The doses of local anesthetics can be decreased with the use of ultrasound guidance. In case of using mixture solutions the benefits and drawbacks are controversial. The plasma concentrations were not studied up to this time in this kind of settings, so investigators believe that this is the first work that shows how lidocaine change the plasma concentration of bupivacaine after axillary approach to brachial plexus employed with different dilute and mixed solutions for upper limb surgery in trauma patients.

Total of 30 American Society of Anesthesiologist (ASA) I-III adult patients scheduled to elective or emergency trauma surgery of hand and forearm under ultrasound-guided (UG) brachial plexus block (BPB) are planned to be assigned into this randomized-prospective observational study after approval by the University Research Ethics Board, Pécs University Medical School, Hungary. All of the patients will receive detailed information about the planned BPB techniques and surgeries, then written informed consents will be obtained.

Study participants are planned to be assigned randomly by the research coordinator into 3 groups (Lidocaine, Bupivacaine and mixture solution) according to the concentration of lidocaine and bupivacaine in the mixture solution.

Standardized UG Axillary-supraclavicular (AX-SC) approach to the BP is planned to be performed under sterile conditions by the same anesthesiologist. The standardized dose is 0.4 ml/kg with the targeted maximized the single-shot volume of 30 ml.

Blood samples will be taken at 0-time point (straight after the administration of BP injection) and 30, 60, 240 and 480 minutes after. Plasma concentrations are determined, the results are collected and analyzed.

Under standard monitorization, vital parameters, data are collected on the onset time and duration of actions of local anesthetics (LAs).

Inclusion Criteria:

• unpremedicated patient scheduled for elective or emergency trauma surgery of hand and forearm under ultrasound-guided BPB

Exclusion Criteria:

• 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.

Patients, the operating team, nurses, and observers involved in the assessment of the follow-up data collection were unaware of group allocation. The labor analyst is unaware of group allocation.

The list of cases will be provided in spreadsheet program by an observer-blinded assistant and was statistically evaluated by an independent analyst.