Epidural catheter block is not uncommon, its causes and management has been discussed.

1. Blocked Epidural Catheter; its prevention and management
Introduction: Epidural anaesthesia is a central neuraxial block technique
with many applications. It is a popular and versatile anaesthetic
technique which can be used as an anaesthetic, analgesic adjuvant to
general anaesthesia, and for postoperative analgesia in procedures
involving the lower limbs, perineum, pelvis, abdomen and thorax. Both
single injection and catheter techniques can be used. Epidural catheter is
introduced in epidural space through epidural needle except when
surgeon puts it in epidural space during spinal surgery for postoperative
analgesia. The catheter works as a conduit to deliver
anaesthetic/analgesic drugs at target (epidural space) during
intraoperative as well as postoperative period.
Epidural catheter helps to maximize the potential of epidural
anaesthesia in intraoperative as well as in postoperative period. However,
blocking of epidural catheter is a technical snag which results in partial or
complete failure of epidural technique. The potential causes, contributing
factors, and proposed mechanisms of blocked epidural catheter may be
grouped into four major categories: anatomic factors; technique,

2. methodology and equipment; patient-related factors; and technical skills, or
performance factors
In present article the various cause of epidural catheter blockade, its
prevention and management to handle the situation once it has occurred are
discussed.
How epidural catheter get Blocked: Epidural catheter is a thin, hollow
tubular structure of polymers opened at both the ends. The terminal
(epidural) end may have either single or multiple openings depending
upon type of catheter; single port or multiport. The lumen of catheter is
very small and may get obstruct either due to blood-clot or tissue debris
in the lumen or due to kinking and knotting. Catheter migration may
result in or out ward movement of catheter which can result in forward
movement and kinking or coiling in subcutaneous area. Improper
fixation of catheter may also be responsible for blocked epidural catheter
by helping in migration. The obstruction may be due to
manufacturing defect in catheter resulting in absence of terminal
openings. Faulty storage technique of catheters also influences this
complication of catheter block as extreme ambient temperature may

3. cause brittleness in the catheter material. This may lead to cracks or
breakage of catheter and obstruction of catheter lumen.
At times the cause of obstruction is within ‘catheter connector assembly’
through which anaesthetic/analgesic drugs are injected. The causes may
be improper attachment (insertion of catheter in assembly) or
manufacturing defect leading to failure of assembly to function properly.
Blocked epidural catheter; historical perspective: For many years, the
catheters used for epidural anaesthesia were simply "plain tubes”. The cut
end of such catheter was relatively traumatic to the tissues and more likely to
penetrate vessels and get blocked by blood clot. Lee's catheter1 was one of
the first with a smooth non-patent tip and a single lateral eye. Over the years
more lateral eyes were incorporated in catheter-design thinking; lesser
possibility of kinking and block.2, 3Today, the two types of epidural catheter
most commonly used world-wide are the terminal eye variant and the one
with three lateral eyes. There is no substantial proof of superiority of one
design over other (terminal hole vs. multi lateral eyed catheters).4 However,
in one series, 8% of the terminal eye catheters had to be replaced compared
to 2% of the lateral eye catheters.2

4. Catheter migration: Migration has been shown to be relatively
common, occurring in approximately one-third of the patients in one study.5
There were significant positive correlations between outward migration and
weight, body mass index, and depth of the epidural space.5 Conventional
dressings do not always prevent epidural catheter movement into or out of
the epidural space, lack of transparency also prevents observation of the
catheter and the puncture site. The "Op-site" surgical dressing is an adherent
membrane which has prevented epidural catheter migration in 200
obstetrical patients.6 However, migration of an epidural catheter related to
flexion and extension of the Spine can result in subcutaneous coiling and
blockade of epidural catheter. It has been noticed that even with the
application of a firm adhesive dressing anchoring the catheter to the skin, the
catheter can move and coil within the patient.7
Several innovative techniques have been used to prevent catheter
migration and proved superior to the conventional dressing; significant
prevention of catheter migration with “Lockit” than with conventional
dressing (p<.001).8 Tunneling of epidural catheter has also been tried to
prevent migration.9 However, till today there is no such ideal device which
can prevent migration in all cases moreover, they are not always superior to
transparent dressings.10

