[The level of analgesia with epidural injection of 2% mepivacaine using combined spinal and epidural analgesia].

We studied the level of analgesia obtained with epidural injection of 2% mepivacaine using combined spinal and epidural analgesia (CSE) and compared with the level obtained by epidural analgesia (EA). We inserted a catheter into the epidural space through the L2/3 interspace, and hyperbaric tetracaine was injected through the L3/4 interspace with 26G spinal needle in thirty patients for CSE. We checked the the level of analgesia 90 min after spinal anesthesia. After this, 23 out of 30 patients showed the extension of analgesia 15 min after injection of mepivacaine into the epidural catheter. In these patients, the level of analgesia and the dose of mepivacaine showed the regression line Y = 10.2-0.4X (Y: the level of analgesia, X: the dose of 2% mepivacaine, P < 0.05). We also showed the regression line Y = 16.1-0.7X (P < 0.05) for EA 15 min after epidural injection of mepivacaine in other 23 patients. To achieve the same level of analgesia of Th8 or Th6 with CSE and EA, the doses for epidural injection were calculated as 5.5 ml, 10.5 ml with CSE and 11.5 ml, 14.4 ml with EA, respectively. These results show that the epidural dose of local anesthetic for CSE is 1/2 to 2/3 of that necessary for EA.