Posterior Quadratus Lumborum Block in Total Hip Arthroplasty: A Randomized Controlled Trial.

BACKGROUND: Pain management is important for ensuring early mobilization after hip arthroplasty; however, the optimal components remain controversial. Recently, the quadratus lumborum block has been proposed as an analgesic option. The current study tested the hypothesis that the posterior quadratus lumborum block combined with multimodal analgesia decreases morphine consumption after hip arthroplasty. METHODS: This study was a prospective, randomized, double-blind, placebo-controlled trial. Before general anesthesia, 100 participating patients scheduled for elective total hip arthroplasty were randomly allocated to receive a 30-ml injection posterior to the quadratus lumborum muscle with either 0.33% ropivacaine (n = 50) or normal saline (n = 50). For all patients, multimodal analgesia included systematic administration of acetaminophen, ketoprofen, and a morphine intravenous patient-controlled analgesia. The primary outcome was total intravenous morphine consumption in the first 24 h. Secondary outcomes recorded intraoperative sufentanil consumption; morphine consumption in the postanesthesia care unit; pain scores at extubation and at 2, 6, 12, and 24 h; motor blockade; time to first standing and ambulation; hospital length of stay; and adverse events. RESULTS: There was no significant difference in the 24-h total morphine consumption (ropivacaine group, median [interquartile range], 13 [7 to 21] versus saline group, 16 [9 to 21] mg; median difference, -1.5; 95% CI, -5 to 2; P = 0.337). Pain scores were not different between the groups (ß = -0.4; 95% CI, -0.9 to 0.2; P = 0.199). There was no statistical difference between the two groups in intraoperative sufentanil consumption, morphine consumption in the postanesthesia care unit, motor blockade, times to first standing (median difference, 0.83 h; 95% CI, -1.7 to 3.4; P = 0.690) and ambulation (median difference, -1.85 h; 95% CI, -4.5 to 0.8; P = 0.173), hospital length of stay, and adverse events. CONCLUSIONS: After elective hip arthroplasty, neither morphine consumption nor pain scores were reduced by the addition of a posterior quadratus lumborum block to a multimodal analgesia regimen.

Real-Time Injection Pressure Sensing and Minimal Intensity Stimulation Combination During Ultrasound-Guided Peripheral Nerve Blocks: An Exploratory Observational Trial.

BACKGROUND: Nerve damage can occur after peripheral nerve block (PNB). Ultrasound guidance does not eliminate the risk of intraneural injection or nerve injury. Combining nerve stimulation and injection pressure (IP) monitoring with ultrasound guidance has been suggested to optimize needle tip location in PNB. In this prospective observational study, we hypothesized that measured pairs of IP and minimum intensity of stimulation (MIS) might differentiate successive needle tip locations established by high-resolution ultrasound during PNB. METHODS: For this exploratory study, 240 observations for 40 ultrasound-guided PNBs were studied in 28 patients scheduled for orthopedic surgery. During the progression of the needle to the nerve observed by ultrasonography, the IP was measured continuously using a computerized pressure-sensing device with a low flow rate of solution. Stimulation thresholds and electrical impedance were obtained by an impedance analyzer coupled to the nerve stimulator at 6 successive needle positions. The median (quartile) or mean (95% confidence interval [CI]) was reported. A mixed model analysis was used, and the sample was also explored using a classification and regression tree (CART) algorithm. RESULTS: Specific combinations of IP and MIS were measured for subcutaneous, epimysium contact, intramuscular, nerve contact (231 mm Hg [203-259 mm Hg] and 1.70 mA [1.38-2.02 mA]), intraneural location (188 mm Hg [152-224 mm Hg] and 0.58 mA [0.46-0.70 mA]), and subparaneural location (47 mm Hg [41-53 mm Hg] and 1.35 mA [1.09-1.61 mA]). The CART algorithm shows that the optimal subparaneural needle tip position might be defined by the lowest pressure (<81.3 mm Hg) and MIS (<1.5 mA) cutoffs. CONCLUSIONS: Our exploratory study evaluated concepts to generate hypotheses. The combinations of IP and MIS might help the physician during a PNB procedure. A low IP and low MIS might confirm a subparaneural location, and a high IP and a low MIS might be an alert for the intraneural location of the needle tip.

