Cardiovascular alterations in severe pregnancy-induced hypertension: Acute effects of intravenous magnesium sulfate

doi:10.1016/S0002-9378(84)80169-6

American Journal of Obstetrics and Gynecology

Volume 148, Issue 2, 15 January 1984, Pages 162-165

https://doi.org/10.1016/S0002-9378(84)80169-6 Get rights and content

The central hemodynamic effects of intravenous magnesium, sulfate were studied in five patients with severe pregnancy-induced hypertension. All five patients had a Swan-Ganz and a radial artery catheter placed prior to initiation of magnesium sulfate therapy. Four grams of magnesium sulfate was given over 15 minutes followed by a continuous infusion of 1.5 gm per hour. There was a 12.5% increase in cardiac index immediately after the infusion but cardiac index returned to pretherapy values by 15 minutes after infusion. The mean arterial pressure was significantly (p < 0.01.) decreased 30 minutes after the 4 gm loading dose but had returned to baseline values by 1 hour. There were no other significant changes in any of the hemodynamic or oxygen-related variables measured. Our data confirm previous hemodynamic studies in patients with severe pregnancy-induced hypertension indicating a hyperdynamic state with large fluctuations in systemic and pulmonary vascular resistances. In addition, magnesium sulfate has been shown,to have a transient hypotensive effect on mean arterial pressure, related to bolus infusion, that is not present with continuous infusion.

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Cited by (111)

