Interscalene Dynamometer Pilot Study

Total shoulder arthroplasty can cause severe postoperative pain. Pain management includes general anesthesia with interscalene block during surgery and intravenous (IV) hydromorphone patient controlled analgesia (PCA) and oral opioid analgesics given after surgery. Side effects, such as motor blockade, may impair participation in physical therapy and diminish patient satisfaction. In order to prepare for a future study that will examine what mixtures of adjuncts/additives will best prevent recovery room pain and minimize motor blockade, the investigators are conducting this pilot study to collect preliminary data on current practice. The investigators believe the current regimen will provide adequate pain relief, but may cause extensive motor blockade and reduce patients' muscle strength after surgery.

Inclusion criteria

• Patients scheduled for primary total shoulder arthroplasty
• Age 18 to 80 years old
• Planned use of general anesthesia via laryngeal mask airway (LMA) and peripheral nerve block
• Ability to follow study protocol
• Patients with American Society of Anesthesiologists (ASA) physical status of I, II or III

Exclusion criteria

• Patients younger than 18 years old and older than 80
• Patients not intending to receive general anesthesia and peripheral nerve block
• Allergy or intolerance to one of the study medications
• Patients with an ASA of IV
• Hepatic or renal insufficiency
• Chronic opioid use (taking opioids for longer than 3 months)