Magnesium Sulfate and Continuous Fetal Monitoring

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OBSTETRICS

Effect of Magnesium Sulphate on Fetal Heart Rate Parameters: A Systematic Review

Abstract

Methods

We undertook a systematic review of randomized controlled trials, observational studies, and case series. Studies were reviewed independently by two reviewers and qualitatively analyzed with regard to CTG/EFM parameters (baseline FHR, variability and acceleration-deceleration patterns), types of participants, interventions offered, and outcomes reported.

Results

Of 18 included studies, two were RCTs (72 women); 12 were prospective observational studies (269 women), 10 of which were of a pre- and post-intervention design; one was a prospective cohort study (36 women) and three were retrospective cohort studies (555 women). Lower baseline FHR was associated with MgSO ₄ exposure in seven of nine relevant studies. Decreased FHR variability was reported in nine of 12 relevant studies. Reductions in reactivity or acceleration pattern were seen in four of six relevant studies without an increase in decelerative patterns. All changes were small and not associated with adverse clinical outcomes.

Conclusion

Maternal administration of MgSO₄ for eclampsia prophylaxis/treatment, tocolysis or fetal neuroprotection appears to have a small negative effect on FHR, variability, and accelerative pattern, but is not sufficient clinically to warrant medical intervention.

Résumé

Objectif

Examiner les effets potentiels de l'administration de sulfate de magnésium (MgSO₄) par voie intraveineuse sur les paramètres de la fréquence cardiaque fœtale (FCF) antepartum et intrapartum mesurés par cardiotocographie (CTG) ou monitorage fœtal électronique (MFÉ).

Méthodes

Nous avons mené une analyse systématique ayant porté sur des essais comparatifs randomisés, des études observationnelles et des séries de cas. Ces études ont été analysées de façon indépendante par deux arbitres scientifiques; de plus, elles ont fait l'objet d'une analyse qualitative en fonction des paramètres de la CTG / du MFÉ (FCF initiale, variabilité et profils d'accélération-décélération), des types de participantes, des interventions offertes et des issues signalées.

Résultats

Parmi les 18 études admises à l'analyse systématique, on comptait deux ECR (72 femmes); 12 études observationnelles prospectives (269 femmes), dont 10 comptaient un devis préintervention et postintervention; une étude de cohorte prospective (36 femmes); et trois études de cohorte rétrospectives (555 femmes). Une FCF initiale moindre a été associée à l'exposition au MgSO₄ dans le cadre de sept des neuf études pertinentes. Une variabilité moindre de la FCF a été signalée dans neuf des 12 études pertinentes. Des baisses des profils de réactivité ou d'accélération ont été constatées dans quatre des six études pertinentes, sans hausse des profils de décélération. Toutes les modifications ont été faibles et n'ont pas été associées à des issues cliniques indésirables.

Conclusion

Bien que l'administration de MgSO₄ à la mère à des fins de prophylaxie / prise en charge de l'éclampsie, de tocolyse ou de neuroprotection fœtale semble exercer un faible effet négatif sur la FCF, la variabilité et le profil d'accélération, cet effet n'est pas suffisant sur le plan clinique pour justifier la tenue d'une intervention médicale.

Section snippets

INTRODUCTION

Magnesium sulphate has been used for a variety of obstetrical indications, including tocolysis for preterm labour for which it is now recognized to be ineffective.¹ At present, MgSO₄ is used for the prevention of eclampsia, for treatment in women with preeclampsia and eclampsia, and for fetal neuroprotection in the setting of imminent preterm birth for any indication at   <   32   weeks' gestation in Canada.2., 3.

