Intraneural Ultrasound-guided Sciatic Nerve Block: Minimum Effective Volume and Electrophysiologic Effects.

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Both extra- and intraneural sciatic injection resulted in significant axonal nerve damage. This study aimed to establish the minimum effective volume of intraneural ropivacaine 1% for complete sensory-motor sciatic nerve block in 90% of patients, and related electrophysiologic variations. METHODS: Forty-seven consecutive American Society of Anesthesiologists physical status I-II patients received an ultrasound-guided popliteal intraneural nerve block following the up-and-down biased coin design. The starting volume was 15 ml. Baseline, 5-week, and 6-month electrophysiologic tests were performed. Amplitude, latency, and velocity were evaluated. A follow-up telephone call at 6 months was also performed. RESULTS: The minimum effective volume of ropivacaine 1% in 90% of patients for complete sensory-motor sciatic nerve block resulted in 6.6 ml (95% CI, 6.4 to 6.7) with an onset time of 19 ± 12 min. Success rate was 98%. Baseline amplitude of action potential (mV) at ankle, fibula, malleolus, and popliteus were 8.4 ± 2.3, 7.1 ± 2.0, 15.4 ± 6.5, and 11.7 ± 5.1 respectively. They were significantly reduced at the fifth week (4.3 ± 2.1, 3.5 ± 1.8, 6.9 ± 3.7, and 5.2 ± 3.0) and at the sixth month (5.9 ± 2.3, 5.1 ± 2.1, 10.3 ± 4.0, and 7.5 ± 2.7) (P < 0.001 in all cases). Latency and velocity did not change from the baseline. No patient reported neurologic symptoms at 6-month follow-up. CONCLUSIONS: The intraneural ultrasound-guided popliteal local anesthetic injection significantly reduces the local anesthetic dose to achieve an effective sensory-motor block, decreasing the risk of systemic toxicity. Persistent electrophysiologic changes suggest possible axonal damage that will require further investigation.

Effects of anaesthesia and analgesia on long-term outcome after total knee replacement: A prospective, observational, multicentre study.

BACKGROUND: Perioperative regional anaesthesia may protect from persistent postsurgical pain (PPSP) and improve outcome after total knee arthroplasty (TKA). OBJECTIVES: Aim of this study was to evaluate the impact of regional anaesthesia on PPSP and long-term functional outcome after TKA. DESIGN: A web-based prospective observational registry. SETTING: Five Italian Private and University Hospitals from 2012 to 2015. PATIENTS: Undergoing primary unilateral TKA, aged more than 18 years, informed consent, American Society of Anesthesiologists (ASA) physical status classes 1 to 3, no previous knee surgery. INTERVENTION(S): Personal data (age, sex, BMI and ASA class), preoperative pain assessed by numerical rating scale (NRS) score, and risk factors for PPSP were registered preoperatively. Data on anaesthetic and analgesic techniques were collected. Postoperative pain (NRS), analgesic consumption, major complications and patient satisfaction were registered up to the time of discharge. PPSP was assessed by a blinded investigator during a phone call after 1, 3 and 6 months, together with patient satisfaction, quality of life (QOL) and walking ability. MAIN OUTCOME MEASURES: Experience of PPSP according to the type of peri-operative analgesia. RESULTS: Five hundred sixty-three patients completed the follow-up. At 6 months, 21.6% of patients experienced PPSP, whereas autonomy was improved only in 56.3%; QOL was worsened or unchanged in 30.7% of patients and improved in 69.3%. Patients receiving continuous regional anaesthesia (epidural or peripheral nerve block) showed a lower NRS through the whole peri-operative period up to 1 month compared with both single shot peripheral nerve block and those who did not receive any type of regional anaesthesia. No difference was found between these latter two groups. Differences in PPSP at 3 or 6 months were not significantly affected by the type of anaesthesia or postoperative analgesia. A higher NRS score at 1 month, younger age, history of anxiety or depression, pro-inflammatory status, higher BMI and a lower ASA physical status were associated with a higher incidence of PPSP and worsened QOL at 6 months. CONCLUSION: Continuous regional anaesthesia provides analgesic benefit for up to 1 month after surgery, but did not influence PPSP at 6 months. Better pain control at 1 month was associated with reduced PPSP. Patients with higher expectations from surgery, enhanced basal inflammation and a pessimistic outlook are more prone to develop PPSP. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT02147730.

