Continuous Peripheral Nerve Blocks: Fewer Excuses
Klein, Stephen M. M.D.
FOR a technique to become widely adopted, it must address an important need or solve a persistent problem better than available alternative choices. The method must also be efficacious and reproducible and have a favorable side effect and safety profile. Many of these attributes can take years to ascertain despite a long period of use and a sound literature base. In this issue of Anesthesiology, Capdevila et al.1
report on a large prospective multicenter trial examining continuous peripheral nerve blocks after orthopedic surgery with a focus on neurologic and infectious adverse events. Using a nonrandomized design, they followed up 1,416 patients in the postanesthesia care unit and every day for up to 5 days, examining efficacy and complications related to the use of continuous catheters. The results are compelling because they demonstrate excellent analgesic results while providing benchmark data on neurologic outcome, bacterial colonization, and incidence of infection. Perhaps most important, their data provide the best evidence to date that continuous peripheral nerve blocks can be implemented over a broad spectrum of institutions, by different individuals, with uniformly excellent success and a low incidence of complications—effectively challenging many of the excuses for avoiding this technique.
Addressing pain is a cornerstone of our profession. Failure to treat severe pain can have profound negative effects, resulting in increased cardiac stress,2
poor surgical outcome,3
and higher healthcare costs. Despite this, achieving prolonged analgesia after painful orthopedic surgery is a persistent challenge. The intense pain after osteotomy and tissue dissection is especially difficult to treat. Despite multimodal approaches, which include intravenous opioids, patients still rate pain as intense after these procedures.5
Opioid-related side effects still remain an obstacle associated with postoperative nausea and vomiting, sedation, sleep disturbances, respiratory depression, and increased morbidity and costs.6
Central neuraxial techniques such as spinal and epidural blockade are fundamental for lower extremity orthopedic procedures and have been well validated. However, with the increased use of low-molecular-weight heparin and heparin analogs, causing concern about epidural hematoma formation, there is an increasing desire to provide continuous delivery of local anesthetics in a more compliant anatomical compartment.
Historically, one of the most effective ways of addressing this has been the use of continuous peripheral nerve blocks. Since first being described by Ansboro in 1946,7
continuous peripheral nerve catheters have been an integral part of acute and chronic pain management. Over more than half a century, numerous clinicians have developed techniques and equipment to facilitate catheter placement with an increasingly higher rate of success. Randomized clinical trials have refined the optimal infusion strategies and demonstrated uniformly excellent results defined by improved patient well-being and minimal adverse effects.8,9
Despite this body of evidence, wide-scale implementation has been slow. Detractors of the technique often site the inconsistencies in success rates. It is argued that wide-scale application requires infrastructure and specialized skills, factors not currently present in many institutions. Equally important is the concern for safety when a technique is implemented beyond the reported experience in one facility or a small clinical trial protocol. Infection, local anesthetic overdose, and neural injury are concerns commonly voiced as a rationale for not performing continuous nerve blocks.
Previous randomized controlled trials have demonstrated sustained effective postoperative analgesia and opioid sparing when comparing continuous peripheral nerve blocks to single-injection techniques,10
In the current study, the authors move beyond their previous collective works and demonstrate impressive pain control for a wide range of painful orthopedic surgical procedures, including shoulder, elbow, hip, and knee arthroplasty, performed in 1,422 patients. Although this study did not include a comparison group, in the postoperative period, the median visual analog pain scores at rest and during movement were impressive—less than 25 mm out of a possible 100 mm. Equally remarkable was the fact that 75% of patients were able to avoid morphine on the first postoperative day, and 84% were able to avoid morphine 1 day after surgery. Obtaining these results in so many patients undergoing painful orthopedic procedures is truly noteworthy and persuasive.
Equally impressive is the fact that failure of pain relief only occurred in 3% of patients. Catheter failure is a reason often cited for avoiding continuous peripheral nerve blocks, but was not supported here. Similarly, despite the fact that the investigators documented increasing pain scores at 24 h and a high (18%) incidence of technical problems with catheter management, these issues were readily surmountable. Rapid resolution of the surgical block at 24 h likely represents the transition to a less intense analgesic block with dilute local anesthetic and emphasizes the potential need for additional analgesics and strategies during this timeframe. Advances in equipment design and catheter localization may increase precision and decrease technical problems, further enhancing these results.
