Effect of Total Dose of Lidocaine on Duration of Adductor Canal Block, Assessed by Different Test Methods: A Report of Two Blinded, Randomized, Crossover Studies in Healthy Volunteers.

BACKGROUND: The binary aims of this study were to investigate the effect of total dose of lidocaine on duration of an adductor canal block (ACB) and to validate different methods used to assess nerve blocks. METHODS: We performed 2 blinded, randomized, controlled crossover trials, including healthy, young men. In study 1, 14 subjects received 4 ACBs with saline and 40, 80, and 160 mg lidocaine. In study 2, 14 new subjects received 2 ACBs with 100 and 300 mg lidocaine. We kept volume constant at 20 mL for all blocks, only altering concentration. ACB duration was assessed every hour postblock using mechanical (primary outcome) and temperature discrimination; warmth and heat pain detection thresholds; pain during heat stimulation; and tolerance to electrical current in the saphenous distribution. Finally, we measured quadriceps femoris muscle strength (clinical trial registration: NCT02172729). RESULTS: In study 1, block duration assessed by mechanical discrimination differed significantly when comparing the 40-mg dose with the 80-mg dose (mean difference, 1.15 hours; 99% confidence interval [CI], 0.38-2.09 hours) and with the 160-mg dose (mean difference, 0.92 ours; 99% CI, 0.17-1.62). However, there was no difference between the 80-mg and 160-mg doses (mean difference, -0.23 hour; 99% CI, -1.12 to 0.46 hours). Neither for the secondary outcomes were there any differences between the 80- and 160-mg doses (99% CI including 0). Because of 38% (5/13) failed blocks in the 40-mg group, we decided to perform study 2. In study 2, all but 1 test showed no difference in duration despite a 3-fold increase in dose. The temperature discrimination test showed 100% sensitivity and specificity for differentiating between the presence and absence of block and was the only test with scores >90% for both parameters. CONCLUSIONS: We did not find evidence that increasing the total dose of lidocaine may prolong duration of an ACB. The temperature discrimination test was the only test with scores >90% for both specificity and sensitivity.

Adductor Canal Block With 10 mL Versus 30 mL Local Anesthetics and Quadriceps Strength: A Paired, Blinded, Randomized Study in Healthy Volunteers.

BACKGROUND AND OBJECTIVES: Adductor canal block (ACB) is predominantly a sensory nerve block, but excess volume may spread to the femoral triangle and reduce quadriceps strength. We hypothesized that reducing the local anesthetic volume from 30 to 10 mL may lead to fewer subjects with quadriceps weakness. METHODS: We performed a paired, blinded, randomized trial including healthy men. All subjects received bilateral ACBs with ropivacaine 0.1%; 10 mL in 1 leg and 30 mL in the other leg. The primary outcome was the difference in number of subjects with quadriceps strength reduced by more than 25% from baseline in 2 consecutive assessments. Secondary outcomes were quadriceps strength as a percentage of baseline at predefined time points, functional outcome assessed by the 30-Second Chair Stand Test (1 leg at a time), and sensory block. Clinicaltrials.gov Identifier: NCT01981746. RESULTS: We included and analyzed 26 subjects. For either volume, 2 subjects had a reduction in quadriceps strength by more than 25% from baseline (difference, 0%; 95% confidence interval, -13 to 13; P > 0.999). Similarly, we found no significant differences between volumes in quadriceps strength at any of the predefined time points or in sensory block. The only statistically significant difference between volumes was found in the 30-Second Chair Stand Test at 2 hours (P = 0.02), but this difference had disappeared at 4 hours (P = 0.06). CONCLUSIONS: Varying the volume of ropivacaine 0.1% used for ACB between 10 and 30 mL did not have a statistically significant or clinically relevant impact on quadriceps strength.

Adductor canal block for postoperative pain treatment after revision knee arthroplasty: a blinded, randomized, placebo-controlled study.

