Shape of Pulmonary Artery Doppler Flow Profile and Right Ventricular Hemodynamics in Neonates

OBJECTIVES

To characterize pulmonary artery Doppler flow profile (PAFP) patterns among infants receiving care in neonatal intensive care units and to examine the association of PAFP patterns with pulmonary and right ventricular (RV) hemodynamics.

STUDY DESIGN

This is a retrospective study at 2 tertiary intensive care units over 4 years that included neonates who demonstrated a complete tricuspid regurgitation envelope on targeted neonatal echocardiography. Separate personnel reviewed TNEs to characterize PAFP patterns, divide cohort into PAFP groups, and measure quantitative indices of RV hemodynamics (RV systolic pressure, pulmonary artery acceleration time and its ratio with RV ejection time, tricuspid annular plane systolic excursion, and RV output), for intergroup comparisons.

RESULTS

We evaluated TNEs from 186 neonates with median gestational age of 28.5 weeks (IQR, 25.9-35.9 weeks). Four distinct PAFP patterns were identified (A) near-isosceles triangle (22%), (B) right-angled triangle (29%), (C) notching (40%), and (D) low peak velocity (<0.4 m/s; 9%). Groups A-C demonstrated a stepwise worsening in all indices of PH, whereas pattern D was associated with lower tricuspid annular plane systolic excursion and RV output. Using common definitions of pulmonary hypertension (PH), pattern A performed best to rule out PH (sensitivity range, 81%-90%) and pattern C for diagnosing PH (specificity range, 63%-78%).

CONCLUSIONS

Inspection of PAFP is a simple bedside echocardiography measure that provides clinically meaningful information on underlying RV hemodynamics and may aid in screening and monitoring of patients for PH in intensive care units.

Dopamine or norepinephrine for sepsis-related hypotension in preterm infants: a retrospective cohort study

The purpose of this study is to compare the clinical effectiveness of dopamine (DA) versus norepinephrine (NE) as first-line therapy for sepsis-related hypotension in preterm infants. This is a retrospective cohort study over 10 years at two tertiary neonatal units. Preterm infants born < 35 weeks post-menstrual age (PMA), who received DA or NE as primary therapy for hypotension during sepsis, defined as culture-positive or culture-negative infections or necrotizing enterocolitis (NEC), were included. Episode-related mortality (< 7 days from treatment), pre-discharge mortality, and major morbidities among survivors were compared between two groups. Analyses were adjusted using the inverse probability of treatment weighting estimated by propensity score (PS). A total of 156 infants were included, 113 received DA and 43 NE. The mean ± SD PMA at birth and at treatment for the DA and NE groups were 25.8 ± 2.3 vs. 25.2 ± 2.0 weeks and 27.7 ± 3.0 vs. 27.1 ± 2.6 weeks, respectively (p > 0.05). Pre-treatment, the NE group had higher mean airway pressure (14 ± 4 vs. 12 ± 4 cmH₂O), heart rate (185 ± 17 vs. 175 ± 17 beats per minute), and median (IQR) fraction of inspired oxygen [0.67 (0.42, 1.0) vs. 0.52 (0.32, 0.82)] (p < 0.05 for all). After PS adjustment, NE was associated with lower episode-related mortality [adjusted odds ratio (95% CI) 0.55 (0.33, 0.92)], pre-discharge mortality [0.60 (0.37, 0.97)], post-illness new diagnosis of significant neurologic injury [0.32 (0.13, 0.82)], and subsequent occurrence of NEC/sepsis among the survivors [0.34, (0.18, 0.65)].

CONCLUSION

NE may be more effective than DA for management of sepsis-related hypotension among preterm infants. These data provide a rationale for prospective evaluation of these commonly used agents.

WHAT IS KNOWN

•Dopamine is the commonest vasoactive agent used to support blood pressure among preterm infants. •For adult patients, norepinephrine is recommended as the preferred therapy over dopamine for septic shock.

WHAT IS NEW

•This is the first study examining the relative clinical effectiveness of dopamine and norepinephrine as first-line pharmacotherapy for sepsis-related hypotension among preterm infants. •Norepinephrine use may be associated with lower mortality and morbidity than dopamine in preterm infants with sepsis.

Multicentre prospective observational study exploring the predictive value of functional echocardiographic indices for early identification of preterm neonates at risk of developing chronic pulmonary hypertension secondary to chronic neonatal lung disease

INTRODUCTION

Although chronic pulmonary hypertension (cPH) secondary to chronic neonatal lung disease is associated with increased mortality and respiratory and neurodevelopmental morbidities, late diagnosis (typically ≥36 weeks postmenstrual age, PMA) and the use of qualitative echocardiographic diagnostic criterion (flat interventricular septum in systole) remain significant limitations in clinical care. Our objective in this study is to evaluate the utility of relevant quantitative echocardiographic indices to identify cPH in preterm neonates, early in postnatal course and to develop a diagnostic test based on the best combination of markers.

METHODS AND ANALYSIS

In this ongoing international prospective multicentre observational diagnostic accuracy study, we aim to recruit 350 neonates born <27 weeks PMA and/or birth weight <1000 g and perform echocardiograms in the third week of age and at 32 weeks PMA (early diagnostic assessments, EDA) in addition to the standard diagnostic assessment (SDA) for cPH at 36 weeks PMA. Predefined echocardiographic markers under investigation will be measured at each EDA and examined to create a scoring system to identify neonates who subsequently meet the primary outcome of cPH/death at SDA. Diagnostic test characteristics will be defined for each EDA. Pulmonary artery acceleration time and tricuspid annular plane systolic excursion are the primary markers of interest.