The potential to cause damage from a percutaneously placed needle has been a consistent concern in regional anesthesia literature. A host of studies have documented a low incidence of complications after continuous catheters.13–16
Most neurologic complications are usually not long lasting, and their etiology is frequently difficult to discern from that associated with the surgery itself. In many respects, this topic has dominated debate and has been a flawed argument or excuse used by anesthesiologist and surgeons alike for avoiding the technique. This is further reinforced in this study, where there were only 0.84% serious adverse events, and only 0.21% of patients had persistent neurologic lesions attributed to the continuous peripheral nerve blocks. In either case, all events resolved without sequelae. The fundamental question is, Are the risks, effort, and maintenance involved in placing these catheters worth the outcome benefits? As we see in this study by Capdevila et al.
the resounding answer is yes.
Infection and colonization from an indwelling foreign body (catheter) is another potential but serious complication that has not received the required level of attention. The relatively few accounts of this complication in the literature suggest that the incidence is low, but only a few studies have set adequate criteria and have been large enough to detect this.14
By diligently collecting data from multiple institutions, Capdevila et al.1
have helped to demonstrate that catheters routinely become colonized (29%) but only 3% have even local inflammatory signs (focal pain, redness, and induration). These signs are associated with a higher rate of colonization (44%), but only one patient in the entire series developed an infection. A psoas muscle abscess and cellulites were detected in woman with diabetes who had a femoral catheter after a total knee replacement. The patient recovered with antibiotic treatment. This finding is important because the true merits of continuous catheters are not briefly extending a single injection block, but rather providing days of safe efficacy to optimize the perioperative experience.
In addition, their specific criteria can also be used to standardize definitions for future trials. By using such a large multicenter design, broader examination of the data can also be performed. This has allowed them to use regression analysis to look at independent risk factors for neurologic and infectious adverse events.
Perhaps the most important aspect of the study by Capdevila et al.1
is not the comprehensive information and follow-up from use of a large number of continuous catheters, but rather their experimental design. They were able to orchestrate a multicenter trial to examine relevant issues that are difficult to assess at a single institution. This created enhanced statistical power to begin examining events that may be rare but important, and it helps to eliminate the criticism that the findings were skewed because of the institution. This spirit of collaboration should not be overlooked. Regional anesthesiologists tend to be enthusiastic and devoted with a firm belief in their techniques. This level of enthusiasm is often viewed with skepticism by those who do not harbor the same passion. The coordination of thought leaders in any field to collaborate is always difficult because of their creativity and independence. For peripheral nerve blocks and catheters, this study is a first.
Ultimately, the greatest strength of the study by Capdevila et al.1
is also its greatest downside. Detractors will still criticize the current study not because of its success but because of the high training and talent level of its participants. Wide-scale reproducibility or “the risk of failure” is still perceived by many as an obstacle to greater implementation. The potential need for an alternative technique and the inherent “failure rate” should not be dissuasive given the growing body of evidence of safety and efficacy in the face of ubiquitous poor pain control offered by systemic analgesic therapy. Based on this and the results of the current study, adopting an alternative perspective seems warranted. Capdevila et al.1
demonstrate in a large population of patients that outstanding analgesia with a favorable side effect profile is obtainable.
Capdevila et al.1
have set a new standard by demonstrating safety and efficacy of continuous peripheral nerve block in a large population of patients. The same standard of a multi-institutional collaboration can be applied in subpopulations such as pediatrics, geriatrics, and those receiving low-dose anticoagulants. These efforts, along with improvements in continuing education, novel teaching designs, and refinements in catheter insertion and precision, may serve to increase use of continuous peripheral nerve blockade and improve patient outcome after surgery.
Stephen M. Klein, M.D.
Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina. email@example.com
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