Percutaneous Needle Tenotomy for the Treatment of Muscle and Tendon Contractures in Adults With Brain Damage: Results and Complications.

OBJECTIVE: To study the results and complications of percutaneous needle tenotomy for superficial retracted tendons in patients with brain damage. DESIGN: Prospective observational study. SETTING: University hospital. PARTICIPANTS: Patients with severe brain damage (N=38; mean age, 60.7y; age range, 24-93y; 21 women) requiring surgical management of contractures and eligible for percutaneous needle tenotomy were enrolled between February 2015 and February 2016. INTERVENTIONS: The percutaneous needle tenotomy gesture was performed by a physical medicine and rehabilitation physician trained by an orthopedic surgeon, under local or locoregional anesthesia. Treated tendons varied among patients. MAIN OUTCOME MEASURES: All patients were evaluated at 1, 3, and 6 months to assess surgical outcomes (joint range of motion [ROM], pain, and functional improvement) while screening for complications. RESULTS: Improvements in ROM (37/38) and contractures-related pain (12/12) were satisfactory. Functional results were satisfactory (Goal Attainment Scale score ≥0) for most patients (37/38): nursing (n=12), putting shoes on (n=8), getting in bed or sitting on a chair (n=6), verticalization (n=7), transfers and gait (n=8), and grip (n=2). Five patients had complications related to the surgical gesture: cast-related complications (n=2), hand hematoma (n=2), and cutaneous necrosis of the Achilles tendon in a patient with previous obliterative arteriopathy of the lower limbs (n=1). CONCLUSIONS: Percutaneous needle tenotomy yields good results in the management of selected superficial muscle and tendon contractures. The complications rate is very low, and this treatment can be an alternative to conventional surgery in frail patients with neurologic diseases.

Diagnosis of Postoperative Urinary Retention Using a Simplified Ultrasound Bladder Measurement.

BACKGROUND: In this study, we sought to determine whether a simplified ultrasound measurement of the largest transverse diameter, using a standard ultrasound machine, could be used to diagnose postoperative urinary retention (POUR). This method may replace expensive bladder volume measuring devices or a more complex ultrasound procedure (involving the measurement of 3 bladder diameters). METHODS: Patients at risk of POUR if unable to void after orthopedic surgery were evaluated in the postanesthesia care unit before discharge. Bladder diameter was first measured using a portable ultrasound device (Vscan®; GE Healthcare, Wauwatosa, WI). An automated evaluation of bladder volume was then performed (Bladderscan® BVI 3000; Diagnostic Ultrasound, Redmond, WA). Finally, when a bladder catheterization was performed, the actual urinary volume was measured. The main outcome was a bladder volume ≥600 mL as measured using the automated ultrasound scanner (Bladderscan BVI 3000) or by catheterization. Correlations between bladder volumes and diameter were studied and receiver operating characteristic curves were constructed to determine the performance in predicting a bladder volume ≥600 mL. A "gray zone" approach was developed because a single cutoff value may not always be clinically significant. RESULTS: One hundred patients were included and underwent a Bladderscan measurement. Urinary volume after catheterization was obtained in 49 patients. A significant correlation was found between the largest transverse diameter and urinary volumes assessed by the 2 methods (Bladderscan and catheterization). Pearson correlation coefficients were r = 0.80 (95% confidence interval [CI], 0.72-0.86; P < 0.001) and r = 0.79 (95% CI, 0.65-0.88; P < 0.001), respectively. The area under the receiver operating characteristic curves for the prediction of a bladder volume ≥600 mL were 0.94 (95% CI, 0.88-0.98) and 0.91 (95% CI, 0.79-0.97), respectively, for urinary volumes assessed by Bladderscan and catheterization. The optimal cutoff value was 9.7 cm for both methods. The gray zone was narrow, ranging from 9.7 to 10.7 cm thus limiting inconclusive measurements. CONCLUSIONS: A simple ultrasound measurement of the largest transverse bladder diameter seemed to be helpful to exclude or confirm POUR.

