A retrospective review of on-admission factors on attainment of therapeutic serum concentrations of magnesium sulfate in women treated for a diagnosis of preeclampsia

The Effect of Body Mass Index on Post-Bolus Magnesium Levels in the Obstetric Patient

OBJECTIVE

In the setting of a growing obese obstetric population, we sought to determine whether differences in body mass index (BMI) and obesity class influenced both serum magnesium levels and the likelihood of achieving therapeutic levels for eclampsia prophylaxis after standard boluses of magnesium sulfate.

STUDY DESIGN

This is a retrospective cohort study of patients treated with magnesium sulfate in the setting of either preeclampsia with severe features or preterm labor between 2010 and 2016. Subjects were categorized by BMI: Normal (BMI < 30 kg/m2), Class 1 (BMI 30-34.9 kg/m2), Class 2 (BMI 35-39.9 kg/m2), and Class 3 (BMI ≥ 40 kg/m2). Study participants' demographics, intrapartum characteristics, and adverse reactions were compared among the groups. Logistic regression models were used to calculate unadjusted and adjusted odds ratios comparing the likelihood of each BMI class reaching therapeutic eclamptic prophylactic levels. Linear regression models were also evaluated to determine the relationship between BMI and post-bolus serum magnesium levels.

RESULTS

Of the 760 people who met the inclusion criteria, 313 (41.1%) had normal BMI, 190 (25.0%) had Class 1 obesity, 135 (17.8%) had Class 2 obesity, and 122 (16.1%) had Class 3 obesity. When adjusted for confounders, those with Class 1 obesity were 54% less likely to achieve serum levels deemed therapeutic for seizure prophylaxis compared with normal BMI counterparts. Meanwhile, those with Class 2 or 3 obesity were 90% less likely. Linear regression models also demonstrated an inverse association between BMI and post-bolus serum magnesium levels.

CONCLUSION

Increasing BMI has a significant effect on post-bolus serum magnesium levels regardless of standard loading dose used. Immediately after bolus administration, obese gravidas are significantly less likely to reach levels effective for eclamptic seizure prophylaxis. When considering which bolus to administer in an obese gravida, it may be more beneficial to choose a 6 g load.

KEY POINTS

· BMI has an inverse relationship with post-bolus serum magnesium levels.. · Obese gravidas were less likely to reach eclampsia prophylaxis levels regardless of bolus type.. · Obesity class, not just the presence or absence of obesity, plays a role in serum magnesium levels..

A retrospective review of the risk factors affecting the therapeutic serum concentrations of magnesium sulfate in pre-eclamptic patients

WHAT IS KNOWN AND OBJECTIVE

To identify factors that may affect the therapeutic serum magnesium levels after intravenous administration for seizure prophylaxis in pre-eclamptic patients.

METHODS

One hundred and two women with PE with severe features were identified categorized into two groups: subtherapeutic and therapeutic group. Multivariate logistic regression analysis and receiver operation characteristic curve analysis were conducted for the risk factors influencing the serum magnesium concentration.

RESULTS

Among 102 eligible patients, 63 (62%) patients did not attain ideal therapeutic serum magnesium levels. Those patients had elevated albumin levels (p < 0.05), higher creatinine clearance (Ccr) (p < 0.001), and higher body mass index (BMI) (p < 0.001). Logistic regression analysis identified BMI and Ccr as independent risk factors for subtherapeutic serum magnesium concentration (p < 0.05). Receiver operating characteristic (ROC) curve analysis revealed a greater area under the curve for BMI than for Ccr in predicting subtherapeutic serum magnesium levels (0.787 vs. 0.774).

WHAT IS NEW AND CONCLUSION

Maternal body weight and renal function were independent risk factors for subtherapeutic serum magnesium concentration in the early stage after administration.

