EXPRESS: Ultrasound-guided quadratus lumborum block versus lumbosacral epidural anaesthesia in cats undergoing ovariohysterectomy: a randomized pilot clinical trial

OBJECTIVES: To compare analgesic and cardiopulmonary effects following bilateral ultrasound-guided quadratus lumborum block (QLB) and lumbosacral epidural (LsE) with levobupivacaine in cats undergoing ovariohysterectomy (OVH). METHODS: A prospective, randomized, blinded clinical trial was conducted. Twenty healthy female cats were allocated (1:1) to the LsE group (0.4 ml/kg 0.25% levobupivacaine) or the QLB group (0.3 ml/kg 0.25% levobupivacaine per hemiabdomen). Cats were premedicated with dexmedetomidine 3 mcg/kg and meloxicam 0.1 mg/kg. Anaesthesia was performed using propofol variable rate infusion (adjusted to clinical depth). Heart rate, respiratory rate, hemoglobin oxygen saturation, end-tidal carbon dioxide, and systolic, mean and diastolic arterial pressures were recorded at seven standardized surgical time points. Postoperative pain (UNESP-Botucatu multidimensional composite pain scale) and sedation were assessed up to 6 h after surgery; methadone (0.25 mg/kg IM) was administered as rescue analgesia when indicated. Recovery milestones and mean propofol infusion rate were also compared. Data were analyzed using repeated measures ANOVA, unpaired t-tests, or non-parametric tests, as appropriate (P < 0.05). RESULTS: No significant between group differences were detected for any cardiopulmonary variable (P > 0.05), and no intraoperative rescue analgesia was required. Mean propofol infusion rates were similar (LsE 0.36 ± 0.07 vs QLB 0.39 ± 0.02 mg/kg/min; P = 0.0863). Postoperative pain scores were not different between groups. Only 1 cat in the QLB group required methadone at 6 h. Recovery milestones (extubation to standing: LsE 73 min; QLB 79 min; P = 0.4182) and sedation scores were comparable. No block related complications or adverse events were observed. CONCLUSIONS AND RELEVANCE: Bilateral ultrasound-guided QLB with 0.25% levobupivacaine provided cardiopulmonary stability and early perioperative analgesic performance comparable to lumbosacral epidural anaesthesia in cats premedicated with dexmedetomidine and meloxicam undergoing OVH, supporting its use as a clinical alternative, particularly when epidural access is contraindicated.