Antenatal betamethasone augments early rise in pulmonary perfusion at birth in preterm lambs: role of ductal shunting and right ventricular outflow distribution

Antenatal betamethasone augments lung perfusion but lowers upper body blood flow and O2 delivery with delayed cord clamping at birth in preterm lambs

Although the corticosteroid betamethasone is routinely administered to accelerate lung and cardiovascular maturation in the preterm fetus prior to birth, and use of delayed cord clamping (DCC) is recommended at birth by professional bodies, it is unknown whether antenatal betamethasone alters perinatal pulmonary or systemic arterial blood flow accompaniments of DCC. To address this issue, preterm fetal lambs [gestation 127 (1) days, term = 147 days] with (n = 10) or without (n = 10) antenatal betamethasone treatment were acutely instrumented under general anaesthesia with flow probes to obtain left (LV) and right ventricular (RV) outputs, major central arterial blood flows and shunt flow across both the ductus arteriosus and foramen ovale (FO). After delivery, lambs underwent initial ventilation for 2 min prior to DCC. During initial ventilation and after DCC, betamethasone (1) augmented rises in pulmonary arterial blood flow, with this greater increase supported during initial ventilation by enhanced pulmonary distribution of a higher RV output that was largely underpinned by newly emergent and substantial left-to-right (L → R) shunting across the FO, and after DCC, by an added contribution from more pronounced L → R ductal shunting; (2) increased a redistribution of LV output away from the upper body region, accompanied by lowering of upper body blood flow and O2 delivery; and (3) accentuated a progressive systemic-to-pulmonary arterial shift in the distribution of the combined LV and RV output that occurred in conjunction with more pronounced perinatal L → R shunting. These findings suggest that antenatal betamethasone substantially alters arterial blood flow effects of initial ventilation and DCC in the preterm birth transition. KEY POINTS: Betamethasone is given to increase fetal lung and cardiovascular maturation prior to preterm birth, while delayed cord clamping (DCC) is recommended at birth. Whether antenatal betamethasone alters perinatal arterial blood flow responses to DCC is unknown. Anaesthetized preterm fetal lambs with or without betamethasone pretreatment were instrumented with central arterial flow probes and, at birth, underwent ∼2 min of ventilation before DCC. Betamethasone augmented perinatal rises in pulmonary arterial blood flow, related to enhanced pulmonary distribution during initial ventilation of a higher right ventricular output largely underpinned by left-to-right (L → R) shunting across the foramen ovale, with an added contribution from more pronounced L → R ductal shunting after DCC. Betamethasone increased a redistribution of left ventricular output away from the upper body region, with lowering of upper body blood flow and O2 delivery. Betamethasone accentuated a systemic-to-pulmonary arterial shift in the distribution of combined ventricular output occurring with greater perinatal L → R shunting.

Improvement in Echocardiographic and Diagnostic Biomarkers after Systemic Glucocorticoid Therapy in Infants with Pulmonary Hypertension

OBJECTIVE

To assess the effect of treating pulmonary hypertension (PH) in infants younger than 1 year of age with systemic glucocorticoids while using echocardiographic and diagnostic biomarkers as measures of efficacy.

STUDY DESIGN

A retrospective chart review was performed on 17 hospitalized infants younger than 1 year of age at St Louis Children's Hospital who received a 5- to 7-day course of systemic glucocorticoid treatment followed by a 3-week taper with no significant intracardiac shunts from January 1, 2017, to December 31, 2021. Quantitative echocardiographic indices for PH, N-terminal pro b-type natriuretic peptide, and/or b-type natriuretic peptide levels were collected before glucocorticoid treatment, after the glucocorticoid burst, and after the 21-day taper.

RESULTS

Mean (±SD) gestational age was 32.1 (±5.8) weeks, 5 infants were (29%) concomitantly treated with sildenafil, and 8 were male. Twelve were classified as World Health Organization group 3 PH (71%) and 5 as World Health Organization group 1 PH. There were significant improvements 30 days after glucocorticoid initiation in b-type natriuretic peptide levels (P = .008), PCO2 (P = .03), eccentricity index (P = .005), right ventricular ejection time (P = .04), pulmonary artery acceleration time (P = .002), and pulmonary artery acceleration time-to-right ventricular ejection time ratio (P = .02). Tricuspid regurgitation velocity was not able to be assessed. There were no mortalities during the study timeline.

