A comparison of the motor effects and analgesic efficacy following lumbar plexus block combined with sciatic nerve block or epidural in dogs undergoing tibial plateau leveling osteotomy.

OBJECTIVE: To compare motor effects and analgesic efficacy following an ultrasound-guided lateral approach to lumbar plexus blockade at L7 and sciatic nerve blockade (LPSNB) against epidural injection in dogs undergoing tibial plateau leveling osteotomy (TPLO). STUDY DESIGN: Prospective, randomized, blinded clinical trial. ANIMALS: A total of 27 healthy adult dogs undergoing unilateral TPLO surgery. METHODS: Dogs were allocated to either LPSNB (bupivacaine 2 mg kg-1, 0.75%) or epidural (morphine PF 0.1 mg kg-1 and bupivacaine 0.5 mg kg-1, 0.75%). Other aspects of clinical management were identical, including anesthetic drug protocol, area of presurgical clipping and bladder care. Time to perform the block, response to surgical stimuli, pain scores, rescue analgesia, time to stand and walk, motor score and time to first urination were recorded. One evaluator, unaware of treatment status, performed all evaluations. Student's t-test or Mann-Whitney U test was used to compare continuous variables between groups, and Fisher's exact test for categorical variables. RESULTS: Median (range) times to stand and walk were shorter for LPSNB [60 (40-120) minutes and 90 (60-150) minutes, respectively, p = 0.003] than for epidural [150 (120-240) minutes and 180 (120-360) minutes, respectively, p = 0.006]. Four dogs required rescue intraoperatively (three in epidural group, one in LPSNB group, p = 0.438). Pain scores over the 24 hour evaluation period were similar, and not significantly different, for each group. Time to spontaneous urination [LPSNB, 330 (240-360) minutes; epidural, 300 (120-1440) minutes, p = 1.0] did not differ between groups. CONCLUSIONS AND CLINICAL RELEVANCE: An ultrasound-guided lateral paravertebral approach to the lumbar plexus within the psoas compartment at L7, combined with sciatic nerve blockade, allows faster return to normal motor function, with similar pain control and impact on urination when compared with epidural in dogs after TPLO surgery.

Sacral nerve stimulation ameliorates colonic barrier functions in a rodent model of colitis.

BACKGROUND: The mucosal barrier damage is recognized as one of the key factors in the pathogenesis of colitis. While sacral nerve stimulation (SNS) was reported to have therapeutic potential for colitis, its mechanisms of actions on colonic permeability remained largely unknown. METHODS: In this study, colitis was induced by intrarectal administration of TNBS in rats. Five days later, they were treated with SNS or sham-SNS for 10 days. The effects of SNS on colonic permeability were assessed by measuring the expression of tight-junction proteins involved in regulating permeability and the FITC-dextran test. The mechanism of actions of SNS was investigated by studying the function of the enteric nervous system (ENS) cells and analyzing the autonomic nervous system. KEY RESULTS: SNS decreased the disease activity index, microscopic and macroscopic scores, myeloperoxidase activity, and pro-inflammatory cytokines (TNF-α, IL-6). SNS increased the expression of Zonula Occludens-1, Occludin, Claudin-1, and Junctional adhesion molecule-A in the colon tissue. The FITC-dextran test showed that the colonic permeability was lower with SCS than sham-SNS. SNS increased ChAT, pancreatic polypeptide, and GDNF and reduced norepinephrine NGF, sub-P, and mast cell overactivation in the colon tissue. Concurrently, SNS increased acetylcholine in colon tissues and elevated vagal efferent activity. CONCLUSIONS & INFERENCES: SNS ameliorates colonic inflammation and enhances colonic barrier function with the proposed mechanisms involving the increase in parasympathetic activity and modulation of the activity of the ENS and immune system, including mast cells.

Combined ultrasound and nerve stimulator-guided deep nerve block may decrease the rate of local anesthetics systemic toxicity: a randomized clinical trial.

