Ultrasound-guided quadratus lumborum block with 0.5 mL of 0.2% bupivacaine/kg is a valuable perioperative analgesic adjunct for cats undergoing ovariectomy.

Abstract

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. 48 healthy female cats. 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. 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. Bilateral US-guided QLB-HV may effectively provide perioperative analgesia in feline patients undergoing ovariectomy.