Can Choice of Vasopressor Therapy Affect Rostral Spread of Spinal Anaesthetic?

Comparison of the ED50 and ED95 of Intrathecal Bupivacaine in Parturients Undergoing Cesarean Delivery With or Without Prophylactic Phenylephrine Infusion

“…Our results demonstrate that a higher dose of intrathecal bupivacaine is needed in the setting of prophylactic phenylephrine infusion and are consistent with at least 1 prior study, 15 in which the ED 50 and ED 95 of intrathecal hyperbaric bupivacaine during cesarean delivery in the absence of prophylactic phenylephrine infusion were 7.6 and 11.2 mg, respectively. Prior studies [8][9][10] have found that administration of vasopressor may affect rostral spread of spinal anesthetic in parturients undergoing cesarean delivery. The rate of anesthetic block at the cervical level has been shown to be lower in subjects who receive prophylactic phenylephrine infusion compared with those who receive ephedrine or a combination of phenylephrine and ephedrine during cesarean delivery under spinal anesthesia.…”

“…4-7 While a prophylactic phenylephrine infusion is often used to decrease the risk of spinal-induced hypotension, its use has been associated with decreased rostral spread of intrathecal local anesthetic in pregnancy. [8][9][10] The purpose of this study was to determine the median effective dose (ED 50 ) and 95% effective dose (ED 95 ) of intrathecal hyperbaric bupivacaine for cesarean delivery in the presence and absence of prophylactic phenylephrine infusion. We hypothesized that a higher dose of intrathecal local anesthetic would be necessary to achieve successful spinal anesthesia during cesarean delivery with the administration of prophylactic phenylephrine infusion.…”

Effect of intravenous phenylephrine infusion on dose requirement of intrathecal plain levobupivacaine for cesarean section: A placebo-controlled preliminary study

“…Decrease in rostral spread of intrathecal plain levobupivacaine was noted earlier with phenylephrine infusion as compared to an ephedrine infusion. [24] The authors explained it by a greater constriction of the epidural venous plexus engorged due to pregnancy by phenylephrine as compared to ephedrine, thereby increasing compliance of epidural space, lowering intrathecal pressure, and reducing the spread of intrathecal injection. Other studies have noted a similar result of decreased rostral spread of intrathecal drug with hyperbaric agent as well.…”

“…It has been shown previously that the choice of vasopressor therapy for managing postspinal hypotension during cesarean section affects the rostral spread of intrathecal local anesthetic (LA). [234] Comparison of phenylephrine versus ephedrine infusion showed decreased rostral spread of plain[24] as well as hyperbaric LA with phenylephrine. [34] Consequent to the decreased rostral spread of intrathecal LA with phenylephrine infusion, the ED50 of hyperbaric bupivacaine for cesarean section was investigated with the results showing lack of anticipated increase in dose requirement.…”

“…[2345] In current obstetric anesthetic practice, phenylephrine is recommended over ephedrine and is thus often used as first-line vasopressor for prevention and treatment of maternal hypotension due to the maintenance of better fetal acid-base status. [1]…”