Eclampsia despite magnesium sulfate prophylaxis

Magnesium sulfate is highly effective for the prophylactic treatment of preeclampsia with severe features, as well as the prevention of recurrent eclamptic seizures. The consequences of developing eclampsia despite treatment with magnesium sulfate prophylaxis have received little attention.

Our aim was to describe maternal and perinatal consequences in patients who develop eclampsia despite treatment with magnesium sulfate therapy.

This was a retrospective study of all patients with eclampsia over 13 years at a single institution. Eclampsia was diagnosed in accordance with the criteria outlined in the 2013 Executive Summary of the American College of Obstetricians and Gynecologists. Hospital records of patients experiencing eclampsia and their perinatal outcomes were independently reviewed by two faculty obstetricians in the Maternal-Fetal Medicine Division.

During the 13-year study period, a total of 166,492 patients were delivered at our institution, with 15,689 (9.4%) receiving magnesium sulfate for seizure prophylaxis in the setting of preeclampsia with severe features or for treatment of eclampsia. One hundred twenty-three patients developed eclampsia (7.4 per 10,000 births), with 94 eclamptic seizures occurring in-hospital. Of these, 26 (21%) seizures occurred despite receiving magnesium sulfate prophylaxis in the setting of preeclampsia with severe features or prior eclampsia. Two-thirds of the 26 (65%) patients developed eclampsia despite a therapeutic (4.8-8.4 mg/dL) serum magnesium concentration following magnesium sulfate administration prior to the convulsion(s). Six occurred prior to routine evaluation of serum magnesium level 2 hours following the loading dose and 3 patients experienced an eclamptic seizure associated with a sub-therapeutic magnesium serum concentration. Maternal outcomes of these 26 patients were as follows: 10 (38%) experienced multiple eclamptic seizures despite magnesium sulfate therapy, 8 (31%) underwent immediate endotracheal intubation following the eclamptic seizure, 6 (23%) developed HELLP syndrome, 5 (19%) required admission to the intensive care unit, 3 (12%) developed aspiration pneumonia, and 3 (12%) experienced placental abruption. Compared to patients with in-hospital eclampsia prior to receiving magnesium sulfate, patients with eclampsia following magnesium sulfate were more likely to have more than one seizure (P<.01), require endotracheal intubation (P=.03), and develop HELLP syndrome (P<.01). The infants of patients with eclampsia following administration of magnesium sulfate were more likely to be admitted to the neonatal intensive care unit (P=.02).

While magnesium sulfate is highly effective in preventing eclampsia, there are patients who experience eclamptic seizures despite magnesium sulfate with resultant morbidity. Eclampsia occurred in 26 (28%) of 94 patients experiencing in-hospital eclamptic seizures at our institution despite receiving magnesium sulfate. Of these 26 patients, the serum magnesium level was within the desired therapeutic range in 65% of patients before the eclamptic episode. Patients who developed eclampsia despite receiving magnesium sulfate prophylaxis experienced significant severe maternal morbidity, including more than one eclamptic seizure, maternal tracheal intubation, HELLP syndrome, and their infants were more likely to be admitted to the neonatal ICU.