Median Nerve Block Research Articles

Ultrasound-guided proximal radial, ulnar, median and musculocutaneous (RUMM) nerve block in rabbit (Oryctolagus cuniculus) cadavers: medial vs lateral approach

Ultrasound-guided proximal radial, ulnar, median and musculocutaneous (RUMM) nerve block in rabbit (Oryctolagus cuniculus) cadavers: medial vs lateral approach

Carpal tunnel release under local anesthesia with or without distal median nerve block: Double-blind randomized clinical trial

Background: Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy of the upper extremity, and its surgical treatment is carpal tunnel release (CTR). It is mostly performed in local anesthesia. There are no clinical randomized controlled trials (RCTs) comparing local infiltration anesthesia with or without a distal median nerve block in CTR. The aim of the PERSONNEL trial (carPal tunnEl ReleaSe lOcal iNfiltratioN mEdian bLockade) is to assess whether a distal median nerve block reduces pain during and after the procedure in addition to local anesthesia. Methods: This is a single-center randomized clinical superiority trial comparing local anesthesia alone and local anesthesia with a distal median nerve block for CTR in patients with CTS. Adult patients will be randomized in one university hospital in Finland, and the intended sample size is 118. The primary outcome is the mean pain level after the procedure during 72 h using a visual analogue scale (VAS). The secondary outcomes include expected pain; pain during the injection of the anesthetic solution caused by pressure, burning, needle sting, and total pain; worst pain during the surgery; duration of anesthesia; number of experienced needle stings; Boston Carpal Tunnel Syndrome Questionnaire (BCTSQ); pain killer consumption;, patient satisfaction using Net Promoter Score (NPS); and complications. Discussion: Patient satisfaction is a crucial factor in modern healthcare. A distal median nerve block may reduce pain during and after CTR, potentially increasing patient satisfaction with the given treatment. It can also be hypothesized that better postoperative pain control may prevent complications, for example, complex regional pain syndrome. However, we lack adequate evidence to justify the use of distal median nerve block, which can itself predispose patients to complications, for example, median nerve injury. Therefore, there is a need for adequate RCTs to assess its efficacy. The results of this study can be used to optimize anesthesia for carpal tunnel surgery, improve patient satisfaction, and possibly prevent complications. Registration: ClinicalTrials.gov NCT05372393.

Median Nerve Measurement and Steroid Injection for Carpal Tunnel Syndrome: A Case Report.

Carpal tunnel syndrome is an entrapment neuropathy that affects 3% of adults in the United States. The current techniques used for diagnosis have limited specificity/sensitivity, and the techniques used for treatment have limited efficacy. A 34-year-old female presented to the emergency department with two months of worsening painful paresthesias in her right thenar eminence. Ultrasound was performed showing a median nerve area of 20.4 square millimeters within the carpal tunnel. Median nerve block was performed within the carpal tunnel causing complete resolution of her pain. Emergency physicians skilled in point-of-care ultrasound and needle-guided procedures can diagnose and treat carpel tunnel syndrome.

Ultrasound-Guided, Mid-Forearm Median Nerve Block for Relief of Carpal Tunnel Syndrome Pain in the Emergency Department: A Case Report.

Carpal tunnel syndrome (CTS) is a common complaint in the emergency department (ED) and accounts for approximately 90% of all peripheral neuropathies.6 Pain control from injection with corticosteroids into the carpal tunnel space is associated with multiple possible complications including atrophy, iatrogenic median nerve injury, and skin changes. Ultrasound (US)-guided mid-forearm median nerve block is an ED procedure that can be used to avoid direct injection into the carpal tunnel space. Here we present a case report proposing the use of US-guided mid-forearm block as a safe and effective adjunct to the management of acute pain caused by CTS. A previously healthy 44-year-old, right-hand dominant female presented to the ED with left wrist pain. Her clinical exam and US findings were consistent with CTS. Given her allergy to non-steroidal anti-inflammatory drugs, she was offered a median nerve block, which was performed in the ED. The patient reported continued pain relief 24 hours after discharge from the ED. There is limited data on the use of US-guided mid-forearm median nerve block as an acute pain management tool for CTS in the ED. The US-guided median nerve block done in the mid-forearm location can provide pain control for those with CTS while reducing the risk of complications associated with direct carpal tunnel injection.

Comparison of a hand-held high-end resolution infrared thermography (FLIR P640) and a smartphone infrared thermographic device (FLIR One) for the assessment of skin surface temperature after anaesthetising the median nerve in Healthy horses.

