In this article, Morris and colleagues differentiate “translational research” into two types: Type 1 (T1) which refers to experimental testing of basic science research findings in human subjects; and Type 2 (T2) which is the process of taking the results of clinical research and changing clinical practice based on them.
Changing physicians’ behavior is rarely easy (although occasionally it can be), and many smart people have tried to study what works and what doesn’t. One study published in JAMA that focused on physician adherence to practice guidelines identified 7 categories of change barriers (2):
Lack of awareness(don’t know guidelines exist)
Lack of familiarity(know guidelines exist but don’t know the details)
Lack of agreement(don’t agree with recommendations)
Lack of self-efficacy(don’t think they can do it)
Lack of outcome expectancy(don’t think it will work)
Inertia(don’t want to change)
External barriers(want to change but blocked by system factors)
Outside of medicine, many industries have explored the reasons behind failure of change management or failure of implementation and have made suggestions intended to facilitate change. While these recommendations make sense, they are often easier said than done. In health care, there is a great deal of “dogma-logy” (the non-scientific practice of doing what you’ve been told to do based on no available evidence) that must be overcome. Implementation researchers suggest “incremental, context-sensitive, evidence-based management strategies for change implementation” and the need for local champions within front line staff (e.g., nurses and unit managers) to drive change (3). This is consistent with lean management. This still may not be enough, especially if the proposed change is perceived as being overly complex or just more work (4).
The evolution of modern communication may help overcome some of the perceived barriers (2). Use of social media, Twitter in particular, may be a powerful tool to rapidly disseminate new knowledge. It can be used to share new journal articles as they are published or exciting research results even before they are published. Physicians can follow their professional societies and scientific journals, but also follow thought leaders, business schools, and economic journals that post on organizational culture and change management. In the era of Twitter chats and “live-tweeting” medical conferences, lack of awareness (#1) or familiarity (#2) is no longer an acceptable excuse.
In addition, social media networks may also provide moral support (#4) through global conversations, and colleagues may provide real-life examples of successful implementation strategies (#5) that may help generate enough motivation to drive change (#6). However, sometimes inertia may be easy to overcome. According to Dr. Audrey Shafer, Stanford Professor and physician anesthesiologist, “There should be some acknowledgement of the complexity-to-benefit ratio. If complexity of the change is low, and the benefit high, then I believe the behavioral change is swifter. The prime example in my lifetime is the use of pulse oximetry. It may have been a long time from the concept of pulse oximetry until the first viable commercially available oximeter was available in clinical practice, but after an anesthesiologist used it once, he/she did not want to do another case without one.”
That still leaves lack of agreement (#3) and external barriers (#7). Even if you don’t agree with the scientific evidence, at least be open to observe. I really like the design thinking approach as described by Ideo and others and think it has a place in health care change implementation. You can download the free toolkit for educators here. I tweeted Ideo’s figure of the design process with its 5 phases recently and got a great response.
This approach makes a lot of sense in medicine. It has many similarities to the way we approach patient care: observe a diagnostic dilemma, order tests and interpret them, consider the differential diagnosis, attempt a treatment, and adjust treatment based on the observed outcome.
To overcome external barriers to change in health care, senior leaders must be engaged and actively participate in improvement efforts (5). I strongly encourage physicians to step up and take on some of these leadership roles. Sometimes saying “yes” to something that seems relatively small will lead to bigger opportunities down the road. By becoming leaders, physicians can be the ones to drive the change that they want to see in clinical practice.
Knee replacement is one of the most commonly performed operations in the United States with over 700,000 procedures performed annually (1). Besides providing anesthesia care in the operating room, anesthesiologists are dedicated to providing the best perioperative pain management in order to improve patients’ function and facilitate rehabilitation after surgery. In the past, pain management was limited to the use of opioids (narcotics). Opioids only attack pain in one way, and just adding more opioids does not usually lead to better pain control.
In 2012, the American Society of Anesthesiologists (ASA) published its guidelines for acute pain management in the perioperative setting (2). This document recommends “multimodal analgesia” which means that two or more classes of pain medications or therapies, working with different mechanisms of action, should be used in the treatment of acute pain.
While opioids are still important pain medications, they should be combined with other classes of medications known to help relieve postoperative pain unless contraindicated. These include:
Non-steroidal anti-inflammatory drugs (NSAIDs): Examples include ibuprofen, diclofenac, ketorolac, celecoxib. NSAIDs act on the prostaglandin system peripherally and work to decrease inflammation.
