Comparison of the effects of antenatal magnesium sulphate and ritodrine exposure on circulatory adaptation in preterm infants

Prenatal Magnesium Sulfate and Functional Connectivity in Offspring at Term-Equivalent Age

Importance

Understanding the effect of antenatal magnesium sulfate (MgSO4) treatment on functional connectivity will help elucidate the mechanism by which it reduces the risk of cerebral palsy and death.

Objective

To determine whether MgSO4 administered to women at risk of imminent preterm birth at a gestational age between 30 and 34 weeks is associated with increased functional connectivity and measures of functional segregation and integration in infants at term-equivalent age, possibly reflecting a protective mechanism of MgSO4.

Design, Setting, and Participants

This cohort study was nested within a randomized placebo-controlled trial performed across 24 tertiary maternity hospitals. Participants included infants born to women at risk of imminent preterm birth at a gestational age between 30 and 34 weeks who participated in the MAGENTA (Magnesium Sulphate at 30 to 34 Weeks' Gestational Age) trial and underwent magnetic resonance imaging (MRI) at term-equivalent age. Ineligibility criteria included illness precluding MRI, congenital or genetic disorders likely to affect brain structure, and living more than 1 hour from the MRI center. One hundred and fourteen of 159 eligible infants were excluded due to incomplete or motion-corrupted MRI. Recruitment occurred between October 22, 2014, and October 25, 2017. Participants were followed up to 2 years of age. Analysis was performed from February 1, 2021, to February 27, 2024. Observers were blind to patient groupings during data collection and processing.

Exposures

Women received 4 g of MgSO4 or isotonic sodium chloride solution given intravenously over 30 minutes.

Main Outcomes and Measures

Prior to data collection, it was hypothesized that infants who were exposed to MgSO4 would show enhanced functional connectivity compared with infants who were not exposed.

Results

A total of 45 infants were included in the analysis: 24 receiving MgSO4 treatment and 21 receiving placebo; 23 (51.1%) were female and 22 (48.9%) were male; and the median gestational age at scan was 40.0 (IQR, 39.1-41.1) weeks. Treatment with MgSO4 was associated with greater voxelwise functional connectivity in the temporal and occipital lobes and deep gray matter structures and with significantly greater clustering coefficients (Hedge g, 0.47 [95% CI, -0.13 to 1.07]), transitivity (Hedge g, 0.51 [95% CI, -0.10 to 1.11]), local efficiency (Hedge g, 0.40 [95% CI, -0.20 to 0.99]), and global efficiency (Hedge g, 0.31 [95% CI, -0.29 to 0.90]), representing enhanced functional segregation and integration.

Conclusions and Relevance

In this cohort study, infants exposed to MgSO4 had greater voxelwise functional connectivity and functional segregation, consistent with increased brain maturation. Enhanced functional connectivity is a possible mechanism by which MgSO4 protects against cerebral palsy and death.

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.

Neonatal heart rate variability: a contemporary scoping review of analysis methods and clinical applications

BACKGROUND

Neonatal heart rate variability (HRV) is widely used as a research tool. However, HRV calculation methods are highly variable making it difficult for comparisons between studies.

OBJECTIVES

To describe the different types of investigations where neonatal HRV was used, study characteristics, and types of analyses performed.

ELIGIBILITY CRITERIA

Human neonates ≤1 month of corrected age.

SOURCES OF EVIDENCE

A protocol and search strategy of the literature was developed in collaboration with the McGill University Health Center's librarians and articles were obtained from searches in the Biosis, Cochrane, Embase, Medline and Web of Science databases published between 1 January 2000 and 1 July 2020.

CHARTING METHODS

A single reviewer screened for eligibility and data were extracted from the included articles. Information collected included the study characteristics and population, type of HRV analysis used (time domain, frequency domain, non-linear, heart rate characteristics (HRC) parameters) and clinical applications (physiological and pathological conditions, responses to various stimuli and outcome prediction).

