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Department of Anesthesiology, Kansai Medical University, Osaka, Japan
Address correspondence and reprint request to Takashi Asai, Department of Anesthesiology, Kansai Medical University, 10-15 Fumizono-cho, Moriguchi City, 570-8507, Osaka, Japan. Address e-mail to asait{at}takii.kmu.ac.jp
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Abstract |
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Implications: Although breakage of an epidural catheter is rare, our ex vivo study suggests that compared with three other epidural catheters, the Arrow catheter is more likely to stretch and break. The segment between the 7- and 8-cm marks may be an area especially vulnerable to breakage.
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Introduction |
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Case Report |
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On the fourth day after surgery, we attempted to remove the catheter with the patient on her side, but we encountered resistance with gentle tugging of the catheter at the skin insertion site. Changing the patient’s position did not help. Further traction stretched the catheter until it became possible to remove it. However, the distal part of the catheter was missing, even though the inner metal coil from the amputated distal segment remained attached to the withdrawn catheter segment. The metal coil was easily pulled from the patient’s body. The catheter tip, which was surgically removed under local anesthesia, was stretched; the breakage point of the catheter was found to be between the 7- and 8-cm marks. No metal coil was left inside ( Figs. 1, 2).
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A pair of forceps was applied vertically to the catheter 5 cm from the distal tip, and the forceps were fixed to a stand, simulating the catheter being caught, for example, by a bony structure in the patient’s body. The catheter was suspended in air, and a small loop was attached 10 cm from the tip with a silk string, simulating the site where the catheter would be grasped during removal.
A weight (200 and 300 g, in turn) was hung from the string loop (at the 10-cm mark), and the length between the 5- and 10-cm marks was measured. The weight was removed. A hand-held scale (TB-611T; Nihon Kohden, Tokyo, Japan) was attached to the string loop, the catheter was pulled manually, and the force required to snap the catheter was recorded. The transducer response is linear over the range of 0 to 1200 g, and this range covers the reported pulling force required to remove an epidural catheter from a patient (2–4). The accuracy of the scale was confirmed before each use by hanging 100, 200, 500, 1000, and 1200-g weights on it. The speed of pulling was not quantified. The site of breakage was recorded.
We specifically assessed whether the site between the 7- and 8-cm marks of the Arrow catheter was inherently weaker. We repeated the study but fixed the catheter at 7.5 cm and pulled it manually at 12.5 cm.
The F test showed that there were significant differences between groups for the variability of required weight for snapping the catheter, whereas variables were not significantly different between groups for the length of the catheter (at either 200 or 300 g weight). Therefore, the Kruskal-Wallis test was used to compare the required weight to snap the catheter, followed (if significant) by the Mann-Whitney U-test to compare the Arrow catheter with each of the other catheters. One-way analysis of variance was used to compare the length of the catheter, followed (if significant) by Student’s t-test between the two groups. Fisher’s exact test was used to compare the incidence between groups of the catheter snapping close to (
0.5 cm distance from) the fixed point (i.e., at 5 or 7.5 cm). A P value of <0.05 was considered significant. The 95% confidence intervals were also calculated.
The Arrow catheter stretched significantly more (P < 0.001) and snapped at a significantly lower weight (P < 0.01) than each of the other three catheters ( Tables 1, 2). All catheters snapped at the fixed site or pulling site and never between. The incidence of the catheter breaking at 5 cm was significantly more for the Arrow catheter than any of the other three catheters (P < 0.01) (Table 2). In the Arrow catheter, the inside metal coil was exposed and snapped somewhere between the 5- and 10-cm marks for two catheters ( Fig. 3) and did not break for the remaining four catheters. For the Arrow catheter, a significantly lower weight was required to snap the 7.5–12.5-cm segment than the 5–10-cm segment (P < 0.05) (Table 2).
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Discussion |
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Although our ex vivo study has limitations and different results might have been obtained by using different methods (5), we attempted to simulate as much as possible the difficulty in removing an epidural catheter. First, we applied a pair of forceps to fix, and a silk loop to pull, the catheter, and this fixation method might have encouraged snapping at the fixed sites that occurred in our study. To measure the tensile strength more accurately, the catheter segment of interest should be fixed by rolling adjacent segments around cylinders with large diameters. Second, the speed of stretching the catheter may also affect when it snaps: the faster the speed, the more likely it is to snap. We attempted only to use a speed similar to that used by clinicians in removing epidural catheters from patients. Third, the breakage of the catheter in our patient might have been caused mainly by prior damage to the catheter. One study has shown that the tensile strength of epidural catheters can be markedly decreased if the catheter has been damaged by the bevel of the Tuohy needle (5).
A few solutions have been proposed for difficulty in removing an epidural catheter (2,3,6–8). First, the patient should be placed in the lateral decubitus position, because greater force is required to remove the catheter in the sitting position (2,3). Second, flexion of the spine is effective (6). Third, injection of saline through the catheter during removal is effective (7). There was a report of successful removal of a catheter by inserting a Tuohy needle over the catheter (8), but the needle may have cut the catheter during reinsertion.
Although the incidence of breakage of epidural catheters during removal is not known, it appears to be very infrequent (9,10). We routinely use the Arrow catheter because of the ease of insertion and have had only one case of breakage during several years of use. In addition to the current case, we have experienced three other cases of difficulty in removing the Arrow catheter. In all patients, it was impossible to remove the catheter with the patient in any position. However, in all these cases, it became possible to remove the catheter easily when attempts were made again 30–60 minutes later. We postulated that patients’ body movements fortuitously relieved the trapped catheters. Therefore, we suggest that, if there is difficulty in removing the catheter, one should avoid pulling the catheter forcefully and should reattempt removal 30–60 minutes later.
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Acknowledgments |
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Footnotes |
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2Junega M, Kargas GA, Miller DL, et al. Incidence of epidural vein cannulation in parturients with three different epidural catheters [abstract]. Reg Anesth 1995;20(Suppl):4.
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