A retrospective evaluation of the failure rate of continuous infraclavicular nerve blockade in the ambulatory setting

Abstract

To the Editor, Continuous peripheral nerve blocks (cPNB) remain a cornerstone of postoperative analgesia after major hand surgery, which is often performed in an outpatient setting. To our knowledge, no studies have evaluated the efficacy of low-rate infusions 24 hr after ambulatory surgery. Thus, we conducted a retrospective observational single-centre study (Centre Hospitalier de l’Université de Montréal) to assess the failure rate of cPNB at 48 hr after outpatient hand surgery. After institutional Research Ethics Board approval (2021-9496), we extracted data for all cPNB for ambulatory major hand surgery conducted between November 2017 and May 2020 from our institutional database. At our centre, cPNB insertion and follow-up is standardized using an ultrasound-guided infraclavicular lateral paracoracoid approach in all cases of ambulatory brachial plexus cPNB and is performed by an experienced anesthesiologist or a trainee under supervision. The perineural catheter is positioned under the axillary artery. After surgery, a variable rate (3–5 mL hr) elastomeric pump containing 300 mL of 0.15% bupivacaine is set up. Patients receive a standardized postoperative oral analgesic regimen, including regular acetaminophen, nonsteroidal anti-inflammatory agents, and, if necessary, hydromorphone. After discharge, daily telephone follow-ups are conducted by the treating physician to assess postoperative pain (via a 0–10 numeric rating scale [NRS]) and potential adverse events. Our primary outcome was the incidence of catheter failure, defined as moderate-to-severe pain (NRS score C 4) on postoperative day (POD) 2. Secondary outcomes included catheter failure on POD 1, unanticipated hospital readmissions, sleep quality, and adverse events related to the cPNB (leakage at the insertion site and local anesthetic systemic toxicity symptoms) for the first two postoperative days. Data are presented descriptively as n (%) and median [interquartile range]. Of the 245 patients considered eligible, 138 were included in the analysis. One hundred and seven were excluded because data were missing for the primary outcome. One hundred and ten patients underwent carpectomy (80%) and 28 underwent arthrodesis or another type of surgery (20%). The cPNB failure rate on POD 2 was 12% (17/138). Of the patients with a catheter failure on POD 2, 65% (11/17) also had a failure at POD 1. The Table shows the complete results for the primary and secondary outcomes. We acknowledge that our definition of catheter failure may be debated. In the literature, there is no consensus on the recommended way to evaluate cPNB efficacy and failure rates. Performing objective tests, such as ultrasound imaging of the injectate or sensory-motor testing, would have been more accurate, but is impractical in the ambulatory setting. Surprisingly, 25% of patients had inadequate analgesia on POD 1. We can hypothesize that the true catheter failure rate on POD 2 is potentially underestimated. This would be more in line with current literature, where incidences between 20% and 30% are reported. It is possible that patients with malfunctioning catheters optimized their oral analgesia between POD 1 and 2, or that pain naturally decreased over time. Another possibility is that the low-rate infusion of local anesthetics led to an analgesic block over M. Roy, MD (&) N. Ramdoyal, MD, FRCPC M. Meouchy , MD S. Garneau, MD, FRCPC F. Robin, MD Department of Anesthesiology, Centre Hospitalier de l’Université de Montréal (CHUM), Montreal, QC, Canada e-mail: [email protected]