To examine the ED₅₀ and 95% effective dose(ED₉₅) of ropivacaine for subarachnoid block in severe preeclamptic patients undergoing cesarean section.

This study enrolled 250 severe preeclamptic patients undergoing cesarean section. They were randomly divided into 5 groups respectively received 0, 7.5, 10.0, 12.5, 15.0 mg and 17.5 mg ropivacaine(n=50). The use of ropivacaine and phenylephrine, and patients' satisfaction, intraoperative complications, and the neonates' Apgar scores were documented.

ED₅₀ and ED₉₅ of ropivacaine for successful subarachnoid block were 9.3 mg(95%CI: 8.6-9.9 mg) and 14.9 mg(95%CI: 13.7-16.9 mg) respectively. The sensory block was significantly different among groups 10 min after intrathecal injection(P<0.05). The incidences of hypotension in group 17.5 mg and group 15.0 mg were higher than those in other 3 groups(P<0.05). The doses of phenylephrine in group 7.5 mg and group 10.0 mg were lesser than those in other 3 groups(P<0.05). The additional doses of ropivacaine in group 7.5 mg were higher than those in other 3 groups(P<0.05). There was no significant difference in patients' satisfaction and the Apgar score of neonates among four groups with different doses of ropivacaine(P>0.05).

Our study showed that the ED₅₀ and ED₉₅ of ropivacaine for subarachnoid block in severe preeclamptic patients undergoing elective cesarean delivery were 9.3 mg and 14.9 mg, respectively.

Ropivacaine; Cesarean section; Severe preeclampsia; Subarachnoid block