Ultrasound-guided quadratus lumborum block vs lumbosacral epidural anesthesia in cats undergoing ovariohysterectomy: a randomized pilot clinical trial.

ObjectivesThe aim of the present study was to compare analgesic and cardiopulmonary effects after bilateral ultrasound-guided quadratus lumborum block (QLB) and lumbosacral epidural (LsE) with levobupivacaine in cats undergoing ovariohysterectomy (OVH).MethodsA prospective, randomized, blinded clinical trial was conducted. A total of 20 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 µg/kg and meloxicam 0.1 mg/kg. Anesthesia 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 rates were also compared. Data were analyzed using repeated measures ANOVA, unpaired t-tests or non-parametric tests, as appropriate (P <0.05).ResultsNo 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 did nor differ between groups. Only one cat in the QLB group required methadone at 6 h. Recovery milestones (extubation to standing: LsE 73 mins, QLB 79 mins; P = 0.4182) and sedation scores were comparable. No block-related complications or adverse events were observed.Conclusions and relevanceBilateral ultrasound-guided QLB with 0.25% levobupivacaine provided cardiopulmonary stability and early perioperative analgesic performance comparable to lumbosacral epidural anesthesia in cats premedicated with dexmedetomidine and meloxicam undergoing OVH, supporting its use as a clinical alternative, particularly when epidural access is contraindicated.