BACKGROUND: Ultrasound guidance might decrease the incidence of local anesthetics systemic toxicity (LAST) for many peripheral nerve blocks compared with nerve stimulator guidance. However, it remains uncertain whether ultrasound guidance is superior to nerve stimulator guidance for deep nerve block of the lower extremity. This study was designed to investigate whether deep nerve block with ultrasound guidance would decrease the incidence of LAST compared with that with nerve stimulator guidance, and to identify associated risk factors of LAST. METHODS: Three hundred patients undergoing elective lower limb surgery and desiring lumbar plexus blocks (LPBs) and sciatic nerve blocks (SNBs) were enrolled in this study. The patients were randomly assigned to receive LPBs and SNBs with ultrasound guidance (group U), nerve stimulator guidance (group N) or dual guidance (group M). The primary outcome was the incidence of LAST. The secondary outcomes were the number of needle redirection, motor and sensory block onset and nerve distribution restoration time, as well as associated risk factors. RESULTS: There were 18 patients with LAST, including 12 in group U, 4 in group N and 2 in group M. By multiple comparisons among the three groups, we found that the incidence of LAST in group U (12%) was significantly higher than that in group N (4%)(P = 0.037) and group M(2%)(P = 0.006). The OR of LAST with hepatitis B (HBV) infection and the female sex was 3.352 (95% CI,1.233-9.108, P = 0.013) and 9.488 (95% CI,2.142-42.093, P = 0.0004), respectively. CONCLUSIONS: Ultrasound guidance, HBV infection and the female sex were risk factors of LAST with LPBs and SNBs. For patients infected with HBV or female patients receiving LPBs and SNBs, we recommended that combined ultrasound and nerve stimulator guidance should be used to improve the safety. TRIAL REGISTRATION: This study was approved by the Ethical Committee of the First Affiliated Hospital of Army Medical University. The protocol was registered prospectively with the Chinese Clinical Trial Registry ( ChiCTR-IOR-16008099 ) on March 15, 2016.

Greater analgesic effect with intermittent compared with continuous mode of lumbar plexus block for total hip arthroplasty: a randomized controlled trial.

BACKGROUND AND OBJECTIVES: Lumbar plexus block (LPB) is an effective perioperative analgesic therapy for patients undergoing total hip arthroplasty (THA). However, the analgesic efficacy of intermittent administration compared with continuous infusion of LPB in patients remains unclear. METHODS: Forty adult patients who underwent THA were randomly divided into two groups: continuous infusion group (6 mL/hour continuous infusion of levobupivacaine [0.125%] in LPB, n=20) and intermittent infusion group (12 mL of levobupivacaine [0.125%] bolus delivered every 2 hours in LPB, n=20). The primary outcome was the cumulative fentanyl consumption administered for rescue analgesia during the first 48 hours after surgery. Secondary outcomes were the number of demands for rescue analgesia and successfully delivered rescue analgesia; extent of sensory blockade (cold tests); and pain score on the visual analog scale (VAS) at rest and during mobilization during the first 48 hours after surgery. RESULTS: Both the cumulative fentanyl consumption administered for rescue analgesia (mean [SD]: 81.5 [58.5] µg vs 438 [101.2] µg among the intermittent infusion and the continuous infusion groups, respectively) and the number of demanded and delivered fentanyl boluses for rescue analgesia were lower in intermittent infusion group than in continuous infusion (p<0.001 for both). The extent of sensory blockade remained constant in intermittent infusion group, but gradually narrowed in continuous infusion. VAS was lower in intermittent infusion group than in continuous infusion, except at 1 and 12 hours postoperatively (p<0.05). CONCLUSIONS: Greater analgesic effect was achieved using the intermittent mode than the continuous mode of LPB administration.

Ultrasound guided erector spinae plane block as a cause of unintended motor block. / Bloqueo en el plano del erector de la columna ecoguiado como causa de bloqueo motor imprevisto.