CONCLUSIONS

In our retrospective study, systemic glucocorticoid therapy was well tolerated and appeared to be associated with significant improvement in cardiopulmonary function in infants with PH. Further prospective study in a larger sample is warranted.

Short-term effects of antenatal betamethasone on fetal cardiovascular and circulation status: A quasi-experimental observational (before-after) study

Background

The administration of antenatal corticosteroid is a standard treatment to reduce the rate of perinatal mortality and morbidity; however, there is limited evidence regarding the potential effects of betamethasone on the constriction of the ductus arteriosus (DA).

Objective

This study aimed to investigate the short-term effects of antenatal betamethasone on fetal cardiovascular and circulation status.

Materials and Methods

This quasi-experimental observational (before-after) study was conducted on 32 singleton fetuses. The participants were healthy pregnant women with a diagnosis of placenta accreta spectrum who were eligible for 2 doses of betamethasone and referred to prenatal care clinic, Vali-E-Asr hospital, Tehran, Iran from January 2021-May 2022. The results of fetal echocardiography and Doppler sonography were compared before and after the administration of antenatal corticosteroid therapy.

Results

Following betamethasone injection, significant increases were observed in peak systolic and diastolic velocity of the DA without constriction of the DA (p < 0.001, p = 0.002 respectively). However, no significant changes were observed in right ventricular function, tricuspid valve function, Doppler of ductus venous, and peak systolic velocity of the aortic isthmus (p > 0.05). Doppler examination of the uterine, umbilical, and middle cerebral arteries also showed no significant changes (p > 0.05).

Conclusion

Considering the benefits of antenatal corticosteroid therapy, its administration seems reasonable in preterm births. The transient changes in ductal blood flow are not prohibitive.

Improvement in fetal pulmonary hypertension and maturity after reversal of ductal constriction: prospective cohort study

OBJECTIVES

To test the hypotheses that estimated mean pulmonary arterial pressure (MPAP) decreases and pulmonary vascular maturation, assessed by the ratio of pulmonary arterial flow acceleration time to ejection time (AT/ET ratio), increases after reversal of fetal ductus arteriosus constriction by reducing maternal intake of the causal agent (prostaglandin inhibitors, such as polyphenol-rich foods or non-steroidal anti-inflammatory drugs), and that these effects are independent of gestational age, which are inferences not yet demonstrated in the clinical setting.

METHODS

This was a prospective cohort study comparing Doppler echocardiographic ductal flow dynamics, MPAP and pulmonary arterial flow AT/ET ratio in third-trimester fetuses (≥ 28 weeks' gestation) with ductus arteriosus constriction, at the time of diagnosis and after 2 weeks of reduced maternal intake of prostaglandin inhibitors either by suspending the use of pharmacological agents with potential for prostaglandin inhibition or by restricting the consumption of polyphenol-rich foods. MPAP was estimated using the Dabestani equation (MPAP = 90 - (0.62 × AT)), and pulmonary vascular maturity was assessed using the AT/ET ratio, according to reported validation studies. Student's t-test was used for comparison of variables at diagnosis with those after reversal of ductal constriction. Change in MPAP and pulmonary AT/ET ratio between the two assessments was compared with the expected change in the same gestational period in normal fetuses based on reference curves of MPAP and pulmonary AT/ET ratio constructed in normal fetuses from healthy pregnant women at 19-37 weeks' gestation, encompassing the same gestational age range as the study group (28-37 weeks).

RESULTS

Seventy pregnancies with fetal ductus arteriosus constriction were included in the study. After 2 weeks of reduced maternal intake of prostaglandin inhibitors, normalization of mean systolic (change from 1.86 ± 0.34 m/s at diagnosis to 1.38 ± 0.41 m/s; P < 0.001) and diastolic (change from 0.41 ± 0.11 m/s to 0.21 ± 0.065 m/s; P < 0.001) ductal velocities and of mean pulsatility index (change from 1.99 ± 0.20 to 2.55 ± 0.42; P < 0.001) was demonstrated. MPAP decreased between the assessments (change from 66.7 ± 6.90 mmHg at diagnosis to 54.5 ± 6.70 mmHg after 2 weeks; P < 0.001) and mean pulmonary AT/ET ratio increased (change from 0.20 ± 0.06 to 0.33 ± 0.07; P < 0.001). Change in MPAP between diagnosis and after 2 weeks of reduced maternal intake of prostaglandin inhibitors was -12.2 ± 0.30 mmHg, which was 5.3-times higher than that in 305 normal fetuses over 2 weeks during the same gestational period (-2.3 ± 0.19 mmHg) (P < 0.001), and change in pulmonary AT/ET ratio between the two assessments was 0.13 ± 0.08, which was 8.7-times higher than that in normal fetuses in the same gestational period (0.015 ± 0.08) (P < 0.001).

