Peripheral nerve catheters for regional anaesthesia

Learning objectives.

By reading this article, you should be able to:

• •Describe the different characteristics of nerve block needles and catheters and choose the appropriate one for your practice.
• •Implement troubleshooting steps for catheters that are difficult to insert.
• •Evaluate the various methods of securing catheters.
• •Explain the attributes of local anaesthetic catheter regimens and customise them for specific nerve blocks.

Key points.

• •The physical design of nerve block needles and catheters vary to suit specific nerve blocks.
• •Many challenges in catheter placement can be overcome with troubleshooting techniques.
• •Catheters can be secured using multiple methods to prevent dislodgement and failure.
• •Local anaesthetic catheter regimens should be tailored to the type of nerve block.

Peripheral nerve catheters (PNCs) are valuable in managing acute pain, providing superior and more prolonged analgesia compared with opioids or single-shot nerve blocks. They allow for precise titration to achieve optimal pain control while minimising adverse effects such as motor weakness. Moreover, evidence suggests that PNCs reduce opioid consumption, decrease opioid-related adverse effects, enhance patients' satisfaction and improve compliance with physiotherapy.¹ The use of PNCs, compared with opioids, is particularly beneficial for certain groups such as children and those with complex chronic pain. In addition, some centres use ambulatory PNCs to enhance long-term pain management and shorten the duration of hospital stay.²

Although effective for managing acute pain, PNCs are not universally suitable for all patients and procedures. Their use is limited by concerns regarding ongoing motor blockade, the shift towards minimally invasive surgery, and Enhanced Recovery After Surgery protocols that aim to minimise the equipment attached to a patient. Moreover, managing inpatient and ambulatory nerve catheters can be challenging. Alternatives such as liposomal bupivacaine and adjuvant drugs have been shown to modestly prolong the duration of action of a single-shot nerve block.³ Repeat single-shot nerve blocks can be performed, albeit with a potentially greater risk of nerve injury. Peripheral nerve stimulation, traditionally a chronic pain intervention, is also being trialled in the acute setting. Despite these alternatives, nerve catheters remain a valuable technique. This article provides an in-depth review of nerve block needles and catheters, shares practical tips for catheter use, outlines local anaesthetic regimens for continuous peripheral nerve blocks (CPNBs) and explores the use of nerve catheters in ambulatory patients.

Nerve catheter needles

Multiple nerve block needles are commercially available, each with varying physical characteristics. These include needle length, needle gauge, tip design, echogenicity, ability to allow for electrical stimulation and type of catheter interface. These features influence not only the ergonomics of needle use but also the risk of iatrogenic nerve injury.

Needle length

Needle length should be selected based on the depth of the target nerve. Nerve depth can be assessed by performing an initial survey scan using minimal transducer pressure. A needle that is too short will not reach the target, whereas an excessively long needle will reduce manoeuvrability, be prone to bending during advancement and can be challenging to insert through the skin. It is generally recommended that the shortest suitable needle is used. Experimental curved needle designs have been developed to overcome the limitations of the straight needle but remain uncommon in clinical practice.

Needle gauge

Regional anaesthesia block needles typically range from 18 to 22 gauge (G). Larger gauges (e.g. 18 G) offer better ultrasound visibility, increased rigidity and easier manoeuvrability but may cause more tissue trauma and increase the risk of haematoma. In contrast, smaller gauges (e.g. 22 G) cause less tissue disruption but are more prone to bending during use and require higher pressures during injection. Larger gauge needles can compensate for some of the disadvantages of longer needles.

Tip design

Nerve block needle tips are generally classified as either short bevel (30–45°) or long bevel (12–15°). Short-bevel tips are blunter and include the Tuohy needle type; these have been shown to reduce the incidence of nerve damage. In a rabbit sciatic nerve model, Selander and colleagues demonstrated that 45° short-bevel needles cause nerve fascicles to slide or roll away from the needle tip, minimising the risk of injury.⁴ However, if nerve or fascicular penetration occurs, the damage may be more severe.⁵ In contrast, long-bevel (12–15°) needles are more likely to penetrate the perineurium and cause fascicular injury, especially when oriented transversely to the nerve fibres.⁴ However, the resultant injury may be less severe than that caused by short-bevel needles.⁵ Blunt or short-bevel needles typically provide better tactile feedback and produce a noticeable ‘pop’ when passing through a fascial layer. However, they require more force to insert through the skin and fascia, leading to patient discomfort and potential overshooting of the target structure.

