A comparison of ultrasound alone vs ultrasound with nerve stimulation guidance for continuous femoral nerve block in patients undergoing total knee arthroplasty.

Study Objective: To compare analgesic efficacy of ultrasound (US) guidance alone and US guidance combined with nerve stimulation (NS) for continuous femoral nerve block (CFNB) in patients undergoing total knee arthroplasty (TKA).

Design: Prospective, randomized double-blind trial.

Setting: Postanesthesia care unit and general ward.

Patients: Fifty American Society of Anesthesiologist physical status I to II patients undergoing TKA under spinal anesthesia.

Interventions: In group A (n = 25), an 18-gauge Tuohy needle was directed at the lower mid-part of the femoral nerve, and a nonstimulating catheter was inserted through the needle under US guidance. In group B (n = 25), an 18-gauge Tuohy needle and stimulating catheter were directed to the lower part of femoral nerve under US guidance, and quadriceps muscle contraction was checked using NS. All patients received a 20-mL loading dose of 0.2% ropivacaine, a continuous infusion of 4 mL/h, and a 4-mL bolus of 0.2% ropivacaine with a lockout time of 60 minutes for patient-controlled analgesia.

Measurements: The primary outcome was resting and exercising pain quality assessed by numeric rating scale. Other outcomes included procedure time for correct catheter placement, block failure rate, patient satisfaction for postoperative pain control, total dose of local anesthetic, additional opioid requirement, and adverse effects postoperatively.

Main Results: There were no significant differences between groups in resting and exercising numeric rating scale. Procedure times were longer in group B than group A (P < .05). There were no significant differences between groups in block failure rate or other outcomes.

Conclusions: US-guided CFNB was associated with similar analgesic efficacy and block failure rate and reduced procedure time compared to US with NS guidance for CFNB in patients undergoing TKA.