Ultrasound-Guided Sciatic and Saphenous Nerve Blocks Enhance Perioperative Analgesia in Sheep Undergoing Experimental Orthopaedic Hindlimb Surgery

Abstract

The demand for refined anaesthetic protocols in ovine experimental surgery has increased due to ethical considerations and the need to improve perioperative stability. This study evaluated the analgesic efficacy of ultrasound-guided combined sciatic and saphenous nerve blocks using two different local anaesthetics in Hair Canarian Sheep undergoing invasive orthopaedic hindlimb surgery. Fifteen clinically healthy sheep were randomly assigned to one of three groups: lidocaine (2%), bupivacaine (0.5%), or control (general anaesthesia alone). Intraoperative physiological parameters, including heart rate, respiratory rate, and arterial blood pressure, were recorded, and postoperative pain was assessed using a modified Melbourne Pain Scale. Sheep receiving locoregional anaesthesia showed significantly lower postoperative pain scores compared with control animals. Intraoperatively, a significant difference between groups was observed only for respiratory rate, with lower values in the bupivacaine group. The bupivacaine group exhibited lower and more stable respiratory rates, with a trend towards lower heart rates during surgery, as well as consistently lower pain scores during the early postoperative period. Lidocaine provided limited intraoperative and postoperative effects compared with the control group. Respiratory rate appeared to be more closely associated with pain scores than other physiological parameters. In conclusion, ultrasound-guided sciatic and saphenous nerve blocks were associated with improved perioperative analgesia in sheep undergoing orthopaedic surgery. The use of bupivacaine was associated with lower respiratory rates intraoperatively and reduced postoperative pain scores, suggesting a potential benefit in perioperative analgesia.