Accuracy of a median nerve block is normally assessed by testing skin sensitivity on the medial and dorsal aspects of fetlock and pastern. The present study evaluated subjective and objective analysis of skin surface temperature obtained with two different infrared (IR) thermography cameras (a high-end [FLIR P640] and a smartphone IR thermography device [FLIR One®]) before and after anaesthesia of the median nerve. Thermographic images were obtained at 0, 30, 60 and 90 minutes after performing a median nerve block with 2% mepivacaine hydrochloride. The subjective analysis of thermographic images using the FLIR P640 camera found assessors had >50% agreement for the presence of a nerve block (p<0.01) based on assessment of skin temperature within the expected dermatome of the median nerve. The objective analysis found skin temperature increases in the treated leg using the FLIR One® in the dorsal fetlock, dorsal pastern and medial pastern at 60 minutes, and the lateral pastern at 90 minutes (p<0.05). The treated leg, imaged using the FLIR P640 camera, had increases in skin temperature at the medial aspect of the fetlock at 60 minutes and lateral pastern at 90 minutes (p<0.05). Images obtained with the P640 camera had higher resolution and finer thermal detail. The images obtained with the FLIR One® camera had a wider temperature range with overall higher temperature measurements than the images obtained using the P640 camera (p<0.001). Skin temperatures in horses should be interpreted with caution when using the FLIR One® camera. Furthermore, the FLIR One® device detected an increase in skin surface temperature in both treated and non-treated legs and should not be used for assessment of a median nerve block. Infrared thermography appears to be useful for determining the presence of a high regional nerve block such as the median nerve block by observing increased temperatures of the skin surface after perineural anaesthesia. Further studies with a larger sample size as well as investigating the use of thermography for assessment of other regional nerve blocks are warranted.

Cure of Fingertip Necrosis after Median Nerve Block Application in Two Cases of Definite and Probable Systemic Sclerosis.

One patient with systemic sclerosis with index fingertip necrosis and another with probable systemic sclerosis with index and middle fingertip impending necrosis were successfully treated with ultrasound-guided median nerve block application on the affected side. The nailfold temperatures of the affected fingers measured using thermography were below 25°C. Immediately after application, the temperature increased substantially. After repeated applications, the mean basal temperature on the affected side increased by 3.6°C in Case 1 and by 5.9°C in Case 2. Peripheral nerve block can be a basic treatment for fingertip necrosis. The thermographical observation of the extent and region in which the temperature increased is novel.

Comparative Study of Radial and Median Nerve Blocks with Hematoma Block under Ultrasound Guide in Distal Radius Fracture Reduction: A Randomized Clinical Trial.

Distal radius fractures are one of the most common upper extremity fractures, and their incidence continues to increase due to an aging population and an increase in osteoporosis. Various methods of analgesia for distal radius fractures have been described-including hematoma blocks and nerve blocks. Hematoma blocks are a simple and effective method of providing analgesia; nonetheless, their efficacy may be limited in some cases. On the other hand, nerve blocks provide more targeted analgesia and may be more effective in reducing pain during fracture reduction. This study aimed to compare the analgesic effectiveness of radial and median nerve blocks with hematoma blocks under ultrasound guidance in treating distal radius fractures. Also, this study aimed to compare the analgesia of radial and median nerve blocks with hematoma blocks under ultrasound guidance to reduce distal radius fractures. In this prospective trial, patients with distal radius fractures referring to 2 academic centers were placed into 2 randomized groups, including hematoma block, and radial median block, both of which were ultrasound-guided. The patient's pain levels were measured and recorded based on the visual analog scale before the block, 5, 10, and 15 minutes after the block, at the start of reduction, during reduction, and 5, 10, and 15 minutes after reduction. Patient satisfaction and physician satisfaction rates were assessed, and side effects were also observed for 1 week. Quantitative variables were reported as mean ± standard deviation, and number and frequency percentages were reported for qualitative variables. The Student t test and the chi-square test were used on a case-by-case basis. The significance level was set at P ˂ 0.05. In this study, 120 patients were included. The groups had no significant differences in pain reduction during the procedure. Analgesic medication was needed during the procedure for 17 patients; nerve blocks were applied for 6 patients, and hematoma blocks for 11 patients, which was statistically significant (P = 0.041). Satisfaction rates for patients and physicians performing the procedure were significantly higher in the nerve block group than in the hematoma block group ( P = 0.001; P ˂ 0.001, respectively). The results of this study suggest that ultrasound-guided radial and median nerve blocks can be used as alternative methods of analgesia with other techniques in the reduction of distal radius fractures in emergency departments.