Acetaminophen: Acetaminophen acts on central prostaglandin synthesis and provides pain relief through multiple mechanisms.
Gabapentinoids: Examples include gabapentin and pregabalin. These medications are membrane stabilizers that essentially decrease nerve firing.
The ASA also strongly recommends the use of regional analgesic techniques as part of the multimodal analgesic protocol when indicated.
When compared to opioids alone, epidural analgesia produces lower pain scores and shorter time to achieve physical therapy goals (3). However, higher dose of local anesthetic (numbing medicine) may lead to muscle weakness that can limit activity (4). In addition, epidural analgesia can lead to common side effects (urinary retention, dizziness, itchiness) and is not selective for the operative leg, meaning that the non-operative leg may also become numb.
The saphenous nerve is the largest sensory branch of the femoral nerve and can be blocked within the adductor canal to provide postoperative pain relief and facilitate rehabilitation (8, 9). In healthy volunteers, quadriceps strength is better preserved when subjects receive an adductor canal block compared to a femoral nerve block (10).
In actual knee replacement patients, quadriceps function decreases regardless of nerve block type after surgery but to a lesser degree with adductor canal blocks (11). Recently there have been reports of quadriceps weakness resulting from adductor canal blocks and catheters that have affected clinical care (12, 13).
According to a large retrospective study of almost 200,000 cases, the incidence of inpatient falls for patients after TKA is 1.6%, and perioperative use of nerve blocks is not associated with increased risk (14). Patient factors that increase the risk of falls include higher age, male sex, sleep apnea, delirium, anemia requiring blood transfusion, and intraoperative use of general anesthesia (14). The bottom line is that all knee replacement patients are at increased risk for falling due to multiple risk factors, and any clinical pathway should include fall prevention strategies and an emphasis on patient safety.
Other Local Anesthetic Techniques
In addition to a femoral nerve or adductor canal block, a sciatic nerve block is sometimes offered to provide a “complete” block of the leg. There are studies for and against this practice. Arguably, the benefit of a sciatic nerve block does not last beyond the first postoperative day (15). Surgeon-administered local anesthetic around the knee joint (local infiltration analgesia) can be combined with nerve block techniques to provide additional postoperative pain relief for the first few hours after surgery (16, 17).
For more information about anesthetic options for knee replacement, please see my post on My Knee Guide.
American Society of Anesthesiologists Task Force on Acute Pain M: Practice guidelines for acute pain management in the perioperative setting: an updated report by the American Society of Anesthesiologists Task Force on Acute Pain Management. Anesthesiology 2012, 116(2):248-273.
Mahoney OM, Noble PC, Davidson J, Tullos HS: The effect of continuous epidural analgesia on postoperative pain, rehabilitation, and duration of hospitalization in total knee arthroplasty. Clin Orthop Relat Res 1990(260):30-37.
Raj PP, Knarr DC, Vigdorth E, Denson DD, Pither CE, Hartrick CT, Hopson CN, Edstrom HH: Comparison of continuous epidural infusion of a local anesthetic and administration of systemic narcotics in the management of pain after total knee replacement surgery. Anesth Analg 1987, 66(5):401-406.
Chan EY, Fransen M, Parker DA, Assam PN, Chua N: Femoral nerve blocks for acute postoperative pain after knee replacement surgery. Cochrane Database Syst Rev 2014, 5:CD009941.
Barrington MJ, Olive D, Low K, Scott DA, Brittain J, Choong P: Continuous femoral nerve blockade or epidural analgesia after total knee replacement: a prospective randomized controlled trial. Anesth Analg 2005, 101(6):1824-1829.
Jenstrup MT, Jaeger P, Lund J, Fomsgaard JS, Bache S, Mathiesen O, Larsen TK, Dahl JB: Effects of adductor-canal-blockade on pain and ambulation after total knee arthroplasty: a randomized study. Acta Anaesthesiol Scand 2012, 56(3):357-364.
Hanson NA, Allen CJ, Hostetter LS, Nagy R, Derby RE, Slee AE, Arslan A, Auyong DB: Continuous ultrasound-guided adductor canal block for total knee arthroplasty: a randomized, double-blind trial. Anesth Analg 2014, 118(6):1370-1377.
