Background and Objectives Microcatheters have been linked in some cases to the development of cauda equina syndrome, which may be further traced to the maldistribution of the local anesthetic. A long injection time via the microcatheters contributes to the inadequate mixing. With the new Spinocath catheter, considerably shorter injection times can be achieved due to larger internal size. This study examined whether this leads to more homogeneous intrathecal distribution without causing greater trauma to the dura.

Methods In an in vitro model of the spinal canal, the distribution of hyperbaric and isobaric 0.5% bupivacaine (2.5 mL) as well as 5% lidocaine (2.5 mL) was examined after injection via the 28-gauge CoSpan catheter (Kendall, Healthcare, Mansfield, MA), the 22-gauge Spinocath catheter (Braun, Melsungen, Germany), and a 29-gauge Quincke needle (Becton Dickinson, Rutherford, NJ). The local anesthetic concentration in the vertebral interspaces T12-L1 to L5-S1 was measured via gas chromatography 3 and 10 minutes after injection. In addition, the morphologic puncture characteristics of human dura were examined with the halftone electron microscope, after puncture with the catheters and needle.

Results After injection through the 28-gauge CoSpan catheter, caudal segments of the spinal canal showed peak concentrations up to a maximum of 1,147 μg/mL bupivacaine or 8.5 mg/mL lidocaine with hyperbaric solutions, which did not decrease over the 10 minutes of measurement. After injection through the Spinocath catheter, there was a homogeneous distribution with data peaks of approximately 350 μg/mL bupivacaine or 4.2 mg/mL lidocaine similar to the data found after injection through the spinal needle.

Conclusions The new Spinocath catheter allows a better mixing of the local anesthetic with the cerebrospinal fluid. Because of significantly shortened injection times, hyperbaric solutions also show a more homogeneous distribution. Although the Spinocath catheter has a larger inner diameter than the other microcatheters, it appeared to cause less trauma to the dura.