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Revista Brasileira de Anestesiologia

Print version ISSN 0034-7094

Rev. Bras. Anestesiol. vol.52 no.2 Campinas Mar./Apr. 2002 



Displaced epidural catheter: a reason for analgesia failure. Case report



Edmundo Zarzur, M.D.



Mr. Editor,

The report of an analgesia failure due to epidural catheter displacement was very interesting 1. In fact, the aim was to describe a case of epidural catheter migration to the right major psoas muscle.

In my opinion, some anatomic considerations in addition to questions in an attempt to answer open questions are needed to analyze and discuss the described technique.

The posterior wall of the lumbar vertebral canal is made up of vertebral blades connected by rectangular ligamentum flavum (LF). At L2-L3, LF is 1.2 to 2 cm high and 1.2 to 2.2 cm wide with the major fact that its lateral border is part of the intervertebral foramen posterior wall, thus reinforcing articular process capsules at this site 2. LF internal border connects and proceeds with the neighbor LF internal border forming an angle equal to or smaller than 90 degrees, which opens to the epidural space. The distance from the vertex of this angle to the dural sac varies from 3 to 5 mm.

With this anatomic knowledge and considering the epidural space shape 3 shown below, the conclusion is that the catheter should not be introduced in the epidural space for more than 2 cm because its shape favors the lateral progression of the catheter toward intervertebral foramen nervous roots causing pain or paresthesias. In those cases, it is mandatory to interrupt the technique.

Which was the reason for introducing the catheter 5 to 10 cm, even after confirmed paresthesias? How to explain the catheter escaping to the major psoas muscle, even after crossing the intervertebral foramen?

After confirming analgesia failure and misplacement, the catheter was replaced with good results. My question is: how easy it was to identify the epidural space and how many centimeters of the catheter were introduced?

In their discussion, the authors state that patient controlled analgesia would probably have a good result and that the catheter malpositioning would not have been investigated. One cannot accept this statement because, at the worst, there would be a partial lumbar plexus block resulting in unsatisfactory unilateral analgesia.

In conclusion: to induce an epidural block it is important to have a thorough anatomic knowledge of the region and manual skills to recognize by touch the structures crossed by the puncture needle.

Yours truly.


Edmundo Zarzur, M.D.
Rua Ziembinsky, 314
05086-020 São Paulo, SP





01. Sudbrack G, Geier KO - Cateter peridural deslocado: uma causa de falha de analgesia. Relato de caso. Rev Bras Anestesiol, 2002;52:55-61.

02. Zarzur E - Anatomic studies of the human lumbar ligamentum flavum. Anesth Analg, 1984;63:499-502.

03. Zarzur E - The shape of the humans lumbar vertebral canal. Arq Neuropsiquiatr, 1996;54:451-454.






Karl Otto Geier, M.D.; Guilherme Sudbrack, M.D.



We acknowledge the interest of E. Zarzur - recognized researcher of the spinal canal - for our case report 1. The writer has very adequately presented important anatomic considerations on the lumbar vertebral canal, which allowed us not only to comment the epidural space (ES) fatty tissue, the density of which at the conjugate foramens is a function of young people’s obesity, as opposed to elderly people in whom this tissue, together with the connective tissue, is transformed in a known barrier at this level 2, but also to answer his questions.

a) Although the recommendation by many authors to introduce the epidural catheter no more than 2 cm, at the expenses of unusual situations, such as migrations related to spinal flexion and extesion 2,3, elbowings 4, vascular catheterization 5, pleural and retroperineal space penetration 6, catheter section within the ES 7, subcutaneous malpositioning and lateral displacement in the ES 8, including interweaving with knotting 9,10, some authors have adequately advanced the catheter more than 10 cm, for different reasons.

b) In experienced hands, peripheral paresthesias during lumbar epidural punctures are very rare and, when present, the procedure should be immediately interrupted. On the other hand, paresthesias during catheterization are deemed to be benign because current catheters quality gives them more consistency and flexibility without neural injury 14,15, even when they interweave with knotting in the ES 10,11. Peripheral paresthesias evoked 2 by catheter contact were mild, probably when spinal anesthesia was being induced. We recognize that epidural catheterization was excessive, however, ... intentional, giving us a good margin to pull it during possible readjustment maneuvers and, especially in this case 1, to totally block the lumbar sympathetic nerve in a patient with a severe ischemic vascular disease.

Peripheral microcirculation vasodilation during sympathetic lumbar block is not only an antidote against pre and/or postoperative lower limb ischemic pain, but also a virtue, because we believe that it better nourishes involved tissues, allowing for a better antibiotics and nutrients perfusion to fight local infections and foster tissue healing, respectively.

c) Several are the reasons for the lateral progression of the catheter: diseases, adquired or not, within the spinal canal; ES triangular shape; epidural needle bevel laterally directed in the ES; epidural fat density; patient’s malpositioning, etc. Patient’s intervetebral lumbar foramens were wide, without clamping spinal nerves and not interfering with the epidural catheter displacement, which traveled a short distance through the paravertebral space before entering the psoas muscle through its papery sheath. The explanation for such remains unclear, but it is possible to think about a confrontation of two opposed and unequal forces involving the catheterization strength on the fragile sheath and the smooth muscle fibers of the psoas muscle, with the prevalence of the former. The incidence of catheter displacement through the conjugate foramen during ES catheterization 17,18 varies from 1.6% to 6.7% 20.