Kwofie MK, Shastri UD, Gadsden JC, Sinha SK, Abrams JH, Xu D, Salviz EA: The effects of ultrasound-guided adductor canal block versus femoral nerve block on quadriceps strength and fall risk: a blinded, randomized trial of volunteers. Reg Anesth Pain Med 2013, 38(4):321-325.
Jaeger P, Zaric D, Fomsgaard JS, Hilsted KL, Bjerregaard J, Gyrn J, Mathiesen O, Larsen TK, Dahl JB: Adductor canal block versus femoral nerve block for analgesia after total knee arthroplasty: a randomized, double-blind study. Reg Anesth Pain Med 2013, 38(6):526-532.
Chen J, Lesser JB, Hadzic A, Reiss W, Resta-Flarer F: Adductor canal block can result in motor block of the quadriceps muscle. Reg Anesth Pain Med 2014, 39(2):170-171.
Veal C, Auyong DB, Hanson NA, Allen CJ, Strodtbeck W: Delayed quadriceps weakness after continuous adductor canal block for total knee arthroplasty: a case report. Acta Anaesthesiol Scand 2014, 58(3):362-364.
Abdallah FW, Brull R: Is sciatic nerve block advantageous when combined with femoral nerve block for postoperative analgesia following total knee arthroplasty? A systematic review. Reg Anesth Pain Med 2011, 36(5):493-498.
Nerve blocks (also referred to as “regional anesthesia”) offer patients many potential advantages in the immediate postoperative period such as decreased pain, nausea and vomiting, and time spent in the recovery room (1,2). However, these beneficial effects are time-limited and do not last beyond the duration of the block (2). While the clinical effects of nerve blocks typically last long enough for patients to meet discharge eligibility from recovery and avoid hospitalization for pain control (3), these results can be easily negated if patients’ pain or opioid-related side effects warrant a return trip to the hospital and readmission following block resolution (4). Thus, extending block duration to provide longer-term, site-specific analgesia for patients on an ambulatory basis has been a high research priority. What options are currently available?
Continuous Peripheral Nerve Blocks
Continuous peripheral nerve block (CPNB) techniques (also known as perineural catheters) permit delivery of local anesthetic solutions to the site of a peripheral nerve on an ongoing basis (5). Portable infusion devices can deliver a solution of plain local anesthetic for days after surgery, often with the ability to titrate the dose up and down or even stop the infusion temporarily when patients feel too numb (6,7). In a meta-analysis comparing CPNB to single-injection peripheral nerve blocks, CPNB results in lower patient-reported worst pain scores and pain scores at rest on postoperative day (POD) 0, 1, and 2 (8). Patients who receive CPNB also experience less nausea, consume less opioids, sleep better, and are more satisfied with pain management (8). We also know how CPNB works: local anesthetic medication interrupts nerve transmission, so patients experience decreased sensation.
Managing CPNB patients (especially at home) can sometimes be challenging, and not all patients are good candidates for outpatient perineural infusion (7). Patients must have a reliable means of follow-up and should have a caretaker at home for at least the first night after surgery (7). A health care provider must be available at all times to manage common issues associated with CPNB and call patients once daily to assess for analgesic efficacy and side effects (9). Patients, especially those undergoing lower extremity surgery, and their caretakers should receive clear instructions regarding the care of their infusion device and catheter as well as their anesthetized extremities (10,11) including fall precautions (12,13).
Although the optimal duration for CPNB is unknown, 2 to 7 days has been reported for orthopedic inpatients (14) with durations as long as 34 days under special circumstances (15). At the completion of the local anesthetic infusion, perineural catheters must be removed. To date, CPNB is the only technique that offers patients the longest potential duration of block paired with the ability to titrate to the desired level of block.
Despite more than a decade of published data supporting CPNB for extending the duration of postoperative pain control, adoption of these techniques is not universal. Many of the issues are arguably system-based, and the lack of a “block” room (16) or time pressure (17) may be responsible. However, lack of training in these techniques may also be a factor (18) or negative experiences with failed placement attempts using traditional techniques (19).