Anatomical proposal of local anesthesia injection for median nerve block in treating hyperhidrosis with botulinum neurotoxin.

Hyperhidrosis, causing excessive sweat, can be treated with Botulinum neurotoxin injection. Botulinum toxin, an effective and safe treatment for hyperhidrosis, unfortunately involves significant pain due to multiple injections. This study aims to propose a more efficient and less painful approach to nerve blocks for relief, by identifying optimal injection points to block the median nerve, thereby enhancing palmar hyperhidrosis treatment. This study, involving 52 Korean cadaver arms (mean age 73.5years), measured the location of the median nerve relative to the transverse line at the pisiform level to establish better nerve block injection sites. In between the extensor carpi radialis and palmaris longus, the median nerve was located at an average distance of 47.39 ± 6.43mm and 29.39 ± 6.43mm from the transverse line at the pisiform level. To minimize discomfort preceding the botulinum neurotoxin injection, we recommend the optimal injection site for local anesthesia to be located 4cm distal to the transverse line of the pisiform, within the tendons of the palmaris longus and flexor carpi radialis muscles.

A case of phantom pain and stump pain that was effectively controlled by ultrasound‐guided ulnar and median peripheral nerve blocks

AbstractPhantom limb pain and stump pain are often intractable, and their incidences are relatively high. We report a case of a patient with phantom limb and stump pain of the finger, who was successfully treated by peripheral nerve blocks. The patient was a male truck driver in his fifties, who had his left annular finger amputated in an accident 2 years previously. Owing to poor pain control at the stump of his finger, he was referred to our department. The initial examination revealed pain about numerical rating scale (NRS) 6/10 in the left annular finger transection as well as allodynia. Although some pain relief had been observed with postoperative medication, he still had persistent resting pain of about NRS 4/10. Therefore, blocks of the ulnar nerve and median nerve were performed. After the blocks were performed, the pain improved to NRS 1 to 2/10, and pain upon movement also almost disappeared. Peripheral nerve blocks can be a useful treatment modality for phantom limb pain and stump pain in the fingers, as in this case.

Thermal Imaging to Predict Failed Supraclavicular Brachial Plexus Block: A Prospective Observational Study.

Successful brachial plexus blockade produces sympathetic blockade, resulting in increased skin temperature in the blocked segments. This study aimed to evaluate the accuracy of infrared thermography in predicting failed segmental supraclavicular brachial plexus block. This prospective observational study included adult patients undergoing upper-limb surgery under supraclavicular brachial plexus block. Sensation was evaluated at the dermatomal distribution of the ulnar, median, and radial nerves. Block failure was defined as absence of complete sensory loss 30 min after block completion. Skin temperature was evaluated by infrared thermography at the dermatomal supply of the ulnar, median, and radial nerves at baseline, 5, 10, 15, and 20 min after block completion. The temperature change from the baseline measurement was calculated for each time point. Outcomes were the ability of temperature change at each site to predict failed block of the corresponding nerve using area under receiver-operating characteristic curve (AUC) analysis. Eighty patients were available for the final analysis. The AUC (95% confidence interval [CI]) for the ability of temperature change at 5 min to predict failed ulnar, median, and radial nerve block was 0.79 (0.68-0.87), 0.77 (0.67-0.86), and 0.79 (0.69-0.88). The AUC (95% CI) increased progressively and reached its maximum values at 15 min (ulnar nerve 0.98 [0.92-1.00], median nerve 0.97 [0.90-0.99], radial nerve 0.96 [0.89-0.99]) with negative predictive value of 100%. Infrared thermography of different skin segments provides an accurate tool for predicting failed supraclavicular brachial plexus block. Increased skin temperature at each segment can exclude block failure in the corresponding nerve with 100% accuracy.

Fentanyl sparing effect of ultrasound-guided proximal radial, ulnar, median, and musculocutaneous nerve (RUMM) block for radial and ulnar fracture repair in dogs: a retrospective case-control study.

