Continuous Plexus and Peripheral Nerve Blocks for Postoperative Analgesia

There is increasing interest in peripheral nerve blocks because of potential benefits and concerns over interactions of anticoagulants and central neuraxial techniques. In a recent survey of members of the American Society of Anesthesiologists and the American Society of Regional Anesthesia and Pain Medicine, nearly half of the respondents anticipated an increased use of peripheral nerve blocks in their practice (1). Continuous plexus and peripheral nerve blocks offer the potential benefits of prolonged analgesia with fewer side effects, greater patient satisfaction, and faster functional recovery after surgery. In this review article, we summarize pertinent anatomy, technical aspects, and current evidence when available in prospective randomized trials for the indications and efficacy of continuous perineural techniques for postoperative analgesia. Brachial Plexus Virtually all published clinical trials have used either an interscalene or axillary approach for placement of continuous catheters, and new anatomic investigations have increased interest in the intersternocleidomastoid (ISCM) approach. Interscalene Approach Initial prospective, randomized, controlled trials demonstrated that the use of continuous interscalene analgesia reduced opioid requirements compared with placebo (2,3) (Table 1A). Compared with IV patient-controlled analgesia (PCA) for open shoulder surgery, prospective, randomized, controlled trials further demonstrated that the use of continuous interscalene analgesia not only reduced requirements for postoperative opioids (4–7), but also provided better analgesia, reduced opioid-related side effects, and provided better patient satisfaction for at least the first 48 h after surgery (Table 1B). Although a case series of 100 patients suggested enhanced physical rehabilitation after shoulder surgery with continuous interscalene analgesia (8), effects on the success of physical rehabilitation or duration of hospitalization are unknown.Table 1: Studies of Continuous: Brachial Plexus AnalgesiaReported success rates of placing an interscalene brachial plexus catheter range from 75% to 100%. Virtually all of these studies used a peripheral-nerve stimulator technique, needle entry in the interscalene groove, and insertion of catheters 5–10 cm into the brachial plexus sheath (3–5,7,9). An interesting modification of the interscalene approach (9) inserts the stimulating needle midway between the mastoid and clavicle and posterior to the posterior border of the clavicular head of the sternocleidomastoid muscle. The needle is advanced caudad and parallel to the vertebral column. After localization of the brachial plexus by the stimulating needle, a metal-tipped catheter that directly allows electrical stimulation is advanced through the needle to confirm accuracy of the final indwelling catheter position. Potential advantages of this technique are that the needle is directed away from the vertebral artery, epidural and subarachnoid space, and the catheter is inserted in a cephalad-to-caudad direction with potentially increased contact surface with the brachial plexus, and decreased block of the phrenic nerve (9,10). One study using this technique reported 100% success rate in catheter placement and an unusually small incidence of phrenic nerve block (25%) with injection of the initial loading dose through the catheter. Another novel technique of interscalene catheter placement is by direct visualization of the brachial plexus in the interscalene groove with real-time ultrasound guidance. One investigation reported successful catheter placement and postoperative analgesia in all 15 patients (11). Further studies are needed to determine optimal technique. Nearly every clinical trial administered a large initial loading dose of local anesthetic suitable for intraoperative anesthesia (20–40 mL of 0.4%–0.5% bupivacaine or 0.4%–0.75% ropivacaine) before initiation of analgesic infusions (2–7,9). The administration of such a large initial loading dose will also block the phrenic nerve (85%–100%), recurrent laryngeal (5%–20%), and sympathetic chain (12%–30%) during interscalene anesthesia (7,9,12). It is unclear what initial loading dose of local anesthetic is optimal if only analgesia is desired. There may be a potential reduction in risk of systemic toxicity and a decrease in undesired neural block with the use of a smaller initial loading dose. For example, smaller doses and concentrations of local anesthetic (0.15%–0.25% bupivacaine or ropivacaine) during continuous analgesia reduced the incidence (0%–75%) and severity (0%–20% reduction in forced vital capacity after 24 h compared with preoperative value) of ipsilateral diaphragmatic paresis (7,9,12,13). Of note, the small reduction in resting and forced respiratory function with interscalene analgesia is similar in magnitude to that seen with IV PCA after open shoulder surgery (7). To evaluate the complications associated with interscalene