Adjuvants to Local Anesthetic Solutions for Single-Injection Peripheral Nerve Blocks
For nerve blocks intended to last 1-2 days, there are a few options. Long-acting local anesthetics (e.g., bupivacaine, levobupivacaine, and ropivacaine) generally provide analgesia of similar duration for 24 hours or less (20-23). Several different drugs have been investigated for their potential to extend single-injection peripheral nerve block duration when added to local anesthetic solutions. Epinephrine when added to local anesthetic solutions provides vasoconstriction to decrease uptake but has little or no clinical effect on the duration of longer-acting local anesthetics (24). Opioids in general do not provide additional benefits in terms of duration (25) except for buprenorphine (26) although how it works is unclear. To date, there are insufficient data to support the addition of tramadol or neostigmine to local anesthetic solutions (25). Of the available adjuvants, clonidine has been demonstrated in clinical studies and systematic reviews to extend the duration of analgesia for intermediate-acting local anesthetics (e.g., mepivacaine) with few side effects in doses up to 150 mcg but probably do not extend long-acting local anesthetics (25,27). There has been increasing interest in dexamethasone as an adjuvant to local anesthetic solutions based on clinical reports of extended duration when added to intermediate-acting local anesthetics (28,29). The mechanism is not well understood and may be less pronounced with long-acting local anesthetics; one study reported block durations of only 22 hours with dexamethasone added to either ropivacaine or bupivacaine (30). Giving dexamethasone intravenously may actually produce the same effect (31). Caution is warranted when experimenting with adjuvant mixtures that have not been specifically approved for nerve blocks (i.e., “off-label” use) as many of the usual FDA safeguards have not been performed, and these drugs may contribute to neurotoxicity or other side effects not yet known.
Novel Extended-Duration Local Anesthetics
There has been interest in liposomal formulations of extended-release bupivacaine for regional anesthesia for over two decades (32,33). A recent formulation consisting of bupivacaine encapsulated in multivesicular liposomes to produce slow release is FDA-approved for local infiltration (34) but not yet for nerve blocks although this is expected soon. A nerve block with liposomal bupivacaine can be expected to last 1-3 days. Initial nerve block studies in animals suggest a lower maximum serum concentration with the liposomal formulation compared to plain bupivacaine (35)–unless co-administered with lidocaine which facilitates release of liposomal bupivacaine (36)–and epidural administration in human volunteers more than doubles duration of sensory block (37). Once it receives FDA approval, I expect many comparative studies versus CPNB for postoperative analgesia. There are still concerns regarding local anesthetic systemic toxicity with liposomal bupivacaine as well as prolonged motor block and unpleasant numbness given the drug’s long-lasting effects. In addition, there is no option for “giving more” to augment a block in the event of inadequate pain relief.
In summary, there are currently few options to extend the duration of regional analgesia at home beyond the one day expected from most single-injection nerve blocks. CPNB with plain local anesthetic perineural infusion is the most established way to provide days of postoperative pain control and allows titration, but training in insertion techniques and a system to manage ambulatory CPNB patients are necessary. Adjuvants or liposomal formulations of local anesthetics may offer potential options for limited extension of block duration, but further studies regarding efficacy and safety for regional anesthesia as well as comparative-effectiveness versus CPNB are necessary. For major surgery like total knee replacement, block duration of several days may be optimal (38).
Liu SS, Strodtbeck WM, Richman JM, Wu CL: A comparison of regional versus general anesthesia for ambulatory anesthesia: a meta-analysis of randomized controlled trials. Anesth Analg 2005; 101: 1634-42
McCartney CJ, Brull R, Chan VW, Katz J, Abbas S, Graham B, Nova H, Rawson R, Anastakis DJ, von Schroeder H: Early but no long-term benefit of regional compared with general anesthesia for ambulatory hand surgery. Anesthesiology 2004; 101: 461-7
Williams BA, Kentor ML, Vogt MT, Williams JP, Chelly JE, Valalik S, Harner CD, Fu FH: Femoral-sciatic nerve blocks for complex outpatient knee surgery are associated with less postoperative pain before same-day discharge: a review of 1,200 consecutive cases from the period 1996-1999. Anesthesiology 2003; 98: 1206-13
