In most instances, removing an epidural catheter should be easy. This should be done (at least initially) in the lateral decubitus position (5). Sometimes, resistance is encountered during removal of the catheter. This can be due to the catheter becoming locked either in the vertebral spaces (in the posterior joints, the processes or the arches) or in the ligamentum flavum (Figure E.2) or due to knotting, kinking or curling of the catheter (1, 2, 3, 10, 11). Catheter knotting occurs very rarely (about 0.0015% of epidurals) (12).

When the catheter cannot be removed using minimal traction a number of manoeuvres may facilitate removal of the catheter. These include:
1. maximal flexion of the back (and, more rarely, extension of the back) with the patient in the lateral decubitus position,
2. rotation of the spine,
3. returning the patient to the position she was in at the time of insertion (eg. the sitting position with legs extended),
4. allowing tissues to soften before another attempt is made,
5. placing the patient in the sitting position with the legs extended or the kneeling position with hands down and back flexed,
6. filling the catheter with a rapid injection of saline to increase the turgor of the catheter and to lubricate it,
7. placing the patient prone on a Wilson (Zimmer) convex or the "Sydney Harbour Bridge" laminectomy frame,
8. complete relaxation using general anaesthesia with muscle relaxant, and 9. surgical removal. (4, 5 , 6, 7, 8, 9.)

Undue force during tugging should not be used because this will cause the catheter to stretch and tear. The tensile strength of most epidural catheters is about 1.7 Kg (8) (Table 42.1). It may be preferable to measure the tension being applied during these difficult extractions by using an electronic scale. Lengthening of the catheter is a sign that further traction is not advisable (Chapter 42).

References:
1. Yoshada H, Yokoyama K. Difficult Removal of Epidural Catheter -Report of a Case. Masui 27:314,1978.

2. Tio T, MacMurdo S, McKenzie R. Mishap with an Epidural Catheter. Anesthesiology 50:260-262, 1979.

3. Browne R, Politi V. Knotting of an Epidural Catheter: a Case Report. Can Anaes Soc J 26:142, 1979.

4. Sia-Kho E, Kudlak T. How to Dislodge a Severely Trapped Epidural Catheter. Anesth Analg 74:929, 1992.

5. Blackshear R, Gravenstein N, Rodson E. Tension applied to Lumbar Epidural Catheters during Removal is much Greater with Patient Sitting versus Lying. Anesthesiology 75:A833, 1991.

6. Gadalla F. Removal of a Tenacious Epidural Catheter. Anesth Analg 75:1071-1072, 1992.

7. Pasquariello C, Betz R. A Case for the Removal of the Retained Intrathecal Catheter. Anesth Analg 72:562, 1991.

8. Gravenstein N, Blackshear R, Wissler R. An approach to spinal or epidural catheters that are difficult to remove. Anesthesiology 75:544, 1991.

9. Start R, Greenberg D, Herman N. Use of a Wilson Convex Frame in Removing "Irretrievable" Epidural Catheters. Anesth Analg 75:305-6, 1992.

10. Saberski L, Schwartz J, Greenhouse B, et al. A Unique Complication of a Lumbar Epidural Catheter. Anesthesiology 69:634-5, 1988.

11. Fibuch E, McNitt J, Cussen T. Knotting of the 'Teracath' after an Uneventful Epidural Insertion for Cesarean Delivery. Anesthesiology 73:1293, 1990.

12. McGregor P. A Reply - Knotting. Anesthesiology 73:1293, 1990.