Stimulating versus non-stimulating catheter for lumbar plexus continuous infusion after total hip replacement.

BACKGROUND: This study was aimed to investigate whether stimulating catheters for continuous lumbar plexus block reduce local anesthetic consumption after hip arthroplasty if compared with traditional non-stimulating catheters. METHODS: Seventy-two ASA I-III, 18-82-year-old, undergoing primary hip replacement (THA) for osteoarthritis with spinal anesthesia were randomized into two groups: Stim group (stimulating catheter, N.=36) and Nonstim group (non-stimulating catheter, N.=36). After surgery, 15 mL of mepivacaine 1% were administered in both groups through the catheter. An electronic pump was connected to deliver ropivacaine 0.2% (3 mL/h, bolus 3 mL, lock out 15 min) for the first 72 h. Patients were given ketorolac 30 mg IV every 8 h, acetaminophen 1g IV every 8 h and oxycodone 10 mg per os for rescue analgesia. Primary outcome was postoperative local anesthetic consumption. Numerical Rating Scale (NRS), complications, both quadriceps and obturator strength measurements, and opioid requirement were also registered. Mixed effect models (random intercept) were built for repeated measures over time. A difference between groups was considered statistically significant if P<0.05. RESULTS : Local anesthetic consumption and NRS were comparable between groups. Patients in the Nonstim group required significant more rescue opioid analgesia compared with the Stim group during the first 36 h (P=0.002). Quadriceps and adductor muscle strength was equally preserved in the two groups. CONCLUSIONS: The study showed comparable local anesthetic consumption, pain scores and muscle strength preservation between the two groups. The stimulating catheter allowed a significant, although underpowered, reduction in opioid consumption.