Background and Objectives: A single injection lumbar plexus block for acute pain management after hip surgery is usually limited to the immediate postoperative period. We conducted a randomized controlled trial to determine the effect of a continuous lumbar plexus block on perioperative opioid requirements and pain intensity.

Methods: Adult patients undergoing elective hip arthroplasty under general anesthesia were randomized to continuous lumbar plexus block combined with patient-controlled analgesia (PCA) or PCA only for postoperative pain. Patients allocated to the lumbar plexus block had the catheter placed before surgery. Patients were followed for 36 hours. Perioperative opioid requirement was the primary outcome; secondary outcomes included assessment of pain intensity, patient and surgeon satisfaction with the analgesic technique, and occurrence of nausea and vomiting.

Results: Seventeen patients were randomized to each treatment group. Compared with patients in the PCA group, patients in the continuous lumbar plexus block group required less morphine (12 mg) (95% CI, −12.9 to −3.9), had on average less pain (−2.1 units on a 0 to 10 scale) (95% CI, −3.8 to −1.1), were more satisfied with their analgesic technique, and experienced less nausea and vomiting. One patient in the continuous lumbar plexus block developed a delayed paresis and 1 patient in the PCA group developed respiratory depression.

Conclusions: Continuous lumbar plexus block combined with PCA is superior to PCA alone for postoperative pain management following hip replacement. It reduces opioid requirements, opioid related side effects, and enhances patient satisfaction. However, additional research is required to determine its safety in light of the neurologic injury observed.