5. Blood in epidural catheter: Clotted blood in epidural catheter is an
important and common cause of epidural catheter blockade. Blood in
epidural catheter can be due to blood vessel trauma while placing the
catheter, accidental intravenous placement or migration and/or a
deranged coagulation profile. The incidence of unintended intravascular
entry by epidural catheters is estimated to be between 4.9% and 7% in
the obstetrical population11 however, the contribution of blood-clot in
overall incidence of blockade of epidural catheter is not known.
There are various factors responsible for vascular injury by epidural
catheter leading to blocked catheter. Patient with inferior vena cava
(IVC) obstruction have dilated epidural veins which may sustain injury
at the time of epidural catheter placement or later, resulting in accidental
intravascular placement or migration of the catheter.12
Prevention & Management: When blood is seen in catheter, withdrawing
the epidural catheter 1 or 2 cm may be helpful in some cases11 Replacing
the catheter may result in repeated intravascular cannulation13 therefore
strategies to avoid epidural vein cannulation during the initial epidural
catheter placement should be used to avoid complication of blood in
catheter. The risk of intravascular placement of a lumbar epidural

6. catheter may be reduced with the lateral patient position, fluid pre-
distension, a single orifice catheter, a wire-embedded polyurethane
epidural catheter and limiting the depth of catheter insertion to 6 cm or
less.14 If obstruction is due to suspected blood clot; insertion of new
stylet of epidural catheter can be tried to dislodge the clot.15 We have
tried and overcome the problem of catheter block due to blood clot by
using 2ml saline filled syringe. However, it is not recommended because
high pressure generated by small syringe may be harmful to micro filter
and tissues.
Kinking & knotting of epidural catheter: Kinking of an epidural catheter
is a rare complication of epidural analgesia. Kinking of an epidural catheter
may occur at any point between the skin and the epidural space.16 Occlusion
of catheter lumen may occur due to acute bending which is obstructing the
lumen of the catheter17 or may be due to a laminar “pincer,” or knotting of
the catheter.18 Kinking of epidural catheter outside the epidural space and
also in the subcutaneous tissue which became blocked after initial successful
functioning, has been reported by several authors.19,20 There are many case
reports in literature regarding such complications involved single knot near
the distal tip of the catheter21,22,23, 24,25 ,26 or double knot after a combined
spinal-epidural anesthesia27 and thoracic epidural anaesthesia.28Definitive

7. etiology of catheter kinking is not known however, an epidural catheter may
be deflected by anatomical obstacles and can curl back on itself. [Figure-1]
The conclusion of some reports is that insertion of excessive amounts of
catheter into the epidural space is a causative factor in knot formation.27, 29, 30
Prevention: Prevention is the only key factor to avoid such complications
because once knot is formed it’s impossible to deliver epidural drug through
that catheter. Moreover, this may further complicate the situation by
difficulty in removal of catheter. Undue force should be avoided during
catheter insertion to avoid coiling and kinking which may result in knot
formation. Several sources have suggested that advancing the catheter a
certain distance in the epidural space increases the incidence of epidural
catheter knotting. Although, ideal length of catheter to be inserted in
epidural space to avoid kinking/knotting is not known Gozal et al31
recommended the catheter be threaded less than 3 to 4 cm beyond the needle
tip. Browne and Politi32 recommended threading the catheter less than 5 cm.
Muneyuki et al33 reported threading thoracic epidural catheters up to
10 cm without catheter curling. However, some authors have recommended
the insertion of no more than 4 cm of catheter into the epidural space and
some others no more than 5 cm22, 23, 30

