Objective: To compare the accuracy of ultrasound (US)-assisted femoral nerve blocks (FNB) with the fascial pop (FP) technique, examining the rates of success and complications.
Methods: This is a prospective unblinded pseudo-randomized controlled trial of US-assisted versus FP FNB techniques. The primary outcome measure was nerve block stratified to level of blockade (intact, partial or complete) with FNB assessed by skin sensation. Participants were assessed at 15 and 60 min post nerve block.
Results: Sixty-seven patients were enrolled. Thirty-four (50.7% [95% CI 44.7-56.8]) underwent the US-assisted technique whereas thirty-three (49.2% [95% CI 43.4-55.2]) underwent the FP technique. At 15 min, FNB using US was intact, partial or complete for 9 (26.5% [95% CI 22.5-30.4]), 15 (44.1% [95% CI 36.8-51.5]) and 10 (29.4% [95% CI 24.9-33.9]) patients, respectively, compared with 14 (42.4% [95% CI 35.3-49.6]), 17 (51.5% [95% CI 42.7-60.3]) and 2 (6.1% [95% CI 5.6-6.6]) patients, respectively (P = 0.038). There was no difference at 60 min. Complete block at 15 min was achieved in 10/34 patients (29% [95% CI 14.1-44.7]) in the US group and 2/33 patients (6% [95% CI -2.1-14.2]) in the FP group (P = 0.029); no difference was seen at 60 min. No complications were recorded in either group.
Conclusions: A more complete blockade is achieved earlier using the US-assisted technique. The US-assisted technique will become the technique of choice for FNB in this department.