Adductor Canal Block With Continuous Infusion Versus Intermittent Boluses and Morphine Consumption: A Randomized, Blinded, Controlled Clinical Trial

BACKGROUND: Based on the assumption that relatively large volumes of local anesthetic optimize an adductor canal block (ACB), we theorized that an ACB administered as repeated boluses would improve analgesia without compromising mobility, compared with a continuous infusion. METHODS: We performed a randomized, blinded, controlled study, including patients scheduled for total knee arthroplasty with spinal anesthesia. Patients received 0.2% ropivacaine via a catheter in the adductor canal administered as either repeated intermittent boluses (21 mL/3 h) or continuous infusion (7 mL/h). The primary outcome was total (postoperative day [POD], 0–2) opioid consumption (mg), administered as patient-controlled analgesia. Pain, ambulation, and quadriceps muscle strength were secondary outcomes. RESULTS: We randomized 110 patients, of whom 107 were analyzed. Total opioid consumption (POD, 0–2) was a median (range) of 23 mg (0–139) in the bolus group and 26 mg (3–120) in the infusion group (estimated median difference, 4 mg; 95% confidence interval [CI], −13 to 5; P = .29). Linear mixed-model analyses revealed no difference in pain during knee flexion (mean difference, 2.6 mm; 95% CI, −2.9 to 8.0) or at rest (mean difference, 1.7 mm; 95% CI, −1.5 to 4.9). Patients in the bolus group had improved quadriceps sparing on POD 2 (median difference, 7.4%; 95% CI, 0.5%–15.5%). However, this difference was not present on POD 1 or reflected in the ambulation tests (P > .05). CONCLUSIONS: Changing the mode of administration for an ACB from continuous infusion to repeated intermittent boluses did not decrease opioid consumption, pain, nor mobility. Accepted for publication October 24, 2017. Funding: This work was supported by an unrestricted research grant from Smiths Medical (St Paul, MN). In addition, Smiths Medical provided the portable infusion pumps used in this trial. The company had no input or influence into any aspect of study conceptualization, design, data analysis, or reporting of the study. None of the authors have a personal financial interest in this research. Conflicts of Interest: See Disclosures at the end of the article. The abstract has been accepted for presentation at the annual meeting of the American Society of Regional Anesthesia, San Francisco, CA, January 6–8, 2017, and at the IX SIMPAR-ISURA SIMPAR-ISURA (Study In Multidisciplinary Pain Research-International Symposium of Ultrasound for Regional Anesthesia and Pain Medicine) Congress, Florence, Italy, March 29 to April 1, 2017. Clinical trial number: Clinicaltrials.gov Identifier: NCT02539628. Ethics committees approval: H-2-2014-114. Pia Jaeger and Jonas Baggesgaard share first authorship. Reprints will not be available from the authors. Address correspondence to Pia Jaeger, MD, PhD, Department of Anaesthesia 4231, Centre of Head and Orthopaedics, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen E, Denmark. Address e-mail to pia.therese.jaeger@regionh.dk. © 2017 International Anesthesia Research Society

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