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.

Ultrasound-guided perineural circumferential median nerve block with and without prior dextrose 5% hydrodissection: a prospective randomized double-blinded noninferiority trial.

BACKGROUND: Ultrasound-guided perineural peripheral nerve block using a hydrodissection technique may reduce the risk of accidental intravascular local anesthetic (LA) injection. In this prospective randomized double-blind study, we tested the hypothesis that median nerve block effectiveness is not reduced when circumferential perineural hydrodissection with dextrose 5% in water (D5W) precedes LA injection. METHODS: Patients scheduled for hand surgery were randomized to receive an ultrasound-guided median nerve block at the elbow to achieve circumferential perineural spread with either 6 mL of D5W followed by 6 mL of LA (lidocaine 1.5% with epinephrine 1:200,000) (D5W-LA group) or with 6 mL of LA alone (LA group). The primary outcome was onset time of successful anesthesia defined by a complete abolition of light touch sensation for the index finger. RESULTS: Data from 95 patients were analyzed: 43 in the D5W-LA group and 52 in the LA group. Noninferiority tests were significant (all P < 0.05) for a critical limit of 7 minutes between D5W-LA and LA groups for onset time of the primary criterion, light touch block at index finger (mean ± SD, respectively: 23.9 ± 7.4 and 22.0 ± 7.9 minutes; 95% confidence interval [CI], -5.9 to 2.1 minutes), and for cold block at index fingertip, sensory blocks at thenar eminence, and motor block. Success rate at 30 minutes (defined as complete abolition for cold and light touch at index finger) was noted in 100% and 98.1% (95% CI, -6% to 10%) and 95.2% and 96.2% (95% CI, -13% to 9%) of patients for the D5W-LA and the LA groups. CONCLUSION: Performing an ultrasound-guided perineural circumferential hydrodissection with D5W into which LA is injected leaves nerve block outcome unchanged. The assumption that this procedure may reduce the risk of intravascular injection and systemic toxicity remains to be demonstrated.