ETHICS AND DISSEMINATION

Ethics approval has been received by the Mount Sinai Hospital Research Ethics Board (REB) (#16-0111-E), Sunnybrook Health Sciences Centre REB (#228-2016), NHS Health Research Authority (IRAS 266498), University of Iowa Human Subjects Office/Institutional Review Board (201903736), Rotunda Hospital Research and Ethics Committee (REC-2019-008), and UBC Children's and Women's REB (H19-02738), and is under review at Boston Children's Hospital Institutional Review Board. Study results will be disseminated to participating families in lay format, presented to the scientific community at paediatric and critical care conferences and published in relevant peer-reviewed journals.

TRAIL REGISTRATION NUMBER

NCT04402645.

Association of hemoglobin and spontaneous closure of the ductus arteriosus during the transitional period in very low birth weight infants

OBJECTIVES

To determine the association between plasma hemoglobin (HB) at three time-points (birth, postnatal days 0-3 and 0-10) and spontaneous closure of the ductus arteriosus (sDAC).

STUDY DESIGN

A retrospective case-control study of preterm infants born (2013-2016) between 24 and 29 weeks of gestational age (GA) was conducted in a level three perinatal center in Switzerland. We collected hemoglobin at birth, between days 0-3 and 0-10 in two distinct groups: (i) patients treated for a PDA and (ii) patients with spontaneous closure of the ductus arteriosus (sDAC). Antenatal and postnatal demographic data and neonatal morbidity were collected. Bivariate analysis was performed and a stepwise logistic regression was done to investigate factors associated with sDAC.

RESULTS

We reviewed the medical chart of 184 premature infants of whom 146 (79.3%) satisfied eligibility criteria. Of these, 74 (51%) were classified as sDAC. Patients with sDAC were older (GA: 28 vs 27, p < 0.001), more stable (clinical risk index for babies score (CRIB score): 2 vs 5, p < 0.001) and had better clinical outcomes than patients who received treatment for a PDA. Infants in the sDAC group had a higher level of hemoglobin during the first ten postnatal days. Multiple logistic regression analysis revealed that lower HB level (day 0-10) were associated with failure of sDAC (p < 0.05).

CONCLUSIONS

This is one of the first studies to highlight a potential association between hemoglobin during the transitional period and sDAC. The biological nature of this observation requires prospective clarification.

Intrauterine growth restriction is associated with sex-specific alterations in the nitric oxide/cyclic GMP relaxing pathway in the human umbilical vein

INTRODUCTION

Intrauterine growth restriction (IUGR) is a leading cause of perinatal mortality and morbidity, and is linked to an increased risk to develop chronic diseases in adulthood. We previously demonstrated that IUGR is associated, in female neonates, with a decreased nitric oxide (NO)-induced relaxation of the umbilical vein (UV). The present study aimed to investigate the contribution of the smooth muscle components of the NO/cyclic GMP (cGMP) pathway to this alteration.

METHODS

UVs were collected in growth-restricted or appropriate for gestational age (AGA) human term newborns. Soluble guanylyl cyclase (sGC) and cGMP-dependent protein kinase (PKG) were studied by Western blot, cGMP production by ELISA and cyclic nucleotide phosphodiesterases (PDEs) activity using a colorimetric assay. Contribution of PDEs was evaluated using the non-specific PDEs inhibitor 3-isobutyl-1-methylxanthine (IBMX) in isolated vessel tension studies.

RESULTS

NO-induced relaxation was reduced in IUGR females despite increased sGC protein and activity, and some increase in PKG protein compared to AGA. In males, no significant difference was observed between both groups. In the presence of IBMX, NO-stimulated cGMP production was significantly higher in IUGR than AGA females. Pre-incubation with IBMX significantly improved NO-induced relaxation in all groups and abolished the difference between IUGR and AGA females.

CONCLUSION

IUGR is associated with sex-specific alterations in the UV's smooth muscle. The impaired NO-induced relaxation observed in growth-restricted females is linked to an imbalance in the NO/cGMP pathway. The beneficial effects of IBMX suggest that PDEs are implicated in such alteration and they could represent promising targets for therapeutic intervention.

Methane ice worms: Hesiocaeca methanicola colonizing fossil fuel reserves

During a research cruise in July 1997 in the Gulf of Mexico we discovered a gas hydrate approximately 1 m thick and over 2 m in diameter which had recently breached the sea floor at a depth of 540 m. The hydrate surface visible from the submarine was considerably greater than that of any other reported hydrate. Two distinct color bands of hydrate were present in the same mound, and the entire exposed surface of the hydrate was infested (2500 individuals/m2) with 2 to 4 cm-long worms, since described as a new species, Hesiocaeca methanicola, in the polychaete family Hesionidae (Desbruyères and Toulmond 1998). H. methanicola tissue stable isotope values are consistent with a chemo-autotrophic food source. No evidence of chemo-autotrophic symbionts was detected, but geochemical data support the presence of abundant free living bacteria on the hydrate. The activities of the polychaetes, grazing on the hydrate bacteria and supplying oxygen to their habitats, appears to contribute to the dissolution of hydrates in surface sediments.