Does femoral nerve catheter placement with stimulating catheters improve effective placement? A randomized, controlled, and observer-blinded trial

Continuous peripheral nerve blocks offer the benefit of extended postoperative analgesia and accelerated functional recovery after major knee surgery. Conventional nerve localization is performed over a stimulating needle followed by blind insertion of the peripheral catheter. Correct catheter placement is confirmed by testing for satisfactory analgesia. Stimulating catheters offer the advantage of verifying correct placement close to the nerve during catheter placement. The aim of this randomized trial was to determine whether accurate catheter positioning under continuous stimulation accelerates the onset of sensory and motor block, improves the quality of postoperative analgesia, and enhances functional recovery. We compared femoral nerve catheters inserted under continuous stimulation with catheters that were placed using the conventional technique of blind advancement in 81 patients undergoing major knee surgery. Time of catheter placement was similar in both groups with 4 min (3/7.3; median, 25th/75th percentile) in the conventional group and 5 min (4/8.8) in the stimulating catheter group. In both groups, 42% of the catheters could be correctly placed (motor response of the patella with a current <= 0.5 mA) at first attempt. In 22 patients (58%) of the stimulating catheter group, the catheter had to be redirected 1-20 times, including 2 that could not be correctly placed within 20 min. The onset time of sensory and motor block was almost similar in both groups. There were no differences in the postoperative IV opioid consumption, and visual analog scale pain scores at rest and movement, or maximal bending and stretching of the knee joint during the 5 days after surgery. We conclude that with continuous femoral nerve blocks, blind catheter advancement is as effective as the stimulating catheter technique with respect to onset time of sensory and motor block as well as for postoperative pain reduction and functional outcome.