Erector spinae plane block (ESPB) as postoperative analgesia method has been successfully carried out in several surgical interventions. Postoperative pain treatment for cesarean section is considered one of the important challenges for anesthesiologists due to the risk of chronic pain development and even pospartum depression. Regional anesthesia techniques were effectively used to prevent the pain together with multimodal analgesia regimes in cesarean section. Formerly, successful erector spinae plane block was documented as postoperative analgesia treatment for cesarean section; however, no motor weakness was recorded as a side effect. In this case report, we present an unexpected motor weakness as a side effect of the erector spinae plane block after cesarean delivery operation in a 29 year old patient. To our knowledge, this is the first report of motor weakness related to the ESPB.

A comparison of the fascia iliaca block to the lumbar plexus block in providing analgesia following arthroscopic hip surgery: A randomized controlled clinical trial.

STUDY OBJECTIVE: This randomized controlled single blinded clinical trial compared the fascia iliaca block (FIB) and the lumbar plexus block (LPB) in patients with moderate to severe pain following hip arthroscopic surgery. DESIGN: Single blinded randomized trial. SETTING: Postoperative recovery area, postoperative days 0 and 1. PATIENTS: Fifty patients undergoing hip arthroscopy were approached in the Post Anesthesia Care Unit (PACU) if they had moderate to severe pain (defined as > or equal 4/10 on the numeric rating scale). Twenty-five patients were allocated to the FIB and twenty-five patients to the LPB. INTERVENTIONS: Fascia iliaca block or lumbar plexus block. MEASUREMENTS: A blinded observer recorded pain scores just prior to the block, 15 min following the block (primary endpoint), and then every 15 min for 2 h (or until the patient was discharged). Total PACU time and opioid use were recorded. Pain scores and analgesic use on postoperative day (POD) 0, and POD 1 were recorded. At 24 h post block the Quality of Recovery 9 questionnaire was administered. RESULTS: The mean pre-block pain scores were comparable between the two groups (P = 0.689). There was no difference in mean post block pain scores between the two groups at 15 min (P = 0.054). In the PACU patients who underwent a LPB consumed less opioids compared to FIB patients (P = 0.02), however no differences were noted between the two groups in PACU length of stay, or POD 0 or 1 opioid use. CONCLUSION: A fascia iliaca block is not inferior to a lumbar plexus block in reducing PACU pain scores in patients with moderate to severe pain following hip arthroscopic surgery and is a viable option to help manage postoperative pain following hip arthroscopic surgery.

Ultrasound with neurostimulation compared with ultrasound guidance alone for lumbar plexus block: A randomised single blinded equivalence trial.

BACKGROUND: Ultrasound-guided lumbar plexus blocks usually require confirmatory neurostimulation. A simpler alternative is to inject local anaesthetic inside the posteromedial quadrant of the psoas muscle under ultrasound guidance. OBJECTIVE: We hypothesised that both techniques would result in similar total anaesthesia time, defined as the sum of performance and onset time. DESIGN: A randomised, observer-blinded, equivalence trial. SETTING: Ramathibodi Hospital and Maharaj Nakorn Chiang Mai Hospital (Thailand) from 12 May 2016 to 10 January 2017. PATIENTS: A total of 110 patients undergoing total hip or knee arthroplasty, who required lumbar plexus block for postoperative analgesia. INTERVENTION: In the combined ultrasonography-neurostimulation group, quadriceps-evoked motor response was sought at a current between 0.2 and 0.8 mA prior to local anaesthetic injection (30 ml of lidocaine 1% and levobupivacaine 0.25% with epinephrine 5 µg ml and 5 mg of dexamethasone). In the ultrasound guidance alone group, local anaesthetic was simply injected inside the posteromedial quadrant of the psoas muscle. MAIN OUTCOMES MEASURES: We measured the total anaesthesia time, the success rate (at 30 min), the number of needle passes, block-related pain, cumulative opioid consumption (at 24 h) and adverse events (vascular puncture, paraesthesia, local anaesthetic spread to the epidural space). The equivalence margin was 7.4 min. RESULTS: Compared with ultrasound guidance alone, combined ultrasonography-neurostimulation resulted in decreased mean (±SD) total anaesthesia time [15.3 (±6.5) vs. 20.1 (±9.0) min; mean difference, -4.8; 95% confidence interval, -8.1 to -1.9; P = 0.005] and mean (±SD) onset time [10.2 (±5.6) vs. 15.5 (±9.0) min; P = 0.004). No inter-group differences were observed in terms of success rate, performance time, number of needle passes, block-related pain, opioid consumption or adverse events. CONCLUSION: Although the ultrasonography-neurostimulation technique results in a shorter total anaesthesia time compared with ultrasound guidance alone, this difference falls within our accepted equivalence margin (±7.4 min). TRIAL REGISTRATION: www.clinicaltrials in the (Study ID: TCTR20160427003).

