Baseline serum and cerebrospinal fluid magnesium levels in normal pregnancy and preeclampsia.

OBJECTIVE: To determine whether baseline cerebrospinal fluid magnesium levels in preeclampsia differ from those in normal pregnancy, and to ascertain whether pre-treatment cerebrospinal fluid magnesium levels correlate with serum levels, which would suggest a baseline alteration in the blood-brain barrier in preeclampsia.

METHODS: When spinal analgesia or anesthesia was administered for delivery, serum and cerebrospinal fluid magnesium levels were determined in 20 normal gravidas and 20 preeclamptic women not treated with magnesium sulfate. Data were analyzed by two-sided Student t test and regression analysis.

RESULTS: Mean (+/- standard deviation) cerebrospinal fluid magnesium level for preeclamptic patients was 2.23 +/- 0.09 mEq/L, which was not significantly different from controls. Regression analysis revealed no significant correlation between cerebrospinal fluid and serum magnesium levels for either normal or preeclamptic gravidas.

CONCLUSION: During the third trimester, there is no difference in baseline, pre-treatment cerebrospinal fluid magnesium levels in preeclamptic patients compared to normal subjects, and no correlation between cerebrospinal fluid and serum magnesium over the range of baseline values.