Continuous catheterized nerve blockade provides effective analgesia, reduced incidence of side effects, and improved quality of life for patients undergoing orthopedic surgery.1,2 Catheter insertion usually involves feeding a catheter through a Tuohy needle towards the target nerve (i.e., catheter-through-needle technique). This technique poses several challenges, and the most important of these is avoidance of leakage at the catheter insertion site. Leakage can result when the puncture hole left after withdrawal of the needle is larger in diameter than that of the catheter. As illustrated in the following case report, this poses a risk of infection during shoulder surgery since any fluid leakage can potentially contaminate the operative field when the patient is in a seated position. We also describe the use of a non-traditional method of catheterization chosen to reduce the risk of leakage. Written consent was obtained from the patient for publication of this report.

Case

A 62-yr-old male was scheduled for a right total shoulder arthroplasty. Apart from chronic shoulder pain, the patient’s medical history was significant for moderate obstructive sleep apnea that required a 5-cm H2O positive airway pressure (CPAP) while sleeping. Following application of routine monitors in the area of the block procedure, an interscalene catheter was inserted preoperatively under ultrasound guidance with a 13-6 MHz high-frequency linear transducer (HFL 38, M-Turbo; SonoSite, Bothell, WA, USA). Nerve stimulation was also used to monitor needle placement. After a local anesthetic wheal was raised, an 18G 100-mm Tuohy needle (Contiplex® Tuohy set, B.Braun, Melsungen AG, Germany) was inserted between the C6 and C7 roots until the needle tip was positioned just lateral to the anterior scalene muscle, 5 cm from the insertion point. Once the needle tip position was confirmed by visualizing the spread of 3 mL of 5% dextrose in water (D5W), 20 mL of local anesthetic (1% ropivacaine and 0.25% bupivacaine 1:1) were used to hydrodissect the space between the sheath and the roots. Ten centimeters of a 20G catheter were fed through an 18G Tuohy needle until 5 cm of the catheter protruded from the needle tip. After removal of the Tuohy needle, the catheter was secured to the patient’s skin at the 13-cm mark. Attempts were made to identify the catheter tip under ultrasound visualization, but it was difficult despite being able to visualize the spread within the sheath surrounding the roots. The catheter was secured with Epi-Guard™ (1 x REF: 8170 LiNA Medical ApS, Copenhagen MedLab, Denmark) and Tegaderm™ (3 M Health Care, St Paul, MN, USA). The procedure from skin puncture with the Tuohy needle to the application of the final piece of Tegaderm™ was performed within 15 minutes. After the tapes were applied, a pocket of accumulated fluid was detected around the catheter insertion site, a common occurrence with this technique.

The patient was transferred to the operating room. Following application of routine monitors, uneventful induction of general anesthesia, and tracheal intubation, leakage from the catheter insertion site become gradually more noticeable after the patient was placed in the beach chair position. The fluid also started to disturb the adhesives of the surgical drapes and began leaking into the potential operative site. The dressing was removed and new dressings were reapplied after the area was wiped; however, the surgeon, concerned about the continual slow leakage, requested that the catheter be removed to avoid potential contamination of the sterile surgical field. The surgery lasted three hours and anesthesia proceeded uneventfully. When the patient was wide awake in the postanesthesia care unit, he agreed to have the interscalene catheter reinserted using an alternative catheter-over-needle technique. A 21G x 95-mm catheter-over-needle unit (MultiSet UPK NanoLine 21156-40E, Pajunk, Germany; 21G refers to needle size) (Fig. 1) was directed towards the interscalene groove between the C6 and C7 roots (Fig. 2). Hydrodissection with D5W enabled the needle/catheter unit (Fig. 1B) to traverse between the roots immediately lateral to the anterior scalene muscle without piercing through into the muscle (Fig. 3). Five millilitres of local anesthetic were injected to hydrodissect the space between the sheath and the roots following negative aspiration of blood or fluid. The needle was removed, and a flexible 20G x 75-mm inner catheter was inserted through the 18G outer catheter and locked in place with the Luer lock (Fig. 1D). A further 5-mL local anesthetic bolus was given via the catheter, and both the catheter tip and local anesthetic spread were visualized under ultrasound (Fig. 4). After the bolus, no leakage was observed at the site of catheter insertion. Epi-Guard and Tegaderm were used to secure the catheter, and no leakage was observed beneath the dressing or at the needle entry site. The time from skin puncture to the application of the final piece of Tegaderm was less than six minutes. A good sensory block was achieved in the C5, C6, and C7 distribution. The local anesthetic infusion continued for two days, and the patient remained comfortable with a visual analogue scale score < 3 throughout this recovery period without requirement for opioids or other co-analgesics. The catheter was removed without any evidence of kinking or leakage, and the dressing remained dry and intact at 72 hr postoperatively.

