Mechanism of Action of an Epidural Top-Up in Combined Spinal Epidural Anesthesia

Abstract

The purpose of this study was to elucidate the mechanism of action by which an epidural top-up reinforces anesthesia in combined spinal epidural anesthesia. Thirty patients scheduled to undergo lower limb orthopedic surgery were randomly allocated to three groups of 10 patients each. In all patients, a 16-gauge Tuohy needle was introduced into the epidural space. Using the needle through needle technique, each patient received a subarachnoid injection of 10 mg plain bupivacaine 0.5% through a long 27-gauge Whitacre spinal needle introduced into the subarachnoid space through the Tuohy needle. After withdrawal of the spinal needle, an epidural catheter was introduced into the epidural space. After the maximum level of sensory block after the subarachnoid injection had been established, an epidural top-up with 10 mL bupivacaine 0.5% (Group 1) or 10 mL saline (Group 2) was administered; patients in Group 3 received no epidural top-up. The maximum level of sensory block was then assessed for an additional 30 min. After the epidural top-up the maximum level of sensory block increased significantly by 4.8 +/- 1.6 segments in Group 1 and 2.0 +/- 2.0 segments in Group 2. In Group 3 there was a nonsignificant increase of 0.3 +/- 0.5 segments. Intergroup comparisons showed that this increase in Group 1 was significant compared with those in Groups 2 and 3, and that the increase in Group 2 was significant compared with that in Group 3. We conclude that the mechanism of action by which an epidural top-up reinforces anesthesia in combined spinal epidural anesthesia can be explained partly by an epidural volume effect and partly by an effect of the local anesthetic itself.

Reinforcement of spinal anesthesia by epidural injection of saline: a comparison of hyperbaric and isobaric tetracaine

“…The isobaric solution may have diffused more easily than the hyperbaric solution within the CSF, because the uniformity is a characteristic of the isobaric solution. In our study, the analgesic levels increased two segments in group B (hyperbaric-saline injection) and group D (isobaric-saline injection) after the injection of 8 ml of saline through the epidural catheter, a result similar to the results of previous studies [2,6]. Contrary to our expectation, there was no significant difference between the two groups regarding the reinforcement of spinal anesthesia.…”

“…Recently, Takiguchi et al [2] demonstrated a shift of the contrast medium within the lumbar subarachnoid space to the rostral side after epidural saline injection using myelography. Thus, the mechanism of the extension of spinal anesthesia after epidural injection is now considered to be the "volume effect" [1,2,6].…”

Combined low-dose spinal-epidural anesthesia versus single-shot spinal anesthesia for elective cesarean delivery

“…11 In the CSE technique, an epidural injection, whether of local anesthetic or simply of saline, has been shown to extend the pre-existing spinal block. 15 A volume effect from epidural saline compressing the dural sac results in rostral migration of freshly administered spinal anesthetic. 16 In our previous study, 13 using 8 mg of hyperbaric bupivacaine, the maximum sensory height was reached at 8.9 min after the subarachnoid injection.…”

Spinal anesthesia using a continuous spinal catheter for cesarean section in a parturient with prior surgical correction of scoliosis

“…Some authors have demonstrated successful spinal anesthesia after an inadequate epidural block [7][8][9]. If spinal anesthesia is performed after the epidural administration of anesthetic, it is possible that the solution administered into the epidural space squeezes the dura mater and cerebrospinal fluid (CFS), resulting in the excessive cephalad spread of the intrathecal anesthetic agent [10]. Previous articles reported that the unexpectedly rapid cephalad spread of a spinal block necessitated respiratory support under tracheal intubation [11,12].…”