PROVIDING extended analgesia after painful surgery remains one of the main barriers to expanding the types of cases performed on an ambulatory basis. This fundamental obstacle also hampers the compassionate care we provide to many current outpatients because they suffer from inadequate analgesia. Chung et al . helped quantify failure of outpatient pain management and noted that after some orthopedic, urologic, and plastic surgeries, the incidence of severe pain postoperatively was between 40 and 70%. 1Although the introduction of short-acting sedatives, anesthetics, and analgesics has improved the reliability of prompt emergence from anesthesia, postoperative pain and narcotic-related side effects, such as nausea and vomiting, remain major sources of patient dissatisfaction, lead to extended hospital stays, and hamper our ability to progress. Typical regional anesthetic techniques like spinal and epidural blockade that can be used intraoperatively provide little postoperative analgesia to aid recovery in the ambulatory patient. The use of outpatient peripheral nerve blocks is frequently criticized because of the intense pain that may ensue after resolution. As perioperative physicians we are challenged to develop a method of analgesia that is site specific, has few side effects, and can facilitate economic yet compassionate care. Continuous peripheral nerve blocks combined with a simple disposable infusion device that can be used at home may offer a novel solution to part of this problem. In initial nonrandomized reports and comparative trials it has provided excellent analgesia for numerous upper and lower extremity outpatient procedures. 2–6In this issue of Anesthesiology, Rawal et al. 7and Ilfeld et al. 8provide two prospective randomized studies designed to examine the effectiveness of ambulatory continuous peripheral nerve blocks. The results are compelling because both studies found a reduction in pain scores, low opioid consumption, high patient satisfaction, and few logistical obstacles when home continuous peripheral nerve blocks were implemented or compared with standard oral pharmacologic management of postoperative pain.
Continuous peripheral nerve catheters have been an integral part of acute and chronic pain management since first being described by Ansboro 9in 1946. Over the ensuing half-century, numerous clinicians have developed techniques to facilitate catheter placement and manage inpatient treatment. These techniques have been gradually refined, enabling a small group of skilled clinicians to incorporate continuous peripheral nerve catheters into their practice with a high degree of success. Continuous peripheral nerve blocks have been associated with sustained, effective, postoperative analgesia 10–12; opioid-sparing, 13–16improved rehabilitation 17; and improved patient well-being with minimal side effects. It is only natural that with the reevaluation of healthcare spending and the increased interest in expanding ambulatory surgery that this method would be tried on an outpatient basis. This is especially true given the economic success and low morbidity and mortality rates that have accompanied the transition of other hospital-based techniques to the ambulatory environment. Making this next transition successfully, on a larger scale, goes beyond the successful placement of individual catheters. It requires further data, improved training, and careful attention to the discharge and follow-up process.
Discharging patients with an insensate extremity and relying on the patient to self-administer local anesthetic remains controversial. Concerns about patient injury from an insensate extremity, catheter migration, and the potential for local anesthetic toxicity persist. Despite the encouraging results in these two randomized prospective trials, further data with larger patient samples will be necessary to confirm safety. In both studies in this issue, the investigators instituted several mechanisms to maximize patient safety that have been prevalent in the initial nonrandomized trials of home perineural infusions. Both Rawal et al. 7and Ilfeld et al. 8required study participants to display comprehension of the verbal and written instructions they were provided, and both teams required the presence of a chaperon. A common theme in several case reports is the careful attention paid to avoidance of inadvertent vascular catheter placement. This is typically done by injecting a large test dose of local anesthetic with epinephrine via the catheter before discharge to ensure the catheter tip is not misplaced. Perhaps more importantly, both groups used diluted concentrations of local anesthetic that have already been found to be safe in inpatients. These concentrations ideally should minimize motor block and provide a margin of safety if delivered intravascularly. This strategy is well articulated in the Rawal et al. 7discussion. In addition, both teams provided an available physician to answer questions by telephone. The importance of this was emphasized by Ilfeld et al. 8who reported that 30% of patients exercised this resource, despite being discharged with verbal and written instructions. Finally, daily telephone calls were placed to each patient to obtain data and to confirm safety.
While both sets of authors in this journal use different catheter insertion techniques, each with their individual advantages, both groups have developed expertise and a system that allows for effective economic use. Centers that do not have the capacity or the physicians to develop this infrastructure or expertise may not feel comfortable using peripheral nerve catheters or transitioning from inpatient catheter use to outpatient implementation. Clearly, competency must be gained first, and currently, these techniques are not widely taught. Large differences exist among training programs for effectiveness in teaching regional anesthesia. Most centers continue to provide adequate training in centroneuraxial techniques, but the majority still does not provide adequate training for peripheral nerve blocks, despite their increased use in outpatient surgery. 18This was demonstrated by Kopacz and Neal 19who documented that the median number of peripheral nerve blocks performed in residency is only 45, and most are associated with pain procedures and not operative anesthetics. This compares with epidural anesthesia, which relies on a similar complexity of equipment, takes similar organization to efficiently place, and relies on dexterity, but is performed 175 times (median) during residency. 19
Given this disparity in teaching peripheral nerve blocks it is no wonder that some practitioners report intermittent success with continuous techniques and find them too time-consuming, while others achieve excellent results and continue to expand their use. As specialists, we should be wary of new claims and insist on data to ensure safety. But we must also be cautious not to discount new techniques that may greatly augment our treatment capability because they seem difficult or beyond our initial training. It is interesting to note that similar difficulties, resistance, and observations accompanied the transition of spinal anesthesia into mainstream acceptance and had to be rigorously defended by its pioneers. Sixty-eight years after the introduction of spinal anesthesia, Drs. Moore and Bridenbaugh at the Mason Clinic still had to defend the technique's efficacy and devote time to proving paralysis was unlikely. 20
Although more research defining the limits for outpatient use of peripheral nerve catheters is necessary to fully characterize the indications, limitations, infusion rates, and delivery devices, the work of Rawal et al. 7and Ilfeld et al. 8demonstrates the potential for these techniques to become routine aspects of anesthesia care. But further training of both residents and established practitioners will be essential.
Continuous outpatient peripheral nerve catheters have the advantage of providing site- specific, dense, extended analgesia with systems and solutions that are readily available. 21Developing this area of anesthesia is essential to increasing the scale and scope of surgery that is compassionately performed on an outpatient basis. It is also crucial to enhancing the quality of care for surgical procedures that are already considered appropriate for ambulatory centers. Given the anesthetic and economic success of ensuring rapid turnover and quick emergence in ambulatory surgery, refocusing perioperative attention beyond the hospital toward extended analgesia and broader economic concerns seems an appropriate path for our profession to follow. The authors of the studies in this issue should be commended, not only for their evidence demonstrating that continuous outpatient catheters are feasible, but also for looking beyond the operating room and scientifically exploring a technique that promises to improve the overall perioperative experience.
