Echogenic Versus Stimulating Needle and Catheter for Sciatic Blocks
Condition: Osteoarthritis Knee; Postoperative Pain
MeSH terms: Osteoarthritis, Knee
Study type: Interventional
Phase: Phase 3

Summary: 
      Patients scheduled for total knee replacements and suitable for sciatic nerve block will be
      randomized to one of 2 groups.

      Group 1 will have the nerve block performed using a standard Pajunk block needle under
      ultrasound guidance and with electrical nerve stimulation (ENS), and have catheter placement
      also guided by electrical nerve stimulation. Group 2 will have the block performed using a
      Sonoplex echogenic block needle and have an echogenic catheter sited, all under ultrasound
      (US) guidance. Group 2 will have needle location aided by ENS, but ENS will not be used for
      catheter location.

      An observer blinded to the needle type will assess the quality of needle visualisation on a
      recording of the US image taken during the procedure, along with adequacy of spread of local
      anesthetic. The primary outcome will be needle visibility, and secondary outcomes will be
      block success rate, block performance time, complication rate, number of needle passes per
      block, and adequacy of spread of local anesthetic.
    

Detailed description: 
      A total of 70 patients with ASA physical status 1 to 4, scheduled for elective total knee
      arthroplasty and deemed suitable to receive a sciatic nerve block will be included in the
      study. They will be randomised to one of two groups prior to the block procedure using a
      closed envelope system.

      Recruitment will take place in the preoperative clinic. All blocks will be performed in the
      block room using standard monitoring, sterile precautions and titrated intravenous sedation.

      Prior to the sciatic nerve block a continuous femoral nerve block will be performed according
      to standard procedure. Once this is complete the patient will be positioned for the sciatic
      nerve block.

      A preprocedural scan will be done as per standard practice and skin will be infiltrated with
      1% lidocaine.

      The anaesthetist performing the block will be aware of the study group allocation due to the
      requirement for physically handling the block needles, and will proceed to position the
      needle into the required location site to facilitate catheter insertion, with the aid of
      electrical nerve stimulation via the needle. This will be recorded using the ultrasound
      machines cineloop facility.

      If after 6 passes the operator is unable either to contact the nerve according to the
      ultrasound image or elicit a twitch response, the procedure will be abandoned and this will
      be considered a failed block. In this case analgesia will be covered with periarticular
      infiltration and opioids.

      During needle positioning, the observer will record the number of needle redirections
      required to optimally locate the needle, each redirection being defined as every movement
      which follows a withdrawal of more than 2cm. The observer will also record the number of skin
      punctures required and any arterial or venous punctures.

      Group E will have the block performed using the echogenic needle, and the echogenic catheter
      will be placed using ultrasound guidance.

      The catheter will be inserted through the needle by a second anesthetist. This process will
      be continuously recording using the cineloop feature of the ultrasound machine. Once the
      catheter is deemed to be in an appropriate position, local anaesthetic will be injected by
      the second anaesthetist while observing the disposition of the local anaesthetic perineurally
      in short axis. This will be confirmed with a long axis view of the nerve (also recorded).

      Group S will have the block performed with a standard needle and catheter, guided by
      electrical nerve stimulation.

      Acceptable muscle twitch response will be plantar- or dorsiflexion, inversion or eversion
      with an initial nerve current strength of 0.5mA at a frequency of 2Hz. If a satisfactory
      motor response cannot be elicited, current will be increased in stages to 1.5mA. If a
      response still cannot be elicited this will be recorded but the catheter will still be used
      if its position is deemed satisfactory using colour Doppler - a medley of colour adjacent to
      the nerve with the injection of agitated dextrose 5%. Once the catheter is deemed to be in an
      appropriate position, local anaesthetic will be injected by the second anaesthetist while
      observing the disposition of the local anaesthetic perineurally in short axis. This will be
      confirmed with a long axis view of the nerve (also recorded).

      Once the catheter has been sited using the above techniques, a bolus of agitated 5% dextrose
      will be injected through the catheter and Doppler ultrasound will be used to locate where in
      the tissues the injected fluid is being deposited. This will also be recorded and
      subsequently assessed.

      An assistant present during the block will time two aspects of the procedure:

        1. Time from first skin contact with needle to first muscle response to nerve stimulation.
           This will be done only on the day of surgery during the block procedure until the
           desired muscle twitch is elicited.

        2. Time from first skin contact to completion of catheter insertion (Block time).This is
           done during the block procedure only on the day of surgery as noted above

      Once catheter position has been assessed a total of 20 millilitres of 2% mepivacaine will be
      injected via the catheter in both groups. Over the subsequent 30 minutes a second blinded
      observer will take observations every 5 minutes to assess the degree of motor and sensory
      block.

      The video recording of the block procedure will be sent along with the data collection form
      to two of the co-investigators, who will independently assess the following:

        1. At the time of nerve contact by the needle, assign a rating for visibility of the needle
           shaft and tip according to the following scale:

             1. not visualised or poorly visualised - needle tip/shaft being isoechoic or only
                slightly more echogenic than background parenchyma.

             2. tip or shaft visualised with some difficulty - tip/shaft readily identified as
                being more echogenic than the background parenchyma but not seen in their entirety

             3. excellent visibility shaft and tip strongly echogenic relative to tissue and
                visualised in their entirety.

        2. Assign the same rating after completion of injection

        3. Judge whether circumferential and longitudinal spread of local anaesthetic is either
           adequate or inadequate.

      Following the operation a standard infusion of 0.1% ropivacaine at 4cc/hr will be commenced
      via the sciatic catheter. Post operative care will be as per the standard practice at this
      institution.

      One week post operatively the patient will be telephoned at home to check for persisting
      neurological symptoms.
    

Intervention name(s): echogenic needle and catheter; Neurostimulation to position needle and catheter
Intervention type(s): Device; Device
Intervention description(s): Visibility of needle shaft and tip with engraved markers. Ultrasonographic Visibility of catheter tip; The non echogenic needle will be positioned using ultrasonography and neurostimulation and the catheter will be positioned using neurostimulation with plantar or dorsiflexion with 0.6-1.5mA current. 20mL of 2% mepivacaine will be injected via the catheter. Sensory motor block will be evaluated every 5 minutes for 30 mins
Other intervention name(s): Pajunk Stimulong plexus catheter set; Pajunk sonolong sonoset; Pajunk Stimulaong Plexus catheter set
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Treatment
Keywords: Ultrasonography; nerve block; catheters; needle; anesthesia