Peripheral nerve blocks provide better pain relief than opioids. Femoral nerve blocks, commonly used for patients undergoing total knee arthroplasty, provide excellent analgesia but have issues, including patient falls. The adductor canal block is primarily a sensory nerve block, so falls should be less of an issue. Surprisingly, the adductor canal block has not undergone rigorous study. Dr. David B. Auyong, Department of Anesthesiology, Virginia Mason Medical Center, Seattle, Washington, and colleagues describe a prospective randomized trial of a continuous infusion of 0.2% ropivacaine (8 mL/hr) via an adductor canal catheter for the postoperative pain management of patients undergoing total knee replacement. Their work appears in this month’s Anesthesia & Analgesia in the article titled “Continuous Ultrasound-Guided Adductor Canal Block for Total Knee Arthroplasty: A Randomized, Double-Blind Trial.”
Other aspects of care for these patients were systematically controlled, including the use of spinal anesthesia and a single-shot femoral nerve block for intraoperative anesthesia. The authors randomized 80 patients (76 of whom completed the protocol as specified) to either a continuous adductor canal block or a sham catheter. The authors demonstrated a significant reduction in the use of intravenous morphine (or equivalent opioid) in the first 48 hours postoperatively for the study group compared to a control group. The difference, amounting to about 25% of the total morphine equivalents used, was both statistically and clinically significant. Study group patients also demonstrated increased quadriceps strength and greater ability to ambulate on the second postoperative day.
This well conducted study adds to our knowledge of best practice for the most common type of surgical anesthesia – by time spent – in America (data personally obtained from the National Anesthesia Clinical Outcomes Registry). The focus of the experimental question on a ‘shared accountability’ outcome, the ability of the patient to work with physical therapy and attempt ambulation as soon as possible after surgery, is important. Reduced use of opioids, through enhanced local pain control, can contribute substantially to this goal. Further, the authors studied a nerve block technique that focuses on sensory pathways while minimizing motor weakness. With the American population aging and the number of knee replacements expected to rise in future years, the authors’ work provides an important clinical advance for our field.