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Background: Among the various factors influencing the success rate, onset time, and duration of peripheral nerve blocks, the role of local anesthetics concentration remains uncertain. In this prospective, randomized, single-blinded study, we evaluated whether varying the dilution of a fixed dose of mepivacaine solution influenced onset time and duration of sciatic nerve block., Methods: Ninety ASA physical status I to II patients scheduled for foot surgery were randomly allocated to receive a double-injection Labat sciatic nerve block with 12 mL mepivacaine 2% (group concentration I = 45 patients) or 24 mL of mepivacaine 1% (group volume II = 45 patients). The nerve stimulator was initially set at 2 Hz, 0.1 millisecond, 1 mA. The total amount of local anesthetic (240 mg) was kept constant and equally divided between the peroneal and tibial nerves. All patients also received an ultrasound-guided popliteal sciatic nerve catheter for postoperative analgesia. Times to readiness for surgery, performance, and offset of local anesthetic were recorded. Our primary end point was to determine a possible difference in offset time between groups. Continuous variables were expressed as median (IQR) and compared with the Wilcoxon-Mann-Whitney U test; WMWodds are reported together with their 95% confidence interval., Results: The overall success rate of sciatic nerve block was 99%. Time of performance was shorter in group I, 120 seconds (90-150 seconds), than that in group II, 150 seconds (120-180 seconds) (P = 0.0048; WMWodds 2.26 [1.35-4.34]). The onset time of sensory and motor sciatic nerve block was 4 minutes (2-9 minutes) in group I and 6 minutes (4-10 minutes) in group II (P = 0.41; WMWodds 1.21 [0.77-1.95]), while the duration of sensory block was 235 minutes (203-250 minutes) in group I, and 240 minutes (218-247 minutes) in group II respectively (P = 0.51; WMWodds 1.20 [0.69-2.16])., Conclusions: We found no evidence that varying volume and concentration while maintaining a fixed total dose of mepivacaine alters the onset time and duration of double-injection sciatic nerve block. Considering our WMWodds results, possible differences in onset time and duration comparable to differences in the performance time between groups cannot be excluded.

Background: The standard technique for implanting a subcutaneous implantable cardioverter defibrillator (S-ICD) requires three incisions and the pocket of the device is created in the subcutaneous tissue of the left lateral thoracic wall. However, a two-incision technique may be adopted, in which the cranial parasternal region is avoided and the device is positioned more deeply, completely under the latissimus dorsi muscle. This can also be combined with ultrasound-guided serratus anterior plane block (US-SAPB) for intraoperative anesthesia and perioperative analgesia. We describe our preliminary experience of US-SAPB combined with the two-incision intermuscular technique. Methods: We performed US-SAPB 40 minutes before starting the procedure, while the patient was in the supine position. The devices were implanted under the latissimus dorsi muscle. All patients were followed-up after hospital discharge. Results: Twelve patients (male 50%, 53 ± 16 years, body mass index 23 ± 4) underwent the S-ICD implantation with the combined technique. The mean procedure duration was 47 ± 11 minutes. The procedure was successful and a shock energy of 65 J was successful in converting the induced ventricular fibrillation in all patients. The US-SAPB was successful in 92% of cases and only one patient required convertion into general anesthesia due to pain during the procedure. In the postoperative period, patients did not report major discomfort and analgesics were not required. During a median follow-up of 12 months, no complications were reported. Conclusions: Serratus anterior plane block combined with the intermuscular and two-incision technique proved to be safe and effective during the S-ICD implantation procedure. [ABSTRACT FROM AUTHOR]