Cerebral spinal fluid and serum ionized magnesium and calcium levels in preeclamptic women during administration of magnesium sulfate

ObjectiveTo study the distribution of ionized and total magnesium (Mg) in serum and cerebral spinal fluid (CSF) in preeclamptic women receiving MgSO4 and how this treatment affects the ionized calcium (Ca2+) and ionized Ca:Mg ratios compared with healthy nonpregnant women and pregnant control women (HP).DesignControlled clinical study.SettingAn academic medical center.Patient(s)African-American women older than 20 and less than 35 years. The pregnant preeclamptic study and pregnant control groups each consisted of 16 women; the nonpregnant group consisted of 10 subjects.Intervention(s)The preeclamptic women received a 6-g bolus of MgSO4 IV started at least 4.5 hours before delivery during 15–20 minutes, then 2 g/h baseline.Main Outcome Measure(s)The CSF and serum levels of Ca2+ and Mg2+ and total Mg were measured in all three groups of women. The Ca2+:Mg2+ ratios were determined. Physiologic monitoring was done and recorded every 4 hours where appropriate. Bloods were drawn every 6 hours for complete blood count, metabolic panel, lactate dehydrogenase, uric acid, and electrolytes. Serum pH, total Mg, Apgar scores, and general health of the infants born to preeclamptic mothers given MgSO4 were followed.Result(s)The HP showed a reduction in mean serum ionized and total Mg, increase in ionized Ca, and a large increase in Ca2+:Mg2+ ratios compared with healthy nonpregnant women. Although the CSF ionized and total Mg and Ca2+:Mg2+ ratios were not altered with MgSO4 treatment in the preeclamptic women receiving MgSO4, the mean serum Mg values increased 3-fold. All infants were full-term, regardless of MgSO4 treatment, and normal with respect to birth weight, Apgar scores, blood pH, total Mg, and neurologic scores.Conclusion(s)The data indicate that there is a direct relationship between the serum and CSF Ca2+:Mg2+ ratios in HP and this ratio may be crucial in preventing vascular and neurologic complications in preeclampsia–eclampsia.