Ultrasound-guided versus conventional injection for caudal block in children: A prospective randomized clinical study.

STUDY OBJECTIVE: The aim of this study was to compare the efficacies of ultrasound guided sacral hiatus injection and conventional sacral canal injection performed for caudal block in children. DESIGN: Randomized controlled clinical trial. SETTING: Operating rooms of university hospital of Erzurum, Turkey. PATIENTS: One hundred-thirty four children, American Society of Anesthesiologists I-II, between the ages of 5 and 12, scheduled for elective phimosis and circumcision surgery. INTERVENTIONS: Patients assigned to two groups for ultrasound guided caudal block (Group U, n=68) or conventional caudal block (Group C, n=66). Caudal solution was prepared as 0.125% levobupivacaine plus 10mcg/kg morphine (total volume: 0.5ml/kg), and was administered to both groups. MEASUREMENTS: The block performing time, the block success rate, the number of needle puncture, the success at first puncture and the complications were recorded. MAIN RESULTS: The block performing time and the success rate of block were similar between Group U and Group C (109.96±49.73s vs 103.17±45.12s, and 97% vs 93%, respectively p>0.05). The first puncture success rate was higher in Group U than in Group C (80% vs 63%, respectively p=0.026). No significant difference was observed between the groups with regard to the number of needle punctures (p=0.060). The rates of vascular puncture and subcutaneus bulging were higher in Group C than in Group U (8/66 vs 1/68, and 8/66 vs 0/68, respectively p<0.05). CONCLUSIONS: Despite the limitations in central neuroaxial anesthesia we recommend the use of ultrasound since it reduces the complications and increases the success rate of first puncture in pediatric caudal injection.

[Overactive bladder-which treatment when?] / Überaktive Blase ­ wann welche Therapie?

The term OAB (overactive bladder) describes a symptom complex. Therefore, initial treatment should be based on clinical symptoms and the results of basic diagnostics. Patient preference is essential for the choice of the initial treatment. Behavioural therapy, electrostimulation and medical treatment are available treatment options. If these are not effective, extended diagnostic examinations should be performed prior to minimally invasive treatments, like onabotulinumtoxin injections in the detrusor or sacral neuromodulation. Surgical interventions like augmentation cystoplasty are rarely required today.

Combined Sciatic and Lumbar Plexus Nerve Blocks for the Analgesic Management of Hip Arthroscopy Procedures: A Retrospective Review.

Hip arthroscopy is a minimally invasive alternative to open hip surgery. Despite its minimally invasive nature, there can still be significant reported pain following these procedures. The impact of combined sciatic and lumbar plexus nerve blocks on postoperative pain scores and opioid consumption in patients undergoing hip arthroscopy was investigated. A retrospective analysis of 176 patients revealed that compared with patients with no preoperative peripheral nerve block, significant reductions in pain scores to 24 hours were reported and decreased opioid consumption during the post anesthesia care unit (PACU) stay was recorded; no significant differences in opioid consumption out to 24 hours were discovered. A subgroup analysis comparing two approaches to the sciatic nerve block in patients receiving the additional lumbar plexus nerve block failed to reveal a significant difference for this patient population. We conclude that peripheral nerve blockade can be a useful analgesic modality for patients undergoing hip arthroscopy.

