Intraoperative Heart Rate and Respiratory Rate Stability in Dogs Undergoing Orthopaedic Limb Surgery with vs. Without Nerve Locator-Guided Regional Anaesthesia: A Retrospective Study (2016–2021)

Objective: To investigate whether the pre-emptive administration of regional anaesthesia using a nerve locator for forelimb or hind limb orthopaedic surgery contributes to maintenance of intraoperative heart rate (HR) and/or respiratory rate (RR) stability in dogs. Methods: A retrospective analysis of 56 client-owned anaesthesia records of dogs that underwent limb orthopaedic surgery between 2016 and 2021 was conducted. Dogs were divided into two main groups: those that received regional anaesthesia with a nerve locator (NL, n = 28) and those that did not (C, n = 28). Heart rate stability was defined as a fluctuation of <25% in heart rate, and respiratory rate stability was defined as a fluctuation of <25% in respiratory rate during the first hour of surgery compared to baseline values (HR0, RR0). Animals that exhibited increases ≥25% for at least two consecutive measurements associated with surgical stimulation received rescue analgesia. Statistical analysis was performed using the Chi-square test (p < 0.05). Results: Statistically significant differences were observed between the groups. In the NL group, 89.3% of the dogs maintained HR stability vs. 10.7% that did not (HR increase > 25% for at least two consecutive measurements) (p < 0.05). Conversely, 92.9% of dogs in the C group did not exhibit HR stability, requiring rescue analgesia, vs. 7.1% that exhibited HR stability (p < 0.05). In the NL group, 82.1% of the dogs maintained RR stability vs. 17.9% that did not (RR increase > 25% for at least two consecutive measurements) (p = 0.01). Conversely, 60.7% of dogs in the C group did not exhibit RR stability, requiring rescue analgesia vs. 39.3% that exhibited RR stability (p = 0.001). Conclusions: Regional anaesthesia using a nerve locator significantly contributes to intraoperative heart and respiratory rate stability in dogs undergoing orthopaedic limb surgery, suggesting improved intraoperative analgesia.