Ultrasound guided fascia iliaca block: a comparison with the loss of resistance technique.

BACKGROUND AND OBJECTIVES: The aim of this study was to compare the efficacy of fascia iliaca block, performed by loss of resistance and ultrasound guidance techniques. METHODS: Eighty patients undergoing either unilateral hip or knee joint replacement surgery were randomly assigned to undergo fascia iliaca compartment block by either loss of resistance or ultrasound guidance. Sensation in the anterior (femoral nerve), lateral (lateral cutaneous nerve) and medial (femoral and variable contribution from obturator nerve) aspects of the thigh were assessed prior to block placement. Femoral motor block (knee extension) was also evaluated. Obturator motor block (hip adduction) was measured using a sphygmomanometer. Sensation and motor function were reassessed after block placement. RESULTS: Using ultrasound guidance, there was a statistically significant increase in the incidence of sensory loss in the medial aspect of the thigh from 60% to 95% (P = .001). Complete loss of sensation in the anterior, medial, and lateral aspects of the thigh increased from 47% to 82% of patients using ultrasound (P = .001). Ultrasound-guided fascia iliaca block resulted in a statistically significant increase in the incidence of femoral (P = .006) and obturator (P = .033) nerve motor block. CONCLUSIONS: Ultrasound-guided fascia iliaca block increased the frequency of sensory loss in the medial aspect of the thigh. Ultrasound guidance also increased the frequency of femoral and obturator motor block.