Decreased Tensile Strength of an Epidural Catheter During its Removal by Grasping with a Hemostat

Apotential complication of continuous epidural anesthesia is breakage and separation of the catheter during its removal. We encountered a case of breakage of an epidural catheter that occurred as it was extracted by using a stainless steel hemostat, as has been occasionally used to remove an entrapped catheter (1,2). This prompted us to compare the tensile strengths of catheters of different materials while they were being held with either a stainless steel hemostat or a hemostat with rubber sleeves. Case Report The patient was a 48-yr-old male without a history of back problems who underwent open reduction internal fixation for a tibia fracture. Using the midline loss-of-resistance technique, a 19-gauge polyurethane catheter (FlexTip Plus catheter, Arrow International, Reading, PA) was inserted through a 17-gauge Tuohy needle into the L2-3 epidural space without difficulty. The catheter was advanced 5 cm into the epidural space and secured. Anesthesia was maintained with 1.5% mepivacaine epidurally together with an IV infusion of propofol. The patient tolerated the procedure well and had an uneventful postoperative recovery. Two days after surgery, an orthopedic surgeon encountered difficulty in removing the epidural catheter with the patient in the sitting position and with his back moderately flexed. As the catheter appeared to be gradually emerging with continuous sustained tension, the surgeon grasped it at the skin with a stainless steel hemostat. While attempting to extract it incrementally, the catheter suddenly broke at the point of the hemostat. A radiograph of the back confirmed the presence of a sequestrated piece of the catheter without knot formation between the spinous processes (Figure 1). Although the patient was asymptomatic, he strongly desired surgical removal of the catheter, which was successfully performed under general anesthesia.Figure 1: Plain radiograph of the lumbar supine showing the retained fragment of sheared catheter (arrows).We studied 7 catheters with a 19-gauge diameter made of different materials. Eight samples of each catheter: polyurethane (Dib Epidural set; Dib International, Tokyo, Japan, and FlexTip Plus catheter; Arrow International), nylon (Epidural Minipacksystem; Portex Ltd., Hythe, Kent, UK, and Perifix; Perifix-B.Braun, Melsungen AG, Germany), polyethylene (Epidural Anesthesia Minikit; Abbott Ireland Ltd., Sligo, Ireland, and Hakko Epidural set EF17I-95; Hakko Medical, Tokyo, Japan), and Teflon (Hakko Epidural set EF17T-95; Hakko Medical) were evaluated with a fully automated, computer-controlled tester (Autograph 10TD; Shimazu Ltd., Kyoto, Japan) that stretched samples at a preset rate while measuring tension. For testing, one side of the catheter segment was fixed in a rubber-coated grip of the tester to which a transducer was attached, while the other side was grasped by either a stainless steel hemostat or a rubber-sleeved hemostat. The resting length of the catheter was set at 3 cm. The catheter was then continuously stretched at 200 mm/min at 23°C ± 1°C. This placed an increasing load on the catheter that was measured by the transducer. The testing was continued until the catheters snapped. The tensile strength was defined as the load (kg) at which a catheter broke. Comparison was made by one-way analysis of variance followed by Scheffé multiple comparison as a post hoc test. Statistical significance was set at P < 0.05. Results The results of tensile strength are shown in Table 1. Tensile strengths of catheters made of nylon and polyurethane were stronger with the rubber-sleeved hemostat than those of polyethylene and Teflon catheters. Use of the stainless steel hemostat, however, markedly decreased the tensile strengths of all catheters tested.Table 1: Tensile Strengths of Various 19 Gauge Epidural Catheters Measured (kg) While Being Held with Either a Rubber-Sleeved Hemostat (Rubber) or a Stainless Steel Hemostat (Steel)Discussion Use of a hemostat has been suggested for removal of an entrapped epidural catheter (1,2); however, we speculate that this technique could has been, at least in part, responsible for its breakage in our case. The catheter removal was attempted in the sitting position that reportedly requires more tension to the lumbar epidural catheter during catheter removal than the lateral decubitus position1. This may have contributed to our difficulty in removing the catheter. Several maneuvers to remove an entrapped catheter have been suggested, including positional changes (3,4), injecting saline (5,6), or passing a venous cannula over the epidural catheter (7). The epidural catheters we used, FlexTip Plus, have fewer incidences of paresthesia and unintentional venous cannulation than the Portex catheter (8). Ateş et al. (9) demonstrated that polyurethane catheters are more elastic and durable than nylon catheters, although traumatization by a needle bevel or surgical blade significantly decreases maximal loads to break in all catheters tested. Although we did not closely examine the sites of breakage, we speculate that decreased tensile strength resulted from “microdamage” to the catheters by gripping with a stainless steel hemostat because all catheters held with the hemostat broke at the grip site. Indeed, breakage of an entrapped caudal catheter was reported during the removal by grasping the catheter with a forceps at the skin edge (10). Thus, holding an elastic and flexible catheter (like FlexTip Plus) with a hemostat, especially proximal to the skin as in our case, may be more dangerous. Should it break, the end of the catheter could retract beneath the skin because of its elasticity. Another issue to consider is whether a retained catheter should be removed. A retained sequestrated catheter has been considered not to have any clinical sequelae because it is thought to be inert and sterile. Thus, it has not been recommended to attempt removal as long as the patient is asymptomatic. Two reports, however, have reported spinal stenosis with leg weakness secondary to a reactive epidural mass around a catheter fragment or radicular pain with segmental sensory loss because of a sequestrated catheter coiled around a nerve root (11,12). Symptoms of both cases resolved after surgical removal of the catheters. In conclusion, we do not recommend the use of a stainless steel hemostat or similar instruments to grasp an entrapped epidural catheter during its removal, especially proximal to the skin, because it may increase the likelihood of accidental breakage owing to a marked decrease in the tensile strength of the catheter. The authors greatly appreciate the helpful comments by Dr. Sivam Ramanathan, Professor of Anesthesiology, University of Pittsburgh.