AN EFFECT OF MAGNESIUM ON NEUROMUSCULAR FUNCTION IN PARTURIENTS

Study Objective: To determine the effects of magnesium sulfate on neur omuscular transmission in parturients. Design: Open-label, clinical st udy. Setting: Preeclamptic patients at a university-affiliated hospita l. Patients: 12 pregnant patients, ages 18 to 40 years, with preeclamp sia or entering preterm labor. Interventions: Patients were treated wi th magnesium sulfate. Train-of-four (TOF) recordings of the adductor p ollicis muscle were obtained before and 30 minutes after the magnesium sulfate infusion. Measurements and Main Result: Each contractile resp onse in the control TOF showed an increase in the tension developed in response to supramaximal stimulation. The TOF responses after magnesi um sulfate did not demonstrate this phenomenon, but rather developed f ade. The T-4/T-1 ratios ranged from 0.72 to 0.92. Conclusions: In this patients population, clinically relevant infusions of magnesium sulfa te produced significant changes in neuromuscular transmission as manif ested by loss of treppe phenomenon and diminished TOF response to ulna r nerve stimulation.