Williams BA, Kentor ML, Vogt MT, Vogt WB, Coley KC, Williams JP, Roberts MS, Chelly JE, Harner CD, Fu FH: Economics of nerve block pain management after anterior cruciate ligament reconstruction: potential hospital cost savings via associated postanesthesia care unit bypass and same-day discharge. Anesthesiology 2004; 100: 697-706
Ilfeld BM: Continuous peripheral nerve blocks: a review of the published evidence. Anesth Analg 2011; 113: 904-25
Ilfeld BM: Continuous peripheral nerve blocks in the hospital and at home. Anesthesiol Clin 2011; 29: 193-211
Ilfeld BM, Enneking FK: Continuous peripheral nerve blocks at home: a review. Anesth Analg 2005; 100: 1822-33
Bingham AE, Fu R, Horn JL, Abrahams MS: Continuous peripheral nerve block compared with single-injection peripheral nerve block: a systematic review and meta-analysis of randomized controlled trials. Reg Anesth Pain Med 2012; 37: 583-94
Ilfeld BM, Esener DE, Morey TE, Enneking FK: Ambulatory perineural infusion: the patients’ perspective. Reg Anesth Pain Med 2003; 28: 418-23
Charous MT, Madison SJ, Suresh PJ, Sandhu NS, Loland VJ, Mariano ER, Donohue MC, Dutton PH, Ferguson EJ, Ilfeld BM: Continuous femoral nerve blocks: varying local anesthetic delivery method (bolus versus basal) to minimize quadriceps motor block while maintaining sensory block. Anesthesiology 2011; 115: 774-81
Ilfeld BM, Moeller LK, Mariano ER, Loland VJ, Stevens-Lapsley JE, Fleisher AS, Girard PJ, Donohue MC, Ferguson EJ, Ball ST: Continuous peripheral nerve blocks: is local anesthetic dose the only factor, or do concentration and volume influence infusion effects as well? Anesthesiology 2010; 112: 347-54
Feibel RJ, Dervin GF, Kim PR, Beaule PE: Major complications associated with femoral nerve catheters for knee arthroplasty: a word of caution. J Arthroplasty 2009; 24: 132-7
Ilfeld BM, Duke KB, Donohue MC: The association between lower extremity continuous peripheral nerve blocks and patient falls after knee and hip arthroplasty. Anesth Analg 2010; 111: 1552-4
Capdevila X, Pirat P, Bringuier S, Gaertner E, Singelyn F, Bernard N, Choquet O, Bouaziz H, Bonnet F: Continuous peripheral nerve blocks in hospital wards after orthopedic surgery: a multicenter prospective analysis of the quality of postoperative analgesia and complications in 1,416 patients. Anesthesiology 2005; 103: 1035-45
Stojadinovic A, Auton A, Peoples GE, McKnight GM, Shields C, Croll SM, Bleckner LL, Winkley J, Maniscalco-Theberge ME, Buckenmaier CC, 3rd: Responding to challenges in modern combat casualty care: innovative use of advanced regional anesthesia. Pain Med 2006; 7: 330-8
Mariano ER, Chu LF, Peinado CR, Mazzei WJ: Anesthesia-controlled time and turnover time for ambulatory upper extremity surgery performed with regional versus general anesthesia. J Clin Anesth 2009; 21: 253-7
Oldman M, McCartney CJ, Leung A, Rawson R, Perlas A, Gadsden J, Chan VW: A survey of orthopedic surgeons’ attitudes and knowledge regarding regional anesthesia. Anesth Analg 2004; 98: 1486-90, table of contents
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Casati A, Borghi B, Fanelli G, Cerchierini E, Santorsola R, Sassoli V, Grispigni C, Torri G: A double-blinded, randomized comparison of either 0.5% levobupivacaine or 0.5% ropivacaine for sciatic nerve block. Anesth Analg 2002; 94: 987-90
Hickey R, Hoffman J, Ramamurthy S: A comparison of ropivacaine 0.5% and bupivacaine 0.5% for brachial plexus block. Anesthesiology 1991; 74: 639-42
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Fanelli G, Casati A, Beccaria P, Aldegheri G, Berti M, Tarantino F, Torri G: A double-blind comparison of ropivacaine, bupivacaine, and mepivacaine during sciatic and femoral nerve blockade. Anesth Analg 1998; 87: 597-600
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Cummings KC, 3rd, Napierkowski DE, Parra-Sanchez I, Kurz A, Dalton JE, Brems JJ, Sessler DI: Effect of dexamethasone on the duration of interscalene nerve blocks with ropivacaine or bupivacaine. Br J Anaesth 2011; 107: 446-53
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The use of ultrasound guidance in the practice of regional anesthesia arguably began in the late 1980s (1), although ultrasound Doppler technology was used to direct needle insertion for peripheral nerve blockade in the 1970s (2). This past decade has seen a rapid increase in practical applications and clinical research in the field of ultrasound-guided regional anesthesia (UGRA), and the American Society of Regional Anesthesia and Pain Medicine (ASRA) and European Society of Regional Anesthesia have even published joint committee guidelines for training in this discipline (3).