blocks, 520 patients (234 with placement of a catheter for continuous analgesia and 286 with a single-injection block) undergoing elective shoulder surgeries were prospectively evaluated for 9 mo (14). The study reported a 0.4% incidence of long-term complications associated with interscalene block without differences between catheter and single-injection techniques. Axillary Approach In contrast to documented benefits of continuous interscalene analgesia, definitive benefits from continuous axillary brachial plexus block have not been established. Case series (Table 1C) reported satisfactory analgesia after hand and forearm procedures with continuous axillary brachial plexus infusions (0.2%–0.25% bupivacaine or 0.5% mepivacaine) but have not compared these regimens with IV PCA or other methods of systemic analgesia (15–20). The importance of clinical trials to determine efficacy of this technique is highlighted in a study examining continuous axillary brachial plexus analgesia for elective hand and forearm surgery. Patients received an initial loading dose of 5 mg/kg of 0.75% ropivacaine and were randomized in a double-blinded manner to receive either ropivacaine 0.1% at 0.125 mg · kg−1 · h−1, ropivacaine 0.2% at 0.25 mg · kg−1 · h−1, or saline at 6–11 mL/h for postoperative analgesia (20). There were no differences in analgesia or need for supplemental systemic analgesics (>50% of patients in each group) between patients receiving ropivacaine or saline (Table 1C). Reported success rates from clinical trials and case series for placing a continuous brachial plexus catheter via the axillary approach guided by a nerve stimulator are >90%(15–20). Periarterial (15), perivenous guided by fluoroscopy (16,21), ultrasound-guided (22), and peripheral-nerve stimulator (19,20) techniques have been described for continuous axillary brachial plexus block, but none have been formally compared with each other for continuous analgesia. Thus, the optimal technique remains to be determined. Axillary catheters are typically inserted 3–10 cm into the brachial plexus sheath, but optimal insertion depth is unknown. Determination of optimal insertion depth is of interest because of the anatomy of the axillary brachial plexus. Ultrasound examination of the axillary brachial plexus in 69 healthy volunteers revealed that the median, ulnar, and radial nerves are most compactly arranged at the most proximal aspect of the axilla (lateral edge of pectoralis minor) and steadily diverge away from the axillary artery and each other as one examines more distally (23). This finding suggests that optimal efficacy may be achieved by deeply inserting the catheter to lie as proximally as possible within the axillary brachial plexus sheath, yet the course of catheter travel with greater insertion depth is unknown. ISCM Approach There are no published trials comparing the ISCM approach with conventional systemic analgesic techniques or to continuous interscalene analgesia (24). The proposed advantages to this approach are readily identifiable landmarks for needle insertion, facilitation of catheter placement (Fig. 1), and minimal risk of pneumothorax. A prospective case series of 70 patients undergoing upper extremity surgery (Table 1D) used a continuous infusion of 0.25% bupivacaine with 1:200,000 epinephrine at an average rate of 4 mL/h for 48 h and reported excellent rest (visual analog scale VAS 0–1/10) and dynamic (VAS 2/10) analgesia (24). Using a peripheral nerve stimulator, the reported success rate of placing a catheter via the ISCM approach was 90%. There was one case of subclavian artery hematoma, a 60% incidence of ipsilateral phrenic nerve block, and no cases of pneumothorax (24).Figure 1: Photograph and schematic drawing of the intersternocleidomastoid approach to the brachial plexus. The patient is supine with the head turned away and the sternocleidomastoid (SCM) triangle is identified. The needle insertion point is located 3 cm above the sternal notch along the inner border of the SCM clavicular head. The stimulating needle is directed caudally, dorsally, and laterally toward the midpoint of the clavicle, passing behind the SCM clavicular head, forming a 40°–50° angle with the plane of the operating table. The needle is advanced until the desired motor response is elicited. Note that the trajectory of the needle facilitates catheter placement along the long axis of the brachial plexus sheath. v = vein, a = artery, m = muscle.Lumbar Plexus Femoral Nerve Sheath Approach Prospective clinical trials support the use of continuous femoral analgesia after total knee replacement (25–27). Continuous femoral analgesia provides comparable or better analgesia with fewer side effects than IV PCA and epidural analgesia for at least the first 48 h after surgery (Table 2A). The improved analgesia provided by continuous femoral nerve blocks consistently resulted in faster short-term functional recovery of knee flexion during rehabilitation than IV PCA, but without significant differences between the two