Management of mediastinal syndromes in pediatrics: a new challenge of ultrasound guidance to avoid high-risk general anesthesia.

Adverse events associated with anesthetic management of anterior mediastinal masses in pediatrics are common. To avoid an extremely hazardous general anesthesia, the use of real-time ultrasonography offers an effective alternative in high-risk cases. We report the anesthetic management including a light sedation and ultrasound guidance for regional anesthesia, surgical node biopsy, and placement of a central venous line in two children with an anterior symptomatic mediastinal mass. For pediatric patients with clinical and/or radiologic signs of airway compression, ultrasound guidance provides safety technical assistance to avoid general anesthesia and should be performed for the initial diagnostic and therapeutic procedures.

Plantar compartment block for hallux valgus surgery: a proof-of-concept anatomic and clinical study.

BACKGROUND: Hallux valgus surgery is associated with moderate to severe postoperative pain. We hypothesized that a plantar compartment block may be a good technique for postoperative analgesia. We describe an anatomic approach to ultrasound-guided plantar compartment block and assess the clinical efficacy of the block for outpatient surgery. METHODS: The anatomic study was aimed to describe the plantar compartment, using both dissection methods and imaging, and to define a volume of local anesthetic. Patients scheduled for hallux valgus surgery with a popliteal sciatic nerve block, and combined plantar compartment and peroneal blocks were included in the clinical study. Data on attaining the criteria for rapid exit from the outpatient center, duration of sensory and analgesic block, visual analog scale (VAS) values for postoperative pain at rest and during movement, and the consumption of morphine as rescue analgesia were recorded. RESULTS: Plane-by-plane dissections and cross-sections were done in five cadaveric lower limbs. The medial calcaneal nerve divides into medial plantar and lateral plantar nerves in the upper part of the plantar compartment. These nerves were surrounded by 5 mL of colored gelatin, and 10 mL of injectates dye spread to the medial calcaneal branches. Thirty patients (26 women) were included in the clinical study. There were no failures of surgical block. Ninety per cent of patients successfully passed functional testing for ambulatory exit from the center within 5 hours (25th-75th centiles, 3.8-5.5 hours). The median duration of plantar compartment sensory block was 17.3 hours (10.5-21.5 hours), and the first request for rescue analgesic was 11.75 hours (10.5-23 hours) after surgery. The median VAS score for maximum pain reported within the 48-hour period was 2 (1-6). Twelve patients received 2.5 mg (0-5 mg) of morphine on day 1. Patients were highly satisfied and no adverse events were noted. CONCLUSIONS: This anatomic description of the ultrasound-guided plantar compartment block reported the injection area to target the medial and lateral plantar nerves with 5 mL of local anesthetic. Normal walking without assistance is attained rapidly with this regional anesthesia technique, and the time to request postoperative analgesia after hallux valgus surgery is long. TRIAL REGISTRATION NUMBER: NCT03815422.

Case report: Three-dimensional high-resolution ultrasound-guided nerve blocks: a new panoramic vision of local anesthetic spread and perineural catheter tip location.

We report in 3 patients that high-frequency ultrasound 3-dimensional imaging enabled us to analyze anatomic variations, evaluate local anesthetic spread, and optimize a perineural catheter location by withdrawing it until its tip was appropriately positioned. This innovative technology may provide answers to different problems facing the operator performing ultrasound-guided nerve blocks. It may enhance predictability and safety aspects of peripheral nerve blocks.

The new technological trends in ultrasound-guided regional anesthesia.