BACKGROUND: Revision knee arthroplasty is assumed to be even more painful than primary knee arthroplasty and predominantly performed in chronic pain patients, which challenges postoperative pain treatment. We hypothesized that the adductor canal block, effective for pain relief after primary total knee arthroplasty, may reduce pain during knee flexion (primary endpoint: at 4 h) compared with placebo after revision total knee arthroplasty. Secondary endpoints were pain at rest, morphine consumption and morphine-related side effects. METHODS: We included patients scheduled for revision knee arthroplasty in general anesthesia into this blinded, placebo-controlled, randomized trial. Patients were allocated to an adductor canal block via a catheter with either ropivacaine or placebo; bolus of 0.75% ropivacaine/saline, followed by infusion of 0.2% ropivacaine/saline. Clinicaltrials.gov ID: NCT01191593. RESULTS: We enrolled 36 patients, of which 30 were analyzed. Mean pain scores during knee flexion at 4 h (primary endpoint) were: 52 ± 22 versus 71 ± 25 mm (mean difference 19, 95% CI: 1 to 37, P = 0.04), ropivacaine and placebo group respectively. When calculated as area under the curve (1-8 h/7 h) pain scores were 55 ± 21 versus 69 ± 21 mm during knee flexion (P = 0.11) and 39 ± 18 versus 45 ± 23 mm at rest (P = 0.43), ropivacaine and placebo group respectively. Groups were similar regarding morphine consumption and morphine-related side effects (P > 0.05). CONCLUSIONS: The only statistically significant difference found between groups was in the primary endpoint: pain during knee flexion at 4 h. However, due to a larger than anticipated dropout rate and heterogeneous study population, the study was underpowered. TRIAL REGISTRATION: Clinicaltrials.gov NCT01191593.

Ultrasound-guided ilioinguinal/iliohypogastric nerve blocks for persistent inguinal postherniorrhaphy pain: a randomized, double-blind, placebo-controlled, crossover trial.

BACKGROUND: Ilioinguinal and iliohypogastric nerve blocks are used in the clinical management of persistent inguinal postherniorrhaphy pain, but no controlled studies have been published on the subject. In this controlled study, we investigated the analgesic and sensory effects of ultrasound-guided blocks of the ilioinguinal and iliohypogastric nerves with lidocaine. METHODS: A randomized, double-blind, placebo-controlled, crossover trial in 12 patients with severe persistent inguinal postherniorrhaphy pain, including a control group of 12 healthy controls, was performed. Assessments included pain ratings under standardized conditions with numerical rating scale (0-10), sensory mapping to a cool roller, and quantitative sensory testing (QST), in the groin regions, before and after each ultrasound-guided block. A needle approach of 1 to 2 cm superior and medial to the anterior superior iliac spine was used. Outcomes were changes in pain ratings, sensory mapping, and QST compared with preblock values. Lidocaine responders were a priori defined by a pain reduction of ≥80% after lidocaine block and ≤25% after placebo block, nonresponders by pain reduction of <80% after lidocaine block and ≤25% after placebo block, and placebo responders by pain reduction of >25% after placebo block. RESULTS: One of 12 pain patients was a lidocaine responder, 6 patients were nonresponders, and 5 patients were placebo responders. No consistent QST changes were observed in patients after the lidocaine block. In 10 of 12 healthy controls, a cool hypoesthesia area developed in the groin after the lidocaine block. Furthermore, QST assessments demonstrated significantly decreased suprathreshold heat pain perception in the groin after lidocaine versus placebo blocks (95% confidence interval = -3.5 to -0.5, P = 0.008). CONCLUSION: Ultrasound-guided lidocaine blocks of the ilioinguinal and iliohypogastric nerves, at the level of the anterior superior iliac spine, are not useful in diagnosis and management of persistent inguinal postherniorrhaphy pain.

Ultrasound-guided peripheral nerve blockade of the upper extremity.

