Epidural versus combined spinal epidural block for caesarean section

Effects of epidural injection on spinal block during combined spinal and epidural anesthesia for cesarean delivery

“…8 Although this technique has been criticized for delaying the onset of surgical anesthesia, it prompts investigation of the effects of subsequent epidural dosing. 9 Blumgart et al 10 showed an enhancement of spinal block after epidural saline injection using Rawal's technique 8 in cesarean patients, and other investigators have supported this "volume effect" of saline epi-dural injection. 11,12 Stienstra et al 11 showed both volume effect and local anesthetic effect of an epidural injection of local anesthetic in orthopedic patients.…”

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

“…Epidural injection of local anesthetics after spinal anesthesia produces rapid extension of analgesia [4,5]. Previously, the mechanism was thought to be the diffusion of local anesthetics from the epidural space to the subarachnoid space.…”

When using spinal anaesthesia for caesarean section after the epidural has failed, the normal dose of spinal anaesthetic should be used

“…Spinal anaesthesia can be easily extended with relatively small doses of drug given epidurally. 14,15 Both the degree and speed of onset of this extension cannot be adequately explained solely by the presence of a small volume of local anaesthetic within a localised area of the epidural space. Various mechanisms have been proposed to explain spinal extension.…”