Fig. 1
figure 1

A) A photograph of the catheter-over-needle unit (MultiSet UPK NanoLine, Pajunk, Germany). B) The catheter-over-needle unit prior to withdrawal of the needle. C) A zoomed-in photograph showing the 21G needle housed within the 18G outer catheter and the needle tip protruding from the catheter. D) The catheter unit containing the 20G inner catheter within the outer catheter secured in place by the Luer lock (bottom) following withdrawal of the needle. E) A zoomed-in photograph showing the protruding tip of the inner catheter beyond the outer catheter

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Fig. 2
figure 2

An ultrasound image showing the catheter-over-needle unit approaching the roots between C6 and C7 in an in-plane approach using the high-frequency linear array transducer

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Fig. 3
figure 3

An ultrasound image showing hydrodissection using D5 W via the catheter-through-needle unit, adopting an in-plane approach with the high-frequency linear transducer. This technique allows the unit to traverse between the C6 and C7 roots

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Fig. 4
figure 4

An ultrasound image showing the two hyperechoic lines of the 20G inner catheter within the 18G outer catheter (see Fig. 1D). The spread of local anesthetic within the neural sheath is also shown

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Discussion

This case report serves to remind anesthesiologists that leakage from the catheter entry site remains a troublesome and potentially hazardous issue during continuous peripheral nerve block. As illustrated by this case, leakage continued and worsened despite efforts to dry the area and reapply dressings when the patient was in a seated position. Consequently, removal of the catheter was required. In cases like these, leakage is due to the loose fit of the catheter within the puncture hole left by the larger diameter Tuohy needle and results in backflow of local anesthetic along the outer wall of the catheter and onto the skin. Indeed, the surgeon expressed that leakage was a common occurrence and should be addressed.

In this case, we have shown the successful use of an alternative catheter-over-needle design to minimize the risk of leakage from the catheter entry site. This approach turned out to be particularly vital for shoulder surgery with the patient in the beach chair position. The advantage of this catheter design is that the catheter is left in a puncture hole created by a needle whose diameter is smaller than the catheter. This results in a “tight fit” between the catheter and the skin and prevents leakage.3 It ensures a dry skin area, which enables the dressing to adhere securely to the skin, prevents dislodgement, and reduces the likelihood of the catheter slipping out.

Although not a novel concept, the catheter-over-needle design is rarely used for regional blocks, even though similar well-described catheter-over-needle assemblies, such as the 20G bullet-tipped needle/catheter (Arrow International, Reading, PA, USA),4 Contiplex® D set (B.Braun, Melsungen AG, Germany),5 and MultiSet (Pajunk, Geisingen, Germany),6 have been marketed by several companies for many years. However, such assemblies were not used on their own since they are known to be susceptible to kinking and are limited by the fixed length of the catheter. Additionally, in these designs, the catheter sheath is typically made from smooth thin Teflon-like materials that facilitate easy skin puncture but render the catheter susceptible to kinking. The design of the new catheter system described here consists of two components, each made of material with distinct properties. The outer catheter’s Teflon-like material and tapered distal end allow easy insertion into the skin. The inner catheter is made from polyamide, a soft flexible material that (Fig. 1D) provides reinforcement and kink-free flexibility to the entire unit when housed inside the outer catheter.

The introduction of ultrasound guidance has mitigated the problem of the limited length of the catheter-over-needle assembly. In the past, most catheters were placed blindly under nerve stimulation, and the optimum length of catheter required to reach the target nerve was largely unknown. To account for this, regional anesthesiologists typically inserted an excess length of catheter in an attempt to prevent dislodgement. The introduction of ultrasound has allowed better prediction of target nerve depth and visualization of catheter positioning in real time.7,8 With this advancement, an appropriate length of needle/catheter set can now be selected to place the catheter tip accurately in desired proximity to a target nerve. The catheter-over-needle technique facilitates positioning the distal end of the outer catheter at the approximate position of the needle tip (Fig. 1B). As such, the catheter/needle assembly can be used in conjunction with electrical stimulation since the uninsulated needle tip protrudes from the catheter (Fig. 1C). After withdrawal of the needle, the inner catheter can be positioned to protrude variably from the distal tip of the outer catheter (Fig. 1E), allowing greater flexibility and accuracy in catheter tip placement within the perineural space and ensuring proper delivery of local anesthetic. This approach also avoids the inherent need associated with traditional catheter-through-needle designs to “over-feed” the catheter. This method of catheter insertion also seems to facilitate better visualization of the catheter tip since a layer of air is created between the two catheters when the inner catheter is placed inside the outer catheter. This results in easily visualized double hyperechoic lines on ultrasound (Fig. 4). Moreover, the catheter-over-needle design is widely used in intravenous fluid delivery systems and is therefore familiar to health care personnel in both function and handling and may be associated with a relatively short learning period.

Alternative methods for securing catheters include the application of adhesive glue9,10 and tunnelling the catheter under the skin.11 Dermabond® Topical Skin Adhesive (2-octyl cyanoacrylate; Ethicon, Somerville, NJ, USA) is a sterile liquid that polymerizes rapidly upon contact with the skin and forms a waterproof connection with the keratin in the epidermis. However, Dermabond® is costly, and patients can potentially suffer from severe allergic reaction12 and contact dermatitis.13-15 Also, removal of catheters secured by Dermabond® and tunnelling may be uncomfortable for the patient. Following this case, we have been successfully using the catheter-over-needle method preoperatively for total shoulder arthroplasty when patients are placed in the beach chair position. This technique has earned our surgical colleagues’ confidence and has been adapted into routine practice at our institution.

In summary, this case report draws attention to the issue of leakage of nerve block catheters and describes a potential solution to maintain the sterility of the surgical field in patients undergoing shoulder surgery. Our experience suggests that insertion of catheter-over-needle assemblies is both easy to perform and time efficient. More importantly, these catheters are effective in delivering local anesthetic via infusion for two days without dislodgement. In the time period following this case, we have been using the catheter-over-needle unit to perform interscalene nerve blocks, and no leakage has been detected at the catheter insertion site even when the patient is in the beach chair position. This enables our surgical colleagues to operate with the confidence that leakage from the catheter entry site will not contaminate the surgical field. Further studies are necessary to assess the qualities, effectiveness, and insertion techniques of these catheters compared with traditional catheter designs to ensure optimal drug delivery systems for optimizing perioperative analgesia while minimizing untoward effects.