PURPOSE OF REVIEW: Is ultrasound guidance changing the practice of upper extremity regional anesthesia? This review will aim to describe the findings published in the literature during the previous 18 months. RECENT FINDINGS: In some approaches to brachial plexus blockade, local anesthetic volumes may be reduced without deterioration of analgesic effect. However, even 10 ml of local injected into the interscalene space may result in diaphragmatic paresis. High-resolution ultrasonography has revealed anatomical variations of C5, C6 and C7 nerve roots in almost half of the patients examined, without negative block effectiveness. The addition of dexamethasone may prolong analgesia after single-shot interscalene and supraclavicular blocks. Insertion of brachial plexus perineural catheters using ultrasound guidance can be successful and provides better postoperative analgesia than single-shot blocks for up to 24 h postoperatively. Infraclavicular catheters provide superior analgesia when compared with supraclavicular catheters. Multiple-site injections of local offer no advantage over a single-site injection during an infraclavicular block. Ultrasound guidance compared with neurostimulation may reduce patient discomfort during axillary blocks compared with neurostimulation. Intra-epineural injections are common during an interscalene blockade, but the incidence of neurological injury remains low. There is an ongoing debate on the effectiveness and safety of ultrasound-guided intra-epineurial injections. SUMMARY: Current literature suggests a reduction of the volume of local anesthetics used for ultrasound-guided upper extremity blockades. Dexamethasone may prolong duration of brachial plexus blocks and more frequent use of perineural catheters is encouraged. Controversy over intra-epineurial injections exists and requires additional large-scale studies.

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.

Ultrasound-guided regional anesthesia (UGRA) is a growing area of both clinical and research interest. The following document contains the work produced by a joint committee from ASRA and the European Society of Regional Anesthesia and Pain Therapy. This joint committee was established to recommend to members and institutions the scope of practice, the teaching curriculum, and the options for implementing the medical practice of UGRA.This document specifically defines the following:1. 10 common tasks used when performing an ultrasound-guided nerve block,2. The core competencies and skill sets associated with UGRA,3. A training practice pathway for postgraduate anesthesiologists, and4. A residency-based training pathway.In both the residency and postgraduate pathways, training, competency, and proficiency requirements include both didactic and experiential components. The Joint Committee recommends that the decision to grant UGRA privileges be based at the individual institution level. Each institution that conducts UGRA is encouraged to support a productive quality improvement process.

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.

Ultrasound-guided regional anesthesia (UGRA) is a growing area of both clinical and research interest. The following document contains the work produced by a joint committee from ASRA and the European Society of Regional Anesthesia and Pain Therapy. This joint committee was established to recommend to members and institutions the scope of practice, the teaching curriculum, and the options for implementing the medical practice of UGRA.This document specifically defines the following:In both the residency and postgraduate pathways, training, competency, and proficiency requirements include both didactic and experiential components. The Joint Committee recommends that the decision to grant UGRA privileges be based at the individual institution level. Each institution that conducts UGRA is encouraged to support a productive quality improvement process.

Long-axis ultrasound imaging of the nerves and advancement of perineural catheters under direct vision: a preliminary report of four cases.

BACKGROUND AND OBJECTIVES: Ultrasound allows visualization of in plane needle insertion toward a nerve and the perineural spread of local anesthetic (LA) solution. However, advancement and final positioning of perineural catheters is difficult to visualize. We assessed the feasibility of long axis nerve scans for controlling perineural catheter placement. METHODS: Four orthopedic patients scheduled for continuous peripheral nerve blocks (interscalene, femoral, midfemoral sciatic, and popliteal sciatic), had perineural catheters inserted under ultrasound guidance. After obtaining adequate short axis images of the target nerves, the high frequency linear transducer was rotated 90 degrees to obtain long axis views. An 18-gauge epidural Tuohy needle was inserted tangentially to the nerve and the correct tip position was confirmed visually by small volume injections of LA. A rigid epidural catheter was inserted under the transducer's long plane and advanced into the desired perineural position. LA was then injected through the catheter and the spread was confirmed both on long axis and short axis scans. RESULTS: The catheters were captured on the long axis scans in all 4 patients, both exiting the needle tip, and during further advancement. They remained in situ for 3 to 5 days providing adequate postoperative analgesia and were removed uneventfully. CONCLUSIONS: This short case series suggests that long axis imaging of the nerve, the needle, and the catheter allows visualization of a catheter's advancement. Using to-and-fro movements, and slight rotation the needle's bevel, the catheter may be maneuvered under the ultrasound beam, which facilitates correct positioning.

