Therapeutic Effect of Long-Term Epidural Block in Rats with Pregnancy Induced Hypertension

Abstract

Background. Pregnancy induced hypertension (PIH) causes a variety of systemic disorders that negatively affect the maternal placenta and fetal growth. Epidural sympathetic block elicits symptoms of decreased blood pressure. This study was designed to determine the therapeutic effect of long-term epidural block in rats with PIH. Methods. Forty healthy pregnant Sprague Dawley rats were randomized into four groups with each group consisting of 10 rats. On gestation day (GD) 14, rats in control group underwent a sham procedure; rats in RUPP group were operated on to obtain reduced uterine perfusion pressure (RUPP); rats in RUPP plus normal saline (NS) group were also subjected to the RUPP procedure and underwent epidural block with 25 μl normal saline twice daily until delivery; rats in RUPP plus epidural block (EB) group were treated as those in RUPP plus NS group except that an epidural block with 25 μl of 0.125% bupivacaine was administered two times per day until delivery. On GD 20, blood pressure was measured in all groups before delivery, and blood samples were collected in order to quantify the serum concentrations of vascular endothelial growth factor (VEGF) and soluble fms-like tyrosine kinase 1 (sFlt-1). Results. The mean arterial pressure (MAP) of rats in RUPP group (147.6±6.0 mmHg) was markedly increased when compared with control group (80.8±4.6 mmHg) (p<0.05). The MAP of rats in RUPP plus EB group (114.4±7.2 mmHg) was clearly decreased in contrast with RUPP group but was still higher than in control group (p<0.05). The variation of fetal weight in all groups followed a similar trend to that of MAP. However, there were no significant differences between control group and RUPP plus EB group with respect to placental weight (p=0.186). Variation in MAP was positively correlated with the expression of sFlt-1 in each group but was negatively correlated with VEGF. Conclusion. This study demonstrates that long-term epidural block decreases blood pressure in PIH rats and improves the serum concentrations of VEGF and sFlt-1. Taken together, long-term epidural block may have a potential role in PIH treatment.