Minimum Local Anesthetic Dose for Adductor Canal Block
Condition: Neuromuscular Blockade
Study type: Interventional

Summary: 
      The purpose of this study is to determine the minimum dose of ropivacaine 0.5%, required to
      produce pain relief without weakening the leg muscles.
    

Detailed description: 
      The post-operative period after a Total Knee Arthroplasty (TKA) is known to be especially
      painful for the first 24 hours. Significant pain can persist up to 3 days in some cases.
      Successful management of pain post TKA is therefore regarded as essential to early recovery,
      rehabilitation and timely discharge.

      Until now, multiple modes of analgesia have been employed including intravenous
      patient-controlled analgesia, continuous femoral nerve block and epidural analgesia. These
      are all effective alternatives but each is limited by side effects. Epidural analgesia
      provides excellent pain control and has been associated with early rehabilitation despite its
      negative impact on ambulation in the immediate peri-operative period. Additionally, an
      increased risk of spinal hematoma has been reported with epidural analgesia and
      peri-operative low molecular weight heparin prophylaxis. For this reason, epidural analgesia
      is not routinely offered to patients undergoing TKA today.

      A multimodal analgesic approach centered on the use of continuous femoral nerve blocks has
      been more recently favoured, providing superior analgesia and less opioid-related side
      effects than a systemic opioid-based regimen. However, femoral nerve blockade is also
      associated with significant quadriceps muscle weakness, which can impair ambulation, delay
      physiotherapy and result in accidental fall.

      Recent reports suggest that saphenous nerve blockade using an adductor canal approach is a
      novel technique with which to provide adequate analgesia for major knee surgery.
      Ultrasound-guided saphenous nerve block in the adductor canal is considered a technically
      simple and reliable block, providing consistent success. Although traditionally used to
      provide anesthesia and analgesia to the foot and ankle, recent reports suggest that saphenous
      nerve blockade in the adductor canal may provide adequate analgesia for major knee surgery.
      Taking into consideration the anatomy of the adductor canal, it appears possible to target
      not only the saphenous nerve but also multiple branches of the femoral and obturator nerve.

      However, the optimal dose of local anesthetic required to establish knee analgesia without
      inducing quadriceps weakness has not yet been determined. Identifying an optimal dose would
      allow for maximum analgesic efficacy with minimal or no motor block, while minimizing other
      unwanted adverse effects.

      This pilot study is designed to determine the optimal dose of ropivacaine 0.5% required to
      initiate sensory knee analgesia for the post-operative.
    

Intervention name(s): Ropivacaine 0.5%
Intervention type(s): Drug
Intervention description(s): The volume of local anesthetic Ropivacaine 0.5% will be determined by the response (success or failure of block, 30 minutes after local anesthetic injection) of the previous patient in that group. Block success is defined as an absence of ice sensation in the knee within 30 min of ropivacaine administration accompanied by tolerance to tetanic electrical stimulation (TES) at 60 mA(milliamp) for 5 seconds.
Other intervention name(s): Naropin
Intervention MeSH terms: Ropivacaine
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Other
Keywords: Neuromuscular blockade