Periosteal Entrapment of an Epidural Catheter in the Intrathecal Space

Abstract

Inability to remove an epidural catheter is rare (1,2). We report a case of possible periosteal entrapment of an epidural catheter in the intrathecal space. Case Report A 25-yr-old woman, 160 cm tall, 113.6 kg, gravida-3, para-0 at 40 wk gestation was admitted in active labor at 3-cm cervical dilation. Her medical history was unremarkable. She elected to receive an epidural for labor analgesia. The patient was placed in the sitting position, and a midline approach was attempted at the L3-4 intervertebral space using the Arrow® Flextip kit (Arrow International, Inc., Reading, PA). The 17-gauge Hustead needle was inserted 6 cm to reach the epidural space, but the catheter met resistance and would not pass despite needle rotation, needle repositioning, or dilating the space with saline. A second anesthesiologist attempted a midline insertion at the L2-3 intervertebral space. The Hustead needle was inserted 6 cm to reach the epidural space and the Arrow® Flextip catheter was advanced 8 cm into the epidural space. Resistance was encountered when the anesthesiologist attempted to pull the catheter back to the 10-cm mark on the skin surface, which would have left 4 cm of catheter in the epidural space (our standard practice). Further attempts to pull the catheter back were abandoned. The catheter was secured with sterile dressing at 16 cm on the skin surface. After negative aspiration of blood or cerebral spinal fluid from the catheter, a 3-mL test dose of lidocaine 1.5% with 1:200,000 epinephrine was administered. The patient complained of lower motor extremity weakness and numbness. She was placed in the supine position with left uterine displacement. The block rapidly ascended to the T1-2 dermatome level. Her blood pressure decreased from 106/56-mm Hg to 84/44-mm Hg. She received a rapid IV infusion of lactated Ringer’s solution and ephedrine was titrated in 5-mg increments to maintain systolic blood pressure more than 100 mm Hg. During this episode, the fetal heart rate remained more than 135-bpm. Her blood pressure, heart rate, and oxygen saturation were monitored until the block regressed to a T4 level. No further injection of local anesthetic was required while she remained in active labor. Four hours after catheter placement, a cesarean delivery was planned as a result of arrest of cervical dilation. The intrathecal catheter was dosed with 2 mL of hyperbaric spinal bupivacaine 0.75% in divided doses over 10 min. The block reached a T-4 dermatome level bilaterally. The cesarean delivery proceeded uneventfully and a healthy neonate was delivered. Postoperatively, when the patient regained full lower extremity sensation, we unsuccessfully attempted to remove the catheter. All attempts to remove it with the patient’s spine positioned in different degrees of flexion and extension in both sitting and lateral position were futile. Because the catheter was trapped in the intrathecal space, neurosurgical consultation was obtained. A computerized tomography scan of the spine, obtained to determine catheter location and to eliminate nerve entrapment, showed the catheter tip in the intrathecal compartment (Fig. 1). Nerve entrapment was not evident. The catheter appeared to lie in close proximity to the periosteum of the vertebral body (Fig. 2), which was felt to be the source of entrapment. The neurosurgeon extracted the catheter 0.5-cm at a time, holding it with a pair of hemostats and applying gentle traction with another pair placed as close to the skin as possible. The neurosurgeon succeeded in removing the catheter, possibly because the hemostats enabled him to apply a firmer grip and a steady incremental pull. A picture of the removed catheter is shown in Figure 3. The distal 5 cm did not show visible areas of surface damage (Fig. 3). However, the stretched catheter revealed surface damage and disruption of the internal flexometallic ring between 5 and 15 cm (Fig. 3). The patient received IV ceftriaxone and vancomycin. She remained afebrile, and the remainder of her hospital course was uneventful.Figure 1: Computerized tomogram of the lumbar spine.Figure 2: Lateral computerized tomography view of the spine.Figure 3: A photograph of the removed epidural catheter.Discussion Epidural catheter entrapment is rare, and removal is not without complication. Hematoma formation, catheter breakage, and neurological complications have been reported (3,4). The reported incidence of epidural entrapment ranges from 1 in 20,000 to 1 in 30,000 (1,3,5). This is the first reported