Given the rapid adoption of UGRA, evidence to support this practice was initially limited; however, many studies have emerged in an attempt to define the role of ultrasound. In 2010, ASRA published a series of important articles which distill the body of evidence related to UGRA up to that time point (4-13). Additional studies have been completed and published since 2010 and will be included in an update that should be published in the next year.
Ultrasound Guidance for Extremity Peripheral Nerve Blocks
The 2010 ASRA systematic reviews covering this subject include 24 RCTs which compare ultrasound guidance to an alternative nerve localization technique for either upper or lower extremity peripheral nerve blockade (5). For both upper and lower extremity blocks, the majority of studies report faster block onset when ultrasound is employed (5,6,11), although 5 of 15 studies in the upper extremity and 2 of 5 studies in the lower extremity fail to find a difference in onset time (5). There is evidence to support a decrease in procedural time when ultrasound is used for upper and lower extremity blocks (6-11); however, set-up time and pre-scanning with ultrasound are not consistently measured or reported. In terms of block quality, lower extremity studies are more likely to report an advantage with ultrasound than upper extremity studies; only 4 of 16 upper extremity studies show improvement with ultrasound, and these studies use nerve stimulation or transarterial injection as the comparator (5). When a fixed time point is used for assessing block success, ultrasound use is more likely to show an advantage although the definitions of successful block vary widely (6,11). Only one study in the upper extremity shows a difference in block duration in favor of ultrasound while all other RCTs do not demonstrate a difference (5). For femoral and subgluteal sciatic nerve blocks, ultrasound use decreases the minimum effective anesthesia volume to achieve a successful block in 50% of patients (11).
Ultrasound for Continuous Peripheral Nerve Blocks
Although many large case series describing ultrasound-guided techniques for continuous peripheral nerve block (CPNB) performance have been published, there are relatively-fewer RCTs comparing ultrasound to other nerve localization techniques for CPNB. When an exclusively ultrasound-guided technique is compared to a stimulating catheter technique, procedural duration is shorter with ultrasound at four distinct insertion sites (14-17) with less procedure-related pain for lower extremity catheters (14,16) and fewer inadvertent vascular punctures for femoral and infraclavicular catheters (14,15). Most studies report similar analgesia and other acute pain outcomes from catheters placed with ultrasound when compared to other methods (18-20), with the exception of one study involving popliteal-sciatic catheters which suggests that stimulating catheters may provide an analgesic advantage although successful placement occurs less often (21).
Ultrasound for Truncal and Neuraxial Blocks
To date, RCTs comparing ultrasound guidance to traditional techniques for paravertebral blockade or transversus abdominis plane (TAP) blocks have yet to be reported. For both of these procedures, the 2010 ASRA systematic review recommends the use of ultrasound although this recommendation is based on case series data only (4). In one study comparing ultrasound-guided TAP to conventional ilioinguinal/iliohypogastric nerve blocks for inguinal hernia repair, subjects who received ultrasound-guided TAP blocks reported lower pain scores for the first 24 hours (22). Ultrasound-guidance and the landmark-based technique for ilioinguinal/iliohypogastric nerve blocks have been compared in children with the ultrasound-guided technique resulting in decreased need for systemic analgesic supplementation (23). For neuraxial blocks, there is evidence to support ultrasound scanning prior to employing conventional neuraxial block techniques rather than relying solely on surface landmarks (10), especially in patients with challenging anatomy (24).
Ultrasound for Regional Anesthesia in Special Populations
Ultrasound-guided techniques for peripheral (25) and neuraxial (26) blocks in children have been described previously. The 2010 ASRA evidence-based review on ultrasound for pediatric regional anesthesia included 6 RCTs involving peripheral nerve blocks and one randomized trial in neuraxial blockade in addition to case series of >10 patients (12). In this population, ultrasound may improve the speed of block onset and duration of analgesia, increase success rates for truncal blocks compared to blind techniques, and reduce the volume of local anesthetic required (12). In obese patients, ultrasound may play a role in identifying target peripheral and neuraxial structures as well as real-time procedural performance (27). When performing CPNB in obese patients, procedural time is not prolonged compared to non-obese patients when as long as ultrasound is used (28).
