A Sequential Allocation Study to Determine the ED50 of Dexmetedomidine as an Adjuvant to Lidocaine Intravenous Regional Anesthesia
Condition: Bier Block; Dexmedetomidine; Tourniquet Pain; Carpal Tunnel; Tendon Release; Tendn Transfer
MeSH terms: Carpal Tunnel Syndrome
Study type: Interventional

Summary: 
      Intravenous Regional Anesthesia (IVRA) is an easy and reliable anesthetic technique for hand
      and forearm surgery. Its use is however limited by the presence of tourniquet pain during the
      surgery and the absence of postoperative analgesia. Many adjuvants to local anesthetics have
      been studied in order to overcome these shortcomings, including α2 adrenergic agonists.
      Clonidine has been shown to be efficacious when used with IVRA at a dose of 1µg/kg.
      Dexmetedomidine (DEX) is a recent more selective α2 adrenergic agonist that has been used
      successfully during IVRA at a dose of 0.5µg/kg. However when comparing potency ratios of
      Clonidine and DEX (8 to 1), the investigators hypothesize that a lower DEX dose would provide
      patients with adequate anesthesia.

      We will determine the population average dose of DEX (ED50) that provides 50 minutes of
      tolerance to the tourniquet during a Lidocaine IVRA by a sequential Dixon up-down allocation
      study.

      Eligible patients will be enrolled after obtaining informed consent. Patients will receive a
      standardized IVRA with Lidocaine and DEX adjuvant following a sequential allocation scheme.
      The first patient will receive a dose of 0.5 µg/kg of DEX. The dose will be then adjusted in
      0.1 µg/kg increments for the following patients dependent on the success of the previous
      patients block. If a patient experiences tourniquet pain prior to 50 minutes after inflation
      of the distal tourniquet the next patient will receive a higher dose, if he does not
      experience pain prior to 50 minutes after inflation of the distal tourniquet the dose for the
      following patient will be decreased.

      Recruitment will continue until 6 independent crossovers are observed with a minimum of 20
      patients. The mean and the standard deviation of the ED50 of DEX will be calculated using the
      modified up-down method.

      This study will help determine the ED50 of DEX used as an adjuvant in IVRA. Based on the
      potency ratios of Clonidine vs. DEX, the investigators hypothesize that the dose of DEX
      needed to achieve 50 minutes of pain free tourniquet time will be closer to 0.125 µg/kg
      rather than 0.5 µg/kg, a 75% reduction in the dose studied.
    


Intervention name(s): Dexmedetomidine
Intervention type(s): Drug
Intervention description(s): Following a sequential allocation scheme, the dexmedetomidine dose for each patient was determined by the Dixon up-and-down method. The dexmedetomidine dose for the first patient was 0.5 µg/kg. The dose was then adjusted in 0.1 µg/kg increments for the following patients depending on the success of the previous patient's block. If a patient experienced tourniquet pain prior to T0 + 50 minutes the next patient received a higher dose. If a patient did not experience pain at T0 + 50 minutes of tourniquet time the dose for the following patient was decreased. Identical syringes containing the solution mix were prepared by the principal investigator and handed to the blinded anesthesiologist in the room. Stopping rules were set at 6 independent crossovers in the same direction (no pain to pain or pain to no pain), with a minimum number of 20 patients
Intervention MeSH terms: Dexmedetomidine
Intervention model: Sequential Assignment
Primary purpose: Treatment