groups after 6–12 wk. Although these trials used different discharge criteria, accelerated physical rehabilitation resulted in a 20% reduction in both hospital stay (26,27) and total length of rehabilitation (25,26) with the use of femoral nerve and epidural analgesia versus IV PCA.Table 2: Studies of Continuous Lower Extremity (Lumbar Plexus and Sciatic Nerve) AnalgesiaPreliminary evidence suggests that continuous femoral analgesia may be beneficial after total hip replacement (THR) (28,29). A prospective survey of 1338 patients evaluated the effectiveness of IV PCA, continuous femoral analgesia, or continuous epidural analgesia after THR (Table 2B). Postoperative analgesia during the 48-h trial period was effective in all three groups, but both continuous femoral analgesia and continuous epidural analgesia had significant morphine-sparing effects, with only 8% of these patients requiring any opioid. Continuous femoral analgesia was associated with a significantly less frequent incidence of nausea, vomiting, pruritus, and sedation versus IV PCA, and with a significantly less frequent incidence of urinary retention and arterial hypotension versus continuous epidural analgesia. There was a 0.4% incidence of complications with the use of continuous femoral analgesia. Reported success rates of placing a catheter via the femoral nerve sheath range from 80% to 100% with most studies using a peripheral-nerve stimulator (25–30). Despite documented benefits of femoral sheath analgesia, the extent that the lumbar plexus is blocked via this approach remains uncertain. In most clinical trials, the catheter was typically inserted 10–15 cm into the femoral sheath to maximize cephalad proximity to the lumbar plexus (25–29), but only 40%–90% of patients reported complete lumbar plexus block after 24–48 h of continuous analgesia (29,31). Thus, it is unclear where femoral catheters travel with increased insertion depth, and the optimal depth is unknown. Finally, the required extent of blockade of the lumbar plexus for effective analgesia is unknown. Magnetic resonance imaging of successful single-injection “3-in-1” block showed primarily lateral, medial, and caudal spread of 30 mL of solution without evidence of cephalad spread to the lumbar plexus, yet provided satisfactory analgesia (32). Fascia Iliaca Approach The fascia iliaca compartment (FIC) block is a modification of the femoral nerve block approach and may share similar indications to femoral analgesia (34). A prospective, randomized trial compared continuous FIC analgesia with 0.2% bupivacaine at 10 mL/h to placebo after total knee replacement (Table 2C), and was associated with significantly less morphine consumption and improved range of motion of the knee during the immediate postoperative (24 h) period (35). Case series and prospective trials reported a 95%–100% success in placement of FIC catheters (35–37). The anatomy and technique are described in Figure 2. A prospective randomized study observed 73% of patients with complete block of the lumbar plexus, and computed tomography evaluation revealed that only 40% of catheters were “ideally located” (superior to the upper third of the sacroiliac joint in the psoas sheath). These incidences of incomplete lumbar plexus block are similar to the femoral nerve approach and suggest no obvious superiority for the FIC approach compared with the femoral nerve approach (35).Figure 2: Inguinal structures depicting the anatomic relationships for the fascia iliaca compartment approach compared with the perivascular femoral nerve approach. The patient is placed supine and a cutaneous projection of the inguinal ligament is drawn from the pubic tubercle to the anterior superior iliac spine and trisected. The needle insertion point for the fascia iliaca compartment approach is 1 cm below the junction of the lateral third and middle third of the cutaneous line, approximately 2–3 cm lateral to the femoral artery. The needle is advanced at a 40°–70° angle to the skin until a “loss of resistance” is encountered twice (first through the fascia lata and then the fascia iliaca), indicating entrance into the fascia iliaca compartment. A nerve stimulator technique may also be used. The angle to the skin is then decreased to 30°, and 20 mL of analgesic solution is injected incrementally to expand the compartment. A catheter is advanced 15–20 cm cephalad and then an additional 10 mL of analgesic solution is injected incrementally via the catheter. a = artery, v = vein, n = nerve. Modified with permission from Agur (72).Complications from either the femoral nerve or FIC technique are few. A prospective observational study patients for incidence of and complications after placement of a continuous femoral nerve catheter via either the femoral nerve sheath approach or the FIC approach The catheters were after 48 h and Although was a frequent incidence of catheter only 3 patients with and and not There was only one case of femoral nerve that for 1 and were no complications during the There was no in the