Using stimulating catheters for continuous sciatic nerve block shortens onset time of surgical block and minimizes postoperative consumption of pain medication after halux valgus repair as compared with conventional nonstimulating catheters.

UNLABELLED: We prospectively tested the hypothesis that the use of a stimulating catheter improves the efficacy of continuous posterior popliteal sciatic nerve block in 100 randomized patients scheduled for elective orthopedic foot surgery. After eliciting a sciatic mediated muscular twitch at < or = 0.5 mA nerve stimulation output, the perineural catheter was advanced 2-4 cm beyond the tip of the introducer either blindly (Group C; n = 50) or stimulating via the catheter (Group S; n = 50). A bolus dose of 25 mL of 1.5% mepivacaine was followed by a postoperative patient-controlled infusion of 0.2% ropivacaine (basal infusion: 3 mL/h; incremental dose: 5 mL; lockout time: 30 min). Propacetamol 2 g IV was administered every 8 h, and opioid rescue analgesia was available if required. Catheter placement required 7 +/- 2 min in Group S and 5 +/- 2 min in Group C (P = 0.056). A significantly shorter onset time of both sensory and motor blocks was noted in Group S. No difference in quality of pain relief at rest and during motion was reported between the groups. Median (range) local anesthetic consumption during the first 48 h after surgery was 239 mL (175-519 mL) and 322 mL (184-508 mL) in Groups S and C, respectively (P = 0.002). Rescue opioid analgesia was required by 12 (25%) and 28 (58%) patients in Groups S and C, respectively (P = 0.002). We conclude that the use of a stimulating catheter results in shorter onset time of posterior popliteal sciatic nerve block, similar pain relief with reduced postoperative consumption of local anesthetic solution, and less rescue opioid consumption. IMPLICATIONS: This prospective, randomized, blind investigation demonstrated that the use of a stimulating catheter for continuous posterior popliteal sciatic nerve block resulted in shorter onset time of sensory and motor blocks and less local anesthetic consumption and need for rescue pain medication after elective orthopedic foot surgery compared with blind catheter advancement.

Clinical evaluation of the lateral sagittal infraclavicular block developed by MRI studies.

BACKGROUND AND OBJECTIVES: Lateral sagittal infraclavicular block by single injection has a faster performance time and causes less discomfort than does axillary block by multiple injections. This prospective, descriptive, multicenter study assessed block effectiveness, onset time, and incidence of adverse events and verified the noninvasive measurements from magnetic resonance imaging (MRI). METHODS: One hundred sixty patients were anesthetized by use of the lateral sagittal infraclavicular block and following the MRI recommendations for needle insertion. Each patient received a mixture that contained equal volumes of ropivacaine 7.5 mg/mL and mepivacaine 20 mg/mL with epinephrine 5 mug/mL, in a total amount that corresponded to 0.5 mL/kg (minimum 30 mL, maximum 50 mL). Block effectiveness (analgesia or anesthesia of all 5 nerves below the elbow after 30 minutes), performance and onset times, needle insertion depth and dorsal angle, twitch type, analgesia of the individual nerves, and incidence of adverse events and complications, as well as patient's acceptance, were recorded. RESULTS: One hundred forty-three patients (91%) had successful blocks, 12 patients required supplementary nerve blocks in the axilla, 3 patients had total failures of blocks (no forearm analgesia at all), and 2 patients were excluded from the assessments. Median block performance time was 4 minutes (range, 2-10 minutes) and the onset time 20 minutes (range, 10-50 minutes). Plexus nerves were found at a mean depth of 53 mm +/- 10 mm and the needle dorsal angle was 23 degrees +/- 9 degrees . Four patients experienced painful paresthesias and 3 patients had accidental punctures of axillary vessels. Signs or symptoms of complications (hematoma, local anesthetic toxicity, pneumothorax, or neuropraxias) were not observed. Only 3 patients would prefer general anesthesia in the future. Finger/wrist extension may be an optimal twitch response (P = .14). CONCLUSIONS: Block effectiveness (91%) and onset time (20 minutes) were satisfactory and comparable to the vertical paracoracoid approach. The low rate of axillary vessel punctures (2%) may be the most important advantage of this block. The needle insertion depth measurements confirmed the MRI findings, but the dorsal angle was steeper than predicted.