This study retrospectively evaluated the fentanyl-sparing effect of ultrasound-guided proximal radial, ulnar, median, and musculocutaneous nerve (RUMM) block for radial and ulnar fracture repair in dogs. Fentanyl was prepared for intraoperative analgesia in dogs, although proximal RUMM block was performed using 0.5% or 0.25% bupivacaine before surgery in the block group. Dogs without a nerve block were assigned to the control group. The fentanyl dose in the block group [0.8 (0-1.9) μg/kg/hr] [median (interquartile range)] was significantly lower than in the control group [8.4 (7.2-10) μg/kg/hr]. Surgery was performed without fentanyl in >50% of the dogs (5/7), using 0.5% bupivacaine. Ultrasound-guided proximal RUMM block can be useful as an intraoperative analgesic for radial and ulnar fracture repair in dogs.

Common flexor plane block: A novel approach to median and ulnar nerve block at elbow.

Common flexor plane block: A novel approach to median and ulnar nerve block at elbow.

Median effective dose of 0.2% ropivacaine for ultrasound-guided median nerve block in young children

ObjectiveTo determine the median effective dose (ED50) and the 95% effective dose (ED95) of 0.2% ropivacaine for ultrasound-guided lower forearm median nerve block in paediatric patients. MethodsEligible children were American Society of Anesthesiologists (ASA) status I–II scheduled to have elective open surgery for trigger thumb repair. Patients were stratified into two age groups: 1- to 3-year-olds and 3- to 6-year-olds. The ED50 was determined by Dixon’s up-and-down method. The first patient received an ultrasound-guided median nerve block by injection of 2 mL of 0.2% ropivacaine. Each subsequent patient’s dose was determined by the response of the previous patient, the doses being adjusted in intervals of 0.2 mL. In addition, the 95% effective dose (ED95) was obtained using a probit regression approach. The patients’ general condition, postoperative pain scores, and adverse events were recorded. ResultsA total of 52 children who were scheduled to undergo open surgery for trigger thumb were included in this study: 28 in the 1- to 3-year-olds group and 24 in the 3- to 6-year-olds group. The ED50 (95% confidence interval) values were 0.9 (0.44–1.36) mL in 1- to 3-year-olds and 1.4 (1.14–1.66) mL in 3- to 6-year-olds. The ED95 (95% confidence interval) values were 1.5 (0.98–1.58) mL in 1- to 3-year-olds and 1.7 (1.54–1.78) mL in 3- to 6-year-olds. No adverse events occurred. ConclusionsA single dose of ropivacaine was an effective agent for young children requiring ultrasound-guided lower forearm median nerve block in open surgery for trigger thumb. The ED50 (95% confidence interval) values were 0.9 (0.44–1.36) mL in 1- to 3-year-olds and 1.4 (1.14–1.66) mL in 3- to 6-year-olds. The ED95 (95% confidence interval) values were 1.5 (0.98–1.58) mL in 1- to 3-year-olds and 1.7 (1.54–1.78) mL in 3- to 6-year-olds.

Median nerve block increases the success rate of radial artery cannulation in women with gestational hypertension undergoing cesarean section

BackgroundThe radial artery cannulation helps to maintain the stability of maternal hemodynamics and reduce complications, however, it is difficult for women with gestational hypertension. Ultrasound-guided median nerve block can cause arterial vasodilation, which may improve the success rate of radial artery cannulation.MethodsNinety-two women with gestational hypertension and risks of intra-operative bleeding undergoing cesarean section following failed ultrasound-guided cannulation were identified and randomized into the median nerve block group and control group. Median nerve block was performed under the guidance of ultrasound in the middle forearm and 5 ml of 0.5% lidocaine was injected. Subcutaneous local block was administered in the control group. The ultrasound-guided radial artery cannulation was performed ten minutes after blocking. Baseline measurements (T1) were performed after 10 minutes of rest. All variables were measured again at 10 (T2) and 30 (T3) minutes after median nerve block or local block. The primary outcome was the success rate of radial artery cannulation within 10 minutes after blocking. The puncture time, number of attempts, the overall complications, and ultrasonographic measurements including radial artery diameter and cross-sectional area were recorded before (T1), 10 minutes (T2) after, and 30 minutes (T3) after block.ResultsA total of 92 pregnant women were identified and completed the follow-up. As compared to control group, the first-attempt success rate of radial artery cannulation was significantly higher (95.7% vs78.3%, p = 0.027) and procedure time to success was significantly shorter (118 ± 19 s vs 172 ± 66 s, p < 0.001) in median nerve group. Median nerve group also had a significantly less overall number of attempts (p = 0.024). Compared with control group, the diameter and cross-sectional area of radial artery increased significantly at the T2 and T3 points in median nerve group (p < 0.001), as well as percentage change of radial artery diameter and CSA. No difference was observed in the overall complication at chosen radial artery, which including vasospasm (21.7% vs 28.3%; p = 0.470) and hematoma (4.3% vs 8.7%; p = 0.677).ConclusionsUltrasound-guided median nerve block can increase the first-attempt success rate of chosen radial artery cannulation in women with gestational hypertension and risks of intra-operative bleeding undergoing cesarean section following failed radial artery cannulation, and especially for those anesthesiologists with less experienced in radial artery cannulation.Trial registrationChiCTR2100052862; http://www.chictr.org.cn, Principal investigator: MEN, Date of registration: 06/11/2021.

