Effects of magnesium sulfate on toxemic patients in labor.

One hundred forty-four toxemic patients were studied by continuous electronic maternal and fetal monitoring. Ninety-seven were treated by intravenous bolus of 2 g MgSO4 every 1-2 hours, and 47 by intravenous drip MgSO4 at a rate of 1 g/hour. Clinical doses of MgSO4 do not affect maternal ECG, temperature, uterine contractions, or fetal heart rate. Intravenous bolus administration is frequently associated with slowing of maternal respirations and hypotension and occasionally with transient apnea.