Echogenicity

Enhanced echogenicity improves visualisation of the needle shaft with ultrasound. This aids accuracy and safety, especially when performing deep blocks or those requiring steep needle insertion angles. Echogenicity is a function of ultrasound signal reflection that can be enhanced by design features such as surface indentations along the needle and echogenic ‘dots’ created by cornerstone reflectors at the needle tip.

Ability to allow for electrical stimulation

Some nerve block needles allow for electrical stimulation. This enhances nerve localisation and identification and is especially useful when ultrasound visibility is challenging. These needles typically feature a connection port for a nerve stimulator, an insulated shaft and a conductive bevel tip. This design enables delivery of electrical current directly at the needle tip, which will elicit a motor response and confirm accurate needle placement near the target nerve. A novel use of nerve stimulation is to use the absence of muscle twitches to confirm correct positioning between muscle planes, which is particularly relevant for fascial plane blocks.

Catheter interface

There are two main catheter interface designs for block needles: catheter-through-needle (CTN) and catheter-over-needle (CON) (Fig. 1). In the CTN design, the needle creates a puncture hole larger than the catheter, which can lead to injectate leaking back to the skin during injection. In contrast, the CON design produces a smaller skin puncture than the catheter diameter, allowing the catheter to be tightly held by the surrounding skin edges. In a randomised controlled trial comparing the two designs, the CON design significantly reduced injectate leakage compared with the CTN design (6.1% vs 34.4%).⁷ Furthermore, the holding force of the CON catheter was found to be much greater than that of the CTN catheter (mean 3.8N vs 0.4N).⁸ This translates to an approximately seven-fold increase in the pulling force required to pull out a CON compared with a CTN catheter.⁸ However, there are conflicting clinical data regarding whether this translates into fewer catheter dislodgements.^7,9

Fig 1.

(A) Schematic illustration comparing the catheter-through-needle (CTN) design (top) with the catheter-over-needle (CON) design (bottom) for perineural catheter insertion. In the CTN design, the needle puncture hole is larger than the catheter, allowing for potential leakage of local anaesthetic during injection. In contrast, the CON design creates a smaller puncture hole than the catheter, ensuring the catheter is tightly secured by the surrounding skin. (B) Photographs of the CTN (top) and the CON devices (bottom). Images used with permission Tsui B, Ip V. Catheter-over-needle method reduces risk of perineural catheter dislocation. Br J Anaesth 2014; 112: 759–60. [Figure 1], Schematic drawing comparing the catheter-through-needle (top) and catheter-over-needle (bottom) designs for perineural catheter insertion; p. 759.⁶

Types of peripheral nerve catheters

Stimulating and non-stimulating catheters

Nerve-stimulating catheters facilitate confirmation of their position both during and after placement. However, their reliability diminishes after a bolus injection as the contact between the catheter and nerve may shift. In contrast, non-stimulating catheters cannot be used for nerve stimulation.

The combined use of ultrasound guidance and nerve stimulation during catheter insertion is known as ‘dual guidance’. This may offer additional protection against catheter misplacement or iatrogenic nerve injury.¹⁰ However, the evidence supporting these benefits is limited and dual guidance has not been shown to significantly improve the success rates of nerve blocks compared with ultrasound alone.¹⁰

Echogenic or non-echogenic catheters

Echogenic nerve catheters are designed with surface modifications such as textured coatings, indentations or embedded reflective markers that enhance their visibility on ultrasound by increasing the reflection of sound waves. These features improve the contrast between the catheter and surrounding tissues, especially in deeper or more challenging anatomical areas. However, the exact position of the catheter may still be difficult to ascertain because of the three-dimensional nature of a catheter in the human body compared with the two-dimensional ultrasound image. In contrast, non-echogenic catheters are typically made from smooth materials that do not significantly reflect ultrasound waves. This makes them harder to visualise during placement.

