Successful removal of a trapped epidural catheter facilitated by using a nickel/titanium alloy (nitinol) suture as a guidewire

Summary

Epidural catheters are often used in the provision of surgical anaesthesia and analgesia. These catheters need to be removed after a certain period, but difficulties may be encountered during this process. We present a case of difficult epidural catheter removal in an elderly woman who had undergone surgery for reduction and internal fixation of a comminuted intertrochanteric fracture at the left femur under combined spinal epidural anaesthesia. Anaesthesia was satisfactory during the operation; however, initial attempts to remove the catheter at the end of the procedure was met with significant resistance. Normal saline (5 ml) was injected through the catheter without difficulty, suggesting that the catheter was likely trapped and compressed but not obstructed. A nickel/titanium memory alloy suture was used as a guidewire to remove the catheter without damaging it. This case was analysed subsequently, and the management of future problematic removals is discussed herein. This article aims to raise awareness of, and to explore techniques for managing difficult epidural catheter removal.

Introduction

Epidural catheters are often used for the continuous or intermittent administration of local anaesthetic mixtures for anaesthesia and analgesia. Inability to remove the epidural catheter is a rare but known complication of this technique. The incidence of difficult epidural catheter extraction is 0.012% [1], and the trapped epidural catheter may break if not handled properly.

Previous reports have described the management of difficult epidural catheter extraction, but no clear management guidelines are available [2, 3]. A variety of techniques have been posited to facilitate catheter removal, including change of patient position; wiggling motions; waiting for the catheter to dislodge by itself [4]; slow traction; and continued traction over an extended timeframe [5].

To our knowledge, this is the first report that describes the use of a nickel titanium alloy (also known as ‘nitinol’) memory suture as a guidewire in managing the difficult removal of an epidural catheter. In our case, after several unsuccessful attempts at catheter removal, a final attempt was made by placing the patient in the right decubitus position and using our described technique, rather than resorting to a more invasive method. The catheter was removed successfully during this final attempt with no adverse sequelae.

Case Report

An 83‐year‐old woman (weight 43 kg, height 150 cm, ASA physical status 3) with a left comminuted intertrochanteric femoral fracture was scheduled for reduction and internal fixation under combined spinal epidural anaesthesia in the right decubitus position. Her pre‐operative imaging showed hyperostosis in the lumbar vertebrae. The epidural space was accessed at the L3/L4 intervertebral space without any difficulty using a 16 gauge Touhy needle (Henan Tuoren Medical Device Company Ltd, Henan, China). After loss of resistance to saline at 4 cm and a positive bubble test, a 25 gauge spinal needle from the same manufacturer was introduced into the subarachnoid space via the Touhy needle. After clear cerebrospinal fluid was observed at the end of the spinal needle, 1 ml of isobaric ropivacaine 1% (diluted with cerebrospinal fluid to 2 ml) was injected. The spinal needle was then withdrawn and the epidural catheter was threaded through the Tuohy needle and advanced 4 cm into the epidural space with the needle bevel directed rostrally; the length the catheter at the skin was 8 cm. After the catheter was secured, 3 ml of lidocaine 2% was injected into the epidural space. Intra‐operative anaesthesia was adequate, and the operation lasted 45 min. However, at the conclusion of the operation and with the patient still in the right decubitus position, significant resistance was met after about 4 cm of the epidural catheter was pulled out. The catheter was observed to elongate and thin when further force was applied. At this point, a senior anaesthetist was immediately consulted. Further attempts at removal were made with the patient positioned with the chin tucked to the chest, in spinal traction. A further 5 ml of lidocaine 1% was infiltrated subcutaneously and 40 mg of propofol was administered intravenously to support these efforts. All attempts were unsuccessful. A bolus of 5 ml of sodium chloride 0.9% was injected through the catheter with minimal resistance, suggesting that the catheter, though trapped and compressed, was not completely obstructed. We then decided to use a nickel titanium memory alloy suture (Jiangsu Huaxia Medical Appliances Company Ltd., Yangzhou, China) as a guidewire (Fig. 1a). The needle was cut off a 3‐0 nitinol alloy suture wire, and the wire was inserted gently into the catheter until it passed the tip. The catheter was then gently pulled with a constant force along the direction of insertion and was removed eventually. Close inspection revealed that the catheter was elongated with an obvious indentation at 1.5 cm from the tip of the catheter, forming a 90° angle (Fig. 1b). When observed with a × 50 objective lens, one side of the catheter wall was noticed to remain intact while the other side had an obvious indentation (Fig. 1c). The patient was later discharged without any further complication.