Effect of Preoperative Inflammatory Status and Comorbidities on Pain Resolution and Persistent Postsurgical Pain after Inguinal Hernia Repair.

Poor acute pain control and inflammation are important risk factors for Persistent Postsurgical Pain (PPSP). The aim of the study is to investigate, in the context of a prospective cohort of patients undergoing hernia repair, potential risk factors for PPSP. Data about BMI, anxious-depressive disorders, neutrophil-tolymphocyte ratio (NLR), proinflammatory medical comorbidities were collected. An analysis for correlation between comorbidities and PPSP was performed in those patients experiencing chronic pain at 3 months after surgery. Tramadol resulted less effective in pain at movement in patients with a proinflammatory status. Preoperative hypertension and NLR > 4 were correlated with PPSP intensity. Regional anesthesia was significantly protective on PPSP when associated with ketorolac. Patients with pain at 1 month were significantly more prone to develop PPSP at 3 months. NSAIDs or weak opioids are equally effective on acute pain and on PPSP development after IHR, but Ketorolac has better profile in patients with inflammatory background or undergoing regional anesthesia. Drug choice should be based on their potential side effects, patient's profile (comorbidities, preoperative inflammation, and hypertension), and type of anesthesia. Close monitoring is necessary to early detect pain conditions more prone to progress to a chronic syndrome.

Effect of local anesthetic dilution on the onset time and duration of double-injection sciatic nerve block: a prospective, randomized, blinded evaluation.

BACKGROUND: Among the various factors influencing the success rate, onset time, and duration of peripheral nerve blocks, the role of local anesthetics concentration remains uncertain. In this prospective, randomized, single-blinded study, we evaluated whether varying the dilution of a fixed dose of mepivacaine solution influenced onset time and duration of sciatic nerve block. METHODS: Ninety ASA physical status I to II patients scheduled for foot surgery were randomly allocated to receive a double-injection Labat sciatic nerve block with 12 mL mepivacaine 2% (group concentration I = 45 patients) or 24 mL of mepivacaine 1% (group volume II = 45 patients). The nerve stimulator was initially set at 2 Hz, 0.1 millisecond, 1 mA. The total amount of local anesthetic (240 mg) was kept constant and equally divided between the peroneal and tibial nerves. All patients also received an ultrasound-guided popliteal sciatic nerve catheter for postoperative analgesia. Times to readiness for surgery, performance, and offset of local anesthetic were recorded. Our primary end point was to determine a possible difference in offset time between groups. Continuous variables were expressed as median (IQR) and compared with the Wilcoxon-Mann-Whitney U test; WMWodds are reported together with their 95% confidence interval. RESULTS: The overall success rate of sciatic nerve block was 99%. Time of performance was shorter in group I, 120 seconds (90-150 seconds), than that in group II, 150 seconds (120-180 seconds) (P = 0.0048; WMWodds 2.26 [1.35-4.34]). The onset time of sensory and motor sciatic nerve block was 4 minutes (2-9 minutes) in group I and 6 minutes (4-10 minutes) in group II (P = 0.41; WMWodds 1.21 [0.77-1.95]), while the duration of sensory block was 235 minutes (203-250 minutes) in group I, and 240 minutes (218-247 minutes) in group II respectively (P = 0.51; WMWodds 1.20 [0.69-2.16]). CONCLUSIONS: We found no evidence that varying volume and concentration while maintaining a fixed total dose of mepivacaine alters the onset time and duration of double-injection sciatic nerve block. Considering our WMWodds results, possible differences in onset time and duration comparable to differences in the performance time between groups cannot be excluded.

