Adductor Canal Blocks With Bupivacaine and Magnesium After Same-day Discharge Total Knee Arthroplasty Improve Post-operative Pain Relief and Decrease Opioid Consumption: a Prospective Randomized Controlled Trial
Condition: Post-operative Pain, Acute
MeSH terms: Pain, Postoperative; Acute Pain
Study type: Interventional

Summary: 
      The purpose of this study is to determine whether the addition of magnesium to bupivacaine
      for the post-operative adductor canal blocks (ACB) can decrease opioid consumption and
      improve pain management for patients after same-day discharge total knee arthroplasty (TKA).

      The investigators will assess whether the addition of magnesium will decrease visual analog
      scale (VAS) pain scores, decrease post-operative total opioid consumption (oral morphine
      equivalents), decrease the incidence of post-operative nausea and vomiting (PONV), and
      improve patient satisfaction in comparison to when magnesium is not administered.
    

Detailed description: 
      Total knee arthroplasty (TKA) is one of the most common elective surgical procedures in the
      United States . The number of TKA procedures has doubled in each of the past two decades and
      is expected to top 3.4 million per year in the United States by 2030.

      Within the last 10-15 years significant changes have taken place in the anesthetic management
      of patients undergoing total knee arthroplasty (TKA). In the past, the majority of patients
      underwent general anesthesia and were managed post-operatively with a PCA (patient controlled
      analgesia) pump.

      More recently anesthesiologists have begun to use neuraxial anesthesia (spinal anesthesia)
      combined with regional anesthesia (peripheral nerve block (PNB)) techniques combined with
      monitored anesthesia care (MAC) for many of these surgeries.

      Regional anesthesia is used to block the sensation in a specific part of body during and
      after surgery. It offers numerous advantages over conventional general anesthesia, including
      faster recovery time, fewer side effects, no need for an airway device during surgery, and a
      dramatic reduction in post-surgical pain and reduction in opioid use following surgery. The
      use of local anesthetic peripheral nerve blocks for surgical anesthesia and postoperative
      pain management has increased significantly with the advent of ultrasound-guided techniques.

      However, the duration of traditional amide-based and ester-based regional anesthesia is
      normally limited to only a few hours. Techniques including continuous catheter placement or
      serial injections can be used to enhance the duration and effect of regional anesthesia for
      postoperative pain control. But these approaches can increase the risk of infection,
      toxicity, and cost. Therefore, alternative methods of extending the clinical duration of
      nerve blocks have been a topic of significant interest.

      Magnesium sulfate, an NMDA receptor antagonist, exerts it analgesic effects by at least two
      mechanisms: it acts as a physiological calcium antagonist by blocking NMDA receptors and it
      inhibits the inflammatory response through the reduction of inflammatory cytokines.

      Magnesium has also been shown to decrease peripheral nerve excitability. Addition of
      magnesium to intravenous regional anesthesia for chronic limb pain management has
      demonstrated improvement in quality of blockade and prolonged the duration of analgesia.
      Magnesium decreased intraoperative opioid consumption and tourniquet pain. Magnesium improved
      the quality of anesthesia and prolonged the time for first postoperative analgesic
      requirement. Overall, the addition of magnesium to local anesthetic is effective both for
      perineural (nerve blocks) and intravenous regional anesthesia.

      In a recent meta-analysis of randomized controlled trials, Li et al. evaluated seven trials
      involving 493 patients. Investigators concluded that the addition of magnesium as an adjuvant
      to PNB prolonged the postoperative duration time of analgesia, sensory, and motor block.

      Studies have consistently shown that addition of magnesium to local anesthetic significantly
      prolongs peripheral nerve blocks, including femoral nerve blocks with bupivacaine,
      interscalene blocks with bupivacaine, and axillary blocks with prilocaine and
      levobupivacaine. All of these papers denied adjuvant-related toxicity or side effects;
      however, nausea was two to three times more likely in the first 12 hours after interscalene
      blocks with 200mg magnesium in the study by Lee et al. This side effect was not reported in
      studies using 150mg magnesium.

      The purpose of this study is to determine whether the addition of magnesium to bupivacaine
      for the post-operative adductor canal blocks can decrease opioid consumption and improve pain
      management for patients after total knee arthroplasty (TKA).

      The investigators will assess whether the addition of magnesium will decrease visual analog
      scale (VAS) pain scores, decrease post-operative total opioid consumption (oral morphine
      equivalents), decrease the incidence of post-operative nausea and vomiting (PONV), and
      improve patient satisfaction in comparison to when magnesium is not administered.
    

Intervention name(s): Adding Magnesium as an adjuvant to the adductor canal Block (ACB) for same-day discharge total knee arthroplasty
Intervention type(s): Drug
Intervention description(s): Post-operatively all patients will have an ultrasound-guided adductor canal block (ACB) with 30cc of 0.25% bupivacaine. Half of the patients (selected randomly using random number table) will receive 150mg of magnesium sulfate (0.3mL) in the block and the other half will receive 0.3 mL of saline in the block.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Triple (Participant, Care Provider, Outcomes Assessor)
Primary purpose: Supportive Care
Keywords: Same-day discharge total knee arthroplasty; Magnesium; Adductor canal block; Post-operative opioid consumption; Post-operative pain management