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

OBJECTIVE: To study the distribution of ionized and total magnesium (Mg) in serum and cerebral spinal fluid (CSF) in preeclamptic women receiving MgSO(4) and how this treatment affects the ionized calcium (Ca(2+)) and ionized Ca:Mg ratios compared with healthy nonpregnant women and pregnant control women (HP). DESIGN: Controlled clinical study. SETTING: An 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 MgSO(4) 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 Ca(2+) and Mg(2+) and total Mg were measured in all three groups of women. The Ca(2+):Mg(2+) 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 MgSO(4) 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 Ca(2+):Mg(2+) ratios compared with healthy nonpregnant women. Although the CSF ionized and total Mg and Ca(2+):Mg(2+) ratios were not altered with MgSO(4) treatment in the preeclamptic women receiving MgSO(4), the mean serum Mg values increased 3-fold. All infants were full-term, regardless of MgSO(4) 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 Ca(2+):Mg(2+) ratios in HP and this ratio may be crucial in preventing vascular and neurologic complications in preeclampsia-eclampsia.