Erector spinae plane versus fascia iliaca block after total hip arthroplasty: a randomized clinical trial comparing analgesic effectiveness and motor block.

BACKGROUND: Ultrasound-guided supra-inguinal fascia iliaca block (FIB) provides effective analgesia after total hip arthroplasty (THA) but is complicated by high rates of motor block. The erector spinae plane block (ESPB) is a promising motor-sparing technique. In this study, we tested the analgesic superiority of the FIB over ESPB and associated motor impairment. METHODS: In this randomized, observer-blinded clinical trial, patients scheduled for THA under spinal anesthesia were randomly assigned to preoperatively receive either the ultrasound-guided FIB or ESPB. The primary outcome was morphine consumption 24 h after surgery. The secondary outcomes were pain scores, assessment of sensory and motor block, incidence of postoperative nausea and vomiting and other complications, and development of chronic post-surgical pain. RESULTS: A total of 60 patients completed the study. No statistically significant differences in morphine consumption at 24 h (P = 0.676) or pain scores were seen at any time point. The FIB produced more reliable sensory block in the femoral nerve (P = 0.001) and lateral femoral cutaneous nerve (P = 0.018) distributions. However, quadriceps motor strength was better preserved in the ESPB group than in the FIB group (P = 0.002). No differences in hip adduction motor strength (P = 0.253), side effects, or incidence of chronic pain were seen between the groups. CONCLUSIONS: ESPBs may be a promising alternative to FIBs for postoperative analgesia after THA. The ESPB and FIB offer similar opioid-sparing benefits in the first 24 h after surgery; however, ESPBs result in less quadriceps motor impairment.

Simulation-Based Medical Education and Training Enhance Anesthesia Residents' Proficiency in Erector Spinae Plane Block.

Background: Advances in regional anesthesia and pain management led to the advent of ultrasound-guided fascial plane blocks, which represent a new and promising route for the administration of local anesthetics. Both practical and theoretical knowledge of locoregional anesthesia are therefore becoming fundamental, requiring specific training programs for residents. Simulation-based medical education and training (SBET) has been recently applied to ultrasound-guided regional anesthesia (UGRA) with remarkable results. With this in mind, the anesthesia and intensive care residency program of the University of Milano-Bicocca organized a 4-h regional anesthesia training workshop with the BlockSim® (Accurate Srl, Cesena) simulator. Our study aimed to measure the residents' improvement in terms of reduction in time required to achieve an erector spinae plane (ESP) block. Methods: Fifty-two first-year anesthesia residents were exposed to a 4-h training workshop focused on peripheral blocks. The course included an introductory theoretical session held by a locoregional anesthetist expert, a practical training on human models and mannequins using Onvision® (B. Braun, Milano) technologies, and two test performances on the BlockSim simulator. Residents were asked to perform two ESP blocks on the BlockSim: the first without previous practice on the simulator, the second at the end of the course. Trainees were also also asked to complete a self-assessment questionnaire. Results: The time needed to achieve the block during the second attempt was significantly shorter (131 [83, 198] vs. 68 [27, 91] s, p < 0.001). We also observed a reduction in the number of needle insertions from 3 [2, 7] to 2 [1, 4] (p = 0.002), and an improvement aiming correctly at the ESP from 30 (58%) to 46 (88%) (p < 0.001). Forty-nine (94%) of the residents reported to have improved their regional anesthesia knowledge, 38 (73%) perceived an improvement in their technical skills and 46 (88%) of the trainees declared to be "satisfied/very satisfied" with the course. Conclusions: A 4-h hands-on course based on SBET may enhance first-year residents' UGRA ability, decrease the number of punctures and time needed to perform the ESP block, and improve the correct aim of the fascia.

The Role of Regional Anesthesia During the SARS-CoV2 Pandemic: Appraisal of Clinical, Pharmacological and Organizational Aspects.