Complications After Continuous Posterior Lumbar Plexus Blockade for Total Hip Arthroplasty: A Retrospective Cohort Study.

BACKGROUND AND OBJECTIVES: While benefits of regional anesthesia in total hip arthroplasty (THA) are well documented, data describing the incidence of complications related to the use of posterior lumbar plexus blockade for THA remain limited. Our primary aim was to evaluate the incidence of infectious, bleeding, and neurological complications related specifically to the use of continuous posterior lumbar plexus block for elective THA. METHODS: We reviewed the electronic medical records of all adult patients who underwent elective THA with continuous posterior lumbar plexus blockade between December 1, 2004, and April 30, 2015, using the Mayo Clinic Total Joint Registry. All complications were verified via manual chart review by 2 reviewers. Patient demographics, type of surgery, and complications were analyzed. RESULTS: A total of 9649 patients who underwent 11,395 THA procedures met the inclusion criteria. There were 8686 (76.2%) primary and 2709 (23.8%) revision THAs. There were no block-related infections (0.00%; 95% confidence interval [CI], 0.00%-0.03%) and only 1 block-related hematoma (0.01%; 95% CI, 0.00%-0.05%) in a patient with multiple risk factors for bleeding. There were 60 (0.53%; 95% CI, 0.40%-0.68%) perioperative nerve injuries. Forty-three were in the sciatic distribution (71.67%; incidence, 0.38%). Although there were no documented overt iatrogenic nerve injuries, the posterior lumbar plexus blockade could not be excluded as the potential cause in 9 cases (incidence, 0.08%) based on clinical distribution or electromyographic findings. CONCLUSIONS: In our large, single-center cohort study, we report no catheter-related infections, whereas catheter-related hemorrhagic and neurological complications also appear to be rare.

Partial displacement of epidural catheter after patient position change: A case report.

Epidural catheter migration is a well-known cause of failed anesthesia and complications. One of the factors that affect catheter movement is when patients change their position after skin fixation. We report a case of an epidural catheter placed without evidence of intravascular or subdural insertion that produced an insufficient block. A 36-year-old woman presented for ankle surgery under epidural anesthesia. Epidural block was conducted at the L3-4 intervertebral space with a catheter threaded 3 cm into the epidural space with the patient in a back flexion and lateral position. The total volume of injected anesthetic was 28 mL, including a 3-mL test dose. The final anesthesia level was L1. The planned operation was completed without a pneumatic tourniquet. A postoperative C-arm fluoroscopic image revealed that 1 side hole of the catheter had moved out of the epidural space. We think that a positional change after catheter fixation was the reason for catheter outmigration leading to insufficient analgesia, which was incompatible with the amount of local anesthetic injected.

One operator's experience of ultrasound guided lumbar plexus block for paediatric hip surgery.

Lumbar plexus block has been shown to be effective for providing postoperative analgesia after major hip surgeries in children. The goal of the study was to evaluate the feasibility of ultrasound guidance during lumbar plexus block in children undergoing hip surgery for congenital hip dislocation. After obtaining local institutional ethical committee approval and parental informed consent, ASA I or II, 1-6 years old children undergoing hip surgery were included into the study. Lumbar plexus block was performed after general anaesthesia using ultrasound guided Shamrock Method. Bupivacaine 0.25 % was used during block performance. Dose of the local anaesthetic was 1 ml/kg and the maximum dose was limited to 20 ml. In the postoperative period pain was assessed using modified CHEOPS (Children's Hospital Eastern Ontario Pain Scale) pain score. If pain score in the postoperative period exceeded 3, patients received IV paracetamol 15 mg/kg-1. Morphine 0.1 mg/kg-1 IV was planned to administer if pain scores were still higher than 3 despite paracetamol treatment. 75 patients whose mean age was 47 months were enrolled into the study. All blocks were performed successfully and without complications. Mean time for the first analgesic is found as 10 h after surgery. Only one patient required morphine in the recovery unit and 23 patients received paracetamol. US guided lumbar plexus block using Shamrock Method is an effective technique for providing postoperative analgesia after hip surgeries in children and it's effect lasts for 8-12 h after surgery.

