Ultrasound-guided femoral and obturator nerves block in the psoas compartment in dogs: anatomical and randomized clinical study.

OBJECTIVE: To evaluate intraoperative and postoperative efficacy of ultrasound (US)-guided femoral (FN) and obturator (ON) nerves block, in the iliopsoas muscle compartment (IPM), using an in-plane technique. STUDY DESIGN: Anatomical research and randomized, prospective, 'blinded' clinical study. ANIMALS: Six dog cadavers and 20 client-owned dogs undergoing tibial plateau levelling osteotomy (TPLO) surgery. METHODS: In phase 1, anatomical dissections and US imaging of the IPM were performed to design an US-guided nerve block involving the FN and ON simultaneously. The technique was considered successful if new methylene blue solution injection (0.1 mL kg-1) stained FN-ON for ≥2 cm. In phase 2, the US-guided nerve block designed in phase 1, combined with US-guided sciatic nerve (ScN) block, was performed in 20 dogs undergoing TPLO surgery. Patients were assigned randomly to one of two treatment groups: ropivacaine 0.3% (R3, n=10) and ropivacaine 0.5% (R5, n=10) at a volume of 0.1 mL kg-1 for each nerve block. Intraoperative success rate (fentanyl requirement < 2.1 mcg kg-1 hour-1) and postoperative pain score [Short Form-Glasgow Composite Measure Pain Scale (SF-GCMPS) ≥ 5/20] were evaluated. RESULTS: In phase 1, the US image of FN-ON was detected between L6 and L7. In-plane needling technique produced a staining of >4 cm in six of six cases. No abdominal or epidural dye spread was found. In phase 2, median fentanyl infusion rates were 0.5 (0.0-0.9) µg kg-1 hour-1 for R3 and 0.6 (0.0-2.2) µg kg-1 hour-1 for R5. At 9 and 11 hours after the peripheral nerve blocks, an SF-GCMPS ≥ 5 was observed for R3 and R5, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: The US-guided FN-ON block in the IPM, using an in-plane technique, combined with US-guided ScN block, provided sufficient analgesia to minimize the use of fentanyl during TPLO surgery. A longer postoperative analgesia was observed in group R5 compared with R3.

Saphenous and Sciatic Nerve Blockade with and without Obturator Nerve Block for Tibial Plateau Levelling Osteotomy Surgery in Dogs: A Randomized Controlled Trial.

The objective of our study was to compare the efficacy of sciatic and saphenous ultrasound nerve blocks with and without US-guided obturator nerve block in dogs undergoing tibial-plateau-levelling-osteotomy (TPLO) surgery. This study was developed in two phases: identification of an ultrasound window in the inguinal region for obturator nerve block and utilization of it in dogs undergoing TPLO. Dogs were assigned randomly to one of two groups: one received the three blocks with 0.5% ropivacaine (ON group) and the second one (NoON group) with NaCl instead of ropivacaine for the obturator block. In phase 1, the obturator nerve was visible between the pectineus and the abductor muscles and was approached using an in-plane technique. It was possible to use the ultrasound window for phase two. The number of dogs that received at least one bolus of intraoperative rescue analgesia in the NoON group (12/15 dogs) was significantly higher (p = 0.003) in comparison with the ON group (4/15). An ultrasound window to block the obturator nerve in the inguinal compartment with an in-plane technique was found. The use of this approach could produce adequate analgesia with less motor function impairment in dogs for TPLO surgery.