping (DCC) augments birth-related rises in pulmonary arterial (PA) blood flow. However, it is unknown whether this greater rise in PA flow is accompanied by increases in left ventricular (LV) output and systemic arterial perfusion or whether it reflects enhanced left-to-right shunting across the ductus arteriosus and/or foramen ovale (FO), with decreased systemic arterial perfusion. Using an established preterm lamb birth transition model, this study compared the effect of a short (∼40 s, n = 11), moderate (∼2 min, n = 11) or extended (∼5 min, n = 12) period of initial mechanical lung ventilation before DCC on flow probe-derived perinatal changes in PA flow, LV output, total systemic arterial blood flow, ductal shunting and FO shunting. The LV output was relatively stable during initial ventilation but increased after DCC, with similar responses in all groups. Systemic arterial flow patterns displayed only minor differences during brief and moderate periods of initial ventilation and were similar after DCC. However, an increase in PA flow was augmented with an extended initial ventilation (P < 0.001), owing to an earlier onset of left-to-right ductal and FO shunting (P < 0.001), and was accompanied by a pronounced reduction in total systemic arterial flow (P = 0.005) that persisted for 4 min after DCC (P ≤ 0.039). These findings suggest that, owing to increased left-to-right shunting and a greater reduction in systemic arterial perfusion, an extended period of ventilation before DCC does not result in greater perinatal circulatory benefits than shorter periods of initial ventilation in the birth transition. KEY POINTS: Previous studies suggest that an extended period of initial ventilation before delayed cord clamping (DCC) augments birth-related rises in pulmonary arterial (PA) blood flow. It is unknown whether this greater rise in PA flow is accompanied by an increased left ventricular output and systemic arterial perfusion or whether it reflects enhanced left-to-right shunting across the ductus arteriosus and/or foramen ovale, with decreased systemic arterial perfusion. Anaesthetized preterm fetal lambs instrumented with central arterial flow probes underwent a brief (∼40 s), moderate (∼2 min) or extended (∼5 min) period of ventilation before DCC. Perinatal changes in left ventricular output were similar in all groups, but extended initial ventilation augmented both perinatal increases in PA flow, owing to earlier onset and greater left-to-right ductal and foramen ovale shunting, and perinatal reductions in total systemic arterial perfusion. Extended ventilation before DCC does not confer a greater perinatal circulatory benefit than shorter periods of initial ventilation.

The vocal cords are predominantly closed in preterm infants <30 weeks gestation during transition after birth; an observational study

AIM

Studies in animals have shown that vocal cords (VCs) close during apnoea before and after birth, thereby impairing the effect of non-invasive ventilation. We tested the feasibility of visualising VCs using ultrasonography (US) and investigated the position and movement of the VCs during non-invasive respiratory support of preterm infants at birth.

METHODS

In an observational study, VCs were visualised using US in infants <30 weeks gestation during both stabilisation after birth and at one hour after birth. Respiratory efforts were simultaneously recorded. The percentage of time the VCs were closed in the first ten minutes was determined from videoframes acquired at 15 Hz and compared with respiratory flow patterns measured using a respiratory function monitor.

RESULTS

US of the VCs could be performed in 20/20 infants included (median (IQR) gestational age 27+6 (27+1-28+6) weeks) without interfering with stabilisation, of whom 60% (12/20) were initially breathing and 40% (8/20) were apnoeic at birth. In breathing infants, the VCs closed between breaths and during breath holds, which accounted for 57% (49-66) of the time. In apnoeic infants receiving positive pressure ventilation, the VCs were closed for 93% (81-99) of the time. US at one hour after birth could be performed in 14/20 infants, VCs were closed between breaths and during breath holds, accounting for 46% (27-52) of the time.

CONCLUSION

Visualising VCs in preterm infants at birth using US is feasible. The VCs were closed during apnoea, in between breaths and during breath holds, impairing the effect of ventilation given.

Protecting the brain of the micropreemie

Advances in perinatal care have seen substantial improvements in survival without disability for extremely preterm infants. Protecting the developing brain and reducing neurodevelopmental sequelae of extremely preterm birth are strategic priorities for both research and clinical care. A number of evidence-based interventions exist for neuroprotection in micropreemies, inclusive of prevention of preterm birth and multiple births with implantation of only one embryo during in vitro fertilisation, as well as antenatal care to optimize fetal wellbeing, strategies for supporting neonatal transition, and neuroprotective developmental care. Avoidance of complications that trigger ischemia and inflammation is vital for minimizing brain dysmaturation and injury, particularly of the white matter. Neurodevelopmental surveillance, early diagnosis of cerebral palsy and early intervention are essential for optimizing long-term outcomes and quality of life. Research priorities include further evaluation of putative neuroprotective agents, and investigation of common neonatal interventions in trials adequately powered to assess neurodevelopmental outcome.