Patients' perception of pain during axillary and humeral blocks using multiple nerve stimulations.

BACKGROUND AND OBJECTIVES: Axillary or humeral blocks by multiple nerve stimulation (MNS) are used for ambulatory hand surgery. This double-blind study identified which of the three main components of the procedure (repeated needle passes, local anesthetic injections, or electrical stimulations) is most painful, quantified its intensity, and recorded patients' preferences for a future anesthetic. METHODS: Eighty unsedated ambulatory patients were randomized to 2 equal groups: axillary (A) and humeral (H). In each patient, 4 terminal motor nerves (musculocutaneous, median, ulnar, and radial) were electrolocated by use of an initial current of 2 mA, 0.1 ms and a target current of 0.1 to 0.5 mA. After block placement and before the start of surgery, patients were requested to identify which of the 3 main components of the block was most unpleasant and to quantify its intensity on a visual analog scale (VAS) of 0 to 100. Twenty minutes after completion of the block, the unblocked nerves were electrolocated at the elbow and supplemented. Patients were declared ready for surgery when they had complete analgesia of the hand and forearm. Before discharge from the hospital, patients indicated which anesthetic method (block alone, block plus sedation, or general anesthesia) they would choose for future hand surgery. RESULTS: Twenty-seven patients in group A vs. 17 patients in group H reported electrical stimulations as the most unpleasant block component (P =.03). No significant differences occurred in any of the VAS scores. Patients' request for the same anesthetic, 35 in group A and 37 in group H, were similar. Group A patients were ready for surgery sooner than group H patients (mean 26 minutes vs. mean 30 minutes for group H patients; P =.04). No serious complications were observed. CONCLUSIONS: This study found that more axillary-block patients compared with humeral-block patients reported electrical stimulation as the most unpleasant part of the block but failed to detect significant differences in the intensity of the 3 block components (repeated needle passes, local anesthetic injections, and electrical stimulations). Most patients in both groups would accept the same block for future hand operations. Patients were ready for surgery sooner after axillary block, but the clinical importance of this finding is doubtful.

Injection pressures by anesthesiologists during simulated peripheral nerve block.

BACKGROUND AND OBJECTIVES: Anesthesiologists typically rely on a subjective evaluation ("syringe feel") of possible abnormal resistance to injection while performing a peripheral nerve block (PNB). A greater force required to perform the injection is believed to be associated with intraneural injection. The hypothesis of this study is that anesthesiologists vary in their perception of "normal" injection force, that the syringe feel method is inconsistent in estimating resistance, and that needle design may affect the injection force. METHODS: Thirty anesthesiologists were asked to inject a local anesthetic, as they would in their everyday practice, through a commonly used syringe and needle assembly. Injection force was measured using an in-line manometer coupled to a computer via an analog-to-digital conversion board. In addition, injection force at clinically relevant injection speeds was determined using 3 differently sized needles from 4 different manufacturers. RESULTS: During a steady injection rate, all anesthesiologists perceived an increase in the force required to inject, even with minor pressures changes (0.6 +/- 0.3 psi). However, the 30 anesthesiologists, 21 (70%) initiated injection using a force that resulted in pressures greater than 20 psi; 15 (50%) used a force greater than 25 psi, and 3 (10%) exerted pressures greater than 30 psi. Pressures varied as much as 20-fold among needles of the same gauge/length from different manufacturers (P <.01). CONCLUSIONS: Anesthesiologists vary widely in their perception of appropriate force and rate of injection during PNB. The syringe-feel method of assessing injection force is inconsistent and may be further affected by variability in needle design.