The severe acute respiratory syndrome coronavirus SARS-CoV2 is spreading over millions of people worldwide, leading to thousands of deaths, even among the healthcare providers. Italy has registered the deaths of 337 physicians and more than 200 nurses as of March 14, 2021. Anesthesiologists are at higher risk as they are the care providers in both ICU and operating rooms.Although the vaccination of healthcare providers has been the prioirity, physicians are still continually exposed to the virus and potentially risk contagion and must thus protect themselves and their patients from the risks of infection while providing the best care to their surgical patients.Regional anesthesia allows for a reduction in airway manipulation, reducing environmental contamination as a result. Furthermore, regional anesthesia reduces the opioid requirements as well as the muscle paralysis due to muscle-relaxants and should be recommended whenever possible in COVID-19 patients. Our aim is to evaluate the advantages and criticisms of regional anesthesia in the management of surgical patients in the pandemic age.

Noninvasive Ventilatory Support of Patients with COVID-19 outside the Intensive Care Units (WARd-COVID).

Rationale: Treatment with noninvasive ventilation (NIV) in coronavirus disease (COVID-19) is frequent. Shortage of intensive care unit (ICU) beds led clinicians to deliver NIV also outside ICUs. Data about the use of NIV in COVID-19 is limited.Objectives: To describe the prevalence and clinical characteristics of patients with COVID-19 treated with NIV outside the ICUs. To investigate the factors associated with NIV failure (need for intubation or death).Methods: In this prospective, single-day observational study, we enrolled adult patients with COVID-19 who were treated with NIV outside the ICU from 31 hospitals in Lombardy, Italy.Results: We collected data on demographic and clinical characteristics, ventilatory management, and patient outcomes. Of 8,753 patients with COVID-19 present in the hospitals on the study day, 909 (10%) were receiving NIV outside the ICU. A majority of patients (778/909; 85%) patients were treated with continuous positive airway pressure (CPAP), which was delivered by helmet in 617 (68%) patients. NIV failed in 300 patients (37.6%), whereas 498 (62.4%) patients were discharged alive without intubation. Overall mortality was 25%. NIV failure occurred in 152/284 (53%) patients with an arterial oxygen pressure (PaO2)/fraction of inspired oxygen (FiO2) ratio <150 mm Hg. Higher C-reactive protein and lower PaO2/FiO2 and platelet counts were independently associated with increased risk of NIV failure.Conclusions: The use of NIV outside the ICUs was common in COVID-19, with a predominant use of helmet CPAP, with a rate of success >60% and close to 75% in full-treatment patients. C-reactive protein, PaO2/FiO2, and platelet counts were independently associated with increased risk of NIV failure.Clinical trial registered with ClinicalTrials.gov (NCT04382235).

Stimulating versus non-stimulating catheter for lumbar plexus continuous infusion after total hip replacement.

BACKGROUND: This study was aimed to investigate whether stimulating catheters for continuous lumbar plexus block reduce local anesthetic consumption after hip arthroplasty if compared with traditional non-stimulating catheters. METHODS: Seventy-two ASA I-III, 18-82-year-old, undergoing primary hip replacement (THA) for osteoarthritis with spinal anesthesia were randomized into two groups: Stim group (stimulating catheter, N.=36) and Nonstim group (non-stimulating catheter, N.=36). After surgery, 15 mL of mepivacaine 1% were administered in both groups through the catheter. An electronic pump was connected to deliver ropivacaine 0.2% (3 mL/h, bolus 3 mL, lock out 15 min) for the first 72 h. Patients were given ketorolac 30 mg IV every 8 h, acetaminophen 1g IV every 8 h and oxycodone 10 mg per os for rescue analgesia. Primary outcome was postoperative local anesthetic consumption. Numerical Rating Scale (NRS), complications, both quadriceps and obturator strength measurements, and opioid requirement were also registered. Mixed effect models (random intercept) were built for repeated measures over time. A difference between groups was considered statistically significant if P<0.05. RESULTS: Local anesthetic consumption and NRS were comparable between groups. Patients in the Nonstim group required significant more rescue opioid analgesia compared with the Stim group during the first 36 h (P=0.002). Quadriceps and adductor muscle strength was equally preserved in the two groups. CONCLUSIONS: The study showed comparable local anesthetic consumption, pain scores and muscle strength preservation between the two groups. The stimulating catheter allowed a significant, although underpowered, reduction in opioid consumption.

