45: Effects of magnesium on central arterial compliance in preeclampsia

Abstract

To investigate the effect of MgSO4 infusion on central arterial compliance, using noninvasive radial artery pulse wave forms by applanation tonometry in women diagnosed with preeclampsia (PRE). This is a prospective observational study. Women diagnosed with PRE were recruited prior to receiving MgSO4. Measurements of the radial pulse waveform were obtained longitudinally. Using a validated internal transfer function, the aortic waveform was derived and the indices Augmentation Pressure (AP) and Augmentation Index corrected @75bpm ([email protected]) were calculated. The AP and [email protected] are surrogate measures of arterial stiffness. We compared the time periods: prior to MgSO4 (t1), 1hr after MgSO4 bolus (t2), 4hrs after MgSO4 maintenance infusion (t3), 24hrs after delivery and MgSO4 completion (t4). An 80% power assuming an increase in compliance of 25%, =0.05, required 70 subjects. Statistical analysis was performed using differences of least squared means with Tukey Kramer adjustment. Institutional IRB approval was obtained. Data was analyzed from seventy women. AP and [email protected] at t2-t4 were significantly lower compared with t1, (pvalue =.008, <.001, and .002) and (pvalue =.039, <.001, and .005) respectively, with greatest decrease in arterial stiffness at t3- 4hrs after MgSO4 maintenance. AP and [email protected] at t3 was significantly lower when compared with t2 (p-value<.001 and .001). AP at t3 was significantly lower compared with t4 (p=.018). No significant difference in [email protected] was noted between t3 and t4. In women with PRE, MgSO4 improved central arterial compliance. This effect was most exaggerated after 4hrs of infusion and remained 24hrs following MgSO4 completion following delivery. This suggests either a sustained vascular compliance effect from MgSO4 or resolution of the vasoconstrictive effect of preeclampsia. Further, MgSO4 may improve perfusion to end organs by decreasing arterial stiffness, this information could be used to direct future management, suggesting a benefit of its use beyond seizure prophylaxis.