PURPOSE OF REVIEW: Real-time two-dimensional ultrasound guidance is undoubtedly one of the most important evolutions in the field of regional anesthesia techniques, for peripheral nerve blocks and neuraxial anesthesia. The recent literature has been analyzed for studies concerning new technological trends in ultrasound-guided regional anesthesia. This review focuses on electromagnetic tracking systems for ultrasound guidance and three/four-dimensional ultrasound imaging in regional anesthesia. RECENT FINDINGS: Electromagnetic tracking can facilitate needle-beam alignment for in-plane approaches and indicates where the needle crosses the beam during out-of-plane ultrasound-guided procedures. Three-dimensional ultrasound imaging can provide more detailed anatomical information and better spatial orientation than two-dimensional imaging. Four-dimensional ultrasound imaging enhances the visualization of a particular anatomy and offers real-time assessment of local anesthetic spread during ultrasound-guided regional anesthesia. These techniques have some limitations and drawbacks limiting their expansion. SUMMARY: This article describes the principles, technology and development of electromagnetic tracking system for ultrasound guidance and three/four-dimensional ultrasound imaging in regional anesthesia, considering whether these new technologies will have impending applications in clinical practice.

Continuous peripheral nerve blocks for analgesia of ventilated critically ill patients with multiple trauma: a prospective randomized study.

BACKGROUND: Sedation of ventilated critically ill trauma patients requires high doses of opioids and hypnotics. We aimed to compare the consumption of opioids and hypnotics, and patient outcomes using sedation with or without continuous regional analgesia (CRA). METHODS: Multiple trauma-ventilated patients were included. The patients were randomized to receive an intravenous analgesia (control group) or an addition of CRA within 24h of admission. A traumatic brain injury (TBI) patients group was analyzed. The primary endpoint was the cumulative consumption of sufentanil at 2 days of admission. Secondary endpoints were cumulative and daily consumption of sufentanil and midazolam, duration of mechanical ventilation, intensive care unit (ICU) stay, and safety of CRA management. RESULTS: Seventy six patients were analyzed: 40 (67.5% males) in the control group and 36 (72% males) in the CRA group, respectively. The median [IQR] Injury Severity Score was 30.5 [23.5-38.5] and 26.0 [22.0-41.0]. The consumption of sufentanil at 48h was 725 [465-960] µg/48h versus 670 [510-940] µg/48h (p = 0.16). Daily consumption did not differ between the groups except on day 1 when consumption of sufentanil was 360 [270-480] µg vs. 480 [352-535] µg (p = 0.03). Consumptions of midazolam did not differ between the groups. No difference was noted between the groups according to the secondary endpoints. CONCLUSIONS: CRA does not decrease significantly sufentanil and midazolam consumption within the first 5 days after ICU admission in multiple trauma-ventilated patients. The use of peripheral nerve blocks in heavily sedated and ventilated trauma patients in the ICU seems safe.

Where should the tip of the needle be located in ultrasound-guided peripheral nerve blocks?

PURPOSE OF REVIEW: Data now exist describing the appropriate positioning of the needle tip and pattern of local anaesthetic spread after injection. The recent literature has been analysed in search of studies on the optimal procedure for common approaches centred on block efficacy, performance time, and safety. RECENT FINDINGS: Large peripheral nerves are surrounded by a gliding layer, the adventitia or paraneurium. Ultrasonically, a circumneural spread corresponds to adventitial extraneural injection. Nerve expansion with fascicular separation matches intraneural injection. Deliberate intraneural injection remains controversial, and is not advisable at the present time. For popliteal sciatic nerve blocks, positioning the needle in the common nerve sheath between the tibial and peroneal components and obtaining a circumneural spread surrounding both divisions predict rapid surgical anaesthesia. Using axillary and infraclavicular approaches, ultrasound-guided perivascular injection aiming at circumferential spread around the artery appears a valuable alternative to individual targeted nerve injections. For single injection interscalene block, an injection into the fascial sheath but far from the plexus proved to be as effective as an injection adjacent to the nerve structures. Fascial plane approaches are appealing alternatives for thin nerves that run between muscles and cannot be regularly visualized with the current resolution of ultrasound systems. SUMMARY: The ultrasound appearance of nerves and target injections are better understood. The specific distributions of local anaesthetic spread that predict success are significantly different from one anatomical site to another. It seems advisable to avoid intraneural injection.

Remote transmission monitoring for postoperative perineural analgesia after major orthopedic surgery: A multicenter, randomized, parallel-group, controlled trial.