In-Plane Ultrasound-Guided Lumbar Plexus Block Using Catheter-Over-Needle Technique in a 14-Month-Old Baby.

This case report details the feasibility of a continuous lumbar plexus block obtained with a paramedian transverse scan of the lumbar paravertebral region, using a catheter-over-needle system, as a main postoperative orthopedic analgesia, in a 14-month-old patient undergoing surgical treatment of a localized Ewing family tumor of the right proximal femur. After surgery, the patient remained in the intensive care unit for 3 days; pain was assessed regularly using the Children's and Infants' Postoperative Pain Scale, and comfort was monitored. Analgesia was provided with continuous levobupivacaine 0.2% infusion 0.2 mL kg h, rectal paracetamol 15 mg kg, and oral ibuprofen 60 mg twice per day, with a dose of morphine 0.05 mg kg intravenously as rescue. Pain relief was excellent, and no additional morphine was needed during the postoperative course. Nausea, vomiting, and disturbed sleep were not reported. Oral diet was resumed on the first postoperative day. In conclusion, this case represents successful postoperative management of orthopedic pain in a child using continuous posterior lumbar plexus infusion.

Population pharmacokinetics of bupivacaine in combined lumbar and sciatic nerve block.

OBJECTIVES: The primary aim of this study was to establish the population pharmacokinetic (PPK) model of bupivacaine after combined lumbar plexus and sciatic nerve blocks and secondary aim is to assess the effect of patient's characteristics including age, body weight and sex on pharmacokinetic parameters. MATERIALS AND METHODS: A total of 31 patients scheduled for elective lower extremity surgery with combined lumbar and sciatic nerve block using plain bupivacaine 0.5% were included. The total bupivacaine plasma concentrations were measured before injection and after two blocks placement and at selected time points. Monitoring of bupivacaine was made by high performance liquid chromatography (HPLC) with ultraviolet detection. Non-linear mixed effects modeling was used to analyze the PPK of bupivacaine. RESULTS: One compartment model with first order absorption, two input compartments and a central elimination was selected. The Shapiro-Wilks test of normality for normalized prediction distribution errors for this model (P = 0.156) showed this as a valid model. The selected model predicts a population clearance of 930 ml/min (residual standard error [RSE] = 15.48%, IC 95% = 930 ± 282.24) with inter individual variability of 75.29%. The central volume of distribution was 134 l (RSE = 12.76%, IC = 134 ± 33.51 L) with inter individual variability of 63.40%. The absorption of bupivacaine in two sites Ka1 and Ka2 were 0.00462/min for the lumbar site and 0.292/min for the sciatic site. Age, body weight and sex have no effect on the bupivacaine pharmacokinetics in this studied population. CONCLUSION: The developed model helps us to assess the systemic absorption of bupivacaine at two injections sites.

Lumbar plexus blockade reduces pain after hip arthroscopy: a prospective randomized controlled trial.

