While it is possible to place catheters at various anatomic locations, they are not equivalent in terms of analgesic benefit. Likewise, analgesia during the infusion has been demonstrated in several high-quality studies, however positive effect on chronic postoperative pain is lacking in evidence. Interscalene and sciatic catheters provide very potent and satisfactory analgesia, whereas supraclavicular, axillary, and transversus abdominus plane catheters have not shown the same level of effect. Placing an infraclavicular catheter has shown promise from an analgesia standpoint, however the dose required often causes complete anesthesia and motor block of the limb. Femoral and lumbar plexus infusions have shown similar effect, causing weakness that may interfere with the recovery process. Studies have reported a fall risk as high as 5 times that of controls when continuous femoral block is placed.4,5 That is not to say these blocks should not be performed, however the patient should be counseled regarding the possible result of placing a PNC in these locations.
As with any invasive procedure, the risks and benefits must be considered, weighed, and disclosed to the patient. Due to the dependence of results of any procedure on provider technique, it is difficult make overarching statements regarding the incidence and prevalence, but severe complications are very rarely reported. Minor complications are reported at a rate similar to that of single-shot peripheral nerve blocks.2,4 Infusion failure has been reported anywhere from 0.5% to 26%, however it must again be noted that these studies exhibit significant heterogeneity in terms of technique, equipment, catheter location, and infusate regimen. If it difficult to generalize based on these limitations however it should be noted that the adoption of ultrasound guidance has significantly decreased the rate of reported block failure.
Nerve damage is a potential complication that may be anxiety provoking for the patient, however studying the true incidence of neuropathy attributable to use of regional anesthesia is difficult. This is partly due the fact that the surgery itself, tourniquet time, and the prolonged positioning without protective reflexes serve as risk factors for nerve damage. What is known from currently available evidence is that the rate of neuropathy is generally low and symptoms in most cases resolve within a year without treatment.5 Prior nerve injury in the planned location or history of neuropathy are relative contraindications due to the increased risk of recurrence or worsening of neuropathy.3 Professional athletes are not at increased risk, however it may be prudent to forego regional techniques given their dependence on reliable return of neuromuscular function and coordination for their occupation.
A relatively common complication of any perineural catheter is dislodgement or malpositioning leading to block failure, which often leads the provider to take extra measures to secure the catheter at the insertion point, and at the skin, either coiled, glued, anchored, or tunneled to prevent tension on the catheter being transmitted to the tip. There has also been a single report of leakage from the catheter site, causing contamination of the surgical field intraoperatively, but skin adhesives like 2-Octyl cyanoacrylate have been found to decrease the incidence of leakage.5 Extremely rare, however potentially fatal, is migration of the catheter into an intravascular, epidural, intrathecal, or intrapleural location.
Another potentially devastating complication of the use of an indwelling catheter of any type is infection, although the reported incidence is less than 1%. Patients at significant risk include those who are immunosuppressed or otherwise immunocompromised, male gender, diabetics, obese patients, victims of trauma, and those being treated in the ICU. Maintenance of a perineural catheter for more than 48hrs is a modifiable risk factor, while other factors such as aseptic drawing of medication, catheter tunneling, and use of aseptic dressings have not shown significance.9 Axillary, femoral, and even interscalene catheters have been reported to have higher risk of infection. Peri-catheter hematoma is also of concern, specifically in patients maintained on anticoagulants at the time of placement, manipulation, or removal of a neuraxial or “deep” perineural catheter, however there is conflicting evidence regarding this risk in most peripheral blocks. Some researchers have recommended substituting erector spinae, paravertebral, or transversus abdominis plane catheters for an epidural when concern for coagulopathy exists.
Finally, there are alternatives to a perineural catheter ranging from opioid-based analgesia, wound infiltration, cryoanalgesia, acupuncture, percutaneous nerve stimulation, single shot peripheral block with liposomal bupivacaine, or single shot neuraxial, each with its own unique set of risks and benefits.5 Careful selection of appropriate patients for peripheral nerve catheter has shown great success in minimizing the consumption of opioids, an emerging priority in healthcare policy as efforts are increased to eradicate the opioid epidemic. Moreover, research and innovation continue to expand the list of approved indications for placement of peripheral nerve catheter. There are still many questions which remain unanswered, heralding a need for on-going experimentation to expand our collective understanding of continuous regional anesthesia.
References
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