A Study of Serum Magnesium Levels Attained in Intravenous Magnesium Sulfate Therapy for Severs Preeclsmpsia: A Comparison between 4 and 6 Grams Loading Dose Regimens*

Abstract

A Study of Serum Magnesium Levels Attained in Intravenous Magnesium Sulfate Therapy for Severs Preeclsmpsia:  A Comparison between 4 and 6 Grams Loading Dose Regimens*

Surawute    Leelahakorn          BSc (Med), MD, Dip Thai Board of Obstetrics and Gynecology, Dip Thai Board of Gynecologic Oncology

Mala             Trewatcharegon    BSc (Med Tech), MSc (Biochemistry) ***

*This work was supported by the Vajira Research Fund (annual research fund 1999

**Department of Obstetrics and Gynecology, BMA Medical College and Vajira Hospital

***Department of Central Laboratory, BMA Medical College and Vajira Hosspital

Objective: To compare the serum magnesium levels obtained from severe preeclamptic patients between the 4 grams and the 6 grams loading dose regimens and to compare the power of two regimens that can made the serum magnesium level to reach the therapeutic level.

Study design: A prospective double blinded randomized controlled trial.

Setting: Department of Obstetrics and Gynecology and Department of Central Laboratory, BMA Medical College and Vajira Hospital

Subjects: Thirty-five severe preeclamptic women of 28 weeks of gestational age.

Methods: The subjects were divided by weight to be  70 Kg and less than 70 Kg.  Then the subjects in each stratum were allocated by randomized to receive the 4 grams or the 6 grams loading dose of magnesium sulfate, followed immediately by the same maintenance dose of 2 grams per hour.  Maternal blood samples were taken for measuring serum magnesium levels before therapy 1, 4 8 hours after therapy before delivery and 6 hours after delivery including cord blood sample and they were compared between the two regimens.  Other patient's characteristics and outcomes were collected and compared between the two regimens also.

Main outcome measures: Serum magnesium levels.

Results: The serum magnesium levels at the first hour after therapy of the 6 grams loading dose group were higher than the 4 grams loading dose group with statistical significant difference (4.400.26 mg/dl vs 3.73 0.38 mg/dl, p-value = 0.011) but the serum magnesium levels at the 4^th and the  8^th hours after therapy before delivery and at the  6^th hours after delivery were no statistical significant difference.  In the comparison of the power of achieving the therapeutic level, the 6 grams loading dose group was higher than the 4 grams loading dose group in achievement of the therapeutic level at the first hour after therapy with statistical significant difference (26.3% vs 0%, p-value = 0.049 ). Even though at the 4^th and  8^th hours after therapy before delivery and at the 6^th hours after delivery  the power of achieving the therapeutic level of the 6 grams loading dose group was higher than the 4 grams loading dose group with no statistical significant difference, but when compared all samplings after therapy the power of the 6 grams loading dose group in achievement of the therapeutic level was higher than the 4 grams loading lose group with statistical significant difference (43.3% vs 10.4%, p-value = 0.0002).  The characteristics and outcomes of the patients and fetuses of two groups were no statistical significant difference.

Conclusion: The 6 grams loading dose regimen was more effectively in rising serum magnesium level and in rising serum magnesium level and in achieving the therapeutic level than the 4 grams loading dose regimen, especially in the first hours after treatment.  Both regimens were safe for treatment and no serious complication was found in mothers and newborns.

Key word: severe preeclampsia, magnesium sulfate, serum magnesium level

Vajira Med J 2003 ; 47 : 103 - 112