Risk of catheter migration during combined spinal epidural block: percutaneous epiduroscopy study

Combined spinal epidural (CSE) block with the needle-through-needle technique has become increasingly popular during recent years. However, the risk of epidural catheter penetrating dura mater through the hole made by the spinal needle (migration) is a major concern. In 15 fresh cadavers a percutaneous epiduroscopy technique with a rigid epiduroscope and video recording was used to assess the risk of catheter migration when a CSE block is performed. The experimental sequence included (a) one dural hole made by the spinal needle, (b) multiple (five) dural holes made by the spinal needle, and (c) a dural hole made by Tuohy needle. Twenty-four experimental sequences were performed in the lumbar region. Four sequences were failures due to technical problems. In the remaining 20 cases, the anatomic structures in the epidural space were recognized easily. The epidural space appears to be only a potential space, kept open either by epiduroscope or by repeated injections of air or saline. The dural holes made by Tuohy and spinal needles, and the ease of difficulty of catheter penetration through these holes, were clearly visible. Extensive tenting of the dura was seen in all subjects. It was impossible to force an 18-gauge epidural catheter through the dural hole after a single dural puncture made by a 25-gauge spinal needle. After multiple (five) dural punctures with the spinal needle, the epidural catheter penetrated the perforated dura in 1 of 20 cases. The epidural catheter penetrated the dural hole made by the Tuohy needle in 9 of 20 cases. The distribution of fat, rather than any dorso median connective tissue band, influences the course of epidural catheter in epidural space.(ABSTRACT TRUNCATED AT 250 WORDS)