ED50 of intrathecal ropivacaine for cesarean section under prophylactic infusion of phenylephrine

Abstract

Background:Studies have reported that prophylactic continuous infusion of phenylephrine during spinal anesthesia for cesarean section can decrease the spread of local anesthetics. We investigated the ED50 of intrathecal hyperbaric ropivacaine in parturient women undergoing cesarean section under prophylactic infusion of phenylephrine.Methods:Sixty parturient women were allocated into 2 groups in this prospective study. Group P received 0.5 mL kg−1 h−1 of phenylephrine (5 mg/50 mL) at the start of intrathecal injection, and Group C (control group) received the same volume of saline. The dose of intrathecal ropivacaine for each subject was decided through up-down allocation method. The initial dose was set as 7.5 mg. Successful anesthesia was defined as the level of T6 or above achieved within 15 minutes after intrathecal injection and no additional epidural drug or venous analgesia to complete operation. The Massey formula was applied to calculate the ED50 of intrathecal ropivacaine in both groups.Results:The ED50 of hyperbaric ropivacaine determined by up-and-down method was 7.2 mg (95% confidence interval (CI), 6.8–7.6 mg) in the Group P, and 6.8 mg (95% CI, 6.4–7.2 mg) in the Group C, there was significant difference between the 2 groups (P < .5). The ED50 of intrathecal ropivacaine increases compared with Group C when phenylephrine is prophylactic infused to prevent spinal induced hypotension in cesarean section.Conclusion:The ED50 of intrathecal hyperbaric ropivacaine is 7.2 mg when phenylephrine is prophylactic infused to prevent spinal induced hypotension in cesarean section, and more ropivacaine demands on spinal anesthesia for cesarean section (www.chictr.org.cn, registration number: ChiCTR-RIC-17011650).

Comparing the minimum local anesthetic dose of ropivacaine in real-time ultrasound-guided spinal anesthesia and traditional landmark-guided spinal anesthesia: a randomized controlled trial of knee surgery patients

“…In a previous study, we demonstrated that for lower limb surgery the MLAD values of 0.75% and 0.5% ropivacaine were 17.176 mg (0.75%) and 20.192 mg (0.5%) when using real-time UG SA to achieve a sensory blockade at the T10 level, while for LG SA the MLAD of ropivacaine was mostly between 7.6-12.8 mg (13)(14)(15)(16). Previous studies have also shown that the ED 50 of ropivacaine for reaching the T6 level of sensory block during cesarean sections under SA was 6.8-11.4 mg (27)(28)(29)(30), and the ED 50 of ropivacaine required to reach the T5 level was 5.92-8.35 mg (31). Kallio et al (32) studied inguinal hernia repair under SA and found that administering 15 mg of ropivacaine allowed 97% of patients to achieve a sensory block plane within 5-20 min of reaching above the T10 level, and also allowed them to remain above T10for 90 min.…”

ED50 and ED95 of intrathecal hyperbaric ropivacaine for parturients undergoing cesarean section with prophylactic infusion of phenylephrine

“…Moreover, Zhang et al compared the ED 50 of intrathecal ropivacaine when with or without phenylephrine infusion, and found a higher dose requirement when using phenylephrine infusion to prevent spinal-induced hypotension. [11] However, the optimum dose for clinical practice is 95% effective dose, which can meet 95% of patients’ analgesia requirement, rather than ED 50 . Additionally, phenylephrine is regarded as the first-line vasopressor for preventing spinal-induced hypotension in cesarean section.…”

“…[8–10] Moreover, one published study has demonstrated that the ED 50 of intrathecal ropivacaine for cesarean section with prophylactic infusion of phenylephrine was higher than without prophylactic infusion of phenylephrine. [11] In clinical practice, as we known, 95% effective dose (ED 95 , the dose is sufficient for 95% of patient to achieve effective anesthesia) is more meaningful than ED 50 for patients undergoing cesarean section. Therefore, in this study, we aimed to determine the ED 95 of intrathecal hyperbaric ropivacaine for patients undergoing cesarean section with intravenous prophylactic infusion of phenylephrine.…”

"The Clinical Effects of Epidural Anethesia with Lidocaine Combined Low Dose Ropivacaine in Elective Cesarean Section"

“…However there are some of disadvantages of SA including nausea, hemodynamic disorders such as hypotension [3]. Hypotension induced by SA is still a common complication [4], which might be up to 80% [5]. Such high incidence is the main limitation of SA in CS [6].…”

“…Thus small dose of local anesthestic was advocated due to low incidence of hypotension induced by SA, however it possibly increased the failures [8,9]. In some cases phenylephrine has to be administered because of its' more advantages to prevent SA related to hypotension [5,10].…”