Continuous Erector Spinae Plane Blocks to Treat Pain after Percutaneous Nephrolithotomy: A Randomized, Triple-masked, Placebo-controlled Clinical Trial

BACKGROUND: Single-injection erector spinae plane blocks (ESPB) provide analgesia after percutaneous nephrolithotomy (PCNL) but are limited in their duration. A continuous ESPB involving local anesthetic administered via a perineural catheter may extend analgesia duration. This study hypothesized that adding a continuous ESPB to a single-injection ESPB after outpatient PCNL would decrease pain severity and/or opioid consumption over the first 2 postoperative days (dual primary outcomes). METHODS: Preoperatively, adults undergoing PCNL had an ultrasound-guided perineural catheter inserted at the eighth transverse process after saline injection. Bupivacaine 0.25% with epinephrine (20 ml) was manually injected via the catheter for all participants who were subsequently randomly allocated to one of two postoperative treatments: active with bupivacaine 0.25% or placebo with normal saline. An automatic intermittent bolus of 21 ml was delivered every 4 h using a portable infusion pump for approximately 57 h. RESULTS: During the first 2 postoperative days, the median [interquartile range] average daily pain intensity as measured with the numeric rating scale for active (n = 25) was 3.5 [2.0, 4.5] compared with 3.0 [1.3, 4.5] for placebo (n = 25; estimated difference, 0.25; 95% CI, -1.0 to 1.5; P = 0.538). Cumulative oxycodone consumption during this same period was 10 [0, 25] mg for active versus 15 [0, 30] mg for placebo (estimated difference, 0; 95% CI, -15 to 5; P = 0.358). During this period, the maximum daily pain for active was 7.0 [4.3, 8.0] compared with 6.5 [5.5, 8.0] for placebo ( P = 0.754). Sleep disturbances the second night were 0 [0, 1] for both groups ( P = 0.423). During the day after surgery, pain interference with physical and emotional functioning was 10 [0, 33] for active and 8 [23, 48] for placebo as measured with the Brief Pain Inventory ( P = 0.587). CONCLUSIONS: This investigation failed to identify benefits of adding a continuous ESPB to a single-injection ESPB after PCNL.