d) The catheter 1 was easily replaced and introduced 3 to 5 cm in the cephalad direction, one intervertebral space above;

e) The statement that “If the epidural catheter were inserted in the compartmental space between the greater psoas and the quadratum lumborum muscle, certainly postoperative analgesia would be different. Patient-Controlled Analgesia would have good results and catheter malpositioning would not be investigated”, is incomplete. We are sorry for not having specified that we were talking about the left compartmental space. With the catheter between the quadratum lumborum and psoas muscles, the anesthetic solution would result in a left psoas compartmental block 21 with the involvement of the lumbosacral plexus, or even in an epidural block with possible pain decrease at the hallux amputation site 21;

f) We totally agree with E. Zarzur’s conclusion. Regional anesthesia is art mingled with multidisciplinary science, including anatomy, pharmacology and physiology. The continuous practice of regional anesthesia leads to ability and experience, thus qualifying anesthesiologists to perform a wide variety of anesthetic blocks.

Yours truly.


Karl Otto Geier, M.D.
Guilherme Sudbrack, M.D.
Rua Cel. Camisão, 172
90540-030 Porto Alegre, RS



01. Sudbrack G, Geier KO - Cateter Peridural Deslocado: Uma Causa de Falha de Analgesia. Rev Bras Anestesiol, 2002;52:55-56.

02. Cousins MJ, Bridenbaugh PO - Neural Blockade. Lippincott. Philadelphia, 2nd Ed, 1998;253-260.

03. Mourisse J, Gielen MJM, Hasenbos MAWM et al - Migration of thoracic epidural catheters. Anaesthesia, 1989;44:574-577.

04. Dunbar S - Migration of an epidural catheter related to flexion and extension of the spine. Anesth Analg 1993;76:4:906.

05. Sidhu MS, Asrani RV, Bassell GM - An unusual complication of extradural catheterization in obstetric anaesthesia. Br J Anaesth, 1983;55:473-475.

06. Evans TJ - Detection of intravascularly located epidural catheter. Anesth Analg, 1993;76:203-204.

07. Koch J, Nielsen JU - Rare misplacements of epidural catheters. Anesthesiology, 1986;65:5:556-557.

08. Hopf H-B, Leischik M - More on problems with removing the arrow flex tip epidural catheter: smooth in - Hardly out?. Anesthesiology, 2000;93:1362.

09. Boezaart AP - Computerized axial tomo-epidurographic and radiographic documentation of unilateral epidural analgesia. Can J Anaesth, 1989;36:697-700.

10. Gozal D, Gozal Y, Beilin B - Removal of knotting epidural catheters. Reg Anesth, 1996;21:71-73.

11. Hsin ST, Chang FC, Tsou MY et al - Inadvertent knotting of a thoracic epidural catheter. Acta Anaesthesiol Scand, 2001;45:255-257.

12. Boesenberg AT, Balnd BAR, Schulte-Steinberg O et al - Thoracic epidural anesthesia via caudal route in infants. Anesthesiology, 1988;69:265-269.

13. Rasch DK, Webster DE, Pollard TG et al - Lumbar and thoracic epidural epidural analgesia via the caudal approach for postoperative pain relief in infants and children. Can J Anaesth 1990;37:3:359-362.

14. Lynch J, Trojan S, Arhelger S et al - Intermittent femoral nerve blockade for anterior cruciate ligament repair. Use of a catheter technique in 208 patients. Acta Anaesthesiol Belg, 1991;42:207-212.

15. Sarma VJ - Long-term continuous axillary plexus blockade using 0.25% bupivacaine. Acta Anaesthesiol Scand, 1990;34:391-393.

16. Cousins MJ, Bridenbaugh PR - Epidural Neural Blockade, em: Cousins MJ, Bridenbaugh PR - Neural Blockade, 2nd Ed, Londres. Lippincott, 1988;253-260.

17. Halpenny DG, Loken RG, Williams JA - Transforaminal escape of a lumbar epidural catheter. Can J Anaesth, 1992;39:594-595.

18. Muller A, Sudbrack G - Treatment d’une algodystrophie du genou: erreur de diagnostic et fausse route du cathéter péridural. Ann Fr Anesth Réanim, 1992;11:214-217.

19. Bridenbaugh LD, Moore DC, Bagdi P et al - The position of plastic tubing in continuous block techniques; an x-ray study of 552 patients. Anesthesiology, 1968;29:1047-1049.

20. Sanchez R, Acuna L, Rocha F - An analysis of the radiological visualization of the catheters placed in the epidural space. Br J Anaesth, 1967;39:485-489.

21. Chayen D, Nathan H, Chayen M - The psoas compartment block. Anesthesiology, 1976;45:95-99.

Agradecemos o interesse de E. Zarzur, reconhecido estudioso do canal raquidiano, referente ao relato de caso 1. O missivista expôs, com muita propriedade, considerações anatômicas importantes do canal vertebral lombar o que nos oportuniza, não apenas de comentar sobre o tecido gorduroso no espaço peridural (EP), cuja densidade na altura dos foramens de conjugação é proporcional à obesidade dos indivíduos jovens contrariamente ao que acontece nas pessoas de idade mais avançada quando este tecido junto com o tecido conectivo, transforma-se numa reconhecida barreira a esse nível 2, mas também de esclarecer suas dúvidas.