RESULTS

Of the 286 articles included, 171 (60%) were small single centre studies (sample size <50) performed on term infants (n=136). There were 138 different types of investigations reported: physiological investigations (n=162), responses to various stimuli (n=136), pathological conditions (n=109) and outcome predictor (n=30). Frequency domain analyses were used in 210 articles (73%), followed by time domain (n=139), non-linear methods (n=74) or HRC analyses (n=25). Additionally, over 60 different measures of HRV were reported; in the frequency domain analyses alone there were 29 different ranges used for the low frequency band and 46 for the high frequency band.

CONCLUSIONS

Neonatal HRV has been used in diverse types of investigations with significant lack of consistency in analysis methods applied. Specific guidelines for HRV analyses in neonates are needed to allow for comparisons between studies.

Antenatal and perinatal factors influencing neonatal blood pressure: a systematic review

OBJECTIVE

A comprehensive understanding of the factors contributing to perinatal blood pressure is vital to ensure optimal postnatal hemodynamic support. The objective of this study was to review existing literature on maternal and perinatal factors influencing blood pressure in neonates up to 3 months corrected age.

METHODS

A systematic search of published literature in OVID Medline, OVID Embase and the COCHRANE library identified publications relating to maternal factors affecting blood pressure of neonates up to corrected age of 3 months. Summary data were extracted and compared (PROSPERO CRD42018092886).

RESULTS

Of the 3683 non-duplicate publications identified, 44 were eligible for inclusion in this review. Topics elicited were sociodemographic factors, maternal health status, medications, smoking during pregnancy, and cord management at birth. Limited data were available for each factor. Results regarding the impact of these factors on neonatal blood pressure were inconsistent across studies.

CONCLUSIONS

There is insufficient evidence to draw definitive conclusions regarding the impact of various maternal and perinatal factors on neonatal blood pressure. Future investigations of neonatal cardiovascular therapies should account for these factors in their study design. Similarly, studies on maternal diseases and perinatal interventions should include neonatal blood pressure as part of their primary or secondary analyses.

Effect of Neuroprotective Magnesium Sulfate Treatment on Brain Transcription Response to Hypoxia Ischemia in Neonate Mice

MgSO₄ is widely used in the prevention of preterm neurological disabilities but its modes of action remain poorly established. We used a co-hybridization approach using the transcriptome in 5-day old mice treated with a single dose of MgSO₄ (600 mg/kg), and/or exposed to hypoxia-ischemia (HI). The transcription of hundreds of genes was altered in all the groups. MgSO₄ mainly produced repressions culminating 6 h after injection. Bio-statistical analysis revealed the repression of synaptogenesis and axonal development. The putative targets of MgSO₄ were Mnk1 and Frm1. A behavioral study of adults did not detect lasting effects of neonatal MgSO₄ and precluded NMDA-receptor-mediated side effects. The effects of MgSO₄ plus HI exceeded the sum of the effects of separate treatments. MgSO₄ prior to HI reduced inflammation and the innate immune response probably as a result of cytokine inhibition (Ccl2, Ifng, interleukins). Conversely, MgSO₄ had little effect on HI-induced transcription by RNA-polymerase II. De novo MgSO₄-HI affected mitochondrial function through the repression of genes of oxidative phosphorylation and many NAD-dehydrogenases. It also likely reduced protein translation by the repression of many ribosomal proteins, essentially located in synapses. All these effects appeared under the putative regulatory MgSO₄ induction of the mTORC2 Rictor coding gene. Lasting effects through Sirt1 and Frm1 could account for this epigenetic footprint.

Neonatal Blood Pressure Standards: What Is "Normal"?

Blood pressure (BP) is routinely measured in newborn infants. Published BP nomograms demonstrate a rise in BP following delivery in healthy infants at all gestational ages (GA) and evidence that BP values are higher with increasing birth weight and GA. However, the complex physiology that occurs in newborn infants and range of BP values observed at all GA make it difficult to identify "normal" BP for a specific infant at a specific time under specific conditions. As such, complete hemodynamic assessment should include the physical examination, perinatal history, other vital signs, and laboratory values in addition to BP values.

Effects of antenatal magnesium sulfate treatment for neonatal neuro-protection on cerebral oxygen kinetics

BACKGROUND

The underlying neuro-protective mechanisms of antenatal magnesium sulfate (MgSO(4)) in infants born preterm remain poorly understood. Early neonatal brain injury may be preceded by low cerebral blood flow (CBF) and elevated cerebral fractional tissue oxygen extraction (cFTOE). This study investigated the effect of antenatal MgSO(4) on cerebral oxygen delivery, consumption, and cFTOE in preterm infants.