Figure 1.

(a) 3‐0 nitinol memory alloy suture used as the guidewire; (b) the extracted epidural catheter with an obvious 90° deformity; (c) epidural catheter viewed with ×50 magnification with the indentation shown (red arrow).

Discussion

Nitinol is flexible, partially elastic, has memory. It has a tensile strength that is stronger than steel and can be sterilised. It is used to manufacture many different catheters and guide wires for interventional procedures. It can conform to hyperacute angles and access anatomic locations that would otherwise be difficult to reach. Nitinol is used to make the ‘scaffolding’ of various intravascular implantable devices, including arterial and venous stents, stent grafts, vascular occlusion devices, venous filtration devices, embolism protector devices and prosthetic heart valves. It is also used to manufacture implantable intraluminal stents of the gastrointestinal tract (oesophagus, biliary tract and intestine), trachea and ear canal [6].

The inability to remove an epidural catheter due to resistance or entrapment has many causes [7, 8]; the most common are listed in Table 1.

Table 1.

Common causes of difficult epidural catheter removal [4].

Catheter entrapment	Diminished intervertebral space Middle‐aged and elderly patients with ligament calcification, hyperosteogeny and spinal lesions May be associated with difficulty accessing the epidural space or feeding the catheter.
	Paraspinal muscle contraction or spasm Strong contraction of paraspinal muscles or spasm may be triggered by pain or prolonged exposure to hypothermia
	Postural malposition Inadequate forward flexion will narrow the intervertebral space reversibly
Catheter knotting	Inappropriate catheter insertion length An excessive catheter length (≥4 cm) in the epidural space may increase the likelihood of entanglement and knotting.
	Pathophysiological changes of the epidural space The catheter may become entangled with nerve roots, blood vessels, lumbar fascia, posterior vertebral arches, vertebral processes and facet joints due to pathophysiological changes such as pregnancy, old age, disc herniation, spinal canal stenosis. Anatomical obstacles may cause the catheter to curl back on itself.

No specific management guidelines are available to address difficult epidural removal, but some suggestions have been made in the literature [4, 5]. These include: using a slow constant force at all times; stop applying force when the catheter begins to stretch; place the patient in the same position as when the catheter was inserted; apply local anaesthesia, general anaesthesia and (if appropriate) administration of neuromuscular‐blocking agents; perform computed tomography imaging to determine the cause of difficulty in removal; provide detailed pre‐operative education and risk assessment to patients at a high risk for catheter removal difficulties (i.e. old age, abnormal anatomy); consult a spinal surgeon in the event that the catheter breaks, or if a catheter fragment is thought to remain beneath the skin.

In our case, several conventional removal techniques were attempted without success. Normal saline was administered through the catheter to rule out the possibility of catheter obstruction. The 3‐0 nitinol suture wire was then used to partially restore the indentation on the catheter. The application of uniform force minimised the risk of catheter breakage. Simultaneously, the force to pull out the catheter was gradually increased, and traction was applied to enlarge the intervertebral space.

The amount of force applied is crucial in epidural catheter removal. The maximum withdrawal force is generally not listed in terms of exerted traction or technique on the manufacturers’ labels. These pressures can be measured clinically using a portable force gauge. Clinically, the average normal force required to remove an epidural catheter is 2.04 N (approximatly equivalent to the force exerted by a mass of 0.2 kg) [4]. Application of excessive traction can cause the catheter to be stretched or even fractured.

In the event, the catheter breaks during removal in an adult patient, some sources suggest surgical extraction is not necessary on the basis that the catheter will trigger little reaction from the surrounding tissues due to its biologically inert material. Surgical removal has however been attempted in children, as they can recover from possible nerve injury through natural development and growth [9]. Surgical removal is only recommended in adults with neurological symptoms, or when the catheter tip is located outside the dura mater [9]. However, as we have described in this report, cases of catheter breakage may be avoided by supporting the epidural catheter using a guidewire if removal is noted to be difficult.