Cardiotocography, or electronic fetal monitoring, is a routine technique for monitoring

METHODS

We searched PubMed (Medline) (1963 to March 2014), the Cochrane Library (1991 to March 2014), EMBASE (1974 to March 2014), and the bibliographies of retrieved articles addressing the effect of MgSO₄ on FHR or FHR pattern. The literature search was conducted using the following search terms: ("magnesium sulfate" OR magnesium sulphate OR "MgSO₄") AND ("fetus" OR "fetal" OR "foetus" OR "foetal") AND "heart" OR "fetal cardiotocography" OR "fetal electronic monitoring" OR "fetus heart rate" OR

RESULTS

Our search of the literature yielded 200 articles published between 1963 and March 2014. Eighteen studies met our inclusion criteria (Figure 1):

1.

two RCTs (72 women, median 36/study)10., 11.;

2.

13 prospective observational studies (311 women, median 16/study), of which 12 used women as their own control subjects in a pre- and post-intervention design,12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23. and one used control subjects matched for gestational age²⁴;

3.

three retrospective cohort

DISCUSSION

Our review of controlled studies examined patterns of parenteral administration (usually IV) of MgSO₄, at loading doses ranging from 2 to 8   g IV and maintenance doses ranging from 1 to 3.5   g IV or adjusted to achieve serum Mg⁺⁺ levels of 5.2 to 6.0   mEq/L, and the impact of administration of MgSO₄ on FHR. We found that most studies of various designs support a modest adverse effect of MgSO₄ on EFM parameters. The changes observed consisted of:

1.

a statistically significant decrease in FHR of up to 15

CONCLUSION

This meta-analysis of the current evidence suggests that maternal administration of MgSO₄ for eclampsia prophylaxis or treatment, tocolysis, or fetal neuroprotection does indeed have a modest adverse effect on baseline FHR, FHR variability, and the accelerative/decelerative pattern of the FHR. However, the effects are small and do not appear to be associated with adverse outcomes. It would be prudent for clinicians to obtain a baseline FHR assessment prior to administration of MgSO₄; any

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• N ^o 376 - Recours au sulfate de magnésium aux fins de neuroprotection fœtale

  2019, Journal of Obstetrics and Gynaecology Canada

  Les essais cliniques randomisés pertinents41 n'ont soulevé aucune préoccupation quant aux effets défavorables néonataux à court terme découlant d'une exposition prénatale au sulfate de magnésium; une évaluation ou des soins néonataux supplémentaires ne sont donc pas nécessaires. Une revue systématique récente a également indiqué que l'exposition prénatale au sulfate de magnésium pour diverses indications semblait avoir un léger effet négatif sur la fréquence cardiaque fœtale ainsi que sur la variabilité et les accélérations de celle-ci, quoiqu'il ait été conclu que cet effet n'était pas statistiquement significatif, puisqu'il ne nécessitait aucune intervention58. Les nouveau-nés qui présentent une hypermagnésémie peuvent également présenter des symptômes d'apnée ou d'hypoventilation, de la faiblesse, une hypotonie, une absence ou une diminution des réflexes tendineux profonds ainsi qu'une stupeur ou un coma.

• No. 376-Magnesium Sulphate for Fetal Neuroprotection

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  The relevant randomized controlled trials41 raise no concerns about short-term neonatal adverse effects of antenatal exposure, and no additional neonatal assessment or care is required. A recent systematic review also indicated that antenatal exposure to magnesium sulphate for various indications appeared to have a small negative effect on fetal heart rate, variability, and accelerative pattern, although this was deemed to be of no clinical significance because it did not warrant intervention.58 Neonates with hypermagnesemia may present with symptoms of apnea or hypoventilation, weakness, hypotonia, absent or reduced deep tendon reflexes, and stupor or coma.

• Antenatal foetal heart monitoring

  2017, Best Practice and Research: Clinical Obstetrics and Gynaecology

  Maternally administered medications can also transiently affect the foetal heart rate. A loading dose of magnesium sulphate 4 g infused IV over 20 min commonly leads to a decrease in heart rate variability for up to 30 min [27,28]. The advent of CTG technology led to an explosion of antenatal monitoring without trials showing a defined benefit and without definitions of normality and compromise.

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Copyright © 2014 Society of Obstetricians and Gynaecologists of Canada. Published by Elsevier Inc. All rights reserved.

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Source: https://www.sciencedirect.com/science/article/abs/pii/S1701216315303820