Minimum Effective Volume Of Local Anesthetic İn USG Guided Axillary Approach Brachial Plexus Block
Condition: Underdosing of Local Anesthetics
Study type: Interventional
Phase: Phase 4

Summary: 
      Background Peripheral nerve blocks with use of USG allowed visualisation of the structures
      and nerves and made the block administrations safe, quick and comfortable. However there are
      few publications concerning the minimum local anesthetic volume capable of providing blocks.
      In this study the investigastors aimed to find Minimum Effective Volume Of Local Anesthetic
      For Ultrasound-Guided Axillary Brachial Plexus Block in hand, elbow and forehand operations.

      Materials & Methods A total of 55 ASA I-II patients underwent hand surgery operation by
      administering USG guided-axillary brachial plexus blockage were included in the study. Ulnar,
      median and radial nerves were seen and the minimum effective local anesthetic volume was
      investigated starting with total 21 ml of %0.5 bupivacain. After accomplishing the blockage,
      volume was decreased by 0.5 for each nerves. Block administration time, block onset times,
      anesthesia times and time to first analgesic requirement were recorded.
    

Detailed description: 
      Matherials and Method This randomized, prospective, double-blinded, single-center study was
      conducted in accordance with the most recent version of the Helsinki Declaration. Approval
      for the study was granted by the Ankara Numune Research and Training Hospital Ethics
      Committee. A total of 55 adult patients classified as American Society of Anesthesiologists
      (ASA) physical status I-II, who were to undergo elective, forearm, wrist or hand surgery were
      recruited in this trial. Written informed consent was obtained from each patient. Exclusion
      criteria were patients with coagulopathy, local anesthetic allergy, local infection, any
      significant neurological, pysychiatric or congnitive disorder, chronic analgesic use, known
      neuropathies, infection in the injection site or unwillingness of the patient. After arrival
      in the operating room, an 20-gauge intravenous catheter was placed in the contralateral
      forearm. Standard monitoring was used throughout the procedure, including non-invasive
      arterial blood pressure, heart rate, and pulse oximetry. Patients were divided into groups
      according to their order of arrival and a five-person group was created. İnitial volume of 7
      ml. Per nerve(ulnar, median, radial), totaly 21 ml local anesthetic administered in first
      group(first five patient). İf the success rate of block is three or more in the group, volume
      was reduced in the next group of 0.5 ml for each nerve. if the success rate is less than
      three in the group, study is ended. And minimum effective volume was calculated to be
      statistically.

      Block prosedures All the brachial plexus blocks were performed by the same anesthesiologist.
      The patient is made comfortable in supine position with the arm abducted and the elbow flexed
      to 90 degrees. After skin and probe preparation, A linear US probe (HFL 38, 6-13MHz) was
      placed in the transverse plane at the lateral border of pectoralis major muscle to obtain the
      best view of the brachial plexus. Image quality is optimised with selection of appropriate
      depth (within 2 cm), focus range (within 1cm) and gain. The structures of interest are very
      superficial with the pulsating axillary artery localised within 1 cm . Surrounding the
      axillary artery, one will find the three out of four terminal branches of the brachial
      plexus: the median (superficial and lateral to the artery), the ulnar (superficial and medial
      to the artery) and the radial (posterior and lateral or medial to the artery) nerves. A 5 cm
      needle (21G, Locoplex, Vygon, Ecouen, France) is inserted parallel to the long axis of the
      transducer from the lateral side. As the needle is in the same plane as an ultrasound beam,
      the path of the advancement can be visualised in real time as the needle approaches the
      target nerves. Ideally, the radial nerve should be targeted first, as it lies posterior to
      artery, in order to prevent displacing the structures of interest to deeper and obscuring the
      median and ulnar nerves. The musculocutaneous nerve was blocked separately outside the
      neurovascular bundle with 3 ml %0.5 bupivacaine at all of the patient. We were also worried
      about the nerve puncture or intraneural injection. In addition, we also confirmed that the
      location of the needle tip was not in hypoechoic area before each injection. For further
      safety, we injected 0.5 ml of local anesthetic as a test dose. If the patients complained of
      paresthesia or pain, or the injection pressure was high, or the spread of local anesthetic
      was not visualized, investigastors stopped injection, and withdrew the needles and tried
      again. The investigastors regarded the paresthesia or pain, or high injection pressure as
      intraneural injection.