STUDY OBJECTIVE: After surgery, patients reported the delay in receiving help as the primary factor for poorly controlled pain. This study aimed to compare the effectiveness of patient management through two communication modalities: remote transmission (RT) versus bedside control (BC). We hypothesized that using remote technology for pump programming may provide the best postoperative infusion regimen for the patient's self-assessment of pain and adverse events. DESIGN: A multicenter, randomized, parallel-group, controlled trial. SETTING: Anesthesiology department and orthopedic surgery ward at three university hospitals. PATIENTS: Eighty patients undergoing orthopedic surgery with postoperative perineural patient-controlled analgesia were included. INTERVENTIONS: Two groups (n = 40 for each group) were formed by randomization. In the postoperative period, perineural analgesia was followed up via an RT system or BC for 72 h. MEASUREMENTS: A nurse assessed daily pain, sensory and motor blocks and adverse events. Patients completed a questionnaire three times a day and alerted for any problem according to the group (RT system or nurses' follow-up). On the third postoperative day, the nurse removed the catheter, completed the final assessment, and collected the historical data from the pump. A physician's shorter response time to change the patient control analgesia (PCA) program was the primary endpoint. RESULTS: Of the 80 patients, 71 were analyzed (34 were randomized to the RT group and 37 to the BC group). Fifty-eight pump setting changes were noted. Analysis of repeated evaluations shows that mean time (SD) to change the PCA pump settings was significantly lower in the RT group (20 min (22.3 min)) than in the BC group (55.9 min (71.1 min)); mean difference [95% CI], -35.9 min [-74.3 to 2.4]); ß estimation [95% CI], -34 [-63 to -6], p = 0.011). Pain relief, sensory and motor blocks did not differ between the groups: ß estimation [95% CI], 0.1 [-0.4 to 0.6], p = 0.753; 0.5 [-0.4 to 1.4], p = 0.255; 0.9 [-0.04 to 1.8], p = 0.687, respectively. ß = -34 [-63 to -6], p = 0.011). The consumption of ropivacaine, nurse workload and the cost of the analgesia regimen decreased in the RT group. No differences were noted in satisfaction scores or complication rates. CONCLUSIONS: The response time for the physician to change the PCA program when necessary was shorter for patients using RT and alerts to the physician were more frequent compared with spot checks by nurses. RT helps to decrease nurses' workload, ropivacaine consumption, and costs but did not affect postoperative pain relief, complication rate, or patient-reported satisfaction score. IRB CONTACT INFORMATION: Comité de Protection des Personnes, Sud Méditerranée III, Montpellier-Nîmes, France, registration number EudraCT A01698-35. CLINICAL TRIAL NUMBER: ClinicalTrials.gov ID:NCT02018068 PROTOCOL: The full trial protocol can be accessed at Department of Anesthesiology and Critical Care Medicine, Medical Research and Statistics Unit, Lapeyronie University Hospital, Avenue Doten G Giraud, Montpellier, France. s-bringuierbranchereau@chu-montpellier.fr.

A new lateral approach to the parasacral sciatic nerve block: an anatomical study.

BACKGROUND: Sciatic nerve block is a commonly used technique for providing anesthesia and analgesia to the lower extremity. At the parasacral level, the nerve block is classically performed via a posterior approach in lateral decubitus position causing patient's discomfort. Therefore, we aimed to conduct an anatomical study describing a new lateral approach to the parasacral sciatic nerve in supine position. METHODS: The skin entry point was located on the vertical line through the greater trochanter (GT) at the midpoint between the anterior superior iliac spine (ASIS) level and the GT. The angle to the skin was 10° dorsally oriented. According to these palpable anatomical landmarks, the parasacral lateral approach was simulated bilaterally in four cadavers in supine position. Anatomical dissection allowed assessment of the needle tip position with regard to the sciatic nerve. Then, to refine the anatomical description of this new lateral approach, 40 pelvic computer tomography (CT) examinations were retrospectively selected and post-processed to bilaterally simulate the needle route to the sciatic nerve. The skin-nerve distance, the optimal angle to the skin, and the sciatic nerve anteroposterior diameter at parasacral and ischial tuberosity levels, respectively were recorded by two independent readers. RESULTS: Cadaver dissection showed that the needle tip was placed in the vicinity of the sciatic nerve in 8/8 cases. Then, CT-simulated lateral approach demonstrated a mean skin-nerve distance of 128 mm (81-173), and a 12° dorsally oriented (5-22) optimal angle to the skin. The sciatic nerve anteroposterior diameter was 10 mm (7-15) at the parasacral level, and 7 mm (5-10) more caudally at the ischial tuberosity level. No significant intra- or inter-observer variability was observed. CONCLUSION: This study describes a new lateral approach to the parasacral sciatic nerve block in supine position. These anatomical results should be confirmed by further clinical studies.