Types of catheter tip

Catheters can be either multifenestrated, with multiple openings, or have a single distal opening. Multifenestrated catheters are commonly used for wound infusion or fascial plane blocks, whereas single-opening catheters are better suited for nerve blocks where the catheter is placed directly adjacent to the target nerve. It is important to note that for multiorifice catheters the number of active orifices depends on the injectate flow rate. In an in vivo study, Fegley and colleagues found that infusion rates below 80 ml h^–1 typically used one orifice, rates between 100 and 280 ml h^–1 used two and rates higher than 300 ml h^–1 engaged three orifices.¹¹ Interestingly, higher flow rates were often achieved with boluses of the nerve catheter delivered manually, compared with continuous pump-driven infusions.

Coiling tip catheters

Self-coiling catheters are designed to coil as soon as they are advanced beyond the needle tip. In theory, this helps the catheter tip remain close to its initial placement, even when the nerve is approached perpendicularly. Although research on these catheters is limited, one study reported reduced rates of dislocation and improved analgesia.¹²

Tips for catheter placement

Catheter placement can be challenging and when visualising the target nerve in the short-axis (SAX) orientation, the choice between an in-plane (IP) and out-of-plane (OOP) approach significantly affects the ease and success of the procedure (Fig. 2). The IP technique allows for a continuous view of the catheter tip and facilitates easier advancement, as the needle creates a tunnel in the tissue through which the catheter can pass. This technique may also enhance the stability of the catheter because it is anchored by surrounding tissues. Certain anatomical sites such as the femoral region are particularly well suited to IP catheter insertion.

Fig 2.

(A) Short-axis (SAX) in-plane (IP) approach. (B) SAX out-of-plane (OOP) approach.

In contrast, the OOP approach can be more technically challenging, but it aligns the needle and catheter along the long axis of the target nerve or plexus. This alignment may promote better catheter advancement and has been shown to result in enhanced analgesia for popliteal sciatic catheters, though not for femoral catheters.^13,14 However, because the OOP approach involves a shorter needle path to the nerve, securing the catheter requires extra care to prevent dislodgement.

Tips for catheter placement (Fig. 3):

• (i)Expanding the perineural space with fluid before catheter placement may assist with catheter insertion. If using a nerve stimulator, dextrose is the preferred fluid to use as saline or local anaesthetic may interfere with subsequent motor responses.
• (ii)If resistance is met while advancing the catheter beyond the needle tip, rotating the needle by 45° and withdrawing it slightly (i.e. 0.5 cm) while maintaining correct tip position may help passage of the catheter.
• (iii)Once adjacent to the target nerve in the IP or OOP approach, threading the catheter a few extra centimetres can provide some degree of safety in the event of inadvertent partial catheter withdrawal. In the case of an OOP approach, hydrodissection along the long axis of the nerve will aid positioning of the catheter parallel to the nerve. For superficial targets, the recommendation is to thread 3 cm of the catheter into the desired area, whereas 5 cm is advised for deeper targets.¹⁵
• (iv)Catheter position can be confirmed using nerve stimulation or ultrasound. Fluid or air injected through the catheter can be seen on ultrasound to confirm correct catheter placement. Alternatively, the initial local anaesthetic bolus can be injected through the catheter rather than the needle. Visualisation of the nerve catheter itself on ultrasound is not always possible or necessary.
• (v)The chosen needle path can help preserve catheter efficacy in the face of minor dislodgement. For example, with femoral nerve catheters, a SAX IP approach under the fascia iliaca is ideal (Fig. 4). This ensures that if the catheter is retracted slightly, it remains within the fascia iliaca plane and can still provide some analgesia even if it is no longer directly adjacent to the nerve. In contrast, similar retraction with a SAX OOP approach may result in the catheter being outside the fascia iliaca, rendering it ineffective.

Fig 3.

Tips and troubleshooting steps for nerve catheter placement.

Fig 4.

Suggested approach within the fascia iliaca compartment (femoral nerve coloured) to place a femoral nerve catheter.¹⁶ Adapted with permission. FA, femoral artery; FI, fascia iliaca; FN, femoral neve; IM, iliacus muscle.