Postoperative analgesia and early functional recovery after day-case anterior cruciate ligament reconstruction: a randomized trial on local anesthetic delivery methods for continuous infusion adductor canal block.

BACKGROUND: This study assessed the effects of different local anesthetic delivery techniques for continuous adductor canal block, after arthroscopic day-case anterior cruciate ligament reconstruction (ACLR). METHODS: We enrolled 80 patients to randomly receive a ropivacaine 0.2% infusion 6 mL per hour through an adductor canal catheter by an electronic pump as follow: intermittent automatic bolus (intermittent group, N.=40) versus continuous infusion (continuous group, N.=40). Patient controlled bolus was 4 mL, lock out 20 minutes. Primary endpoint was postoperative pain by a numerical rating scale (NRS), secondary endpoints were rescue local anesthetic dose, opioid consumption, and physical performance at 72 h. A P<0.05 was considered significant. RESULTS: No difference was found between the groups in NRS, opioid consumption, and physical performance at 72 h. The intermittent group required significantly less local anesthetic than continuous group throughout the postoperative period; the median [IQR (range)] at 24 h was 149 [140-164 (140-227)] mL in the intermittent group versus 165 [147-210 (140-280)] mL in the continuous group (P=0.004). At 48 h it was 295 [284-310 (280-367)] mL in the intermittent group versus 308 [296-367 (284-500)] mL in the continuous group (P=0.002), while at 72 h it was 432 [426-450 (320-528)] mL in the intermittent group and 452 [436-487 (412-671)] mL in the continuous group respectively (P<0.001). CONCLUSIONS: Intermittent boluses did not provide superior analgesia over continuous infusion for adductor canal block after outpatient ACLR, but significantly decreased the local anesthetic consumption. Both techniques are suitable for the early functional recovery.

Effects of using the posterior or anterior approaches to the lumbar plexus on the minimum effective anesthetic concentration (MEAC) of mepivacaine required to block the femoral nerve: a prospective, randomized, up-and-down study.

BACKGROUND AND OBJECTIVES: To evaluate if psoas compartment block requires a larger concentration of mepivacaine to block the femoral nerve than does an anterior 3-in-1 femoral nerve block. METHODS: Forty eight patients undergoing anterior cruciate ligament repair were randomly allocated to receive an anterior 3-in-1 femoral block (femoral group, n = 24) or a posterior psoas compartment block (psoas group, n = 24) with 30 mL of mepivacaine. The concentration of the injected solution was varied for consecutive patients using an up-and-down staircase method (initial concentration: 1%; up-and-down steps: 0.1%). RESULTS: The minimum effective anesthetic concentration of mepivacaine blocking the femoral nerve in 50% of cases (ED(50)) was 1.06% +/- 0.31% (95% confidence interval [CI], 0.45%-1.68%) in the femoral group and 1.03% +/- 0.21% (95% CI, 0.6%-1.45%) in the psoas group (P = .83). The lateral femoral cutaneous and obturator nerves were blocked in 4 (16%) and 5 (20%) femoral group patients as compared with 20 (83%) and 19 (80%) psoas group patients (P = .005 and P = .0005, respectively). Intraoperative analgesic supplementation was required by 15 (60%) and 5 (20%) patients in the femoral and psoas groups, respectively (P = .01). CONCLUSIONS: Using a posterior psoas compartment approach to the lumbar plexus does not increase the minimum effective anesthetic concentration of mepivacaine required to block the femoral nerve as compared with the anterior 3-in-1 approach, and provides better quality of intraoperative anesthesia due to the more reliable block of the lateral femoral cutaneous and obturator nerves.