8. Management of knotted epidural catheter: Once knotting is suspected
and injection through catheter is not possible, catheter has to be removed.
Multiple reports show that they can often be removed intact with
traction.21,23,,24,25,26,29 However, catheter breakage is a reported risk potentially
entailing extensive surgical exploration.34 Renehan et al26 have suggested an
approach to the management of a trapped lumbar epidural catheter:
1. Gentle traction on the catheter with the patient in various positions
and in various degrees of lumbar flexion and extension. There is some
evidence that the force required for catheter removal is reduced when
the patient is in the lateral decubitus position
2. Determination of the patency of the catheter by attempting to inject
sterile, preservative-free normal saline through the catheter
3. Radiological imaging with radiopaque dye if the catheter is patent or
with a guide wire if the catheter is occluded
4. Radiological evaluation on the position relative to the epidural space
and orientation of a knot to guide the decision on whether consultation
with a surgical specialty is required
If difficulty is anticipated or faced during catheter removal, visualization can
be facilitated with computer tomography (CT) and magnetic resonance
impedance (MRI).35, 36

9. Catheter malfunction and catheter defects: The use of plastic catheters
was first described by Flowers et al. in 1949 the first polymer (plastic) was
polyethylene. It was soon replaced by polyvinyl chloride because of its low
melting point, which, similar to the lacquered silk catheter, made it prone to
swelling and deformity with sterilization. More recent polymers are nylon,
Teflon, polyurethane and silicone which are resistant to deform on routine
use and storage.
Although the rate of isolated manufacture catheter defects is
unknown, it seems to be relatively low. Manufacturing defects in terminal
holes may result in either absence of hole(s),37, 38 or blocked catheter eyes
(mostly terminal eye catheters)2 Manufacturing defects may result in only
narrowing of lumen39 or with absence of terminal eyes which leads to block
in epidural catheter.40 Quality of catheter material may also responsible for
easy kinking and catheter block.41 To avoid this complication a simple pre-
insertion test is helpful to detect catheter with faulty material.42 Goyal M,
43
has suggested using reinforced epidural catheter to avoid the problem of
kinking.

10. Manufacturing defects in Connector assembly: There are several reports
in literature where epidural catheter failed to deliver drugs either in the
beginning while test dose was given or at the subsequent dosing. Other than
the defects in catheter itself 44 (defects in lateral eyes/terminal opening or
catheter tube), connector assembly may be responsible for such ‘blocked
epidural catheter’ incidences.45 Nagi H46 reported an incidence of blocked
epidural catheter where block was in connector assembly due to manufacture
error during the injection moulding process. There are reported incidences
of blocked epidural catheter because the catheter was not inserted into the
connector to its full length.47, 48, 49
Prevention & Management: It’s desirable to detect manufacturing defect
before insertion of epidural catheter by visual inspection and patency testing
of connector assembly and then of catheter by connecting it to connector.
This exercise will easily detect the site of blockade.50Whether air or saline is
ideal for patency testing is not known. However, one report suggested that
defects which are missed by testing with air could have been prevented by
saline.47
Conclusion: Difficult or impossible injection via the epidural catheter can
be a result of several causes, resulting in mechanical obstruction of the

11. epidural catheter at various levels. Apart from accidental kinking,
knotting, axial torsion, and malposition of the catheter, occasional
manufacturing defects of the catheter (e.g., catheter without terminal
helical “eyes”) can lead to this problem. Many of such problems can
simply be avoided by patency test before insertion of catheter. If nothing
works it’s advisable to reinsert the epidural catheter taking precaution by
patency testing of catheter and connector assembly to avoid such
complications. Proper fixation is in integral exercise for proper
functioning of catheter which should be done preferably with transparent
dressing and should be followed by regular check for in-and- out
movement of catheter. This exercise will give early warning to initiate
necessary action.

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19. Figure-1: rolling of epidural catheter on its own during insertion
Dr Ashok Jadon, MD DNB MNAMS
Chief Consultant Anaesthesia
Tata Motors Hospital, Jamshedpur-831004
Ashok.jadon@tatamotors.com
Mob: +919234554341