Background Erector spinae plane blocks are used to improve outcomes after spine surgery, but pain frequently outlasts the duration of single injection blocks. We hypothesized continuous erector spinae plane (cESP) catheters would provide superior analgesia. We terminated a prospective double-blinded randomized clinical trial (RCT) comparing outcomes after multilevel spine surgery among patients randomized to saline versus ropivacaine cESP catheters. We present two cases of undesired epidural spread of ropivacaine and discuss etiology, management, and future research directions.

Case presentation Nine out of 44 patients (planned) enrolled in the RCT; 6/9 were randomized to receive ropivacaine infusions via bilateral cESP catheters. Two patients underwent uncomplicated posterior lumbar fusion and were recovering well with minimal pain and opioid requirements through postoperative day 1. Both had new-onset urinary retention and bilateral lower extremity numbness, weakness and paresthesias (24 and 30 hours after infusion-start time, respectively). One patient underwent MRI, which was remarkable for an epidural fluid collection compressing the thecal sac. Infusions were stopped, cESP catheters were removed and symptoms fully resolved over the next 3–5 hours.

Conclusions Unwanted neuraxial spread of local anesthetic from cESP catheters may be a unique consideration after spine surgery, accounted for by unpredictable local anesthetic distribution within disrupted surgical planes. Future studies are indicated to determine optimal catheter regimens together with guidance for extended monitoring in parallel with further studies of efficacy in spine surgery cohorts.

Trial registration number NCT05494125.