Ultrasound guidance versus electrical stimulation for femoral perineural catheter insertion

Continuous femoral nerve blocks provide potent analgesia and other benefits after knee surgery. Perineural catheter placement techniques using ultrasound guidance and electrical stimulation (ES) have been described, but the optimal method remains undetermined. We tested the hypothesis that ultrasound guidance alone requires less time for femoral perineural catheter insertion and produces equivalent results compared with ES alone.

Preoperatively, patients receiving a femoral perineural catheter for knee surgery were randomly assigned to either ultrasound guidance with a nonstimulating catheter or ES with a stimulating catheter. The primary outcome was the catheter placement procedure time (minutes) starting when the ultrasound transducer (ultrasound group) or catheter insertion needle (ES group) first touched the patient and ending when the catheter insertion needle was removed after catheter insertion.

Perineural catheters placed with ultrasound guidance (n = 20) took a median (10th-90th percentiles) of 5.0 (3.9-10.0) minutes compared with 8.5 (4.8-30.0) minutes for ES (n = 20; P = .012). All ultrasound-guided catheters were placed according to the protocol (n = 20) versus 85% of ES-guided catheters (n = 20; P = .086). Patients in the ultrasound group had a median procedure-related discomfort score of 0.5 (0.0-3.1) compared with 2.5 (0.0-7.6) for the ES group (P = .015). There were no vascular punctures with ultrasound guidance versus 4 in the ES group (P = .039).

Placement of femoral perineural catheters takes less time with ultrasound guidance compared with ES. In addition, ultrasound guidance produces less procedure-related pain and prevents inadvertent vascular puncture.