Saphenous Nerve Block for Foot and Ankle Surgery
Condition: Saphenous Nerve Block
Study type: Interventional

Summary: 
      Patients undergoing foot and ankle surgery have the option of having a nerve block
      administered by their Anesthesiologist. The nerve block numbs the foot and results in less
      post-operative nausea and vomiting, and better pain control. Two different techniques for
      blocking the saphenous nerve to the foot have been described and are both commonly used at
      St. Paul's hospital. The goal of this study is to compare the success rates of these two
      techniques.
    

Detailed description: 
      Purpose / Hypothesis This clinical study is a prospective, controlled, randomized,
      single-blinded trial designed to investigate the hypothesis that ultrasound-guided blockade
      of the saphenous nerve in conjunction with nerve stimulation has a higher success rate when
      compared to ultrasound alone. These research interventions represent what is considered to be
      an improvement on the standard practice at St. Paul's, which is to block the saphenous nerve
      with one of any number of saphenous nerve blocks, using a number of different techniques
      (i.e. ultrasound-guided, nerve stimulation, blind field block); the effectiveness of which
      has been inconsistent. The purpose of this study is to identify if one technique has a great
      success rate over another, which would ultimately result in increased success rates of
      saphenous nerve blocks and patient care.

      Study Design The study will be a randomized, single-blinded trial of 80 subjects who are
      undergoing foot and ankle surgery. Informed consent will be obtained from all study subjects.
      Subjects will be randomized to one of two saphenous nerve block techniques to be administered
      by an experienced regional anesthesiologist at St. Paul's Hospital. Once the nerve block is
      completed the success will be evaluated by an investigator blinded to the procedure. Once the
      30min evaluation is completed anesthetic care will be provided according to regular
      institutional practice and at the discretion of the attending anesthesiologist. The subject
      will then be contacted at 2 and 7 days after block administration to assess for delayed
      complications.

      Intravenous access will be gained and non-invasive blood pressure measurements will be
      recorded every five minutes. Continuous electrocardiography and oxygen saturation monitoring
      will be maintained throughout the procedure and for at least 60 minutes afterwards. Light
      sedation will be provided, with the goal of maintaining verbal contact with the subject
      throughout the procedure. Where clinically appropriate, the study block may be preceded by an
      ultrasound-guided popliteal sciatic nerve block at the discretion of the attending
      anesthesiologist.

      Saphenous nerve blockade will be preformed using a transsartorial approach. Subjects in both
      groups will be positioned prone. The ultrasound probe will be placed in the transverse plane
      on the medial aspect of the thigh 3-5cm cephalad to the superior border of the patella (area
      marked). An attempt will then be made to identify the saphenous nerve, which runs deep to the
      sartorius muscle within the subsartorial fascial plane. The nerve will appear hyperechoic,
      round or oval shaped. The anesthesiologist will have a maximum scan time of 3 minutes prior
      to needle entry. Up to 5 mL of 1% Lidocaine will be used for skin infiltration of the
      injection site. The block will then be preformed as to the protocols below depending on group
      allocation. A thirty minute evaluation of the saphenous nerve block will occur during the
      normal monitoring period after the placement of a block.

      Following completion of the thirty-minute evaluation, anesthetic care will be provided
      according to regular institutional practice and at the discretion of the attending
      anesthesiologist. This may include spinal or general anesthesia.

      All subjects will be contacted by telephone at two and seven days post procedure for a follow
      up interview to assess for delayed complications associated with the procedure.

      The medications used for the nerve blocks in the study will include only ropivacaine 0.5% and
      lidocaine 1%. For subject sedation, midazolam and fentanyl will be used. None of these
      medications are considered study drugs; rather they are commonly used anesthetic medications.
      While used in the study, these drugs themselves are not being investigated. The same
      medications will be used on subjects not enrolled in the study.

      Study Treatment Group 1 - Saphenous nerve block using ultrasound guidance The needle will be
      placed with the needle tip in close proximity (1-2 mm) of the target structures (the
      saphenous nerve if visible or in the subsartorial facial plane of the sartorius muscle if the
      nerve is not visible). A total of 10 mL of 0.5% ropivacaine will be used for the block.
      Before injection of any local anesthetic a gentle aspiration will be preformed, with a second
      aspiration after 5 mL of ropivacaine has been injected. Once injection of local anesthetic
      has commenced small needle adjustments are allowed to enhance spread. This will be done at
      the discretion of the regional anesthesiologist performing the block.

      Study Treatment Group 2 - Saphenous nerve blockade using ultrasound guidance and nerve
      stimulation The needle will be place with the needle tip in close proximity (1-2 mm) of the
      target structure (the saphenous nerve if visible or in the subsartorial fascial plane if the
      nerve is not visible). The Pajunk MultiStim SENSOR nerve stimulator will then be turned on,
      starting at 1.0 milliamp (mA) until a tapping sensation is elicited in the medial or anterior
      aspect of the ankle. The amplitude of the nerve stimulator will then be gradually decreased
      with maintenance of the tapping sensation by making small adjustments in needle location. The
      end-point for nerve localization will be a tapping sensation in the area of the medial
      malleolus at ≤ 0.6 mA. The anesthesiologist will have a maximum search time of 5 minutes from
      needle entry to elicitation of the tapping sensation. Once a tapping sensation is elicited in
      the ≤ 0.6 mA range, 10 mL of 0.5% ropivacaine will be injected at the site. If a tapping
      sensation is elicited but not ≤ 0.6 mA within 5 minutes then 10 mL of 0.5% ropivacaine will
      be injected at the site where the lowest amplitude tapping sensation was elicited. If no
      tapping sensation is elicited from the subject after 5 minutes, an injection of 10 mL of
      ropivacaine will be made below the Sartorius muscle in the subsartorial fascial plane. Before
      injection of any local anesthetic a gentle aspiration will be preformed, with a second
      aspiration after 5 mL of ropivacaine has been injected. Once injection of local anesthetic
      has commenced small needle adjustments are allowed to enhance spread. This will be done at
      the discretion of the regional anesthesiologist performing the block.
    

Intervention name(s): Ultrasound Guidance; Ultrasound guidance + nerve stimulation
Intervention type(s): Device; Device
Intervention description(s): Ultrasound guidance will be used to place a saphenous nerve block; Ultrasound guidance and nerve stimulation will be used to place a saphenous nerve block
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: Saphenous Nerve; Nerve Block; Ultrasound guided; Neurostimulation; Regional Anesthesia; Ropivacaine; Foot Surgery; Nerve Stimulation; Ankle Surgery