Hemodynamic consequences of respiratory interventions in preterm infants

Advances in perinatal management have led to improvements in survival rates for premature infants. It is known that the transitional period soon after birth, and the subsequent weeks, remain periods of rapid circulatory changes. Preterm infants, especially those born at the limits of viability, are susceptible to hemodynamic effects of routine respiratory care practices. In particular, the immature myocardium and cardiovascular system is developmentally vulnerable. Standard of care (but essential) respiratory interventions, administered as part of neonatal care, may negatively impact heart function and/or pulmonary or systemic hemodynamics. The available evidence regarding the hemodynamic impact of these respiratory practices is not well elucidated. Enhanced diagnostic precision and therapeutic judiciousness are warranted. In this narrative, we outline (1) the vulnerability of preterm infants to hemodynamic disturbances (2) the hemodynamic effects of common respiratory practices; including positive pressure ventilation and surfactant therapy, and (3) identify tools to assess cardiopulmonary interactions and guide management.

FIGO good practice recommendations on delayed umbilical cord clamping

Delayed cord clamping in the first minute in preterm infants born before 34 weeks of gestation improves neonatal hematologic measures and may reduce mortality without increasing any other morbidity. In term-born babies, it also seems to improve both the short- and long-term outcomes and shows favorable scores in fine motor and social domains. However, there is insufficient evidence to show what duration of delay is best. The current evidence supports not clamping the cord before 30 seconds for preterm births. Future trials could compare different lengths of delay. Until then, a period of 30 seconds to 3 minutes seems justified for term-born babies.

Impact of neonatal resuscitation changes on outcomes of very-low-birth-weight infants

The improvement of delivery room care, according to the 2015 International Consensus, may affect neonatal outcome, especially in very-low-birth-weight infants. We aimed to investigate the current practice of neonatal resuscitation by year and analyze the association with neonatal outcomes. A total of 8142 very-low-birth-weight infants, registered in the Korean Neonatal Network between 2014 and 2017 were included. A significant decreasing trend of intubation (64.5% vs 55.1%, P < 0.0001) and markedly increasing trend of positive pressure ventilation (PPV) (11.5% vs 22.9%, P < 0.0001) were noted. The annual PPV rate differed significantly by gestation (P < 0.0001). The highest level of resuscitation was also shown as an independent risk factor for mortality within 7 days and for bronchopulmonary dysplasia (BPD), intraventricular hemorrhage (IVH), and periventricular leukomalacia. PPV and intubation were associated with significantly decreased risk of mortality and morbidities compared to epinephrine use. When considering association, the incidence of mortality within 7 days, IVH, PVL, and BPD or mortality showed significant differences by combination of year, gestational age, and level of resuscitation. According to updated guidelines, changes in the highest level of resuscitation significantly associated with reducing mortality and morbidities. More meticulous delivery room resuscitation focusing on extreme prematurity is needed.

Newborn resuscitation devices: The known unknowns and the unknown unknowns

Infant resuscitation devices used at birth must be capable of delivering adequate and consistent ventilation in a controlled and predictable manner to a wide patient weight range, and combinations of transitional lung states. Manual inflation resuscitation devices delivering positive pressure lung inflation at birth can be classified broadly into two types: 1) flow generating, ie silicone self-inflating bags (SIB) also known as bag valve mask (BVM) and 2) flow dependent, ie anaesthetic flow inflating bag (FIB) and t-piece resuscitator (TPR) systems (eg: Neopuff, GE Panda and Draeger Resuscitaires). Globalization, lower production costs, and an expanding market need for devices, has led to a proliferation of brands (both reusable and single use) within a class type. T-piece resuscitators have become the dominant device particularly in high income countries. There remains a paucity of information on the performance characteristics of these devices and their ability to provide the required respiratory parameters for effective and safe ventilation across the full-expected weight range and lung states to which they will be applied. This review aims to inform current clinical practise on the biomechanical efficiency, reliability and efficacy of the most common devices used to apply PPV to newborns and infants ≤10 kgs.

Reflexes that impact spontaneous breathing of preterm infants at birth: a narrative review

Some neural circuits within infants are not fully developed at birth, especially in preterm infants. Therefore, it is unclear whether reflexes that affect breathing may or may not be activated during the neonatal stabilisation at birth. Both sensory reflexes (eg, tactile stimulation) and non-invasive ventilation (NIV) can promote spontaneous breathing at birth, but the application of NIV can also compromise breathing by inducing facial reflexes that inhibit spontaneous breathing. Applying an interface could provoke the trigeminocardiac reflex (TCR) by stimulating the trigeminal nerve resulting in apnoea and a reduction in heart rate. Similarly, airflow within the nasopharynx can elicit the TCR and/or laryngeal chemoreflex (LCR), resulting in glottal closure and ineffective ventilation, whereas providing pressure via inflations could stimulate multiple receptors that affect breathing. Stimulating the fast adapting pulmonary receptors may activate Head's paradoxical reflex to stimulate spontaneous breathing. In contrast, stimulating the slow adapting pulmonary receptors or laryngeal receptors could induce the Hering-Breuer inflation reflex or LCR, respectively, and thereby inhibit spontaneous breathing. As clinicians are most often unaware that starting primary care might affect the breathing they intend to support, this narrative review summarises the currently available evidence on (vagally mediated) reflexes that might promote or inhibit spontaneous breathing at birth.