• Edward R Mariano, T Edward Kim, Michael J Wagner, Natasha Funck, T Kyle Harrison, Tessa Walters, Nicholas Giori, Steven Woolson, Toni Ganaway, and Steven K Howard.
• Departments of Anesthesiology, Perioperative and Pain Medicine (E.R.M., T.E.K., M.J.W., N.F., T.K.H., T.W., T.G., S.K.H.) and Orthopedic Surgery (N.G., S.W.), VA Palo Alto Health Care System, Palo Alto, California USA; and Stanford University School of Medicine, Stanford, California USA. emariano@stanford.edu.
• J Ultrasound Med. 2014 Sep 1; 33 (9): 1653-62.

ObjectivesProximal and distal (mid-thigh) ultrasound-guided continuous adductor canal block techniques have been described but not yet compared, and infusion benefits or side effects may be determined by catheter location. We hypothesized that proximal placement will result in faster onset of saphenous nerve anesthesia, without additional motor block, compared to a distal technique.MethodsPreoperatively, patients receiving an ultrasound-guided nonstimulating adductor canal catheter for knee arthroplasty were randomly assigned to either proximal or distal insertion. A local anesthetic bolus was administered via the catheter after successful placement. The primary outcome was the time to achieve complete sensory anesthesia in the saphenous nerve distribution. Secondary outcomes included procedural time, procedure-related pain and complications, postoperative pain, opioid consumption, and motor weakness.ResultsProximal insertion (n = 23) took a median (10th-90th percentiles) of 12.0 (3.0-21.0) minutes versus 6.0 (3.0-21.0) minutes for distal insertion (n = 21; P= .106) to anesthetize the medial calf. Only 10 of 25 (40%) and 10 of 24 (42%) patients in the proximal and distal groups, respectively, developed anesthesia at both the medial calf and top of the patella (P= .978). Bolus-induced motor weakness occurred in 19 of 25 (76%) and 16 of 24 (67%) patients in the proximal and distal groups (P = .529). Ten of 24 patients (42%) in the distal group required intravenous morphine postoperatively, compared to 2 of 24 (8%) in the proximal group (P = .008), but there were no differences in other secondary outcomes.ConclusionsContinuous adductor canal blocks can be performed reliably at both proximal and distal locations. The proximal approach may offer minor analgesic and logistic advantages without an increase in motor block.© 2014 by the American Institute of Ultrasound in Medicine.

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