Effect of magnesium sulfate on epidural labor analgesia with ropivacaine in patients with preeclamp-sia / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effect of magnesium sulfate on epidural labor analgesia with ropivacaine in the patients with preeclampsia. Methods Seventy nulliparous parturients with pre?eclampsia, aged 23-34 yr, of American Society of Anesthesiologists physical status Ⅱ or Ⅲ, weighing 63-81 kg, with a singleton fetus in vertex presentation, without contradications to neuraxial anesthesia, waiting for vaginal delivery, received epidural analgesia for labor. The patients were divided into magnesi?um sulfate group and control group using a random number table, with 35 patients in each group. In magne?sium sulfate group, magnesium sulfate 50 mg∕kg ( 30 ml) was infused intravenously over 15 min when their cervical dilation was 3 cm, while the equal volume of normal saline was given in control group. Epi?dural labor analgesia was performed with ropivacaine. The up?and?down sequential allocation was used to determine the median effective concentration of epidural ropivacaine ( EC50 ) . The severity of pain was as?sessed with visual analogue scale score. Effective analgesia was defined as visual analogue scale score of≤1. The initial concentration of ropivacaine was 0.15%. Each time the concentration was increased∕decreased according to whether or not analgesia was effective, and the ratio between the two successive concentrations was 0.9. The EC50 and 95% confidence interval ( CI) of ropivacaine for epidural labor analgesia was calcu?lated. Results The EC50 (95% CI) of ropivacaine for epidural labor analgesia was 0.066% (0.062%-0.071%) in magnesium sulfate group. The EC50 (95% CI) of ropivacaine for epidural labor analgesia was 0.078% (0.072%-0.085%) in control group. The EC50 of ropivacaine was significantly lower in magnesi?um sulfate group than in control group ( P<0.05) . Conclusion Magnesium sulfate can enhance the effica?cy of ropivacaine for epidural labor analgesia in the patients with preeclampsia.