METHODS

CBF and tissue oxygenation index were measured, and oxygen delivery, consumption, and cFTOE calculated within 24 h of birth and at 48 and 72 h of life in 36 infants ≤ 30 wk gestation exposed to MgSO(4) and 29 unexposed infants.

RESULTS

Total internal carotid blood flow and cerebral oxygen delivery did not differ between the groups at the three study time-points. Cerebral oxygen consumption and cFTOE were lower in infants exposed to antenatal MgSO(4) (P = 0.012) compared to unexposed infants within 24 h of delivery. This difference was not evident by 48 h of age. Fewer infants in the MgSO(4) group developed P/IVH by 72 h of age (P = 0.03).

CONCLUSION

Infants exposed to MgSO(4) had similar systemic and cerebral hemodynamics but lower cFTOE compared to nonexposed. These findings suggest reduced cerebral metabolism maybe a component of the neuro-protective actions of antenatal MgSO(4).

Antenatal magnesium sulfate exposure and acute cardiorespiratory events in preterm infants

OBJECTIVE

Antenatal magnesium (anteMg) is used for various obstetric indications including fetal neuroprotection. Infants exposed to anteMg may be at risk for respiratory depression and delivery room (DR) resuscitation. The study objective was to compare the risk of acute cardiorespiratory events among preterm infants who were and were not exposed to anteMg.

STUDY DESIGN

This was a retrospective analysis of prospective data collected in the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network's Generic Database from April 1, 2011, through March 31, 2012. The primary outcome was DR intubation or respiratory support at birth or on day 1 of life. Secondary outcomes were invasive mechanical ventilation, hypotension treatment, neonatal morbidities, and mortality. Logistic regression analysis evaluated the risk of primary outcome after adjustment for covariates.

RESULTS

We evaluated 1544 infants <29 weeks' gestational age (1091 in anteMg group and 453 in nonexposed group). Mothers in the anteMg group were more likely to have higher education, pregnancy-induced hypertension, and antenatal corticosteroids, while their infants were younger in gestation and weighed less (P < .05). The primary outcome (odds ratio [OR], 1.2; 95% confidence interval [CI], 0.88-1.65) was similar between groups. Hypotension treatment (OR, 0.70; 95% CI, 0.51-0.97) and invasive mechanical ventilation (OR, 0.54; 95% CI, 0.41-0.72) were significantly less in the anteMg group.

CONCLUSION

Among preterm infants age <29 weeks' gestation, anteMg exposure was not associated with an increase in cardiorespiratory events in the early newborn period. The safety of anteMg as measured by the need for DR intubation or respiratory support on day 1 of life was comparable between groups.

Magnesium sulphate at 30 to 34 weeks' gestational age: neuroprotection trial (MAGENTA)--study protocol

Background

Magnesium sulphate is currently recommended for neuroprotection of preterm infants for women at risk of preterm birth at less than 30 weeks’ gestation, based on high quality evidence of benefit. However there remains uncertainty as to whether these benefits apply at higher gestational ages.

The aim of this randomised controlled trial is to assess whether giving magnesium sulphate compared with placebo to women immediately prior to preterm birth between 30 and 34 weeks’ gestation reduces the risk of death or cerebral palsy in their children at two years’ corrected age.

Methods/design

Design: Randomised, multicentre, placebo controlled trial.

Inclusion criteria: Women, giving informed consent, at risk of preterm birth between 30 to 34 weeks’ gestation, where birth is planned or definitely expected within 24 hours, with a singleton or twin pregnancy and no contraindications to the use of magnesium sulphate.

Trial entry & randomisation: Eligible women will be randomly allocated to receive either magnesium sulphate or placebo.

Treatment groups: Women in the magnesium sulphate group will be administered 50 ml of a 100 ml infusion bag containing 8 g magnesium sulphate heptahydrate [16 mmol magnesium ions]. Women in the placebo group will be administered 50 ml of a 100 ml infusion bag containing isotonic sodium chloride solution (0.9%). Both treatments will be administered through a dedicated IV infusion line over 30 minutes.

