Ultrasound-guided dorsal approach for femoral nerve blockade in cats: an imaging study

This study was conducted to describe and validate a dorsal ultrasound-guided approach to block the femoral nerve (FN) in cats by means of anatomical and computed tomography (CT) studies. The anatomical study was carried out in four fresh feline cadavers to determine the anatomic landmarks to approach this nerve. Then, an ultrasonographic study of the FN was performed in another eight cadavers using a 13 MHz linear transducer. The accuracy of the neurolocation by ultrasonography (US) was determined in four cadavers by the injection of 1 ml blue ink around the FN. The staining of the nerve was evaluated in anatomical studies. The feasibility of this technique was also evaluated by CT after injecting 1 ml of an iodinated contrast medium (150 mgl/ml) around the FN in the other four cadavers. The landmarks to approach the FN were the cranial border of the iliac crest and the dorsal processes of L6 and L7. The FN was visualised as a round hypoechogenic structure surrounded by a hyperechogenic rim located within the iliopsoas muscle on transverse scans. The anatomical and CT studies confirmed the accuracy of the US location of the FN. The dorsal ultrasound-guided approach may allow feasible and accurate access to the FN in cats and it could be useful in producing successful blockade.