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Objective: To assess the perioperative analgesic effects of bilateral ultrasound (US)-guided quadratus lumborum block (QLB) using low-volume (LV) or high-volume (HV) bupivacaine, compared to a control group, in cats undergoing ovariectomy., Animals: 48 healthy female cats., Methods: Cats were sedated with IM dexmedetomidine (5 µg/kg), ketamine (1 mg/kg), and methadone (0.2 mg/kg) followed by IV propofol induction and isoflurane maintenance. Cats were randomly assigned to 3 groups of 16 patients each: QLB-LV group (0.3 mL/kg/side), QLB-HV group (0.5 mL/kg/side), and control group (no QLB). Bilateral, in-plane, US-guided QLB was performed with lateral approach at the L2 transverse process with bupivacaine 0.2%. Physiological variables were recorded intraoperatively by a masked investigator. If intraoperative nociception occurred, fentanyl (1 µg/kg) was administered IV. Rescue postoperative analgesia (buprenorphine, 0.2 mg/kg) was administered in case of a Feline Grimace Scale score ≥ 4 after a 4-hour evaluation period., Results: In the control group, heart rate (HR) was higher than the QLB-LV group during the first ovarian manipulation (P < .001) and higher than the QLB-HV group during both ovarian manipulations (P < .001 and P = .006). The need for intraoperative rescue analgesia and postoperative pain scores were significantly higher in the QLB-LV (P = .005 and P = .047) and control (P < .001 and P < .001) groups compared to the QLB-HV group. Buprenorphine was administered once in the control group. No clinical signs of bupivacaine toxicity or QLB complications were observed., Clinical Relevance: Bilateral US-guided QLB-HV may effectively provide perioperative analgesia in feline patients undergoing ovariectomy.

Objective: To compare the perioperative analgesic effects of an opioid-free (OFA) and an opioid-sparing (OSA) anaesthetic protocol in dogs undergoing laparoscopic ovariectomy., Study Design: Prospective, randomized, blinded, clinical trial., Animals: A group of 28 client-owned dogs., Methods: Dogs were allocated to one of two groups. The OFA group was administered intramuscular (IM) dexmedetomidine 5 μg kg -1 and ketamine 1 mg kg -1 , followed by two intraoperative constant rate infusions (CRIs) of dexmedetomidine (3 μg kg -1 hour -1 ) and lidocaine (1 mg kg -1 loading dose, 2 mg kg -1 hour -1 ). The OSA group was administered IM dexmedetomidine 5 μg kg -1 , ketamine 1 mg kg -1 and methadone 0.2 mg kg -1 , followed by two intraoperative saline CRIs. In both groups, anaesthesia was induced with intravenous (IV) propofol 2 mg kg -1 and diazepam 0.2 mg kg -1 and maintained with isoflurane. Rescue dexmedetomidine (0.5 μg kg -1 ) was administered IV if there was a 20% increase in cardiovascular variables compared with pre-stimulation values. Ketorolac (0.5 mg kg -1 ) was administered IV when the surgery ended. Postoperative analgesia was evaluated using the Short Form-Glasgow Composite Measure Pain Scale and methadone (0.2 mg kg -1 ) was administered IM if the pain score was ≥ 6/24. Statistical analysis included mixed analysis of variance, Chi-square test and Mann-Whitney U test., Results: There were no significant differences in the intraoperative monitored variables between groups. The OFA group showed a significantly lower intraoperative rescue analgesia requirement (p = 0.016) and lower postoperative pain scores at 3 (p =0.001) and 6 (p < 0.001) hours. No dogs were administered rescue methadone postoperatively., Conclusions and Clinical Relevance: Although both groups achieved acceptable postoperative pain scores with no need for further intervention, the analgesic efficacy of the OFA protocol was significantly superior to that of the OSA protocol presented and was associated with a lower intraoperative rescue analgesia requirement and early postoperative pain scores., (Copyright © 2024 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)