Effectiveness of Peripheral Median, Radial, and Ulnar Nerve Block at Wrist along with Intra-Articular Steroid Injection in Shoulder Joint in Management of Complex Regional Pain Syndrome of Upper Limb: 1-Week Follow-Up Study.

Complex regional pain syndrome (CRPS) of upper limbs is one of the under-recognized painful disabling condition seen in many neurological conditions. To see the effectiveness of peripheral nerve blocks (PNB) along with intra-articular injection in shoulder joint in the improvement of pain, swelling and range of motion (ROM) of the upper limb in CRPS. It was a single-center, prospective study in male and female patients between 18 and 70 years with CRPS of the upper limb due to any etiology, within one year of illness. Single-dose of the intra-articular shoulder joint injection and peripheral nerve blocks at the wrist with steroid, 2% lignocaine, and sterile water was given. The primary outcome measure was a reduction in pain in the upper limb, assessed with a visual analog scale (VAS). Secondary outcome measures were an improvement in passive ROM of joints and a decrease in swelling of the hand. The significance of the P value was adjudged against an alpha of 0.05. Thirty-three patients (25 men), with a mean (SD) age of 55.2 (9.4) years, and mean (SD) duration of illness of 101.9 (76.8) days were included. After 1 week, there was a significant improvement (P < 0.05) in the ROM of joints. The decrease in pain scores on VAS [mean difference -5.1 (CI -5.7, -4.5)] and reduction in hand swelling [mean difference -0.9 (CI -1.1, -0.7)] was also significant. Peripheral median, radial, and ulnar nerve block at wrist along with intra-articular steroid injection in the shoulder joint is an effective method of management of CRPS of the upper limb.

The 90% minimum effective volume and concentration of ropivacaine for ultrasound-guided median nerve block in children aged 1–3 years: A biased-coin design up-and-down sequential allocation trial

BackgroundMedian nerve block can provide excellent analgesia during open surgery for trigger thumb in children. However, no data on the 90% minimum effective volume (MEV90) and concentration (MEC90) of ropivacaine for ultrasound-guided median nerve block in pediatric patients have been reported. DesignA prospective two-phase study with an up-and-down sequential allocation trial using a biased coin design. PatientsChildren aged 1–3 years are experiencing open surgery for trigger thumb. InterventionThis study has 2 parts, one for MEV90 and subsequently studied MEC90 from the former part of the study. The MEV90 and MEC90 of ropivacaine for each subsequent patient were determined by the response of the previous patient, with the biased coin design up-and-down sequential allocation trial. The interval of -volume or concentration was -0.1 ml or 0.01%, respectively. MeasurementsThe MEV90 and MEC90 of ropivacaine for ultrasound-guided median nerve block in pediatric patients, were then used to estimate the 99% minimum effective volume (MEV99) and concentration (MEC99). The patient's general condition, postoperative pain, and adverse events. Main resultsA total of one hundred and eighteen children were enrolled for the study, and 56 and 62 patients were enrolled for the MEV90 and MEC90 studies, respectively. The MEV90 of 0.2% ropivacaine was 1.44 ml (95% CI 1.043 ml, 1.466 ml), and the MEC90 of 1.5 ml ropivacaine was 0.195% (95% CI 0.159%, 0.197%). There were no adverse events that occurred. ConclusionFor ultrasound-guided median nerve block in children aged 1–3 years old with trigger finger undergoing open surgery, the MEV90 of 0.2% ropivacaine is 1.44 ml (95% CI 1.043 ml, 1.466 ml), and the MEC90 of 1.5 ml of ropivacaine is 0.195% (95% CI 0.159%, 0.197%).