Use of direct oral anticoagulants with regional anesthesia in orthopedic patients.

The use of direct oral anticoagulants including apixaban, rivaroxaban, and dabigatran, which are approved for several therapeutic indications, can simplify perioperative and postoperative management of anticoagulation. Utilization of regional neuraxial anesthesia in patients receiving anticoagulants carries a relatively small risk of hematoma, the serious complications of which must be acknowledged. Given the extensive use of regional anesthesia in surgery and the increasing number of patients receiving direct oral anticoagulants, it is crucial to understand the current clinical data on the risk of hemorrhagic complications in this setting, particularly for anesthesiologists. We discuss current data, guideline recommendations, and best practice advice on effective management of the direct oral anticoagulants and regional anesthesia, including in specific clinical situations, such as patients undergoing major orthopedic surgery at high risk of a thromboembolic event, or patients with renal impairment at an increased risk of bleeding.

Iatrogenic Pseudoaneurysm After Continuous Adductor Canal Block.

No major complications have been associated with the ultrasound-guided continuous adductor canal block (cACB). We present a case of iatrogenic pseudoaneurysm in a branch of the superficial femoral artery in a 44-year-old patient after a cACB for knee surgery. Both anesthesia and surgery were completed uneventfully. The postoperative day 3 examination showed a complete quadricep impairment and a large hematoma in a medial-anterior part of the thigh, and laboratory tests reported hemoglobin = 7.2 g dL. The computed tomography scan revealed the pseudoaneurysm (16 × 16 × 18 mm) that was successfully embolized after selective catheterization. The patient was discharged regularly on postoperative day 12.

Effects of the Intraneural and Subparaneural Ultrasound-Guided Popliteal Sciatic Nerve Block: A Prospective, Randomized, Double-Blind Clinical and Electrophysiological Comparison.

BACKGROUND AND OBJECTIVES: This prospective, randomized, double-blind study compared the effects of the ultrasound-guided popliteal sciatic nerve block performed by either intraneural or subparaneural approach followed by an electrophysiological evaluation. We hypothesized that intraneural injection provides a faster onset with a better success rate compared with the subparaneural approach. METHODS: Eighty-eight patients were enrolled and randomized to receive an ultrasound-guided popliteal sciatic nerve block injecting 15 mL ropivacaine 1% according to an intraneural injection (group INTRA = 44) or a subparaneural injection (group SUBPARA = 44). The primary end point was the onset time of sensory and motor block, whereas secondary end points were successful, duration of the block, and the variation of the electrophysiological assessment after 5 weeks. The study was registered prior to patient enrollment (clinicaltrials.gov identifier NCT01987128). RESULTS: The median onset time for successful sciatic nerve block in the INTRA group was 10 (5-15 [5-30]) minutes versus 25 (15-35 [5-45]) minutes in the SUBPARA group (P < 0.001), with a rate of 41/43 (95.3%) compared with 25/40 (62.5%) in the SUBPARA group (P < 0.001). No difference was found regardless of the duration of the block. Fifty-three patients also performed the electrophysiological assessment at 5 weeks, showing a subclinical, significant reduction in amplitude of the action potentials with no difference between groups. No patients reported any clinical neurological complications after 6 months. CONCLUSIONS: In ultrasound-guided popliteal sciatic nerve block, intraneural injection provided a faster onset and better success rate compared with subparaneural. Both techniques resulted in a similar subclinical reduction in amplitude of the sciatic action potentials at 5 weeks after surgery. These findings should not be extended to other approaches.

Does continuous sciatic nerve block improve postoperative analgesia and early rehabilitation after total knee arthroplasty? A prospective, randomized, double-blinded study.