Evidence for different methods of securing catheters

Once a nerve catheter is placed, it must be secured to maintain its position and sterility while allowing for movement of the patient. Catheter dislodgement is a common issue that occurs in up to 40% of cases.¹³ This is an issue particularly in high-mobility areas (e.g. neck) or areas prone to friction (e.g. subgluteal catheters). Although several methods exist for securing catheters, no single approach has been shown to be superior.

Catheters shift because of movement at the interface of the skin, subcutaneous tissue and muscles. This can be caused by internal (e.g. muscle movement) or external forces (e.g. pulling on the catheter). To minimise internal movement, inserting the catheter through a longer muscle path provides added stability. Tunnelling can further secure placement and reduce infection risk, although it carries a slight risk of displacement during the process.¹⁷ Protection against external forces may be enhanced by using adhesives or anchoring devices. Dermabond (Ethicon, Somerville, NJ, USA)(2-octylcyanoacrylate) forms a strong seal that lasts 5–10 days and reduces local anaesthetic leakage, outperforming Steri-Strips (3M, Maplewood, MN, USA).¹⁸ StatLock(Bard Medical, Covington, GA, USA)(an anchoring device) is another option that holds the catheter in place against the skin and allows slight catheter withdrawal. However, it may not be as protective against leakage. Although StatLock has shown better fixation than Tegaderm (3M, Maplewood, MN, USA) alone, direct comparisons with Dermabond are lacking.¹⁹ Overall, Dermabond is typically recommended because of its properties of preventing leakage and the infrequent need for catheter adjustment.

The catheter and the catheter dressing also play a key role in ensuring external fixation. Looping the catheter near the insertion site and securing it with Dermabond, topical benzoin or medical adhesive spray improves stability. These adhesives have been shown to significantly increase the force required to dislodge the catheter.²⁰ They should be applied broadly, extending just beyond the edges of the transparent, sterile occlusive dressing (e.g. Tegaderm). In addition, medical tape such as Fixomull (Essity, Stockholm, Sweden) can be used to reinforce the dressing by creating a border around its edges (Supplementary Fig. 1). Clipping excess body hair before catheter placement further enhances fixation.

Risks of peripheral nerve catheters

Although generally safe, PNCs are associated with potential complications. While placing a PNC, accidental vascular puncture has been reported to occur in 5.7% and 6.6% of femoral and sciatic catheters, respectively.²¹ Vascular puncture can also occur in other sites, with the risk being reduced with the use of ultrasound guidance.¹⁰ Difficulty threading the catheter is another potential complication, reported to occur in 9.5% of patients having a femoral nerve catheter placed.²² This risk also differs by site.²³ In the days that follow catheter insertion, catheter dislodgement or migration can lead to secondary failure of the catheter. Local anaesthetic systemic toxicity (LAST) may occur, with limited data indicating an incidence of up to 0.48% with truncal catheters.²⁴ Lastly infection is a potentially serious complication. Studies have reported infrequent occurrences of localised inflammation (0–13.7%), local infection (0–3.2%) and even rarer abscess formation (0–0.9%) around catheters.²⁵ Certain body sites such as the neck or groin are associated with a higher risk of infection.²⁵ Aseptic technique and barrier precautions as per local policy should be followed when placing all nerve catheters, with international consensus recommendations also available.²⁶

The risk of catheter infection is related in part to the duration the PNC has been in situ. Capdevila and colleagues²³ found PNC durations of > 48 h were associated with a higher odds ratio of local inflammation or infection (odds ratio [95% confidence interval], 4.61 [1.57–15.9]). In a prospective study, Neuburger and colleagues found perineural catheters that developed local inflammation or infection were in situ longer than catheters without these complications (median 4.6, 4.6, 4.0 days, respectively). Perineural catheters associated with the development of an infection requiring surgical drainage were in situ for a median of 5.1 days.²⁷ However, inflammation is not always a harbinger of infection. Similarly, a multitude of other factors such as PNC insertion site, aseptic insertion technique, patient immunosuppression and current use of antibiotics affect the incidence of PNC infection.¹⁵ Therefore it is reasonable to keep PNCs in for 3–4 days, with longer durations acceptable if the patient-specific benefits outweigh the risks. If a PNC is kept in for a longer period, diligent monitoring will help to detect any complications. This includes daily observation of the catheter site and connections, monitoring of patient vital signs and of blood test results. The catheter can be tunnelled preemptively to reduce the risk of infection if it is known the catheter will be kept in for a longer period.²⁷