An uncommon cause of nerve stimulator's malfunction during a dual guidance lumbar plexus block: A technical brief report and an algorithm for prevention of complications.

Posterior Lumbar plexus block (PLPB) combined with an ipsilateral sacral plexus block is a valuable anaesthetic technique in patients undergoing hip fracture surgery. PLPB is performed through the acoustic window of the lumbar ultrasound trident and the position of the needle tip, before injection of LA, was confirmed by observing quadriceps femoris muscle contraction to peripheral nerve stimulation (i.e., dual guidance). We report an uncommon cause of nerve stimulator malfunction that might impair block performance and promote complications. We add an algorithm to limit the risk of complications.

Impact of multiple nerves blocks anaesthesia on intraoperative hypotension and mortality in hip fracture surgery intermediate-risk elderly patients: A propensity score-matched comparison with spinal and general anaesthesia.

BACKGROUND: A Hip fracture in the intermediate-risk elderly patient is common and associated with a high rate of postoperative morbidity and mortality. There is a lack of consensus on the optimal anaesthetic technique but there is a clear association between intraoperative hypotension and postoperative morbidity and mortality. We aimed to compare the haemodynamic stability of three anaesthesia techniques: general anaesthesia (GA), continuous spinal anaesthesia (CSA), and multiple nerve blocks (MNB). METHODS: The primary outcome was the occurrence of intraoperative hypotension defined by a 30% decrease in mean arterial pressure (MAP) from baseline. Secondary outcomes included incidence of hypotension under 50 mmHg of MAP, time spent below MAP 50 mmHg, use of vasopressors, in-hospital and 30-day mortality. A propensity score-matched analysis was performed. RESULTS: After screening and application of the exclusion criteria, 593 patients undergoing hip fracture surgery between the 1st of January 2015 and the 31st of December 2016 were included. The propensity score match analysis selected 43 patients in each group. The incidence of hypotension was significantly higher in the GA group than in the MNB and CSA groups: 39 (90%), 22 (51%), and 23 (53.5%), respectively; p < 0.0001. The incidence of MAP < 50 mmHg (59.5%, 23.3%, and 16.3%; p < 0.0001) and the use of vasopressors (93%, 39.5%, and 25.6%; p < 0.0001) were increased significantly in the GA group. With the GA group as a reference, odds ratios were reported in the MNB group at 0.08 [0.022-0.30] (p = 0.0002) for hypotension episodes; 0.17 [0.04-0.66] (p = 0.01) for hypotension < 50 mmHg for more than 3 min and 0.049 [0.013-0.018] (p < 0.0001) for use of vasopressors. The duration of hospital stay, postoperative complications, in-hospital and 30-day mortality rates did not differ significantly between the groups. CONCLUSION: CSA and MNB provide better haemodynamic stability than GA. However, whatever the anaesthesia technique used, the mortality rates do not change even if MNB leads to less hypotension. IRB contact information: CERAR IRB 00010254-2016-118. Clinical Trial Number: ClinicalTrials.gov. ID: NCT03356704.

Combination of real-time needle-tip pressure sensing and minimal intensity stimulation limits unintentional intraneural injection during an ultrasound-guided peripheral nerve block procedure: A randomized, parallel group, controlled trial.

