Evaluation of Continuous Saphenous Nerve Block to Supplement a Continuous Sciatic Nerve Block After Ankle Surgery
Condition: Orthopedic Surgery of Lower Extremity
Study type: Interventional

Summary: 
      A nerve block catheter is a small tube placed next to a nerve through a needle, and the
      needle is then removed. Numbing medicine is dripped through the tube to reduce pain sensation
      from the nerve.

      The purpose of this research study is to test whether the placement of a second nerve block
      catheter, rather than a single injection for the saphenous nerve block will improve pain
      relief and/or reduce pain medication needed after surgery enough to justify two nerve block
      catheters.

      There are two nerves that carry pain sensations from the ankle, the large (sciatic) nerve and
      the smaller (saphenous) nerve. Patients undergoing ankle fusion or fracture surgery at Wake
      Forest University typically have a nerve block catheter placed next to the sciatic nerve to
      give local anesthetic (numbing medicine) for 24-72 hours. In addition, a single injection of
      local anesthetic is usually performed to block the saphenous nerve for 12-16 hours
      postoperatively.
    

Detailed description: 
      Interventions and Interactions Study participants will be asked to report a preoperative
      baseline pain score (Numeric Pain Scale (0-10)), and have quadriceps strength measured (see
      below) prior to any sedation being administered. Patients will undergo placement of a
      continuous subgluteal sciatic nerve catheter, and dosage with 25ml of 0.25% bupivacaine with
      epinephrine 1:200,000 and clonidine 25 mcg per usual technique after sedation. A perineural
      catheter will then be placed for primary saphenous nerve block and postoperative saphenous
      infusion. This continuous saphenous catheter will be placed using ultrasound guidance
      (Sonosite Turbo ™, Bothell, WA) (6-13MHz linear probe). The superficial femoral artery will
      be identified in short axis at approximately the midpoint or distal third of the femur as the
      artery lies deep to the sartorius muscle in the adductor canal. Using aseptic technique, an
      18 gauge tuohy needle will be inserted in-plane from lateral to the transducer and advanced
      to a position anteromedial to the artery, between sartorius and vastus medialis muscles.
      Proper positioning will be confirmed by injection of saline, a 20g multiorifice catheter will
      be inserted 3-4 cm beyond the needle tip and the catheter will be tunneled and taped up the
      medial surface of the thigh. The catheter will be test dosed with 1.5% lidocaine with
      1:200,000epinephrine to confirm position and rule out IV injection. The primary saphenous
      nerve block will be produced by incremental injection through the catheter of 10ml of 0.25%
      bupivacaine with epinephrine 1:200,000 and clonidine 15 mcg. Successful saphenous block will
      be defined as loss of sensation to pinprick in the mid, anteromedial leg measured at 15 and
      30 minutes post-block. A 3-point scale will be used to define sensory block: 0=full
      sensation, 1= touch without sharp sensation, 2=absent sensation.

      To determine the effect of saphenous block on quadriceps function, patients will have knee
      extension muscle strength tested pre-block and 30 min post-block using a Hoggan Health
      microFET 2 MT Digital Handheld Dynamometer. After placement of both the saphenous and sciatic
      nerve catheters, patients will receive either neuraxial or general anesthesia for surgical
      anesthesia at the discretion of the attending anesthesiologist medically directing their
      primary anesthetic technique.

      Patients with evidence of sciatic and saphenous nerve block will be randomized to receive a
      postoperative continuous infusion of either saline (control) or 0.2% ropivacaine by
      elastomeric infusion pump at 5ml/h started within 6h of catheter placement. The randomization
      will occur by sealed envelope provided to the OR Pharmacy (block randomization in blocks of
      10) and the OR pharmacy will prepare the 300 ml elastomeric pump with active or control
      solution. The On-Q C-Bloc™(300ml capacity) (I-Flow corporation) pump will be attached to the
      saphenous catheter in the PACU, or within 6h of primary block; the catheter will infuse for
      60 hours.

      The patients, physicians, nurses and investigators will be blinded to treatment group.

      The sciatic infusion will be managed per usual practice: postoperatively all patients will
      receive 0.2% ropivacaine through their sciatic nerve catheter at a basal infusion rate of
      10ml/h, . The sciatic pump will be an On-Q™ pump per usual practice. All patients will have
      oral and IV opioids prescribed while hospitalized, and oral opioids prescribed after hospital
      discharge. In the event of breakthrough pain, patients will be instructed to adjust the
      sciatic nerve pump, and/or to take oral opioids for the pain.

      While patients are hospitalized, opioid administration and pain scores will be recorded by
      nursing staff on the patient care record. Side effects including nausea, vomiting, or itching
      will also be recorded. Patients will be seen on a daily basis while in the hospital by the
      acute pain service, and adjustment of their sciatic infusion performed if indicated. They
      will be questioned about sleep quality, pain score, opioid side effects, and sensory function
      in the sciatic and saphenous distributions. This information will be recorded by the acute
      pain management team. On postoperative day 1, all patients will again have their quadriceps
      muscle group strength assessed with the hand-held dynamometer, and the catheter sites will be
      inspected per standard protocol.

      Patients will be generally discharged home with peripheral nerve catheters in place on POD
      #1, after receiving written and verbal instructions in perineural catheter management. These
      patients will be called at 24 and 48 hours post discharge to determine rest and incident
      numeric pain scores, opioid usage, sleep quality (as number of awakenings for pain), and the
      presence of nausea or vomiting. Patients will be given contact numbers and instructions to
      call with any questions or concerns per usual practice.

      Outcome Measure(s) The primary endpoint of this study will be a reduction of the rest and
      incident verbal pain scores 48hpost-nerve blockade when the primary saphenous single-shot
      block is expected to have resolved. Secondary endpoints of reduction of opioid use, nausea
      and vomiting, sleep disturbance (as number of awakenings), and reduction of quadriceps
      strength will also be evaluated.
    

Intervention name(s): 0.2% ropivacaine; saline
Intervention type(s): Device; Drug
Intervention description(s): 0.2% ropivacaine by elastomeric infusion pump at 5ml/h started within 6h of catheter placement; saline (control) by elastomeric infusion pump at 5ml/h started within 6h of catheter placement
Other intervention name(s): NAROPIN®
Intervention MeSH terms: Ropivacaine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Treatment
Keywords: ankle; arthrodesis; internal fixation; bi/tri malleolar fracture