References: 1. Campoy, L., Martin-Flores, M., Looney, AL., Erb, HN., Ludders, JW., Stewart, JE., Gleed, RD., Asakawa, M., 2008. Distribution of a lidocaine-methylene blue solution staining in brachial plexus, lumbar plexus and sciatic nerve blocks in the dog. Veterinary anaesthesia and analgesia 35,

348-54.

2. Echeverry, D.F., Laredo, F., Gil, F., Belda, E., Soler, M., Agut, A., 2011. Ventral ultrasound-guided suprainguinal approach to block the femoral nerve in the dog. The Veterinary Journal in press doi:10.1016/j.tvjl.2011.06.043.

Assessment of a ventral ultrasound-guided suprainguinal approach to block the lumbar plexus in

dogs cadavers

D. Echeverry¹⁻², F. Laredo², E. Belda², M. Soler², F. Gil², A. Agut²

The blockade of the Sciatic (ScN) and femoral nerves (FN) is a suitable alternative to the epidurals in dogs. Nevertheless, these blocks are associated with incomplete analgesia during some surgical procedures performed on the knee and hip in humans. The combined blockade of the lumbar plexus (LP) and the ScN is the technique of choice when reliable analgesia of the entire pelvic limb is required in humans. The LP block include the blockade of the FN, obturator nerve (ON), and lateral femoral cutaneous nerve (LFCN). In a previous study performed in dogs, the distribution of three volumes of staining solution injected at the LP by a dorsal approach and using neurolocation was evaluated ¹. This study found that a volume of 0.4 mL Kg¯¹ might be adequate to perform the LP block and described the staining of the FN and ON but information regarding the LFCN was not provided ¹. It has been described that ultrasounds (US) may improve the efficacy and safety of the LP block. The aim of our study is to evaluate the extent and dye distribution at the LP of three volumes of staining solution administered close to the FN by a ventral US-guided suprainguinal approach (SIA) ² to block the FN in the dog.

Fig. 1 . A. Position of the needle and the transducer to approach the FN. B. Ultrasonographic image corresponding to A. C. Ultrasonographic image of the spread of the staining solution. 1. femoral nerve; 2. Iliopsoas muscle; 3. Ilion; 4. needle; 5. staining solution

Faculty of Veterinary Medicine and Zootechnic, University of Tolima (Colombia)1 Faculty of Veterinary, Murcia University (Spain)2

1. Introduction:

A total of 12 mongrel dog cadavers with a mean weight 17.7 ± 3.8 kg were randomly assigned to 3 experimental groups (n=4). Three volumes of staining solution (0.2 mL kg¯¹ low (L); 0.4 mL kg¯¹ medium (M) and 0.6 mL kg¯¹ high (H)) were administered close to the FN to block the three main components of the LP: femoral (FN), obturator (ON) and lateral femoral cutaneous nerve (LFCN) by a single injection technique. The FN was located by US using a 13 MHz linear probe² (Fig. 1A). Then, the LPs were dissected to measure the length in which the target nerves were stained. A successful block was defined by the staining of the target nerves in a length ≥ 2 cm

2. Materials & Methods:

The SIA allowed monitoring in real time the spread of the staining solution close to the FN in all the cases (Figs. 1 B-C). From the injection site the staining solution was distributed in three directions within the body of the iliopsoas muscle (IPM) (Figure 2): craneal, lateral and caudal. The cranial distribution was found to be the more relevant. Theb lateral distribution occurred between the quadratus lumborum muscle and the IPM. In the caudal distribution the dye reached the femoral triangle. The FN and the ON were staining in a length > 2 cm in all the cases at the 3 volumes studied, mainly by the cranial distribution of the injectate. One cadaver in the H group was excluded from the study because the FN was not identified by US. The LFCN was not successfully blocked in any case.

3. Results :

The US-guided SIA was useful to produce a simultaneous blockade of the FN and the ON in the dog. Similar findings were described in an early study.¹ In the present study, a volume of 0.2 mL kg⁻¹ was found to be sufficient to stain the target nerves in the cadavers. Further research should be conducted to validate the efficacy of this technique in a clinical setting.

4. Discussion :

caudal A B ventral

1

3

2 2

2

4

4

lateral

C ventral

1

5

5

5

lateral

Figure 2. A Anatomical dissection after the injection of staining solution. Picture in the insert shows the dissected area. (1) FN, (2) ON, (3) LFCN arising through the psoas minor muscle; (4) IPM (the muscle has been split to expose the nerves), (5) psoas minor muscle, (6) sartorius muscle, (7) abdominal wall, (8) detail of the lateral distribution of the dye between the IPM and the quadratus lumborum muscle, (9) detail of the caudal distribution of the dye within the femoral triangle.

Association of Veterinary Anesthetists´ Congress Liverpool (United Kingdom) 14–16 September 2011