Use of a quadratus lumborum block in queens undergoing ovariectomy: a randomised controlled trial.

Objectives: The aim of the study was to evaluate the perioperative analgesic effect of a quadratus lumborum (QL) block in queens undergoing ovariectomy.

Methods: A total of 37 healthy queens admitted for elective ovariectomy were randomised into two groups: control (CTRL, n = 19) and QL block (QL, n = 18). All cats were premedicated with dexmedetomidine 0.005 mg/kg, alfaxalone 1 mg/kg and methadone 0.1 mg/kg IM. Under general anaesthesia, cats allocated to the QL group received a bilateral ultrasound-guided QL block with 0.4 ml/kg of ropivacaine 0.4% (3.2 mg/kg). No treatment was administered to cats in the CTRL group. Intraoperative rescue fentanyl boluses were administered if haemodynamic and/or respiratory parameters exceeded 30% of the pre-incisional values. Postoperative methadone boluses were administered based on Feline Grimace Scale scores. Demographics, baseline vital parameter values, requirement for rescue analgesia, incidence of hypotension, sialorrhoea, vomiting and dysphoria, and number of cats accepting food at 6 h after extubation were compared between groups.

Results: A higher number of queens required intraoperative fentanyl in the CTRL group (14/18, 77.8%) compared with the QL group (1/19, 5.3%) (P <0.001). The median total fentanyl dose was 4 µg/kg (range 0-4) in the CTRL group and 0 µg/kg (range 0-4) in the QL group (P <0.001). No statistically significant difference was found between groups when comparing the number of animals requiring postoperative methadone, total methadone dose, episodes of hypotension, sialorrhoea, vomiting and dysphoria, and number of queens accepting food at 6 h postoperatively. No adverse effect or complication potentially related to the block was recorded.

Conclusions and relevance: The QL block resulted in a lower intraoperative fentanyl requirement in queens undergoing ovariectomy. Further studies are needed to clarify the postoperative analgesic effect of this technique in cats.