Reassessment of intravenous MgSO4 therapy in preeclampsia-eclampsia.

The occurrence of seizures in preeclamptic and eclamptic women is considered very unlikely during treatment with the standard dose of continuous intravenous magnesium sulfate. During a 21-month period, the authors encountered 13 patients who developed seizure activity while receiving intravenous MgSO4. Serum magnesium (Mg) levels at the time of seizure were below the therapeutic range in 11 of the 13 patients, thus prompting a study of serum Mg levels in preeclamptic patients treated with MgSO4. Random serum Mg samples were obtained from 120 patients treated with intravenous MgSO4 for preeclampsia-eclampsia. The samples were collected 2 to 48 hours after the loading dose and while the patients were taking a maintenance dose of either 1, 2, or 3 g/hr. When a maintenance dose of 1 or 2 g/hr was used, 98 and 50% of the respective serum magnesium values were below levels considered therapeutic by several authors. Therapeutic levels were achieved in ll patients receiving a maintenance dose of 3 g/hr. The recommended maintenance dose of MgSO4 of 1 g/hr was found insufficient to prevent the occurrence of eclamptic seizures in some preeclamptic patients.