In summary, there is sufficient evidence to support the use of ultrasound guidance for peripheral nerve blockade based on short-term outcomes, and the results of a large prospective registry study suggest that ultrasound may decrease in the risk of local anesthetic systemic toxicity (29). Additional prospective studies are needed to further define the role of ultrasound in neuraxial blockade, long-term patient outcomes, and advantages in special populations.
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Sites BD, Chan VW, Neal JM, Weller R, Grau T, Koscielniak-Nielsen ZJ, Ivani G: The American Society of Regional Anesthesia and Pain Medicine and the European Society Of Regional Anaesthesia and Pain Therapy Joint Committee recommendations for education and training in ultrasound-guided regional anesthesia. Reg Anesth Pain Med 2009; 34: 40-6
Abrahams MS, Horn JL, Noles LM, Aziz MF: Evidence-based medicine: ultrasound guidance for truncal blocks. Reg Anesth Pain Med 2010; 35: S36-42
Liu SS, Ngeow J, John RS: Evidence basis for ultrasound-guided block characteristics: onset, quality, and duration. Reg Anesth Pain Med 2010; 35: S26-35
McCartney CJ, Lin L, Shastri U: Evidence basis for the use of ultrasound for upper-extremity blocks. Reg Anesth Pain Med 2010; 35: S10-5
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Neal JM, Brull R, Chan VW, Grant SA, Horn JL, Liu SS, McCartney CJ, Narouze SN, Perlas A, Salinas FV, Sites BD, Tsui BC: The ASRA evidence-based medicine assessment of ultrasound-guided regional anesthesia and pain medicine: Executive summary. Reg Anesth Pain Med 2010; 35: S1-9
Perlas A: Evidence for the use of ultrasound in neuraxial blocks. Reg Anesth Pain Med 2010; 35: S43-6
Salinas FV: Ultrasound and review of evidence for lower extremity peripheral nerve blocks. Reg Anesth Pain Med 2010; 35: S16-25
Tsui BC, Pillay JJ: Evidence-based medicine: Assessment of ultrasound imaging for regional anesthesia in infants, children, and adolescents. Reg Anesth Pain Med 2010; 35: S47-54
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Among Medicare beneficiaries in the United States, the number of primary total knee arthroplasty (TKA) procedures from 1991 to 2010 increased by 161.5% (1). Postoperative pain remains one of patients’ top concerns when undergoing elective surgery (2) and can limit patients’ functional ability in the early postoperative period (3). Providing effective perioperative pain control has potential longer-term implications since early rehabilitation may lead to improvements in functional outcomes later on (4). With the ability to select specific targets for local anesthetic injection and infusion, regional anesthesia techniques, neuraxial and peripheral, are commonly included in the perioperative analgesic protocol for joint arthroplasty patients (5-11). While the data supporting the analgesic efficacy of regional anesthesia techniques in this setting are strongly positive, studies attempting to attribute functional outcome benefits to regional anesthesia demonstrate mixed results.
The main challenge in assessing functional outcomes following joint replacement is the selection of outcomes; these can be divided into performance-based outcomes and self-reported outcomes (12, 13). Performance-based outcomes are measurable and arguably more objective, although often subject to effort. Examples of these outcomes and their units of measure include joint range of motion in degrees (e.g., flexion, extension, rotation); timed walking tests in meters (e.g., 6 minute walking test [6MWT], 2 minute walking test [2MWT]); muscle strength in units of force using a dynamometer (e.g., maximum voluntary isometric contraction [MVIC]); and timed up-and-go (TUG) in minutes (12, 13). Self-reported outcomes are typically survey-based; examples include the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC), Knee Society Score, and Lower Extremity Functional Scale (12, 13). Since patient perception of successful rehabilitation is an important factor, self-reported outcomes should be reported with performance-based outcomes (12). Another important challenge when measuring and comparing functional outcomes is that clinical pathways for joint arthroplasty that integrate pain management (including regional analgesia), physical therapy, nursing, and surgical care are often specific to individual institutions, and institutions may vary with respect to rehabilitation goals and the timeline to achieve them.
