[Failures of lumbar epidural analgesia caused by transforaminal passage of an epidural catheter in two cases].

In one case, analgesia level obtained with a 20 ml of 1.5% mepivacaine was unilateral and inadequate. In the other case, an epidural catheter was inserted after a 20 ml of 2% mepivacaine was injected through a Tuohy needle. Toxicity by local anesthetic was induced by an overdose of local anesthetic through the catheter. In both cases, transforaminal passage of a catheter was confirmed by epidurogram with iohexol. If an epidural catheter is advanced beyond 5 cm into the epidural space, it may migrate outwards through the intervertebral foramen. Therefore, the insertion of an epidural catheter should be limited to 3-4 cm.