Effects of magnesium sulfate infusion upon clotting parameters in patients with pre-eclampsia.
The objectives of this study were to evaluate the possible mechanisms involved in prolongation of bleeding time in pre-eclamptic patients receiving a magnesium sulfate infusion to prevent convulsions. Eighteen pre-eclamptic patients near term or at term (4 cases 33 to 35 weeks; the remainder > 36 weeks) were studied. Fifteen of them received magnesium sulfate infusion; 3 did not and served as controls. Bleeding time (modified Ivy method with Surgicutt), platelet count, platelet aggregation pattern, as well as serum arachidonic acid metabolites [thromboxane B2 (TxB2) and 6-Keto-prostaglandin F1 alpha (6-Keto-PGF1 alpha)] werde done on admission to the labor floor (before magnesium infusion) and repeated at discontinuation of the infusion, 12-24 hours postpartum; the controls received the second test 24 hours postpartum. Thirteen of 15 patients receiving magnesium sulfate had an increase in bleeding time from an average of 6 minutes 31 seconds to 11 minutes 56 seconds, an 82% rise (p < 0.004). In 2 there was a decrease. Among the 3 controls the averages were 6 minutes 38 seconds and 6 minutes 3 seconds. The total magnesium given ranged from 52.5 to 145 grams. Platelet counts averaged 251,000/mm3 (range 145,000-519,000). Platelet aggregation pattern done in 11 patients and was normal and unchanged after magnesium in 10 of the patients with increased bleeding time and one control. TxB2 and 6-Keto-PGF1 alpha levels did not change significantly either after magnesium administration (688 and 135 pgm/ml, to 654 and 117) or in controls (695 and 230 pgm/ml, to 445 and 225). Likewise, the ratio of these 2 substances did not change in either group (6.3 to 6.6, and 4.2 to 2.2). There was no correlation between duration of infusion or total magnesium given and directions of small changes observed. This study confirms a prior preliminary observation that magnesium sulfate infusion, as currently used to prevent eclamptic convulsions, induces a significant prolongation of bleeding time. This effect is mediated neither by changes in platelets count or aggregation pattern, nor by changing the level or ratios of serum arachidonic acid metabolites (TxB2 and 6-Keto-PGF1 alpha). Further studies are needed to clarify the mechanism of this clinically important observation of increased bleeding following magnesium sulfate infusion.
Assaley
J
J
Chicago Lying-in Hospital, University of Chicago, Illinois, USA.
Baron
J M
JM
Cibils
L A
LA
D015121:6-Ketoprostaglandin F1 alpha / Q000097:blood; D000293:Adolescent; D000328:Adult; D001760:Bleeding Time; D005260:Female; D005865:Gestational Age; D006801:Humans; D008278:Magnesium Sulfate / Q000008:administration & dosage / Q000009:adverse effects* / Q000627:therapeutic use; D010974:Platelet Aggregation; D010976:Platelet Count; D006473:Postpartum Hemorrhage / Q000139:chemically induced*; D011225:Pre-Eclampsia / Q000150:complications / Q000188:drug therapy*; D011247:Pregnancy; D012640:Seizures / Q000209:etiology / Q000517:prevention & control; D013929:Thromboxane B2 / Q000097:blood
D013929:Thromboxane B2; D015121:6-Ketoprostaglandin F1 alpha; D008278:Magnesium Sulfate