Total of 93 American Society of Anesthesiologist (ASA) I-III consecutive adult patients aged between 19 and 83 years old scheduled for elective or emergency trauma surgery of hand and forearm under ultrasound-guided brachial plexus block (UG BPB) between 17.01. and 15.08. in 2017 were assigned to this randomized-prospective observational study after approval by the University Research Ethics Board. Patients were excluded if continuous peripheral nerve catheter technique or bilateral block was planned, or the patient refused to participate. Exclusion criteria included psycho-mental conditions interfering with consent or assessment; pre-existing chronic pain condition or daily analgesic or sedative consumption; sedative or analgesic premedication; pre-existing neurological disorders aﬀecting the brachial plexus (BP); obstructive sleep apnea; contraindications to BPB including local skin infections or allergy to local anesthetic (LA) agents. After exclusion, eligible patients for the study were randomized to four LA mixture solution groups and analyzed and presented in a Consolidated Standards of Reporting Trials flow diagram. Standardized UG axillary-supraclavicular (AX-SC) approach to the BP was performed under sterile conditions by the same anesthesiologist. The standardized dose was 0.4 ml/kg, the targeted maximized single shot volume was 30 ml. After administration of LA, standard anesthesia monitoring was started in the operating room. Data were collected as baseline (T0); intraoperative mean values (Top); postoperative values straight after surgery (Tpop); 6 and 24 after surgery (T6; T24) including measurement of heart rate (HR), non-invasive arterial blood pressure (NIBP), and verbal numeric rate (VNR, 11 point scale) of pain intensity. The extent of sensory and motor blockade was assessed meticulously in the corresponding region after the total dose of LA was injected until the blockade was defined as completed. Sensory block was tested by pinching and touching the skin of the arm and hand at the areas innervated by the four nerves. A von Frey filament with a standard target force of 10 gr (Touch Test ® Sensory Evaluator, Red 5,07; USA) was used for the assessment of the loss of protective sensation. The outcome quality and success rate of BPB was assessed by a composite tool designed for evaluating the loss of sensory (S, 0-4: failed to excellent), motor function (M, 0-4: failed to excellent), the coping of the patient (C, 0-4: failed to excellent) and the postoperative pain at the end of surgery and 24 h after (P, 0-4: pain before the end of surgery to long-lasting - 24 h - analgesia). The overall quality of PNB was evaluated by independent examiners, based on the aggregate 0-16 point scale. Under 7 Point the block was defined as failed, 8-11 = Tolerable; 12-13 = Good; 14-16 = Excellent. The duration of anesthesia was defined as the time between the end of the LA injection for BPB and the return of the sensory function reported by the patient or the necessity for first analgesic medication.

The study was conducted comparing the onset times and the duration of sensory effects of the same volumes of lidocaine-bupivacaine 1:1 mixture (LB), bupivacaine in normal saline (BS), lidocaine in normal saline (LS), and bupivacaine-lidocaine 2:1 mixture (BL) for BPB. Midazolam and fentanyl consumption were analyzed in the four groups, the outcome quality of blocks, vital parameters, visual numeric rate (VNR) of pain intensity values and non-steroid analgesic consumptions were compared between the four groups.

The IBM SPSS Statistics (Windows, version 24, 2016) was used in our analyses. Paired samples t-test, Kruskal-Wallis test combined with the Mann-Whitney U test for post hoc testing were used in analyzing the ordinal data. The Chi-square test was used for comparison of the categorical variables between the groups. ANOVA combined with Bonferroni post hoc test was used in analyzing the variance of linear data between groups. P\<0.05 was considered significant.

Priori power calculation was performed by GPower 3.1.9.2 version: effect size f=0.4, alfa err=0.05; power=0.85; number of groups=4; total sample size=84.