INTRODUCTION: The aim of this prospective, randomized, double-blind study was to evaluate whether continuous sciatic nerve block can improve postoperative pain relief and early rehabilitation compared with single-injection sciatic nerve block in patients undergoing total knee arthroplasty (TKA) and lumbar plexus block. METHODS: After ethical committee approval and written informed consent, 38 patients with ASA physical status I to II were enrolled. The first group received continuous sciatic and continuous lumbar plexus blocks (group regional or R, n = 19), whereas the second group received a single sciatic nerve block followed by saline infusion through the sciatic catheter and continuous lumbar plexus block (group control or C, n = 19). We assessed morphine consumption, scores for visual analog scale for pain at rest (VASr), and during continuous passive motion (VASi during CPM) for 48 hours postoperatively. Effectiveness of early ambulation was also evaluated. RESULTS: Scores for VASr and VASi during CPM, as well as morphine consumption, were significantly higher in group C than in group R (P < 0.01). Moreover, patients in group R showed earlier rehabilitation with more effective ambulation (P < 0.05). CONCLUSIONS: Continuous sciatic nerve block improves analgesia, decreases morphine request, and improves early rehabilitation compared with single-injection sciatic nerve block in patients undergoing TKA and lumbar plexus block.

Minimum effective anesthetic concentration (MEAC) for sciatic nerve block: subgluteus and popliteal approaches.

BACKGROUND: We tested the hypothesis that using a subgluteus approach to the sciatic nerve requires a lower concentration of mepivacaine to obtain complete anesthesia as compared with the popliteal approach. METHODS: With midazolam premedication (0.05 mg kg(-1) iv), 48 patients undergoing hallux valgus repair were randomly allocated to receive a sciatic nerve block using either a posterior popliteal (group Popliteal, n = 24) or subgluteus (group Subgluteus, n = 24) approach with 30 mL of local anesthetic injected after elicitation of plantar flexion of the foot with a current

Adding clonidine to the induction bolus and postoperative infusion during continuous femoral nerve block delays recovery of motor function after total knee arthroplasty.

We evaluated the effects of adding clonidine for continuous peripheral nerve infusions. Sixty patients undergoing total knee arthroplasty under combined single-injection sciatic block and continuous femoral infusion were randomly allocated to three groups: block induction with 0.75% ropivacaine followed by 0.2% ropivacaine (group control; n = 20); block induction with 0.75% ropivacaine and 1 microg/kg clonidine followed by 0.2% ropivacaine (group cloni-bolus; n = 20), and block induction with 0.75% ropivacaine and 1 microg/kg clonidine followed by 0.2% ropivacaine with 1 microg/mL clonidine (group cloni-infusion; n = 20). After surgery, continuous femoral infusion was provided with a patient-controlled infusion pump (basal infusion rate, 6 mL/h; incremental dose, 2 mL; lockout time, 15 min). The median (range) onset time of surgical block was 15 min (5-30 min) in group control, 10 min (5-35 min) in group cloni-bolus, and 10 min (5-30 min) in group cloni-infusion (P = 0.07). No differences were reported among groups in the degree of pain measured with the visual analog scale. The total consumption of local anesthetic solution after a 24-h infusion was 170 mL (144-220 mL) in group control, 169 mL (144-260 mL) in group cloni-bolus, and 164 mL (144-248 mL) in group cloni-infusion (P = 0.51); after the second day of infusion, total consumption was 168 mL (144-200 mL) in group control, 156 mL (144-288 mL) in group cloni-bolus, and 150 mL (144-210 mL) in group cloni-infusion (P = 0.48). Hemodynamic profiles and sedation were similar in the three groups. Motor function impairment after 48 h of infusion was observed in 27% of cloni-infusion patients but in only 6% of both the control and cloni-bolus groups (P = 0.05). We conclude that adding clonidine 1 microg/mL to local anesthetic for continuous femoral nerve block does not improve the quality of pain relief but has the potential for delaying recovery of motor function.