Delivery devices

Infusion pumps are either classified as non-electronic (disposable elastomeric, spring or vacuum powered) or electronic. Electronic and elastomeric pumps are the two most common ways to infuse local anaesthetic through a catheter. Electronic pumps offer superior accuracy, safety and programmability and are interrogatable, even remotely.²⁰ However, they require a power source (although some have a battery) and are traditionally limited to the inpatient setting because of their complexity. In contrast, elastomeric pumps are portable and powered by pressure from an internal elastomeric layer, eliminating the need for electricity.²⁰ They offer various delivery options, including fixed flow rates, basal infusions with on-demand boluses or adjustable flow rates with boluses.²⁰ However, they cannot detect occlusions or malfunctions and their accuracy can be affected by temperature changes.²⁰ The choice of pump type depends on the specific clinical context and the patient’s needs.

Typical local anaesthetic catheter regimens for various blocks

The various regional anaesthetic block types require different concentrations, volumes and delivery frequencies of local anaesthetic. These requirements are affected by nerve thickness, nerve location and type of block (perineural vs fascial plane). Although there is no strong evidence favouring a programmed intermittent bolus (PIB) technique over a continuous infusion (CI) for most blocks, the PIB method is generally preferred. Based on epidural studies, it is believed that intermittent boluses may provide better distribution of local anaesthetic compared with a CI.²⁸ This enhanced spread is particularly important with fascial plane blocks, where block efficacy depends on the degree of local anaesthetic spread within the plane. Furthermore, this improved spread could lead to a greater progressive reduction in the action potential amplitude as the nerve(s) travels through the exposed region, resulting in a more effective conduction block.²⁹ This effect is particularly noticeable with lower concentrations of local anaesthetic.²⁹ The use of patient-controlled rescue boluses, although attractive in theory, has not proved beneficial for all types of block.²⁰ However, it may allow for a reduced baseline infusion rate and potential lowering of the incidence of adverse effects.²⁰

Dilute solutions of long-acting local anaesthetic drugs such as ropivacaine, bupivacaine and levobupivacaine are commonly used in CPNB, providing extended sensory blockade with minimal motor impairment. Although ropivacaine is less toxic both in terms of cardiotoxicity and the maximum dose that can be safely given, bupivacaine can also be used.²⁰ At equipotent doses no significant difference in motor blockade has been observed, with ropivacaine being approximately three-quarters as potent as bupivacaine.³⁰ A key consideration in the management of CPNB is the speed of recovery after discontinuing the infusion. Research indicates that ropivacaine may allow for a faster recovery of sensory and motor function compared with bupivacaine.²⁰ However, the relative significance of local anaesthetic drug concentration compared with total dose in continuous nerve blocks remains debated.²⁰ No consensus has been reached on the optimal anaesthetic concentration for continuous nerve blocks. Typical nerve catheter regimens are suggested in Table 1 and the decision-making process regarding their insertion is shown in Figure 5.

Table 1.

Recommended block-specific analgesic regimens. CI, continuous infusion; LA, local anaesthetic; PCB, patient-controlled bolus; PIB, programmed intermittent bolus.

Block type	Recommended regimen	Notes
Interscalene31	Ropivacaine 0.2% CI OR PIB (2–5 ml h–1), plus PCB (4–5 ml every 30–60 min)	Ropivacaine 0.2% is optimal to maximise analgesia and minimise motor block
Infraclavicular32	Ropivacaine 0.2% CI or PIB (2–5 ml h–1), plus PCB (4–5 ml every 30–60 min)	Similar to interscalene regimen
Erector spinae plane33	20 ml ropivacaine 0.2% as bolus every 4–6 h	Insufficient evidence to favour CI vs PIB
Serratus anterior plane34	20 ml ropivacaine 0.2% as bolus every 4–6 h	PIB regimen preferred, although evidence is limited
Paravertebral35	15 ml ropivacaine 0.2% every 3 h	PIB regimen supported because of enhanced LA spread
Rectus sheath36	15–20 ml ropivacaine 0.2% every 4 h	Intermittent bolus regimen with low concentration LA (extrapolated from other blocks)
Transversus abdominis plane37	15–20 ml ropivacaine 0.375% every 4–6 h or 8 ml h–1 CI	No evidence favouring PIB over CI; higher LA concentrations may be beneficial
Fascia iliaca38	5–10 ml h–1 ropivacaine 0.2% CI	PIB regimens have not been studied
Femoral nerve39	10 ml ropivacaine 0.2% hourly	PIB regimen supported; ropivacaine 0.1% concentration does not prevent motor block and is not recommended
Adductor canal40	10–15 ml ropivacaine 0.2% every 3 h	PIB regimens may improve analgesia, motor function and ambulation

