Effective volumes of 1.5% mepivacaine with different sodium concentration for ultrasound guided popliteal block

• Published in: Journal of clinical anesthesia 2017-02, Vol.37, p.139-144
• Main Authors: López, Mercedes, Calvo, Miguel, Sancho, Azahara, Brogly, Nicolas, Guasch, Emilia, Gilsanz, Fernando
• Format: Article
• Language: English
• Subjects: Adult; Aged; Anesthesia; Anesthesia & Perioperative Care; Anesthetics, Local - administration & dosage; Dilution; Dose-Response Relationship, Drug; Female; Glucose - administration & dosage; Hallux Valgus - surgery; Humans; Male; Mepivacaine; Mepivacaine - administration & dosage; Mepivacaine - pharmacology; Middle Aged; Nerve block; Nerve Block - methods; Pain Medicine; Patients; Sciatic nerve; Sciatic Nerve - drug effects; Sodium - administration & dosage; Sodium - pharmacology; Surgery; Ultrasonic imaging; Ultrasonography, Interventional; Ultrasound; Variables
• ISSN: 0952-8180; 1873-4529
• DOI: 10.1016/j.jclinane.2016.12.009

Abstract Study objective To determine if a solution of 1.5% mepivacaine diluted with 5% dextrose, which decreases the sodium concentration by 30%, results in reduced volume requirements for a complete sensory block, in the case of an ultrasound guided popliteal nerve block. Design A randomized controlled study. Setting Operating room. Patients We included seventy ASA 1–3 patients, undergoing unilateral “hallux valgus” repair under ultrasound guided popliteal nerve block. Interventions An ultrasound guided popliteal nerve block was performed on all patients, with 1.5% mepivacaine using the normal dilution (ND group, thirty-five patients) or the 5% dextrose dilution (D5 group, thirty-five patients). Starting with 25 ml in each group, increasing or decreasing it by 1 ml on subsequent patients, depending on the success or failure in the previous one (Dixon's “up-and-down” sequential allocation). Measurements Effective dose in 50, 90, and 95% of patients (ED50, ED90, and ED95) of 1.5% mepivacaine in both groups. Onset time and duration of the blocks, side effects, and neurological complications. Main results There were no statistically significant differences between ED50 in ND group (6.2 ml; 95% confidence interval, 5.2–7.5), and D5 group (5.8 ml; 95% CI, 5.1–7). Also no statistically significant differences in ED90 (7.7 ml, 95% CI 6.9–8.1 in the D5 group; 7.8 ml, 95% CI 7–8.1 in the ND) or in ED95 (7.9 ml, 95% CI 7.1–8.2 in the D5 group; 8 ml, 95% CI 7.2–8.2 in the ND) were found. Onset time for a complete sensory block in D5 group was 14 min (95% CI, 12–17) and 15 min in ND (95% CI, 13–18), p = 0.66. Neither severe side effects, nor neurological complications were reported. Conclusions A dilution of 1.5% mepivacaine with 30% less sodium concentration does not decrease volume requirement for ultrasound guided sciatic nerve block at popliteal level.