Prostacyclin and thromboxane levels in women with severe preeclampsia undergoing magnesium sulfate therapy during antepartum and postpartum periods

Abstract

Objective: To study effects of magnesium sulfate (MgSO(4)) on prostacyclin (PGI(2)) and thromboxane A(2) (TXA(2)) levels in women with severe preeclampsia during antepartum and postpartum periods.

Methods: Women with severe preeclampsia were randomized into two groups. Patients in Group A were continuously infused with MgSO(4) for 24 hours postpartum. In Group B, MgSO(4) administration was discontinued when urinary output was of > or =100 ml/hr for 2 consecutive hours. Patient demographic data were collected. Venous blood was drawn at time of MgSO(4) administration and 24 hours after delivery. Plasma levels of 6-keto-PGF1alpha and TXB(2), stable metabolites of PGI(2) and TXA(2), were measured by enzyme-linked immunosorbent assay (ELISA). Data are presented as mean +/- SE, and analyzed by paired t-test.

Results: A total of 50 patients were recruited, with 27 in Group A and 23 in Group B. There were no statistical differences for demographic data between the two groups with regards to maternal age; gestational age; systolic and diastolic blood pressures at admission, 12 hours postpartum, and 24 hours postpartum; and mode of delivery. Platelet counts were all within the normal range at the time of enrollment. MgSO(4) was administered for an average of 10 hours postpartum in Group B. Maternal blood pressures returned to normal or close to normal levels in both groups at 24 hours postpartum. 6-keto PGF1alpha levels were significantly decreased 24 hours after delivery compared with the levels at enrollment in both groups, (Group A: 98 +/- 13 vs. 180 +/- 28 pg/mL; Group B: 142 + 17 vs. 194 +/- 31 pg/mL, p < 0.05, respectively). However, there was no difference detected between the two groups. TXB(2) levels were not different between group A and Group B at the time of enrollment, 38 +/- 9 vs. 33 +/- 8 pg/mL, and 24 hours postpartum, 26 +/- 5 vs. 25 +/- 3 pg/mL, respectively.

Conclusions: Administration of MgSO(4) does not affect prostacyclin and thromboxane levels in the maternal circulation in women with preeclampsia during antepartum and postpartum periods. We speculate that a higher level of prostacyclin before delivery may reflect compensatory effects of this vasodilator to offset increased maternal blood pressure during pregnancy.

Figure 1

Plasma levels of 6-keto PGF1α in women with preeclampsia at admission and 24 hours postpartum. (A) shows the mean levels of 6-keto PGF1α at admission (Pre) and 24 hours postpartum (Post) in the group A and the group B. (B) shows the change of 6-keto PGF1α levels in each individual patient at admission (Pre) and 24 hours postpartum (Post) in Group A and Group B. *p < 0.05, respectively.

Figure 2

Plasma levels of TXB₂ in women with preeclampsia at admission and 24 hours postpartum. (A) shows the mean levels of TXB₂ at admission (Pre) and 24 hours postpartum (Post) in Group A and Group B. (B) shows the change of TXB₂ levels in each individual patient at admission (Pre) and 24 hours postpartum (Post) in Group A and Group B, respectively.

Figure 3

Correlation of plasma TXB₂ levels with platelet counts at admission and 24 hours postpartum. There was no correlation of plasma TXB₂ levels with platelet counts at admission and 24 hours postpartum in both groups. The pattern of the correlation for TXB₂ levels to platelet counts was fairly similar in both groups at admission and 24 hours postpartum. Group A (Fig. 3A): y = 0.000 × −0.014, r² = 0.029 (antepartum) and y = 0.000 × +0.016, r² = 0.015 (postpartum); Group B (Fig. 3B): y = −0.000 × + 0.028, r² = 0.000 (antepartum) and y = −0.000 × +0.032, r² = 0.025 (postpartum), respectively.