BACKGROUND: Hip arthroscopy causes moderate to severe postoperative pain. We hypothesized that performance of a lumbar plexus block (LPB) would reduce postoperative pain in the postanesthesia care unit (PACU) for patients discharged home on the day of surgery. METHODS: Patients received a combined spinal epidural with IV sedation, ondansetron, and ketorolac. Half of the patients (n = 42) also underwent a single-injection bupivacaine LPB. Postoperative analgesia (PACU and after discharge) was provided with oral hydrocodone/acetaminophen (5/500 mg) and an oral nonsteroidal antiinflammatory drug. IV hydromorphone was given as needed in the PACU. RESULTS: The LPB reduced pain at rest in the PACU (GEE: ß estimate of the mean on a 0 to 10 scale = -0.9; 95% confidence interval = -1.7 to -0.1; P = 0.037). Mean PACU pain scores at rest were reduced by the LPB from 4.2 to 3.3 (P = 0.048, 95% confidence interval for difference = 0.007-1.8; uncorrected for multiple values per patient, using independent samples t test for preliminary evaluation comparing pain between the groups). There were no statistically significant differences in PACU analgesic usage, PACU pain with movement, and patient satisfaction. No permanent adverse events occurred, but 2 LPB patients fell in the PACU bathroom, without injury. Three unplanned admissions occurred; one LPB patient was admitted for epidural spread and urinary retention. Two control patients were admitted, one for oxygen desaturation and one for pain and nausea. CONCLUSION: LPB resulted in statistically significant reductions in PACU resting pain after hip arthroscopy, but the absence of improvement in most secondary outcomes suggests that assessment of risks and benefits of LPB should be individualized.

[Influence of femoral catheter stimulation intensity on post-surgical analgesia after total knee replacement]. / Influencia de la intensidad de estimulación del catéter femoral sobre analgesia postoperatoria tras prótesis de rodilla.

INTRODUCTION: Stimulating catheters allow the catheter point to be positioned near the nerve, thus reducing the amount of local anaesthetic required for a successful block. There is currently a debate on what is the stimulation intensity required to provide adequate analgesia, although it does seem that if it is obtained with 1mAmp or less the block is more effective. The objective of the study was to demonstrate whether different neurostimulation intensities with the stimulating catheter at femoral nerve level, had an influence on the adequacy of post-surgical analgesia during the 48h after total knee arthroplasty. MATERIAL AND METHODS: A comparative, prospective and randomised study was conducted on patients subjected to total knee replacement. After surgery with subarachnoid anaesthesia, a continuous femoral block was performed with a stimulating catheter at a neurostimulation intensity 0.2 and 0.5mAmp in Group 1, between 0.6 and 1mAmp in Group 2, equal or higher than 1.1mAmp in Group 3, and in Group 4 the catheter was introduced between 3-5cm without looking for a motor response. A dose of 0.2% ropivacaine 0.4mL/kg and an infusion at 5mL/h, with boluses of 10mL/30min, was administered via the catheter. Sciatic nerve block was also performed on all patients with 20ml of 0.5% ropivacaine. The patient demographics were recorded, as well as, post-surgical analgesia details, sensory and motor block in each area, boluses requested, rescue analgesia, and undesirable effects at 8, 16, 24, 36 and 48h. RESULTS: A total of 124 patients were included, 32 in Group 1 (25.8%), 21 in Group 2 (16.9%), 31 in Group 3 (25%), and 40 in group 4 (32.3%). The 4 groups were homogeneous as regards age, height, weight and ASA. There were no statistically significant differences found in the post-operative pain, except during movement in the femoral area at 36 hours (p=.032). There were also no statistically significant differences found in the sensory block in the femoral area at 48 hours (p=.019) and in the femoral cutaneous nerve block at 8 hours (p=.049) or at 24 hours (p=.045). As regards motor block, differences were only found in the obturator nerve at 24 hours (p=.016). There were no differences in rescue analgesia, patient controlled analgesia (PCA) boluses requested or administered, except that the number of boluses requested at 16 hours was less in Group 3 (p=.049). There were also no significant differences in undesirable effects or in the level of satisfaction of the patients between the four groups. CONCLUSIONS: In our study, no influence was found on the level of analgesia provided after knee replacement surgery with the neurostimulation intensity to which the neuromuscular system involved responded when a stimulating catheter is inserted at femoral level.