Identification of factors associated with delayed treatment of obstetric hypertensive emergencies
2020, American Journal of Obstetrics and Gynecology
Obstetric hypertensive emergency is defined as having systolic blood pressure ≥160 mm Hg or diastolic blood pressure ≥110 mm Hg, confirmed 15 minutes apart. The American College of Obstetricians and Gynecologists recommends that acute-onset, severe hypertension be treated with first line-therapy (intravenous labetalol, intravenous hydralazine or oral nifedipine) within 60 minutes to reduce risk of maternal morbidity and death.
Our objective was to identify barriers that lead to delayed treatment of obstetric hypertensive emergency.
A retrospective cohort study was performed that compared women who were treated appropriately within 60 minutes vs those with delay in first-line therapy. We identified 604 patients with discharge diagnoses of chronic hypertension, gestational hypertension, or preeclampsia using International Classification of Diseases–10 codes and obstetric antihypertensive usage in a pharmacy database at 1 academic institution from January 2017 through June 2018. Of these, 267 women (44.2%) experienced obstetric hypertensive emergency in the intrapartum period or within 2 days of delivery; the results from 213 women were used for analysis. We evaluated maternal characteristics, presenting symptoms and circumstances, timing of hypertensive emergency, gestational age at presentation, and administered medications. Chi square, Fisher’s exact, Wilcoxon rank-sum, and sample t-tests were used to compare the 2 groups. Univariable logistic regression was applied to determine predictors of delayed treatment. Multivariable regression model was also performed; C-statistic and Hosmer and Lemeshow goodness-of-fit test were used to assess the model fit. A result was considered statistically significant at P<.05.
Of the 213 women, 110 (51.6%) had delayed treatment vs 103 (48.4%) who were treated within 60 minutes. Patients who had delayed treatment were 3.2 times more likely to have an initial blood pressure in the nonsevere range vs those who had timely treatment (odds ratio, 3.24; 95% confidence interval, 1.85–5.68). Timeliness of treatment was associated with presence or absence of preeclampsia symptoms; patients without preeclampsia symptoms were 2.7 times more likely to have delayed treatment (odds ratio, 2.68; 95% confidence interval, 1.50–4.80). Patients with hypertensive emergencies that occurred overnight between 10 pm and 6 am were 2.7 times more likely to have delayed treatment vs those emergencies that occurred between 6 am and 10 pm (odds ratio, 2.72; 95% confidence interval, 1.27–5.83). Delayed treatment also had an association with race, with white patients being 1.8 times more likely to have delayed treatment (odds ratio, 1.79; 95% confidence interval, 1.04–3.08). Patients who were treated at <60 minutes had a lower gestational age at presentation vs those with delayed treatment (34.6±5 vs 36.6±4 weeks, respectively; P<.001). For every 1-week increase in gestational age at presentation, there was a 9% increase in the likelihood of delayed treatment (odds ratio, 1.11; 95% confidence interval, 1.04–1.19). Another factor that was associated with delay of treatment was having a complaint of labor symptoms, which made patients 2.2 times as likely to experience treatment delay (odds ratio, 2.17; 95% confidence interval, 1.07–4.41).
Initial blood pressure in the nonsevere range, absence of preeclampsia symptoms, presentation overnight, white race, having complaint of labor symptoms, and increasing gestational age at presentation are barriers that lead to a delay in the treatment of obstetric hypertensive emergency. Quality improvement initiatives that target these barriers should be instituted to improve timely treatment.
Diagnosis, evaluation, and management of the hypertensive disorders of pregnancy
2014, Pregnancy Hypertension
Citation Excerpt :
The risk of neuromuscular blockade (reversed with calcium gluconate) with contemporaneous use of nifedipine and MgSO4 is <1% [329,330]. MgSO4 is not an antihypertensive, having the potential to lower BP transiently 30 min after a loading dose [331–334]. Infused nitrogylcerin (vs. oral nifedipine) is comparably effective without adverse effects [335–337].
This guideline summarizes the quality of the evidence to date and provides a reasonable approach to the diagnosis, evaluation and treatment of the hypertensive disorders of pregnancy (HDP).
The literature reviewed included the previous Society of Obstetricians and Gynaecologists of Canada (SOGC) HDP guidelines from 2008 and their reference lists, and an update from 2006. Medline, Cochrane Database of Systematic Reviews (CDSR), Cochrane Central Registry of Controlled Trials (CCRCT) and Database of Abstracts and Reviews of Effects (DARE) were searched for literature published between January 2006 and March 2012. Articles were restricted to those published in French or English. Recommendations were evaluated using the criteria of the Canadian Task Force on Preventive Health Care and GRADE.
Inhaled and intravenous treatment in acute severe and life-threatening asthma