case of an entrapped epidural catheter, which was unintentionally inserted into the subarachnoid space. The incidence of intrathecal epidural placement at our institution is approximately 0.1%. This case clearly demonstrates aspiration alone is not always indicative of a spinal catheter, thus reaffirming the benefits of an epidural “test dose” with incremental dosing. Although the catheter was removed in a single piece, it did sustain surface and internal damage. It is not clear whether damage occurred during insertion or attempts at removal. Regardless, disruption of the flexometallic ring may dispose to entrapment because it could distort the smooth outer surface of the catheter. Ellis and Ramamurthy (6) reported a case where a spring wire reinforced fluoropolymer epidural catheter (Arrow-Racz) fractured into pieces on removal and the exposed metal spiral spring became unraveled. Using excessive force in removing an entrapped catheter may result in breakage and partial catheter retention. Epidural catheter entrapment can occur in a variety of ways, including knotting, kinking, looping, and vertebral fixation (2,5). In the present case, the close proximity and catheter irregularity suggest periosteal entrapment along the inferior vertebral body. An epidural catheter may be deflected by blood vessels and nerve roots and can double back on itself even when inserted only 4–5 cm into the epidural space (7). A catheter can also become entangled with nerve roots, blood vessels, lumbar fascia, posterior vertebral arches, vertebral processes, and facet joints (2,8,9). Excessive catheter threading may increase the likelihood of entanglement. Arrow International recommends advancing the catheter only 3 to 4 cm beyond the needle tip because advancing more than 5 cm may result in anterolateral placement or catheter knotting. It is not clear whether the catheter design may predispose to catheter entrapment. Several suggestions have been made to remove an entrapped catheter. Catheters are best removed when the patient is repositioned in the original placement position (11,12). Injection of sterile saline may help determine if the catheter is knotted (7). Gentle but firm traction can tighten the knot thus decreasing its size and facilitating removal (3,7). Boey and Carrie (13) determined the force required to remove a lumbar catheter is 2.5 times more in the sitting position than the lateral position. Clinically, the normal force required to remove an epidural catheter does not exceed 0.6 kg (14). The tensile strength of the 19-gauge nylon Portex catheter is 3.7 kg and the tensile strength of a 19-gauge polyurethane Arrow® Flextip catheter is 4.1 kg (personal communication, Arrow International). Additionally, clear nylon catheters can be stretched 30% of their original length before breaking, but polyurethane catheters (Arrow) can be stretched more than 300% of their original length without breaking (4). Compared with nylon catheters, Ates et al. (4), concluded polyurethane catheters were less prone to breakage. If removal is still difficult, general anesthesia with muscle relaxants has been suggested (2). Waiting a few days to let back muscles relax may help in catheter removal (2). Catheter removal should be abandoned if pain or paresthesia develops, and neurosurgical consultation with radiographic evaluation obtained. Radiographic evaluation, including a computerized tomography scan and/or magnetic resonance imaging with injection of radiopaque dye, may prove useful in determining entrapment location (2,3). However, magnetic resonance imaging would not be advisable with an Arrow® epidural catheter because of the flexometallic ring. Surgical removal should be reserved for patients who are symptomatic (2,15). If an epidural catheter breaks during removal, surgery is frequently unnecessary because the catheter is inert and complications are rare (2). However, neurological complications from retained epidural catheter parts can occur, requiring surgical intervention (9,15). Compared with epidural catheters, entrapped intrathecal catheters and/or a broken fragment in the subarachnoid space should be removed because of concerns of granuloma formation and infection (15). In conclusion, we report entrapment of an epidural catheter unintentionally inserted into the intrathecal space. Because of possible serious sequela of a foreign body in the intrathecal space, radiologic evaluation, antibiotic treatment, aggressive attempts at catheter removal, and neurosurgical consultation were undertaken. If removal had been unsuccessful, laminectomy was planned.