Blocked Epidural Catheter; its prevention and managementIntroduction: 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 epiduralanaesthesia in intraoperative as well as in postoperative period. However,blocking of epidural catheter is a technical snag which results in partial orcomplete failure of epidural technique. The potential causes, contributingfactors, and proposed mechanisms of blocked epidural catheter may begrouped into four major categories: anatomic factors; technique,
methodology and equipment; patient-related factors; and technical skills, orperformance factors In present article the various cause of epidural catheter blockade, itsprevention and management to handle the situation once it has occurred arediscussed.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
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, thecatheters used for epidural anaesthesia were simply "plain tubes”. The cutend of such catheter was relatively traumatic to the tissues and more likely topenetrate vessels and get blocked by blood clot. Lees catheter1 was one ofthe first with a smooth non-patent tip and a single lateral eye. Over the yearsmore lateral eyes were incorporated in catheter-design thinking; lesserpossibility of kinking and block.2, 3Today, the two types of epidural cathetermost commonly used world-wide are the terminal eye variant and the onewith three lateral eyes. There is no substantial proof of superiority of onedesign over other (terminal hole vs. multi lateral eyed catheters).4 However,in one series, 8% of the terminal eye catheters had to be replaced comparedto 2% of the lateral eye catheters.2
Catheter migration: Migration has been shown to be relativelycommon, occurring in approximately one-third of the patients in one study.5There were significant positive correlations between outward migration andweight, body mass index, and depth of the epidural space.5 Conventionaldressings do not always prevent epidural catheter movement into or out ofthe epidural space, lack of transparency also prevents observation of thecatheter and the puncture site. The "Op-site" surgical dressing is an adherentmembrane which has prevented epidural catheter migration in 200obstetrical patients.6 However, migration of an epidural catheter related toflexion and extension of the Spine can result in subcutaneous coiling andblockade of epidural catheter. It has been noticed that even with theapplication of a firm adhesive dressing anchoring the catheter to the skin, thecatheter can move and coil within the patient.7 Several innovative techniques have been used to prevent cathetermigration and proved superior to the conventional dressing; significantprevention of catheter migration with “Lockit” than with conventionaldressing (p<.001).8 Tunneling of epidural catheter has also been tried toprevent migration.9 However, till today there is no such ideal device whichcan prevent migration in all cases moreover, they are not always superior totransparent dressings.10
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.12Prevention & 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
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 catheteris a rare complication of epidural analgesia. Kinking of an epidural cathetermay occur at any point between the skin and the epidural space.16 Occlusionof catheter lumen may occur due to acute bending which is obstructing thelumen of the catheter17 or may be due to a laminar “pincer,” or knotting ofthe catheter.18 Kinking of epidural catheter outside the epidural space andalso in the subcutaneous tissue which became blocked after initial successfulfunctioning, has been reported by several authors.19,20 There are many casereports in literature regarding such complications involved single knot nearthe distal tip of the catheter21,22,23, 24,25 ,26 or double knot after a combinedspinal-epidural anesthesia27 and thoracic epidural anaesthesia.28Definitive
etiology of catheter kinking is not known however, an epidural catheter maybe deflected by anatomical obstacles and can curl back on itself. [Figure-1]The conclusion of some reports is that insertion of excessive amounts ofcatheter into the epidural space is a causative factor in knot formation.27, 29, 30Prevention: Prevention is the only key factor to avoid such complicationsbecause once knot is formed it’s impossible to deliver epidural drug throughthat catheter. Moreover, this may further complicate the situation bydifficulty in removal of catheter. Undue force should be avoided duringcatheter insertion to avoid coiling and kinking which may result in knotformation. Several sources have suggested that advancing the catheter acertain distance in the epidural space increases the incidence of epiduralcatheter knotting. Although, ideal length of catheter to be inserted inepidural space to avoid kinking/knotting is not known Gozal et al31recommended the catheter be threaded less than 3 to 4 cm beyond the needletip. Browne and Politi32 recommended threading the catheter less than 5 cm. Muneyuki et al33 reported threading thoracic epidural catheters up to10 cm without catheter curling. However, some authors have recommendedthe insertion of no more than 4 cm of catheter into the epidural space andsome others no more than 5 cm22, 23, 30
Management of knotted epidural catheter: Once knotting is suspectedand injection through catheter is not possible, catheter has to be removed.Multiple reports show that they can often be removed intact withtraction.21,23,,24,25,26,29 However, catheter breakage is a reported risk potentiallyentailing extensive surgical exploration.34 Renehan et al26 have suggested anapproach 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 requiredIf difficulty is anticipated or faced during catheter removal, visualization canbe facilitated with computer tomography (CT) and magnetic resonanceimpedance (MRI).35, 36
Catheter malfunction and catheter defects: The use of plastic catheterswas first described by Flowers et al. in 1949 the first polymer (plastic) waspolyethylene. It was soon replaced by polyvinyl chloride because of its lowmelting point, which, similar to the lacquered silk catheter, made it prone toswelling and deformity with sterilization. More recent polymers are nylon,Teflon, polyurethane and silicone which are resistant to deform on routineuse and storage. Although the rate of isolated manufacture catheter defects isunknown, it seems to be relatively low. Manufacturing defects in terminalholes may result in either absence of hole(s),37, 38 or blocked catheter eyes(mostly terminal eye catheters)2 Manufacturing defects may result in onlynarrowing of lumen39 or with absence of terminal eyes which leads to blockin epidural catheter.40 Quality of catheter material may also responsible foreasy 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 ofkinking.
Manufacturing defects in Connector assembly: There are several reportsin literature where epidural catheter failed to deliver drugs either in thebeginning while test dose was given or at the subsequent dosing. Other thanthe defects in catheter itself 44 (defects in lateral eyes/terminal opening orcatheter tube), connector assembly may be responsible for such ‘blockedepidural catheter’ incidences.45 Nagi H46 reported an incidence of blockedepidural catheter where block was in connector assembly due to manufactureerror during the injection moulding process. There are reported incidencesof blocked epidural catheter because the catheter was not inserted into theconnector to its full length.47, 48, 49Prevention & Management: It’s desirable to detect manufacturing defectbefore insertion of epidural catheter by visual inspection and patency testingof connector assembly and then of catheter by connecting it to connector.This exercise will easily detect the site of blockade.50Whether air or saline isideal for patency testing is not known. However, one report suggested thatdefects which are missed by testing with air could have been prevented bysaline.47Conclusion: Difficult or impossible injection via the epidural catheter can be a result of several causes, resulting in mechanical obstruction of the
epidural catheter at various levels. Apart from accidental kinking,knotting, axial torsion, and malposition of the catheter, occasionalmanufacturing defects of the catheter (e.g., catheter without terminalhelical “eyes”) can lead to this problem. Many of such problems cansimply be avoided by patency test before insertion of catheter. If nothingworks it’s advisable to reinsert the epidural catheter taking precaution bypatency testing of catheter and connector assembly to avoid suchcomplications. Proper fixation is in integral exercise for properfunctioning of catheter which should be done preferably with transparentdressing and should be followed by regular check for in-and- outmovement of catheter. This exercise will give early warning to initiatenecessary action.
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Figure-1: rolling of epidural catheter on its own during insertionDr Ashok Jadon, MD DNB MNAMSChief Consultant AnaesthesiaTata Motors Hospital, Jamshedpur-831004Ashok.firstname.lastname@example.orgMob: +919234554341