2013, British Journal of Anaesthesia
Citation Excerpt :
In the great majority of cases of eclampsia, 4 g i.v. no faster than 1 g min−1 and followed immediately by 10 g i.m., promptly arrested seizures and the patients were oriented and without profound central nervous system depression.28 Acute effects of magnesium 4 g i.v. over 15 min followed by 1.5 g h−1 in severe pregnancy-induced hypertension showed a transient hypotensive effect on mean arterial pressure.29 In a study of six hypertensive and four normotensive male and female volunteers, magnesium sulphate was administered through a central venous catheter in a dose of 4 g given over 10 min.
Management of life-threatening acute severe asthma in children and adults may require anaesthetic and intensive care. The inhaled route for drug delivery is not appropriate when only small respiratory gas volumes are shifted; the i.v. route may be associated with greater side-effects. Magnesium sulphate i.v. has a place in acute asthma management because it is a mild bronchodilator, and has a stabilizing effect on the atria which may attenuate tachycardia occurring after inhaled and i.v. salbutamol. If intubation and ventilation are required, a reduction in bronchoconstriction by any means before and during these procedures should reduce morbidity. This narrative review aims to show strengths and weakness of the evidence, present controversies, and forward opinions of the author. The review contains a practical guide to the setting up, use and efficiency of nebulizers, metered dose inhalers, and spacers (chambers). It also presents a commonsense approach to the management of severe asthmatics in whom delay in bronchodilatation would cause clinical deterioration. When self-inhaled agents have had no effect, i.v. drugs may help avoid intubation and ventilation. The review includes suggestions for the use of inhaled anaesthetics, anaesthetic induction, and brief notes on subsequent ventilation of the lungs.
Pharmacotherapy for Preeclampsia in Low and Middle Income Countries: An Analysis of Essential Medicines Lists
2013, Journal of Obstetrics and Gynaecology Canada
To determine the prevalence of drugs for comprehensive management of preeclampsia in national essential medicine lists (EMLs) in low and middle income countries (LMICs)
We collected EMLs from the 144 LMICs identified by the World Bank through broad-based Internet searches and in collaboration with the World Health Organization. We identified therapies for hypertension, eclampsia, preeclampsia complications (e.g., pulmonary edema, thrombosis), preterm birth, and labour induction contained in the EMLs.
In 91 EMLs obtained from 144 LMICs, the most commonly listed parenteral antihypertensive therapies were verapamil (63.7%), hydralazine (61.5%), sodium nitroprusside (48.3%), and propranolol (39.6%). The most prevalent oral antihypertensive therapies were nifedipine (95.6%), methyldopa (93.4%), propranolol (90.1%), and atenolol (87.9%). For eclampsia/ preeclampsia, magnesium sulphate was present in 84.6% of EMLs and calcium gluconate in 85.7%. For pulmonary edema, most EMLs (94.5%) listed oral furosemide, for thrombosis 92.3% listed heparin, for acceleration of fetal pulmonary maturity 90.1% listed parenteral dexamethasone, and for labour induction 97.8% listed oxytocin or a prostanoid (usually misoprostol, 40.7%).
EMLs of LMICs provide comprehensive coverage of preeclampsia pharmacotherapy. These EMLs may be used as advocacy tools to ensure the availability of these therapies within each country.
Déterminer la prévalence des médicaments permettant la prise en charge exhaustive de la prééclampsie au sein des listes de médicaments essentiels (LME) nationales des pays ne disposant que d’un revenu faible ou moyen (PRFM)
Nous avons regroupé les LME des 144 PRFM identifiés par la Banque mondiale par l’intermédiaire de recherches généralisées sur Internet et en collaboration avec l’Organisation mondiale de la santé. Nous avons identifié, au sein des LME, les traitements visant l’hypertension, l’éclampsie, les complications de la prééclampsie (p. ex. œdème pulmonaire, thrombose), l’accouchement préterme et le déclenchement du travail.
Au sein des 91 LME obtenues auprès de 144 PRFM, les traitements antihypertenseurs parentéraux apparaissant le plus couramment ont été les suivants : vérapamil (63,7 %), hydralazine (61,5 %), nitroprussiate de sodium (48,3 %) et propranolol (39,6 %). Les traitements antihypertenseurs oraux les plus prévalents ont été les suivants : nifédipine (95,6 %), méthyldopa (93,4 %), propranolol (90,1 %) et aténolol (87,9 %). Pour ce qui est de l’éclampsie / la prééclampsie, le sulfate de magnésium figurait dans 84,6 % des LME et le gluconate de calcium, dans 85,7 % de celles-ci. Pour ce qui est de l’œdème pulmonaire, le furosémide oral figurait dans la plupart des LME (94,5 %); pour ce qui est de la thrombose, l’héparine figurait dans 92,3 % des LME; pour ce qui est de l’accélération de la maturité pulmonaire fœtale, la dexaméthasone parentérale figurait dans 90,1 % des LME; et pour ce qui est du déclenchement du travail, l’oxytocine ou un prostanoïde (habituellement le misoprostol, 40,7 %) figurait dans 97.8% des LME.
