Indwelling catheters (nylon/Teflon) are frequently used as a conduit to inject various substances including neurolytic solutions in the treatment of particular chronic pain syndromes. In certain clinical situations, these catheters are kept in place for varying periods and serially injected with neurolytic solutions for management of chronic pain until optimal effect has been obtained. There is concern that these substances may disrupt the structural integrity of these catheters, possibly causing premature catheter fracture during removal. This study was designed to investigate the tensile strength of three types of stock epidural catheters after in vitro exposure to clinically used concentrations of five different neurolytic solutions. METHODS: Ten segments (8cm) each of three different stock epidural catheters were injected with and then soaked in the following neurolytic solutions: 6% aqueous phenol, 6% phenol in 60% glycerol, 10% phenol in non-ionic contrast, 50% ethanol, and 100% ethanol. A normal saline bath served as the control. Additionally, five catheter segments were bathed separately in 1% lidocaine, 0.25% bupivacaine, 60% glycerol, and non-ionic contrast for further comparison. Two nylon (Perifix(r), and Epi-Cath(r)) and one Teflon catheter were evaluated. Samples were incubated at 37 °C for 72 hours. We determined the maximum axial load until sample fracture in newtons (N) with an Instron universal testing machine using a crosshead speed of 500 mm/min. and a spacing of 35 mm. Data were analyzed by ANOVA with appropriate post hoc testing, and a p value of <0.05 was considered significant. RESULTS: All Epi-Cath catheter segments showed significant tensile strength degradation when soaked in neurolytic solutions compared to saline (see Fig.l). All neurolytic soaked Perifix catheters, except for the 50% ethanol solution, had significant decreases as well. 6% aqueous phenol produced the greatest decrease in tensile strength in both of the nylon catheter groups. Neither of the nylon catheters showed any loss of tensile strength when exposed to local anesthetics, contrast, or plain glycerol. None of the tested Teflon catheters demonstrated significant changes when soaked in any of the solutions studied. DISCUSSION: The effect of neurolytic solutions on catheters needs to be one of the factors considered when type of catheter is being selected. While Teflon catheters were least effected, other considerations include kink resistance and orifice location. The lowest measured load until fracture in any of the samples (6% phenol-Perifix) was 10.8 N which correlates to I.ikg (lkg=9.8 N). This represents a two third decrease in tensile strength when compared to saline (10.8 N vs. 32 N). Therefore, if during nylon catheter removal resistance is encountered or if stretching of the catheter is observed, it is recommended that the patient should be repositioned and then reattempt removal.
|Original language||English (US)|
|Number of pages||1|
|Issue number||2 SUPPL.|
|State||Published - Dec 1 1996|
ASJC Scopus subject areas
- Anesthesiology and Pain Medicine