Combined distal median nerve block and local anesthesia with lidocaine:epinephrine for carpal tunnel release

AimEvaluating patient comfort during full awake local anesthesia in carpal tunnel release surgery, without tourniquet use, by using epinephrine to obtain a completely dry surgical field. MethodsWe included into the study 41 patients who underwent carpal tunnel syndrome surgery under full awake combined anesthesia, using a 9-point questionnaire. Pain and anxiety in all patients were evaluated through a Wang-Baker 0–5 scale. The injection solution consisted of 0.1cc of epinephrine and 10cc of 1% lidocaine (1:100.000); 5cc were used for local cutaneous anesthesia, and 5cc were used for distal median nerve block. All patients underwent a classic, open carpal tunnel release. ResultsAnxiety scores during anesthesia and the post-operative period did not show a statistically significant difference (p > 0.01), with keeping their levels at low perception scores (average score of 1.68 ± 0.38 CI 95%, with a modal value of 2, compared to an average of 0.78 ± 0.29 CI 95% with a modal value of 0). Similar results were obtained for pain scores during anesthesia (1.73 ± 0.48 CI 95% with a most frequent modal score of 1). Our results also showed that the effects of combined anesthesia in carpal tunnel release surgery persisted well into the 6-hour post-operative moment, pain scores remaining low, statistically significant similar to recorded values during the anesthesia moment (p > 0.01), at an average of 2.29 ± 0.5 CI 95% with a modal value of 1. No serious complications were recorded. ConclusionCombined distal median nerve block and local anesthesia with epinephrine:lidocaine provides a comfortable option for patients, with minimal risks of complications.

Neurofibroma of the Median Nerve Managed With Ultrasound Guided Nerve Block: A Case Report

Background: Median nerve neurofibroma can mimic carpal tunnel syndrome. In unilateral carpal tunnel syndrome, wrist imaging is suggested to exclude tumors. Diagnosis and management of peripheral nerve sheath tumors can be challenging.&#x0D; Case: This is a case report of 42-year-old female with median nerve neurofibroma who presented with excruciating pain as the main symptom. Though surgical excision is the preferred treatment, it is associated with the risk of functional deficit. In this case, patient was unwilling for surgery. This report highlights the evaluation of neurofibroma and the role of median nerve block in the symptomatic as well as functional improvement.&#x0D; Conclusion: Nerve block can be effective if neurofibroma presents with pain as the main symptom without any impairment of motor function or daily activities.

Motor-Sparing Nerve Blocks Can Improve the Results of Digit Tendon Surgery: A Case Report

A 56-year-old woman presented with flexion dysfunction of the fifth digit 6 weeks after surgical repair of a flexor digitorum profundus laceration. She was scheduled for surgical adhesiolysis and restoration of the functionality of the finger. Intraoperative monitoring of the range of motion by active flexion was deemed important to prevent incomplete release of the tendon and residual dysfunction. Distal median and ulnar nerve blocks were used for anesthesia with the patient's ability to flex the finger. This case suggests that motor-sparing peripheral nerve blocks can improve functional outcome in certain hand surgeries.

A randomized trial to determine the minimum effective lidocaine volume for median nerve block using hydrodissection

Ultrasound-guided hydrodissection with 5% dextrose in water (DW5) creates a peri-nervous compartment, separating the nerve from the neighboring anatomical structures. The aim of this randomized study was to determine the minimum volume of lidocaine 2% with epinephrine 1:200,000 required when using this technique to achieve an effective median nerve block at the elbow in 95% of patients (MEAV95). Fifty-two patients scheduled for elective hand surgery received an ultrasound-guided circumferential perineural injection of 4 ml DW5 and an injection of local anesthetic (LA) following a biased coin up-and-down sequential allocation method. A successful block was defined as a light touch completely suppressed on the two distal phalanges of the index finger within a 30-min evaluation period. The MEAV95 of lidocaine 2% with epinephrine was 4 ml [IQR 3.5–4.0]. Successful median nerve block was obtained in 38 cases (82.6%) with median onset time of 20.0 [10.0–21.2] minutes (95% CI 15–20). The analgesia duration was 248 [208–286] minutes (95% CI 222–276). Using an ultrasound-guided hydrodissection technique with DW5, the MEAV95 to block the median nerve at the elbow with 2% lidocaine with epinephrine was 4 ml [IQR 3.5–4.0]. This volume is close to that usually recommended in clinical practice.Trial registration clinicaltrials.gov. NCT02438657, Date of registration: May 8, 2015.