Median Effective Concentration of Ropivacaine for Ultrasound-Guided T11 Thoracic Paravertebral Block in Patients with End-Stage Renal Disease: A Dixon Up-and-Down Dose-Finding Study

Abstract

Background Patients with end-stage renal disease (ESRD) may exhibit altered pharmacokinetic and pharmacodynamic responses to local anesthetics. But the ropivacaine concentration-response profile for ultrasound-guided T11 thoracic paravertebral block (TPVB) in this population remains undefined. This study aimed to determine the median effective concentration (EC50) of ropivacaine for TPVB in ESRD patients undergoing peritoneal dialysis catheterization (PDC) and evaluate early postoperative recovery. Methods In this prospective dose-finding study, patients aged 18–75 years with ESRD and ASA physical status II–III undergoing elective PDC received ultrasound-guided T11 TPVB with 20 mL ropivacaine. Concentrations were assigned by the Dixon up-and-down method, starting at 0.50%: decrease by 0.05% after a successful analgesic or increased by 0.05% after a failed response. A successful response was defined as VAS ≤3 at skin incision without rescue analgesia; a failed response was defined as VAS >3 or rescue analgesia before or during incision. EC50 was estimated primarily by centered isotonic regression with the pool-adjacent-violators algorithm (CIR-PAVA), a nonparametric method suited to small Dixon samples; with probit regression, a parametric approach commonly used in prior EC50 studies, also performed for comparison. Recovery was assessed using the Quality of Recovery-40 (QoR-40) questionnaire at 24 hours postoperatively. This was a small single-arm exploratory study with no formal sample-size calculation, consistent with the sequential design. Results 27 patients completed the study. EC50 was 0.173% (95% CI: 0.100%–0.500%) by CIR-PAVA and 0.180% (95% CI: 0.109%-0.225%) by probit regression. The wider CIR-PAVA CI reflects the small sample size and limited precision. Median global QoR-40 score at 24 hours was 184.0. Five patients (18.5%) required rescue analgesia. No serious adverse events, local anesthetic systemic toxicity, pneumothorax, or neurological complications occurred. Conclusion The EC50 of ropivacaine for TPVB in ESRD patients undergoing PDC was approximately 0.17%-0.18%, with favorable early recovery and acceptable safety. Given that EC50 reflects efficacy in only 50% of patients, EC90/EC95 studies are needed before definitive dosing recommendations.