CONCLUSIONS

Resolution of fetal ductal constriction is followed by a fall in MPAP and by an increase in pulmonary vascular maturity, to a significantly greater degree than is observed in normal fetuses in the same gestational-age period. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Randomized Trial of Oxygen Saturation Targets during and after Resuscitation and Reversal of Ductal Flow in an Ovine Model of Meconium Aspiration and Pulmonary Hypertension

Neonatal resuscitation (NRP) guidelines suggest targeting 85-95% preductal SpO₂ by 10 min after birth. Optimal oxygen saturation (SpO₂) targets during resuscitation and in the post-resuscitation management of neonatal meconium aspiration syndrome (MAS) with persistent pulmonary hypertension (PPHN) remains uncertain. Our objective was to compare the time to reversal of ductal flow from fetal pattern (right-to-left), to left-to-right, and to evaluate pulmonary (Q_PA), carotid (Q_CA)and ductal (Q_DA) blood flows between standard (85-94%) and high (95-99%) SpO₂ targets during and after resuscitation. Twelve lambs asphyxiated by endotracheal meconium instillation and cord occlusion to induce MAS and PPHN were resuscitated per NRP guidelines and were randomized to either standard (85-94%) or high (95-99%) SpO₂ targets. Out of twelve lambs with MAS and PPHN, six each were randomized to standard and high SpO₂ targets. Median [interquartile range] time to change in direction of blood flow across the ductus arteriosus from right-to-left, to left-to-right was significantly shorter with high SpO₂ target (7.4 (4.4-10.8) min) compared to standard SpO₂ target (31.5 (21-66.2) min, p = 0.03). Q_PA was significantly higher during the first 10 min after birth with higher SpO₂ target. At 60 min after birth, the Q_PA, Q_CA and Q_DA were not different between the groups. To conclude, targeting SpO₂ of 95-99% during and after resuscitation may hasten reversal of ductal flow in lambs with MAS and PPHN and transiently increase Q_PA but no differences were observed at 60 min. Clinical studies comparing low and high SpO₂ targets assessing hemodynamics and neurodevelopmental outcomes are warranted.

Antenatal betamethasone redistributes central blood flows and preferentially augments right ventricular output and pump function in preterm fetal lambs

The glucocorticosteroid betamethasone, which is routinely administered prior to anticipated preterm birth to enhance maturation of the lungs and the cardiovascular system, has diverse fetal regional blood flow effects ranging from increased pulmonary flow to decreased cerebral flow. The aim of this study was to test the hypothesis that these diverse effects reflect alterations in major central flow patterns that are associated with complementary shifts in left ventricular (LV) and right ventricular (RV) pumping performance. Studies were performed in anesthetized preterm fetal lambs (gestation = 127 ± 1 days, term = 147 days) with (n = 14) or without (n = 12) preceding betamethasone treatment via maternal intramuscular injection. High-fidelity central arterial blood pressure and flow signals were obtained to calculate LV and RV outputs and total hydraulic power. Betamethasone therapy was accompanied by 1) increased RV, but not LV, output; 2) a greater RV than LV increase in total power; 3) a redistribution of LV output away from the fetal upper body region and toward the lower body and placenta; 4) a greater proportion of RV output passing to the lungs, and a lesser proportion to the lower body and placenta; and 5) a change in the relative contribution of venous streams to ventricular filling, with the LV having increased pulmonary venous and decreased foramen ovale components, and the RV having lesser superior vena caval and greater inferior vena caval portions. Taken together, these findings suggest that antenatal betamethasone produces a widespread redistribution of central arterial and venous flows in the fetus, accompanied by a preferential rise in RV pumping performance.