Date Published: June 18, 2012
Publisher: Hindawi Publishing Corporation
Author(s): José Aguirre, Alicia Del Moral, Irina Cobo, Alain Borgeat, Stephan Blumenthal.
A continuous peripheral nerve block (cPNB) is provided in the hospital and ambulatory setting. The most common use of CPNBs is in the peri- and postoperative period but different indications have been described like the treatment of chronic pain such as cancer-induced pain, complex regional pain syndrome or phantom limb pain. The documented benefits strongly depend on the analgesia quality and include decreasing baseline/dynamic pain, reducing additional analgesic requirements, decrease of postoperative joint inflammation and inflammatory markers, sleep disturbances and opioid-related side effects, increase of patient satisfaction and ambulation/functioning improvement, an accelerated resumption of passive joint range-of-motion, reducing time until discharge readiness, decrease in blood loss/blood transfusions, potential reduction of the incidence of postsurgical chronic pain and reduction of costs. Evidence deriving from randomized controlled trials suggests that in some situations there are also prolonged benefits of regional anesthesia after catheter removal in addition to the immediate postoperative effects. Unfortunately, there are only few data demonstrating benefits after catheter removal and the evidence of medium- or long-term improvements in health-related quality of life measures is still lacking. This review will give an overview of the advantages and adverse effects of cPNBs.
Since its first description in 1946, cPNB has evolved from a case report of a needle inserted through a cork taped to a patient’s chest to a wide-spread and validated analgesic technique in the postoperative setting . The earliest reports of cPNB focused on prolonging intraoperative surgical anesthesia and the treatment of intractable hiccups [1–3]. The indication for cPNB has evolved since then, and many indications have been described in the literature: treatment of vasospasm induced by Raynaud disease ; induction of sympathectomy and vasodilation for improvement of blood flow after vascular surgery/trauma [5, 6], replantation or limb salvage [7, 8]; treatment of peripheral embolism [9, 10]; analgesia in the setting of trauma ; treatment of chronic pain syndrome such as trigeminal neuralgia , complex regional pain syndrome , terminal cancer pain, , and phantom limb pain [15, 16]. Independently of these indications, the majority of publications dealing with cPNB focus on postsurgical pain treatment, where evidence supports the concept that regional anesthesia and analgesia offers superior pain relief to systemic opioid analgesia following major surgery . However, postsurgical pain is the only indication which has been validated using randomized controlled trials (RCTs) [18–22]. Compared with opioid analgesics cPNBs provide superior analgesia with a lower incidence of opioid-induced side effects like nausea, vomiting, pruritus, and sedation . Moreover, in a meta-analysis Rodgers et al. suggested that mortality associated with major surgery was reduced by 30% when central regional anesthesia was used combined or not with general anesthesia . On the other hand, a Cochrane review showed no impact of regional anesthesia compared to general anesthesia on mortality after hip fracture. Only the acute postoperative confusion was reduced after regional anesthesia . However, for continuous peripheral regional anesthesia these findings cannot be extrapolated. Though, continuous peripheral regional anesthesia offers improved functional outcomes after extremity surgery at least for a short term period (up to 6 months) [25–27].
In western countries, 50–70% of in hospital patients suffer from moderate-to-severe pain after surgery , and 40% of ambulatory surgical patients have moderate/severe pain during the first 24–48 h . Orthopedic surgery remains the major indication for peripheral nerve blocks for anesthesia and postoperative analgesia . Orthopedic surgery is one of the most if not the most painful surgery [31, 32]. In fact, after orthopedic surgery significant increases in pain scores may persist for 2 to 3 days [33, 34]. In postoperative evaluations of hip and knee surgeries using questionnaires 28% of patients after total hip arthroplasty  and 33% of patients after total knee arthroplasty  suffered from chronic pain. The common finding between these patients was the intensity of immediate postoperative pain. Intense persistent postsurgical pain has indeed been described as a risk factor for the development of chronic pain [37, 38]. Therefore, an improvement in postsurgical pain therapy could be an important factor to reduce pain chronification and its adverse effects on health system costs  (Table 1).
Apart from the classical postoperative setting, cPNB has been successfully introduced in the ambulatory surgery setting for both adults [134, 191] and pediatric patients .
The advantages of sPNB over general anesthesia related to cost-effectiveness in the operation theatre have been recently described by Gonano et al. for shoulder arthroscopy . Authors could show that ultrasound-guided interscalene blocks lead to an improvement of anesthesia-related workflow and to a reduction of postanesthesia care unit (PACU) time compared to general anesthesia. The positive effects of regional anesthesia on the anesthesia-related costs are well known: reduction of postoperative nausea and vomiting, reduced length of stay, successful same day discharge, reduction of unplanned admission or readmission, reduction of multiple-day hospitalizations to single days, earlier discharge, reduction or even elimination of PACU length of stay leading to reduced postoperative nursing interventions, faster discharge times, and reduction of operating room time without increase in turnover time [211, 243–245]. Fredrickson and Stewartcompared recently continuous interscalene nerve block for rotator cuff repair to combined single injection interscalene block with additional postoperative intermittent intra-articular local anaesthetic infiltration and to intermittent intra-articular only local anaesthetic infiltration. Authors concluded that continuous interscalene nerve block following rotator cuff repair in a multiprovider setting was associated with reduced total opioid/tramadol and antiemetic consumption, without a significant increase in the monetary costs .
The impact of cPNBs on analgesia has been described in many RCTs and has been elucidated above . The related dramatic decrease in required supplemental opioids, opioid-related side effects, and sleep disturbances, while simultaneously increasing patient satisfaction are further benefits . Moreover, a decreased time to adequate ambulation with additional optimization of daily activities after ambulatory cPNB compared with intravenous opioids has been described . For continuous regional anesthesia following shoulder and knee arthroplasty, an accelerated improvement of passive joint range of motion potentially leading to shorter hospitalization has been described [25, 27, 216, 230].
Two prospective investigations involving more than 2.100 patients suggest that the incidence of cPNB-related complications is very low and comparable to sPNB techniques [58, 252]. However, different catheter insertion techniques, different anatomic locations, variations in equipment and different infusion regimens make comparisons difficult. In fact, several prospective studies report an incidence of secondary block (during infusion) failure of 1% , 20% , and 50% . Therefore, all reported complications in this chapter cannot be translated to the different clinical practices.
Local anesthetics act on the voltage-gated sodium channels . The Nav1.7is the main channel for pain transmission in the peripheral nerves [286, 287]. Selective blocking of this channel for the postoperative period could be of special interest for ambulant cPNB avoiding the risk of falls. A high selective Nav1.7 local anesthetic would increase the ambulant use of cPNB with probably a remarkable impact in health costs.
The Literature provides a plethora of information involving cPNB, but some aspects of perineural infusion remain controversial: the optimal catheter insertion modality, the optimal technique for each indication, the infusates offering the best safety, standardized local anesthetic delivery regimens, and optimization of continuous ambulatory infusion to reduce possible risks (as falling). The optimal analgesic technique for many surgical procedures has to be further elucidated, and cPNB must be compared with possible new analgesic techniques/regimens .