Primary study outcome: Death or cerebral palsy measured in children at two years’ corrected age.

Sample size: 1676 children are required to detect a decrease in the combined outcome of death or cerebral palsy, from 9.6% with placebo to 5.4% with magnesium sulphate (two-sided alpha 0.05, 80% power, 5% loss to follow up, design effect 1.2).

Discussion

Given the magnitude of the protective effect in the systematic review, the ongoing uncertainty about benefits at later gestational ages, the serious health and cost consequences of cerebral palsy for the child, family and society, a trial of magnesium sulphate for women at risk of preterm birth between 30 to 34 weeks’ gestation is both important and relevant for clinical practice globally.

Trial registration

Australian New Zealand Clinical Trials Registry - ACTRN12611000491965

Antenatal magnesium individual participant data international collaboration: assessing the benefits for babies using the best level of evidence (AMICABLE)

BACKGROUND

The primary aim of this study is to assess, using individual participant data (IPD) meta-analysis, the effects of administration of antenatal magnesium sulphate given to women at risk of preterm birth on important clinical outcomes for their child such as death and neurosensory disability. The secondary aim is to determine whether treatment effects differ depending on important pre-specified participant and treatment characteristics, such as reasons at risk of preterm birth, gestational age, or type, dose and mode of administration of magnesium sulphate.

METHODS

DESIGN

The Antenatal Magnesium Individual Participant Data (IPD) International Collaboration: assessing the benefits for babies using the best level of evidence (AMICABLE) Group will perform an IPD meta-analysis to answer these important clinical questions. SETTING/TIMELINE: The AMICABLE Group was formed in 2009 with data collection commencing late 2010.

INCLUSION CRITERIA

Five trials involving a total 6,145 babies are eligible for inclusion in the IPD meta-analysis. PRIMARY STUDY OUTCOMES: For the infants/children: Death or cerebral palsy. For the women: Any severe maternal outcome potentially related to treatment (death, respiratory arrest or cardiac arrest).

DISCUSSION

Results are expected to be publicly available in 2012.

The effect of maternal ketanserin use on the circulation of the neonate: a prospective, observational study

OBJECTIVE

High ketanserin levels are found in the umbilical cord after maternal treatment. However, the effect on the circulation of the neonate has never been investigated.

STUDY DESIGN

A prospective, observational study was performed at the neonate ward at the Medical Centre Leeuwarden, The Netherlands. All neonates exposed in utero to ketanserin administered to the mother, from May 2007 to December 2009 (n=58), were included. We studied the effect of ketanserin exposure on the circulation of the neonate, by monitoring heart rate and blood pressure during the first 24h of life. Non-parametric as well as parametric tests were used to analyze the effect of gestational age, birth weight, gender, various ketanserin factors (cumulative dosage, duration of therapy and last dosage rate), other maternal drug use and maternal diagnosis on the blood pressure of the neonate.

RESULTS

Eight neonates became hypotensive during the first 8h of life (13.8%). The last dosage rate as well as the mean dosage rate (cumulative dosage divided by duration of therapy in hours) were significantly higher in the group with hypotension (P=.005 and P=.002, respectively). All hypotensive neonates were exposed to a last dosage rate of at least 8 mg/h. Maternal HELLP syndrome was diagnosed more often in hypotensive compared to normotensive neonates (P=.048).

CONCLUSION

In utero exposure to ketanserin lowers the blood pressure of the neonate. The risk of hypotension is associated with the last dosage rate of maternal ketanserin treatment and the co-existence of maternal HELLP syndrome.

Antenatal magnesium sulphate neuroprotection in the preterm infant

Very preterm infants have high rates of neurological impairments and disabilities. These rates have not diminished as the survival rates have improved. Basic science research suggests that magnesium sulphate before birth can be neuroprotective for the preterm fetus. Some, but not all, observational studies in humans also suggest a protective effect of antenatal magnesium sulphate on cerebral palsy. Four randomised controlled trials of antenatal magnesium sulphate have reported long-term neurological effects in surviving infants, but only one of these was designed specifically to evaluate the long-term effects of treatment. These studies found that, overall, antenatal magnesium sulphate therapy had no significant effect on paediatric mortality or neurological outcomes in the first few years of life, including cerebral palsy, but it was found to lower the rate of motor problems at 2 years of age in one study. The role for antenatal magnesium sulphate therapy as a neuroprotective agent for the preterm fetus is not yet established.

