The effet of parenteral magnesium sulfate therapy on blood loss at delivery

Abstract

M A G N E s I u M sulfate is commonly used in obstetrics because it so effectively prevents the convulsions of eclampsia when administered in doses that rarely, if ever, produce any grossly deleterious effect on the mother or fetus. Hall and co-workers,1 however, have demonstrated that the magnesium ion in vitro inhibits the contractions of isolated strips of human gravid myometrium. Furthermore, they noted that in patients who received magnesium sulfate in large amounts by intravenous infusion, the duration of labor was longer than in those who did not. They concluded that the magnesium ion may also have a depressant action on uterine motility in vivo. While carrying out extensive hematological studies upon patients with eclampsia, we were impressed that not infrequently rather large volumes of red blood cells disappeared from the maternal circulation during parturition and the early puerperium. Moreover, it was often the impression that the observed external blood loss, during and soon after delivery, was excessive. Could it be that therapy with magnesium sulfate in these patients impaired myometrial contractility after the separation of the placenta, and as a