Epidural analgesia has been used for perioperative pain management in joint replacement patients since at least the 1980s (14, 15). In 1987, Raj and colleagues compared postoperative systemic opioid analgesia to continuous epidural analgesia (bupivacaine 0.25% at 6-15 ml/hr) for TKA patients in a prospective non-randomized study (14). Although pain scores were lower in the epidural group, not surprisingly a high proportion of these patients experienced complete motor block of the lower extremities; although the authors mention “rigorous passive exercises,” specific rehabilitation outcomes were not reported (14). Later studies have reported functional benefits associated with continuous epidural analgesia, such as shorter time to achieve ambulation distance and range of motion goals, when compared to parenteral opioids alone (16). At institutions where continuous epidural analgesia is currently employed as part of a multimodal analgesic protocol, very low doses of local anesthetic (e.g., 0.06% bupivacaine) in combination with opioid are used in order to minimize motor block (17).
Peripheral Nerve Blocks
The innervation of the knee is complex and involves contributions from both the lumbar and sacral plexuses. While epidural analgesia is effective, it is also associated with clinically-significant side effects (e.g., nausea/vomiting and motor block of the non-operative limb) (5, 18) and the potential for neuraxial hematoma in patients on pharmacologic thromboprophylaxis (19). Thus, peripheral nerve block options, either single-injection or continuous infusions, have been explored for postoperative pain management.
Two early studies by Capdevila (6) and Singelyn (20) have shown continuous femoral nerve block (FNB) to provide comparable analgesia and physical therapy outcome achievement with fewer side effects when compared to epidural analgesia. Both of these studies also demonstrated shorter hospital length of stay for the regional anesthesia groups compared to an opioid-only group (6, 20), but hospitalization duration for these studies was, on average, greater than what has been reported in other studies (21). Triple-masked, placebo-controlled randomized clinical trials have shown that CPNB can shorten the time to achieve discharge criteria, including 100 m ambulation distance, for TKA (10, 22) and total hip arthroplasty (THA) (9) patients, but actual hospital duration was similar in these studies.
One of the interesting findings from the Singelyn study was that regional anesthesia patients maintained a knee flexion advantage over the opioid-only group at 6 week follow-up (20); although this advantage did not remain at 3 months, this finding supported the potential for long-term functional improvement resulting from effective pain management and early rehabilitation in the immediate perioperative period (4). In a randomized comparison of continuous FNB to local infiltration analgesia (LIA) for TKA, the FNB group spent more time out of bed walking; at 6 weeks, the FNB group showed more improvement in performance-based (6MWT) and self-reported functional outcome assessments (23). In contrast, the one year follow-up studies of randomized clinical trial subjects (9, 10, 22) using self-reported outcome measures for functional status (WOMAC) did not show long-term improvement associated with regional anesthesia techniques (24-27).
The rehabilitation outcome measured in the immediate postoperative period that correlates best with long-term functional improvement is not yet established. Ambulation distance is often measured by physical therapists and included in discharge criteria (9, 10, 22). For institutions that emphasize ambulation in their clinical pathway for lower extremity joint arthroplasty, a major concern raised with regard to FNBs is the potential association with increased fall risk (28, 29) although a recent large database study disputes this finding. In-hospital falls can lead to prolonged hospital stays with higher costs and are associated with more frequent postoperative complications, including serious organ system dysfunction and death (30). With currently-available local anesthetic solutions and typical doses, perineural infusion does produce clinically-significant quadriceps weakness when administered near the femoral nerve or lumbar plexus (31, 32). Since the local anesthetics themselves cannot select sensory over motor nerves( 33), anesthesiologists have started exploring alternate nerve block locations to minimize the risk of motor block and maximize patient rehabilitation.
For TKA, a more distal nerve block location in the adductor canal can provide effective analgesia postoperatively (34) and has been shown to better preserve quadriceps strength compared to a FNB in both volunteers (35) and clinical patients (11). Regional analgesic techniques are only one part of the overall pain management plan. While they are often included in multimodal analgesic protocols along with non-steroidal anti-inflammatory drugs (NSAIDs), acetaminophen, and low-dose opioids (36), there is a growing body of evidence to support the adductor canal block as the regional analgesic technique of choice for promoting postoperative ambulation within a clinical pathway (37, 38).
For patient information with answers to frequently-asked questions about regional anesthesia, please see “Regional Anesthesia FAQs.”
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Edward R. Mariano, MD, MAS, FASA is a physician specializing in anesthesiology, professor, husband, and father working to improve pain control, outcomes, and the overall experience for patients having surgery