Shearing of a Peripheral Nerve Catheter

Femoral nerve block can provide good perioperative analgesia for surgery to the hip and knee (1), and the use of a femoral nerve catheter for intermittent bolus or continuous infusion of local anesthetics extends this analgesia (2,3). The development of kits for continuous peripheral nerve block now makes this form of pain relief more practical. We report a complication of this technique where a retained segment from a sheared catheter resulted in femoral neuralgia. Case Report An 85-yr-old woman sustained an intertrochanteric fracture of her left femur. She had a history of chronic renal failure and previous myocardial infarction with persistent angina on minimal exertion. Her surgical history included aortobifemoral bypass grafting and internal fixation of a right fractured neck of femur. For surgery, spinal anesthesia was established with 2 mL of 0.5% hyperbaric bupivacaine. A femoral nerve catheter using a Plexolong 531151–31A kit (Plexolong, Pajunk, Germany) was inserted for postoperative analgesia. The kit contained a 19.5-gauge × 50-mm insulated needle with a facet tip and a 20-gauge × 50-cm-long plexus catheter with a radio opaque strip; the catheter has 1-cm markings up to 30 cm from its centrally opening tip and has an introducing guidewire. A 50-cm connection tube for injection is also supplied. Aiming rostrally, the needle was inserted lateral to the femoral artery just below the inguinal ligament. The femoral nerve was located with a nerve stimulator observing muscle contraction in the quadriceps, and 10 mL of normal saline was injected to expand the tissue planes. The 20-gauge polyamide catheter with the indwelling guidewire was then inserted to a depth of 9 cm. The guidewire and then the insulated needle were removed. Five milliliters of 0.75% ropivacaine was administered. The catheter was secured with a clear self-adhesive dressing. In the postanesthetic care unit, an infusion of 0.25% bupivacaine at 8 mL/h was commenced. On the first postoperative day, the patient complained of severe left hip pain on movement, and the dressing around the catheter entry site was noted to be wet. A bolus dose of 5 mL of 0.25% bupivacaine leaked through the catheter entry site. It was planned to remove and then replace the catheter. During removal, with only very gentle traction, the catheter seemed to break 1–2 cm below the skin. (Fig. 1) A replacement catheter was not inserted, and small subcutaneous doses of morphine were offered for pain relief. The postoperative course was complicated by myocardial infarction, hematemesis from a gastric ulcer, and intermittent confusion. The patient’s medical problems stabilized for a 1-wk period. However, she complained of persistent severe pain in the left groin, anterior thigh, and knee. At this stage, our Pain Management Service was consulted. The pain was exacerbated by movement and was not relieved by morphine. Radiographs of the left hip showed satisfactory internal fixation. Despite the retained fragment of the catheter having part of the radio-opaque strip, it could not be identified with plain radiographs. However, a computerized tomographic scan did clearly reveal the fragment in the region of the femoral nerve (Fig. 2). The provisional diagnosis was femoral nerve neuralgia secondary to a retained catheter segment. Because of continuing pain, the catheter site was surgically explored, and a 6-cm catheter fragment was removed from posterolateral to the femoral artery in the vicinity of the femoral nerve. The neuralgic thigh pain resolved in the week after removal of the catheter.Figure 1: Distal end of the proximal part of the sheared catheter.Figure 2: Computerized tomogram of the left hip showing the retained catheter fragment posterolateral to the femoral artery (arrow).Discussion After hip and knee surgery, continuous femoral nerve infusions of local anesthetic can provide pain relief comparable to epidural analgesia with fewer side effects and technical problems, such as catheter kinking or catheter dislodgement (2,3). In this case, shearing or weakening of the catheter most likely occurred during guidewire removal with the needle still in situ; complete breakage was noted at the time of catheter removal. Factors that may contribute to catheter shearing would include both the sharpness (4) and the bevel angle of the insulated needle. Because this case was reported to the manufacturer, the instructions for use of this product have been modified to include a warning about the importance of removing the needle before the guidewire is withdrawn. Particular problems and relative contraindications in our patient would include possible scarring from her previous aortobifemoral surgery and the placement of the catheter after a spinal anesthetic, which may have masked pain in the distribution of the femoral nerve during catheter insertion. We have been unable to find previous reports of neuropathy or shearing secondary to peripheral nerve catheter placement. However, Singelyn et al. (5) reported a 25% postoperative technical complication rate (kinked or broken catheters) in a series of 60 patients receiving continuous popliteal sciatic nerve block. There have also been reports of two cases of brachial plexus irritation caused by interscalene catheters (6) and an acute radiculopathy because of a retained epidural catheter (7). This case illustrates the importance of needle removal before withdrawal of the catheter guidewire. Although reported to be radio-opaque, fine-gauge peripheral nerve catheters can be difficult to visualize on plain radiographs, and computed tomography scanning should be considered to identify catheter location.