Les LME des PRFM offrent une couverture exhaustive de la pharmacothérapie visant la prééclampsie. Ces LME peuvent être utilisées à titre d’outils de défense des droits en vue d’assurer la disponibilité de ces traitements au sein de chaque pays.
Therapeutics and anaesthesia
2011, Best Practice and Research: Clinical Obstetrics and Gynaecology
Citation Excerpt :
MgSO4 should not be used as an antihypertensive per se. When MgSO4 is used for other indications (such as eclampsia prophylaxis or treatment, or for fetal neuroprotection), a loading intravenous (iv) dose of 2–5 g may be associated with a transient fall in blood pressure 30 min later,27–30 but this has not been consistently shown.31 The concomitant use of MgSO4 and nifedipine has no contraindication, as the risk of neuromuscular blockade is less than 1%,32 and blockade is reversed with 10 g of intravenous calcium gluconate.
Many aspects of hypertension care outside pregnancy may be applied in pregnancy, but little information is available on which to base decision-making. It would seem reasonable to continue previous dietary salt restriction and physical activity in women with pre-existing (and controlled) hypertension, encourage a heart-healthy diet in all women with a hypertension disorder of pregnancy, and take patient preference into account when deciding on place of care. Although bed rest has become a key part of obstetric practice and for care of women with a hypertension disorder of pregnancy, in particular, the evidence is lacking to support this practice. This may also increase thromboembolic risk. Antihypertensive treatment is strongly advised for women with severe hypertension. The most common agents are parenteral labetalol, hydralazine, or oral nifedipine capsules. Clinicians should familiarise themselves with multiple agents. Until the role of antihypertensive treatment for non-severe hypertension in pregnancy is clarified by ongoing research, clinicians should explicitly state an individual patient’s blood pressure goal, which could reasonably be anywhere between 130/80 and 155/105 mmHg. Labetalol and methyldopa are used most commonly. Breastfeeding should be encouraged. Many risk factors for hypertension (e.g. obesity), as well as hospitalisation and pre-eclampsia, all increase the thromboembolic risk for pregnant women, and care providers should consider thromboprophylaxis in the appropriate setting. Finally, anaesthetists play a critical role in the management of women with a hypertension disorder of pregnancy, and should be involved earlier rather than later in the course of their care.
Magnesium in obstetrics
2010, Best Practice and Research: Clinical Obstetrics and Gynaecology
Citation Excerpt :
Provided that respiratory failure and hypoxia are avoided, magnesium is remarkably safe from a cardiac perspective with plasma Mg2+ concentrations as high as 12.5 mol l−1 being required before cardiac arrest occurs.29 Studies in animal models26 and pregnant women30 have failed to demonstrate any myocardial depression and have reported an increase in cardiac output associated with raised plasma Mg2+ concentrations. In dogs, magnesium enhanced inotropy and lusitropy with increased cardiac output up to plasma concentrations of 6 mmol l−1, and this level was described as ‘haemodynamically safe’.27
Magnesium is a critical physiological ion, and magnesium deficiency might contribute to the development of pre-eclampsia, to impaired neonatal development and to metabolic problems extending into adult life. Pharmacologically, magnesium is a calcium antagonist with substantial vasodilator properties but without myocardial depression. Cardiac output usually increases following magnesium administration, compensating for the vasodilatation and minimising hypotension. Neurologically, the inhibition of calcium channels and antagonism of the N-methyl-d-aspartic acid (NMDA) receptor raises the possibility of neuronal protection, and magnesium administration to women with premature labour may decrease the incidence of cerebral palsy. It is the first-line anticonvulsant for the management of pre-eclampsia and eclampsia, and it should be administered to all patients with severe pre-eclampsia or eclampsia. Magnesium is a moderate tocolytic but the evidence for its effectiveness remains disputed. The side effects of magnesium therapy are generally mild but the major hazard of magnesium therapy is neuromuscular weakness.

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: This study was presented in part to the Society for Obstetric Anesthesia and Perinatology, May 28, 1983, Vancouver, British Columbia, Canada.

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Cardiovascular alterations in severe pregnancy-induced hypertension: Acute effects of intravenous magnesium sulfate

Am. J. Obstet. Gynecol.

J. Chronic Dis.

Am. J. Obstet. Gynecol.

Am. J. Obstet. Gynecol.

Am. J. Obstet. Gynecol.

The value of magnesium sulfate in intensive care of severe toxemias of pregnancy

Geburtshilfe Fraunheilkd.

Clinical trial of an algorithm for outcome prediction in acute respiratory failure

Crit. Care Med.