EXPRESS: Intraoperative opioid-sparing effect of a quadratus lumborum block using low-concentration bupivacaine and dexmedetomidine in cats undergoing ovariohysterectomy.

Adding dexmedetomidine to low-concentration bupivacaine QLB modestly reduces intraoperative opioid needs in cats undergoing ovariohysterectomy.

This prospective, randomized controlled trial evaluated the intraoperative opioid-sparing effect of a quadratus lumborum block (QLB) using low-concentration bupivacaine (0.125%) combined with dexmedetomidine (1 µg/kg) in cats undergoing ovariohysterectomy. Twenty-eight ASA I cats were randomly allocated to receive ultrasound-guided QLB with either bupivacaine plus saline (BS group) or bupivacaine plus dexmedetomidine (BD group) in sternal recumbency. Rescue analgesia (fentanyl 2 µg/kg IV) was administered intraoperatively when heart rate or mean arterial pressure increased ≥20% from baseline. Postoperative pain was assessed using the Short-Form UNESP-Botucatu scale at multiple time points, with buprenorphine administered for scores ≥4/12. The BD group demonstrated a statistically significant reduction in cumulative intraoperative fentanyl requirements compared to the BS group (1 [0–6] µg/kg vs. 2 [0–8] µg/kg; P = 0.030). However, no significant differences were identified between groups in the proportion of cats requiring rescue analgesia intraoperatively or postoperatively, postoperative pain scores, intraoperative physiological parameters, or procedure-related time variables. While the addition of dexmedetomidine to low-concentration bupivacaine for QLB provided a modest but statistically significant reduction in intraoperative opioid consumption, the clinical magnitude of this benefit was limited. A key limitation is the inability to distinguish local perineural from systemic effects of dexmedetomidine, necessitating further research to determine optimal dosing and relative contributions of each mechanism.

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