Determination of Minimum Effective Volume of Local Anesthetic in Patients Undergoing Ultrasound-Guided Infraclavicular Approach for Brachial Plexus Blockade

This study was planned as a controlled, double-blind, single center study. Patients between 18-70 years of age who were determined as ASA I-III and underwent upper limb surgery from November 2015 to November 2016 and provided informed consent, were included in the study. Patients who had any of the following conditions were excluded: ASA risk score of IV or V, serious cardiac, respiratory, hepatic or renal comorbidities, mental disorder, coagulopathy, pregnancy, local anesthetic allergy, neuromuscular and/or neurological disease, and infection at the site of injection field of application. Patients who were unwilling to participate were also excluded. Randomization was done according to the time of patient referral with the sealed envelope system. Ethical approval was obtained from Ankara University Clinical Research Ethic Committee. All patients providedgave informed consent.

All procedures were performed by the same physician (S.B). In each patient, routine anesthesia monitoring was established and patients were administeredgiven 0.03 mg/kg midazolam and 1µg/kg of fentanyl for sedation. Field of applicationThe site of injection was properly prepared according to asepsis and antisepsis guidelines.

The infraclavicular blockade was performed according to the lateral sagittal infraclavicular block (LSIB) technique reported by Klaastad et al. [8]. The technique was modified to include ultrasound guidance, which was performed with a 6-12 mHz lineer ultrasound probe. The infraclavicular blockade was performed according to the lateral sagittal infraclavicular block (LSIB) technique reported by Klaastad et al. [8]. The technique was modified to include ultrasound guidance, which was performed with a 6-12 mHz lineer ultrasound probe. During the procedure, the patient was in the supine position with the head turned away from the application sidewith the head turned away from the application side and the shoulder was relaxed. The arm on the operative side undergoing surgery was slightly abducted, the elbow was flexed 90° and placed on the body of the patient. The anesthesiologist performing the procedure was positioned beside the head of the patient. The US probe was placed 1 cm inferior to the point of intersection between the clavicula and coracoid process on the sagittal axis. The in-plane technique was used during the procedure and the needle was visualized at all times. In order to obtain appropriate spread, the local anesthetic (0.5% [5 mg/ml] bupivacaine) was applied in a U shape from 3 to 11 o'clock around the axillary artery. U-shape distribution was achieved with (iğne pozisyonu yazılmalı); however, if distribution could not be achieved, the needle was repositioned when necessary.

The order of surgery was decided in a first come-first serve manner and Tthe volume of local anesthetic was reduced from a starting dose of 30 ml's in the first group. Five patients were included in each volume group and at least 3 applications out of 5 had to be successful to consider the volume to be sufficient. If the previous group's anesthesia was deemed as successful, the anesthesiologist reduced the dose by 2 ml's every 5 patients. When the anesthesia of a group of patients was determined to be unsuccessful (≤2 successful blockageblockades) the study was ended (Figure 1).

The researcher which determined whetherif the blockade was successful (N.A.E) was blinded to the study protocol. Sensorial and motor block measurements were used to determine blockade success. In the evaluation of sensorial blockade, touch and cold sensation tests were used to evaluate each region innervated by axillary, musculocutaneous, median, radial, and ulnar nerves. Touch sensation was evaluated with the cotton wool test and cold sensation was evaluated with ice packs. Evaluation was performed by comparing each region with the corresponding contralateral region. A score of 0 meant no blockade, 1 meant analgesia (touch sensation present, heat sensation absent), and 2 meant complete blockade of that specific region.