      The investigator who testing the block is don't know the dose. Sensory block was evaluated
      for each nerve distribution using ice to test cold sensation, comparing the anaesthetized arm
      with the contralateral arm, and graded on a three-point scale (0, no difference between
      sides; 1, some difference between arms but cold still sensed in the blocked arm; 2, no cold
      sensation in the blocked arm). Motor block for each nerve was evaluated by asking the patient
      to extend the flexed arm and wrist (radial nerve), flex the wrist and oppose the second and
      third fingers and thumb (median nerve), flex and oppose fifth finger towards the thumb (ulnar
      nerve) and was graded as 0, no change; 1, reduced contraction; 2, no contraction. Data were
      collected every 5 min for the first 60 min, and then 1,2,4,6,8,10,12,18,24 hours. motor and
      sensory scale, the total value should be higher than 10, if not surgical anesthesia was
      considered unsuccessful. sensitive block score must be at least five. VAS determination was
      performed with a scale of numbers between 0 and 10 cm. 1mg/kg tramadol and 15 mg/kg
      paracetamol IV infusion were administered to patients with a reequirement for additional
      analgesia (VAS ≥ 4) . The total number of patients who required additional analgesic drugs
      was noted. During the initial procedures, the operation and postoperatively, patient
      satisfaction was evaluated as poor (1), moderate (2), good (3) or very good (4).

      Statical Analysis Statistical analysis was applied using SPSS 19.0 statistical software.our
      sample size calculation method is dixon and massey up and down method. According to this
      account, n = 2 (SD / SEM) ²; n: sample size, SD (standard deviation): The standard deviation,
      SEM (standard error of mean) is calculated as the standard error of the mean (SD = 5 mL, SEM
      = 1.0 mL) n were found in 50 patients. For the aplicational errors we add 5 patient (%10 ). A
      total of 55 patients were included in the study.

      The sample size calculation, made by G * Power 3.0.10 statistical software package (effect
      size (effect size) = 0.4, α = 0.05, degrees of freedom (df) = 48 and 0.85 power (power (1-
      β)), the number of 50 patients were found to be adequate. However for practical magnification
      error with a sample of 10% of 55 patients were included in the study.
    

Intervention name(s): bupivakain % 0,5
Intervention type(s): Procedure
Intervention description(s): Bupivacaine 0,5% The study method was a step-up/step-down sequence model where the dose for following patients was determined by the outcome of the preceding block. The starting dose of bupivacaine was 5 mL per nerve. In the case of block failure, the dose was increased by 0.5 mL per nerve. Conversely, block success resulted in a reduction in dose by 0.5 mL per nerve. Each of the three nerves was treated as a separate entity. Dose adjustments were made to each nerve individually. The volume dose was increased in 0.5 mL at every 5 consecutive cases regardless of the result of the previous block in order to minimize bias occurence. A blinded assistant assessed sensory and motor blockade at 5-min intervals up to 30 min.
Intervention model: Sequential Assignment
Intervention model description: A total of 55 ASA I-II patients underwent hand surgery operation by administering USG guided-axillary brachial plexus blockage were included in the study. Ulnar, median and radial nerves were seen and the minimum effective LA volume was investigated starting with total 21 ml of %0.5 bupivacain. After accomplishing the blockage, volume was decreased by 0.5 for each nerves. Block administration time, block onset times, anesthesia times and time to first analgesic requirement were recorded.
Masking: None (Open Label)
Primary purpose: Prevention