RISK OF CATHETER MIGRATION DURING COMBINED SPINAL EPIDURAL BLOCK - PERCUTANEOUS EPIDUROSCOPY STUDY

Combined spinal epidural (CSE) block with the needle-through-needle te chnique 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 epidurosco pe and video recording was used to assess the risk of catheter migrati on 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 n eedle. Twenty-four experimental sequences were performed in the lumbar region. Four sequences were failures due to technical problems. In th e remaining 20 cases, the anatomic structures in the epidural space we re recognized easily. The epidural space appears to be only a potentia l 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, we re clearly visible. Extensive tenting of the dura was seen in all subj ects. It was impossible to force an 18-gauge epidural catheter through the dural hole after a single dural puncture made by a 25-gauge spina l needle. After multiple (five) dural punctures with the spinal needle , the epidural catheter penetrated the perforated dura in 1 of 20 case s. The epidural catheter penetrated the dural hole made by the Tuohy n eedle in 9 of 20 cases. The distribution of fat, rather than any dorso median connective tissue band, influences the course of epidural cath eter in epidural space. We conclude that the risk of epidural catheter migration through the dural hole during uncomplicated combined spinal -epidural block is very small.