Aluminum and magnesium status during pregnancy and placenta oxidative stress and inflammatory mRNA expression: China Ma'anshan birth cohort study

The aim of this study was to explore the impact of prenatal Al and Mg on placental oxidative stress and inflammatory mRNA expression. A total of 2519 pregnant women from the China Ma'anshan birth cohort participated in this study. Al and Mg levels were measured by inductively coupled plasma mass spectrometry (ICP-MS). Placental stress and inflammatory mRNA expression were assessed by RT-PCR. The median Al levels in the first and second trimesters of pregnancy and in cord blood were higher than the corresponding median Mg levels. Predictors of lower Al and Mg levels included Han ethnicity and high education according to a mixed linear model. Multiple linear regression analysis revealed that Al and Al/Mg levels had a positive association with inflammatory mRNA expression and placental oxidative stress in the second trimester of pregnancy. A negative association existed between Al and Al/Mg levels and inflammatory mRNA expression and placenta oxidative stress in the cord blood, with the exception of IL-1β expression. In conclusion, prenatal Al and Mg status was associated with placental oxidative stress and inflammatory mRNA expression. More preclinical studies are needed to confirm the relevant mechanism.

Risk factors for sub-therapeutic serum concentrations of magnesium sulfate in severe preeclampsia of Chinese patients

Background

Magnesium sulfate (MgSO₄) is the standard drug for eclampsia prophylaxis and treatment. In China, the effective therapeutic serum magnesium level is 1.8–3.0 mmol/L. There is little information on how to achieve and maintain effective therapeutic concentrations. This study aimed to investigate risk factors for sub-therapeutic serum concentrations of MgSO₄ in patients with severe preeclampsia.

Methods

Patients with severe preeclampsia who received MgSO₄ intravenous infusion were retrospectively reviewed. The maternal demographic characteristics, regimens for the administration of MgSO₄, and lab test results of patients were collected. Multivariate logistic regression analysis and receiver operating characteristic (ROC) curve analysis were conducted for the risk factors influencing the serum magnesium concentration.

Results

A total of 93 patients with severe preeclampsia were included in the study. 52 (55.91%) patients did not attain therapeutic serum magnesium levels. A multivariate logistic regression analysis identified creatinine clearance (Ccr), whether the loading dose was given, and measurement time of serum magnesium concentration (referring to the time from start of MgSO4 infusion to blood draw for serum sampling) as independent risk factors for sub-therapeutic serum magnesium concentration (P < 0.05). ROC curve analysis indicated that the continuous variable Ccr had a significant predictive value for the serum magnesium concentration, which resulted in a cutoff point of 133 mL/min; while measurement time had limited predictive value, with cutoff point of 2.375 h.

Conclusions

Ccr, whether the loading dose was given, and measurement time were independent risk factors for sub-therapeutic serum magnesium concentration. A loading dose of MgSO₄ everytime before the maintenance dose, as well as the duration of MgSO4 maintenance dose of more than 2.375 h are recommended for all the patients with severe PE. Routine evaluation of serum magnesium levels is a recommended practice for women with severe PE and whose Ccr is ≥133 mL/min.

Clinical Experiences of Intravenous Hydralazine and Labetalol for Acute Treatment of Severe Hypertension in Pregnant Thai Women

Response to acute treatment of severe hypertension during pregnancy in Asian women was not known. Labor and delivery checklists of Thai women treated with intravenous hydralazine or labetalol for systolic blood pressure (SBP) ≥ 160 or diastolic blood pressure (DBP) ≥ 110 mm Hg from January 2011 to December 2013 were reviewed as parts of an audit. Primary outcome was prompt achievement of SBP 140-150 and DBP 90-100 mm Hg after the first bolus. Secondary outcomes were medication-related undesired effects. The mean ± standard deviation age and prevalence of chronic hypertension in hydralazine (n = 62) versus labetalol (n = 64) groups were 32.5 ± 6 versus 29.9 ± 6.8 years and 50% versus 21.9%, respectively (P < .05). Magnesium sulfate was promptly administered on admission to every woman to prevent seizure. Targeted blood pressure was timely achieved in 41.9% and 67.2% of the hydralazine and labetalol groups, respectively (P < .05). Nonreassuring fetal heart rate occurred in 51.6% and 32.8% of the hydralazine and labetalol groups, respectively (P = .05). The prevalence of cesarean section and Apgar score < 7 were not significantly different (P > .05). Real-life clinical experiences suggested significant advantages of intravenous labetalol over hydralazine in pregnant women with severe hypertension.