Cerebrospinal fluid levels of magnesium in patients with preeclampsia after treatment with intravenous magnesium sulfate: a preliminary report.

The purpose of this study is twofold: (1) to correlate magnesium levels of serum with those of cerebrospinal fluid in patients with preeclampsia receiving intravenous magnesium sulfate, and (2) to determine whether the magnesium ion crosses the blood-brain barrier in significant amounts after intravenous magnesium sulfate therapy. Of the 21 patients in whom spinal anesthesia was used for delivery, ten patients with preeclampsia with therapeutic serum magnesium levels made up the study group and 11 term nontreated normotensive gravid women served as controls. At the time of spinal anesthesia, a 1 ml aliquot of cerebrospinal fluid was obtained from each patient. The mean cerebrospinal fluid magnesium level for the control group was 2.56 +/- 0.19 mg/dl (range 2.2 to 2.8 mg/dl). For the preeclamptic group who received intravenous magnesium sulfate, the mean cerebrospinal fluid magnesium level was 3.04 +/- 0.12 mg/dl (range 2.9 to 3.2 mg/dl). Although only a small amount of magnesium crosses the blood-brain barrier after intravenous magnesium sulfate treatment, this increment is highly significant (p less than 0.001).