Early neonatal hypotension in premature infants born to preeclamptic mothers

BACKGROUND

Early neonatal hypotension (ENH) is common in premature infants and has been claimed to occur more frequently in infants born to mothers with severe preeclampsia. Previous studies that showed a relationship between maternal preeclampsia and neonatal hypotension did not control for potential confounding factors such as birth weight and maternal treatment with magnesium sulfate (MgSO4).

OBJECTIVE

To determine whether maternal preeclampsia is an independent risk factor for ENH.

STUDY DESIGN

We conducted a retrospective review of all viable singleton infants with gestational age of 23 to 30 weeks who were admitted to the neonatal intensive care unit over a 2-year period. ENH was defined as the persistence of the mean arterial pressure lower than the gestational age in weeks requiring volume expansion and inotropic support in the first 24 h of life.

RESULTS

One hundred and eighty four infants were enrolled. Seventy-five (41%) infants met the diagnostic criteria for ENH. Maternal preeclampsia, the presence of labor, maternal treatment with MgSO4, Apgar scores, birth weight, gestational age and respiratory distress syndrome were significantly associated with ENH by univariate analysis. Only gestational age and maternal preeclampsia were significantly associated with ENH by multiple logistic regression.

CONCLUSION

Gestational age and maternal preeclampsia were independent risk factors for ENH in our population of premature infants.

Effect of Lomodex-MgSO(4) in the prevention of reperfusion injury following unilateral testicular torsion: an experimental study in rats

Fertility in patients treated for unilateral testicular torsion has been shown to be significantly reduced in all the reported series to date, implying that the present-day treatment requires further refinement in the form of adjunct pharmacotherapeutic intervention (Lomodex and MgSO(4)) in addition to scrotal exploration. Prepubertal Holtzman strain rats (35 days old) were used for our study. Two sets were formed with six groups of rats in each set. Rats were treated as follows: group 1, sham-operated group; group 2, torsion (4 h); group 3, torsion + detorsion (1 h); group 4, torsion + ATP-MgCl(2) + detorsion; group 5, torsion + Lomodex-MgSO(4) + detorsion; group 6, torsion + normal saline + detorsion. Whereas the first set of animals was sacrificed immediately at the end of experiment, animals in set 2 were sacrificed 8 weeks after the end of the experiment to look for the development of antisperm antibodies. Parameters studied were thiobarbituric acid reductase (TBAR) assay, histology of testicular tissue, and sperm agglutination test. Student's t-test was used for significance. With detorsion (149.95+/-30.68) there was a significant rise in the TBAR values (P<0.05) compared with torsion (57.39+/-14.47). Treatment with both Lomodex-MgSO(4) (40.74+/-6.39) and ATP-MgCl(2) (48.30+/-18.35) yielded TBAR levels comparable to those in the sham group (31.35+/-11.96). Similar injury was also seen on the contralateral testis, with detorsion (114.28+/-10.68) much more detrimental than torsion (40.59+/-15.02) and rescue seen following treatment with Lomodex-MgSO(4) (27.55+/-8.64) as well as ATP-MgCl(2) (38.61+/-12.23). Regarding th histology, with detorsion there was evidence of severe distortion of tubules, with almost all the tubules showing maturation arrest and a few tubules completely devoid of any germinal cells. Treatment with Lomodex-MgSO(4) as well as ATP-MgCl(2) showed preservation of tubular morphology. Our study failed to document the presence of agglutinating antibodies (antisperm antibodies) in any of the groups. Unilateral testicular torsion has bilateral effects and is a form of ischemia-reperfusion injury. Treatment of torsion by detorsion alone does not prevent testicular damage. The results of the present study show that administration of Lomodex + MgSO(4) prior to detorsion results in prolonged testicular salvage with a potential of subsequent improvement in semen quality and fertility and reduction in long-term morbidity. The presence of agglutinating antibodies could not be detected in the present study.