Extending Nerve Block Pain Relief after Surgery: Review of the Evidence

nerve firingNerve 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).


  1. 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
  2. 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
  3. 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
  4. 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
  5. Ilfeld BM: Continuous peripheral nerve blocks: a review of the published evidence. Anesth Analg 2011; 113: 904-25
  6. Ilfeld BM: Continuous peripheral nerve blocks in the hospital and at home. Anesthesiol Clin 2011; 29: 193-211
  7. Ilfeld BM, Enneking FK: Continuous peripheral nerve blocks at home: a review. Anesth Analg 2005; 100: 1822-33
  8. 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
  9. Ilfeld BM, Esener DE, Morey TE, Enneking FK: Ambulatory perineural infusion: the patients’ perspective. Reg Anesth Pain Med 2003; 28: 418-23
  10. 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
  11. 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
  12. 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
  13. 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
  14. 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
  15. 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
  16. 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
  17. 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
  18. Hadzic A, Vloka JD, Kuroda MM, Koorn R, Birnbach DJ: The practice of peripheral nerve blocks in the United States: a national survey [p2e comments]. Reg Anesth Pain Med 1998; 23: 241-6
  19. Salinas FV: Location, location, location: Continuous peripheral nerve blocks and stimulating catheters. Reg Anesth Pain Med 2003; 28: 79-82
  20. 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
  21. 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
  22. Klein SM, Greengrass RA, Steele SM, D’Ercole FJ, Speer KP, Gleason DH, DeLong ER, Warner DS: A comparison of 0.5% bupivacaine, 0.5% ropivacaine, and 0.75% ropivacaine for interscalene brachial plexus block. Anesth Analg 1998; 87: 1316-9
  23. 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
  24. Weber A, Fournier R, Van Gessel E, Riand N, Gamulin Z: Epinephrine does not prolong the analgesia of 20 mL ropivacaine 0.5% or 0.2% in a femoral three-in-one block. Anesth Analg 2001; 93: 1327-31
  25. Murphy DB, McCartney CJ, Chan VW: Novel analgesic adjuncts for brachial plexus block: a systematic review. Anesth Analg 2000; 90: 1122-8
  26. Candido KD, Franco CD, Khan MA, Winnie AP, Raja DS: Buprenorphine added to the local anesthetic for brachial plexus block to provide postoperative analgesia in outpatients. Reg Anesth Pain Med 2001; 26: 352-6
  27. McCartney CJ, Duggan E, Apatu E: Should we add clonidine to local anesthetic for peripheral nerve blockade? A qualitative systematic review of the literature. Reg Anesth Pain Med 2007; 32: 330-8
  28. Movafegh A, Razazian M, Hajimaohamadi F, Meysamie A: Dexamethasone added to lidocaine prolongs axillary brachial plexus blockade. Anesth Analg 2006; 102: 263-7
  29. Parrington SJ, O’Donnell D, Chan VW, Brown-Shreves D, Subramanyam R, Qu M, Brull R: Dexamethasone added to mepivacaine prolongs the duration of analgesia after supraclavicular brachial plexus blockade. Reg Anesth Pain Med 2010; 35: 422-6
  30. 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
  31. Desmet M, Braems H, Reynvoet M, et al: I.V. and perineural dexamethasone are equivalent in increasing the analgesic duration of a single-shot interscalene block with ropivacaine for shoulder surgery: a prospective, randomized, placebo-controlled study. Br J Anaesth 2013; 111: 445-52
  32. Boogaerts J, Lafont N, Donnay M, Luo H, Legros FJ: Motor blockade and absence of local nerve toxicity induced by liposomal bupivacaine injected into the brachial plexus of rabbits. Acta Anaesthesiol Belg 1995; 46: 19-24
  33. Boogaerts JG, Lafont ND, Declercq AG, Luo HC, Gravet ET, Bianchi JA, Legros FJ: Epidural administration of liposome-associated bupivacaine for the management of postsurgical pain: a first study. J Clin Anesth 1994; 6: 315-20
  34. Chahar P, Cummings KC, 3rd: Liposomal bupivacaine: a review of a new bupivacaine formulation. J Pain Res 2012; 5: 257-64
  35. Richard BM, Newton P, Ott LR, Haan D, Brubaker AN, Cole PI, Ross PE, Rebelatto MC, Nelson KG: The Safety of EXPAREL (R) (Bupivacaine Liposome Injectable Suspension) Administered by Peripheral Nerve Block in Rabbits and Dogs. J Drug Deliv 2012; 2012: 962101
  36. Richard BM, Rickert DE, Doolittle D, Mize A, Liu J, Lawson CF: Pharmacokinetic Compatibility Study of Lidocaine with EXPAREL in Yucatan Miniature Pigs. ISRN Pharm 2011; 2011: 582351
  37. Viscusi ER, Candiotti KA, Onel E, Morren M, Ludbrook GL: The pharmacokinetics and pharmacodynamics of liposome bupivacaine administered via a single epidural injection to healthy volunteers. Reg Anesth Pain Med 2012; 37: 616-22
  38. Lavand’homme PM, Grosu I, France MN, Thienpont E: Pain trajectories identify patients at risk of persistent pain after knee arthroplasty: an observational study. Clin Orthop Relat Res 2014; 472: 1409-15.

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Ultrasound in Regional Anesthesia: What is the Evidence?

Medical scannerThe 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).

MedianIn 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.