rate of complications between the two Approach The lumbar plexus may also be blocked by the psoas compartment provides a more block of the nerve than either the femoral or FIC approach For continuous analgesia, the posterior approach may less for catheter compared with the anterior approach because the the catheter away from an joint is a of large case series or prospective clinical trials the efficacy of continuous psoas compartment analgesia, and are no comparing it with the femoral approach (Table A recent prospective series the efficacy of continuous psoas compartment analgesia ropivacaine at after THR reported a success rate for catheter with of the patients excellent postoperative analgesia at rest and with without the need for systemic opioid One prospective randomized trial compared it with IV PCA with after of hip (Table and reported better analgesia over 3 and a more frequent incidence of patient satisfaction with continuous psoas compartment analgesia case series and clinical trials reported an success rate of placing catheters by this approach at the the anatomy is in Figure the patient in the lateral and side the needle insertion is 3 cm caudad and 5 cm lateral to the the needle is of the will be and within these and of the with a current of proximity of the needle to the lumbar plexus. The catheter is then advanced cm the needle depicting the psoas compartment approach. The patient is placed in the lateral with the extremity The needle insertion point is 3 cm caudal and 5 cm lateral to the A stimulating needle is advanced to the skin and directed until the is The needle is then the superior aspect of the and advanced until stimulation of the is elicited. A catheter is then advanced through the needle, cm the needle into the psoas compartment. m = muscle. [Modified with permission from prospective randomized clinical trial superior analgesia with continuous psoas compartment analgesia versus IV PCA reported success in block of the lumbar plexus during continuous analgesia with 0.25% bupivacaine This in block of the lumbar plexus with continuous analgesia is with recent and tomography indicating that the lumbar nerves lie within the psoas at the vertebral and the of a psoas compartment Sciatic Nerve In a prospective series of patients undergoing continuous nerve block was compared with from a review of patients receiving IV PCA Compared with IV PCA, continuous block was associated with superior analgesia consumption over 48 h in the IV PCA mg compared with 1 mg in the block only 8% of these patients requiring any There was also a significantly less frequent incidence of versus urinary retention versus and sedation versus in the continuous block There were no immediate or long-term complications in the study (Table The posterior approach is with the patient in the position. The skin behind the knee as the of the and the and lateral are to complete the studies revealed that the nerve into the nerve and nerve at a of above the This study that needle insertion 100 above the placement of the needle in the or proximal the of the nerve in 100% of A peripheral needle is at an angle of to the skin to catheter insertion approximately cm the needle The posterior placement of the catheter at an joint potentially for catheter and and one study reported a incidence of either or catheters The lateral approach to the block may offer an for placement of a continuous catheter. the patient supine and the at the knee a stimulating needle is inserted in a plane cm cephalad to the most point of the lateral femoral in the groove between the and Potential advantages are supine patient and more placement of the catheter between the and away from the knee Although this approach may be have been no clinical trials to determine the lateral approach is optimal for continuous analgesia. proximal for continuous analgesia have also been Case series using continuous perineural infusions via a approach the posterior approach of and a novel posterior (Fig. approach reported effective postoperative analgesia in patients undergoing procedures of the and Further clinical trials are needed to the efficacy and superiority of initial insertion and technical of the of these different for continuous perineural approach to continuous perineural analgesia The patient is placed in the lateral with the extremity and the upper approximately The greater and are and a cutaneous projection of the nerve is drawn from the of the to midway between the two A stimulating needle is inserted to the skin to the upper of the and advanced until the desired motor response is elicited. A needle is inserted through the skin approximately 5 cm proximal to the first stimulating needle and to at The electrical is to the needle and advanced until the desired motor response is elicited. A stimulating catheter is then advanced 5–10 cm the needle with electrical stimulation via the catheter to confirm catheter placement along the nerve. Note that the trajectory of the needle placement facilitates catheter placement along the