STUDY OBJECTIVE: Ultrasound guidance does not eliminate the risk of intraneural injection, which must be avoided during PNB. Combining ultrasound guidance (USG), nerve stimulation (NS), and injection pressure monitoring is advocated to prevent nerve injury during PNB. We hypothesized that combining patient-tailored dynamic NS and real-time pressure sensing (RTPS) could reduce the incidence of intraneural injection and nerve puncture during USG PNB compared with a traditional fixed thresholds (Control) procedure. DESIGN: Randomized, prospective study. SETTING: Operating room. PATIENTS: One hundred ASA physical status I to III patients undergoing orthopedic surgery. INTERVENTIONS: Patient anesthetized using axillary, sciatic or femoral USG PNB were randomized to the PresStim group (Dynamic RTPS and NS set at 1.5 mA then decreased; n = 50) or Control group (fixed thresholds for in-line pressure mechanical manometer and NS at 0.2 mA; n = 50). MEASUREMENTS: Procedural ultrasound images and videos were recorded, stored and reviewed in random order by two experts in ultrasound-guided PNB blinded to the group. They noted the needle-to-nerve relationship and intraneural injection for all blocked nerves. MAIN RESULTS: One hundred and twenty-three USG PNBs were performed (56 axillary brachial plexus blocks, 40 femoral nerve blocks and 27 sciatic popliteal nerve blocks); 235 blocked nerves and videos were recorded and analyzed (PresStim, 118; Control, 117). Less paresthesia was noted in the PresStim group (12.7%) compared with the Control group (18.8%). The risk of intraneural injection was significantly higher in the Control group (odds ratio [OR], 17.1; 95% confidence interval [CI], 2.2-135, P = 0.007). The risk of nerve puncture (OR, 22.7; 95% CI, 2.9-175, p = 0.003) and needle-nerve contact (OR, 4.7; 95% CI, 2.4-9.5, p < 0.001) was significantly higher in the Control group than the PresStim group. CONCLUSIONS: Under the conditions of the study, dynamic triple monitoring combining RTPS, NS and USG decreases intraneural injection and unintentional needle-nerve contact and puncture during a PNB procedure.

Estimation and pharmacodynamic consequences of the minimum effective anesthetic volumes for median and ulnar nerve blocks: a randomized, double-blind, controlled comparison between ultrasound and nerve stimulation guidance.

BACKGROUND: Nerve stimulation and ultrasound guidance are the most popular techniques for peripheral nerve blocks. However, the minimum effective anesthetic volume (MEAV) in selected nerves for both techniques and the consequences of decreasing the local anesthetic volume on the pharmacodynamic characteristics of nerve block remain unstudied. We designed a randomized, double-blind controlled comparison between neurostimulation and ultrasound guidance to estimate the MEAV of 1.5% mepivacaine and pharmacodynamics in median and ulnar nerve blocks. METHODS: Patients scheduled for carpal tunnel release were randomized to ultrasound guidance (UG) or neurostimulation (NS) groups. A step-up/step-down study model (Dixon method) was used to determine the MEAV with nonprobability sequential dosing based on the outcome of the previous patient. The starting dose of 1.5% mepivacaine was 13 and 11 mL for median and ulnar nerves at the humeral canal. Block success/failure resulted in a decrease/increase of 2 mL. A blinded physician assessed sensory blockade at 2-minute intervals for 20 minutes. Block onset time and duration were noted. RESULTS: The MEAV50 (SD) of the median nerve was lower in the UG group 2 (0.1) mL (95% confidence interval [CI] = [1, 96] to [2, 04]) than in the NS group 4 (3.8) mL (95% CI = [2, 4] to [5, 6]) (P = 0.017). There was no difference for the ulnar nerve between UG group 2 (0.1) mL (95% CI = [1, 96] to [2, 04]) and NS group 2.4 (0.6) mL (95% CI = [2, 1] to [2, 7]). The duration of sensory blockade was significantly correlated to local anesthetic volume, but onset time was not modified. CONCLUSION: Ultrasound guidance selectively provided a 50% reduction in the MEAV of mepivacaine 1.5% for median nerve sensory blockade in comparison with neurostimulation. Decreasing the local anesthetic volume can decrease sensory block duration but not onset time.