  1. Ting PL, Sivagnanaratnam V: Ultrasonographic study of the spread of local anaesthetic during axillary brachial plexus block. Br J Anaesth 1989; 63: 326-9
  2. la Grange P, Foster PA, Pretorius LK: Application of the Doppler ultrasound bloodflow detector in supraclavicular brachial plexus block. Br J Anaesth 1978; 50: 965-7
  3. 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
  4. Abrahams MS, Horn JL, Noles LM, Aziz MF: Evidence-based medicine: ultrasound guidance for truncal blocks. Reg Anesth Pain Med 2010; 35: S36-42
  5. 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
  6. 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
  7. Narouze SN: Ultrasound-guided interventional procedures in pain management: Evidence-based medicine. Reg Anesth Pain Med 2010; 35: S55-8
  8. Neal JM: Ultrasound-guided regional anesthesia and patient safety: An evidence-based analysis. Reg Anesth Pain Med 2010; 35: S59-67
  9. 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
  10. Perlas A: Evidence for the use of ultrasound in neuraxial blocks. Reg Anesth Pain Med 2010; 35: S43-6
  11. Salinas FV: Ultrasound and review of evidence for lower extremity peripheral nerve blocks. Reg Anesth Pain Med 2010; 35: S16-25
  12. 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
  13. Jadad AR, Moore RA, Carroll D, Jenkinson C, Reynolds DJ, Gavaghan DJ, McQuay HJ: Assessing the quality of reports of randomized clinical trials: is blinding necessary? Control Clin Trials 1996; 17: 1-12
  14. Mariano ER, Cheng GS, Choy LP, Loland VJ, Bellars RH, Sandhu NS, Bishop ML, Lee DK, Maldonado RC, Ilfeld BM: Electrical stimulation versus ultrasound guidance for popliteal-sciatic perineural catheter insertion: a randomized controlled trial. Reg Anesth Pain Med 2009; 34: 480-5
  15. Mariano ER, Loland VJ, Bellars RH, Sandhu NS, Bishop ML, Abrams RA, Meunier MJ, Maldonado RC, Ferguson EJ, Ilfeld BM: Ultrasound guidance versus electrical stimulation for infraclavicular brachial plexus perineural catheter insertion. J Ultrasound Med 2009; 28: 1211-8
  16. Mariano ER, Loland VJ, Sandhu NS, Bellars RH, Bishop ML, Afra R, Ball ST, Meyer RS, Maldonado RC, Ilfeld BM: Ultrasound guidance versus electrical stimulation for femoral perineural catheter insertion. J Ultrasound Med 2009; 28: 1453-60
  17. Mariano ER, Loland VJ, Sandhu NS, Bellars RH, Bishop ML, Meunier MJ, Afra R, Ferguson EJ, Ilfeld BM: A trainee-based randomized comparison of stimulating interscalene perineural catheters with a new technique using ultrasound guidance alone. J Ultrasound Med 2010; 29: 329-336
  18. Ilfeld BM: Continuous peripheral nerve blocks: a review of the published evidence. Anesth Analg 2011; 113: 904-25
  19. Fredrickson MJ, Danesh-Clough TK: Ambulatory continuous femoral analgesia for major knee surgery: a randomised study of ultrasound-guided femoral catheter placement. Anaesth Intensive Care 2009; 37: 758-66
  20. Choi S, Brull R: Is ultrasound guidance advantageous for interventional pain management? A review of acute pain outcomes. Anesth Analg 2011; 113: 596-604
  21. Mariano ER, Loland VJ, Sandhu NS, Bishop ML, Lee DK, Schwartz AK, Girard PJ, Ferguson EJ, Ilfeld BM: Comparative efficacy of ultrasound-guided and stimulating popliteal-sciatic perineural catheters for postoperative analgesia. Can J Anaesth 2010; 57: 919-926
  22. Aveline C, Le Hetet H, Le Roux A, Vautier P, Cognet F, Vinet E, Tison C, Bonnet F: Comparison between ultrasound-guided transversus abdominis plane and conventional ilioinguinal/iliohypogastric nerve blocks for day-case open inguinal hernia repair. Br J Anaesth 2011; 106: 380-6
  23. Willschke H, Marhofer P, Bosenberg A, Johnston S, Wanzel O, Cox SG, Sitzwohl C, Kapral S: Ultrasonography for ilioinguinal/iliohypogastric nerve blocks in children. Br J Anaesth 2005; 95: 226-30
  24. Chin KJ, Perlas A, Chan V, Brown-Shreves D, Koshkin A, Vaishnav V: Ultrasound imaging facilitates spinal anesthesia in adults with difficult surface anatomic landmarks. Anesthesiology 2011; 115: 94-101
  25. Tsui B, Suresh S: Ultrasound imaging for regional anesthesia in infants, children, and adolescents: a review of current literature and its application in the practice of extremity and trunk blocks. Anesthesiology 2010; 112: 473-92
  26. Tsui BC, Suresh S: Ultrasound imaging for regional anesthesia in infants, children, and adolescents: a review of current literature and its application in the practice of neuraxial blocks. Anesthesiology 2010; 112: 719-28
  27. Brodsky JB, Mariano ER: Regional anaesthesia in the obese patient: lost landmarks and evolving ultrasound guidance. Best Pract Res Clin Anaesthesiol 2011; 25: 61-72
  28. Mariano ER, Brodsky JB: Comparison of procedural times for ultrasound-guided perineural catheter insertion in obese and nonobese patients. J Ultrasound Med 2011; 30: 1357-61
  29. Barrington MJ, Kluger R: Ultrasound guidance reduces the risk of local anesthetic systemic toxicity following peripheral nerve blockade. Reg Anesth Pain Med 2013; 38: 289-297


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