long axis of the for Continuous There are to determine an optimal analgesic solution for the of continuous plexus analgesia. and ropivacaine have all been used as the local anesthetic for continuous plexus analgesia, with bupivacaine and ropivacaine the most used The use of bupivacaine typically not in when used for postoperative analgesia for h in current regimens 1 and total bupivacaine during continuous brachial plexus analgesia are and during continuous lumbar plexus analgesia are are The use of ropivacaine may advantages over bupivacaine and for continuous plexus analgesia. Studies suggest that ropivacaine less motor block compared with may in improved in postoperative rehabilitation A of continuous interscalene analgesia with ropivacaine 0.2% versus bupivacaine observed analgesia in both groups, but significantly less motor block with ropivacaine The potential for systemic toxicity from a large initial loading dose may be a clinical in the decreased of ropivacaine may an over both bupivacaine and studies comparing and bupivacaine suggest toxicity of approximately more the to a smaller initial loading dose of any local anesthetic for only postoperative analgesia may potential but not been formally The of analgesic to local anesthetic potentially the to local motor and blocks, and the of analgesia. The most used and opioids in 1 and There are no studies that have the optimal analgesic for continuous analgesia, and we will review from single-injection peripheral nerve The of epinephrine the duration of single-injection peripheral nerve blocks by and also by via with the of ropivacaine the potential for direct and because concentrations of epinephrine in nerve by in studies by through and by block of local The analgesic effects of are with the effective dose of to local anesthetic a in the duration of analgesia after single-injection peripheral nerve block The of small doses of to for continuous infusions (Table is not and not sedation or hypotension opioid are located primarily on of and their is enhanced in the of peripheral opioid is typically located at the for continuous plexus analgesia, this to be an for analgesia. In a it was that the from the of opioid to single-injection peripheral nerve blocks was in the of these large doses of local anesthetic were used for intraoperative anesthesia 0.5% In a recent it was observed that the of 100 of to mL 0.25% bupivacaine for axillary block provided a in the duration of postoperative analgesia the use of smaller doses and concentrations of local anesthetic suitable for postoperative analgesia may effects of of Continuous Plexus Continuous plexus analgesia may be provided with continuous PCA, or a of infusion and PCA There is a of clinical trials to determine optimal of for each evidence that patient-controlled infusions infusion patient-controlled or patient-controlled may be for of continuous plexus analgesia. The use of these methods allows comparable analgesia and improved patient satisfaction, but with decreased consumption of local compared with continuous infusions without patient-controlled techniques during interscalene analgesia and femoral analgesia (29,31). at the block and to nerve blocks have been to in the one be of the potential for perineural in these patients with of One case described psoas with lumbar after psoas compartment block in a patient receiving of peripheral nerve catheters be for the and the may be to the continuous catheter during a central neuraxial or anesthesia to patient The use of a nerve stimulator not of and a recent clinical study that a needle in axillary block a motor response at in of to the of motor This interesting finding suggests that one a more proximally blocked nerve without evidence of motor stimulation and There is evidence for superior analgesia and a less frequent incidence of opioid-related side effects of continuous perineural infusions compared with IV PCA for open shoulder procedures and total knee but are to for all of continuous plexus analgesia. will need to determine procedures from continuous perineural analgesia, what are optimal analgesic for each and optimal of for each the increased associated with continuous perineural techniques for placement of catheters and of and for postoperative further trials may need to advantages improved analgesia and decreased side effects as decreased hospital length of stay or total length of to their A of importance will be the of continuous plexus analgesia for In a recent patients undergoing upper and extremity procedures were with continuous peripheral nerve block catheters for 24 h within an surgery In this of catheters were functional after 24 and no patients reported complications at 1 and of patients required or IV opioid during the first 24 and this technique is effective for patients remains to be determined. A final will be these techniques local are for peripheral nerve blocks of duration that placement and of a continuous catheter may be more than a injection of a and of such may continuous catheter techniques.