Fig 5.

Decision-making process when inserting peripheral nerve catheters.

Use of ambulatory nerve catheters

Ambulatory catheters have been shown to reduce the length of hospital admissions and enable same-day discharges for many procedures.^2,41,42 Cruz Eng and colleagues randomised patients undergoing complex arthroscopic elbow surgery to either expedited (24-h admission) or control (72-h admission) pathways, with both groups receiving an infraclavicular catheter continued for 60 h after surgery.² The expedited group had similar analgesia and rehabilitation outcomes to the control group, with a 15% lower hospitalisation cost.² Another study reported a reduced time to discharge readiness, defined as achieving adequate analgesia, independence from i.v. analgesics and meeting rehabilitation goals.⁴² However, discharge readiness does not always equate to being discharged, as medical and social factors must be considered. After discharge, ambulatory nerve catheters also improve analgesia, sleep quality and overall comfort.⁴³ This is particularly of benefit in painful surgeries where rehabilitation is key and can be performed out of the hospital.

The risk profile of ambulatory catheters is similar to that of PNCs. However given their use after hospital discharge, certain complications can be difficult to manage. Leakage can disrupt dressings and lead to catheter dislodgement, but the incidence of this in ambulatory catheters is low (5.9%).⁴¹ Infection rates in ambulatory catheters also appear low, with one study reporting an incidence of 1.2% in supraclavicular and popliteal catheters.⁴⁴ Reports of LAST are rare, usually limited to tinnitus.⁴¹ The risk of LAST can be minimised by giving the first bolus of local anaesthetic before discharge (with or without adrenaline [epinephrine] 2.5 μg ml^–1) and by using low concentration local anaesthetic in the reservoir. Pump malfunctions can also occur. An ambulatory PNC programme must monitor for and manage these complications.

Successful implementation of an ambulatory PNC programme requires careful selection of patients, as not all candidates for regional anaesthesia are suitable for ambulatory catheters. Education before surgery is essential and should cover expectations, instructions on caring for the equipment, potential complications, catheter removal and pump functionalities. This information should be repeated at discharge with written material and 24-h contact information provided. Daily follow-up, through phone calls or apps, is effective and most patients are comfortable with home catheter removal, with videoconferencing available for extra support. A follow-up survey of 131 patients who had a variety of ambulatory catheters showed that 98% were comfortable removing it at home themselves.⁴⁵ With proper coordination, ambulatory nerve catheters can improve outcomes and reduce hospital costs.

Conclusions

Peripheral nerve catheters provide effective and long-lasting analgesia, reduce opioid consumption and improve patients’ satisfaction. They are particularly beneficial for specific groups, such as patients with chronic pain, and can be used in ambulatory settings to enhance longer-term pain control and shorten the duration of hospital admissions.

MCQs

The associated MCQs (to support CME/CPD activity) will be accessible at www.bjaed.org/cme/home by subscribers to BJA Education.

Declaration of interests

The authors declare that they have no conflicts of interest.

Biographies

Siaavash Maghami FANZCA is a consultant anaesthetist at Royal Perth Hospital and has completed a regional fellowship at University College London Hospitals, UK.

Toby Ashken FRCA is a consultant anaesthetist at University College London Hospitals and sits on the board of Regional Anaesthesia UK.

Clara Lobo MD is a consultant anaesthesiologist at the Cleveland Clinic, Abu Dhabi.

Matrix codes: 2G01, 2G02, 2G03

Appendix A. Supplementary data

The following is the Supplementary data to this article: