The analgesic evaluation of an opioid-free anaesthesia protocol in cats undergoing ovariectomy

Opioid-free protocols are increasingly used in veterinary medicine although there are few studies concerning the feline species. In 2022, Rufiange et al. (1) compared the analgesic power of an opioid-free protocol with that of a standard protocol (using opioids) in ovariohysterectomized female cats, evaluating the degree of analgesia and sedation using the Feline Grimace Scale (FGS), obtaining as a result an equivalence between the opioid-free and standard protocols in the management of intraoperative pain and the degree of anesthesia achieved. Among the most commonly used drugs in opioid-free protocols is dexmedetomidine. Gupert A. et al. (2), have shown that this causes no side effects to the respiratory system, as well as having an analgesic, sedative and anxiolytic effect. The use in continuous intraoperative infusion of dexmedetomidine in cats was studied in 2018 by authors who demonstrated its usefulness also in reducing the volatile anaesthetic agent used to maintain general anaesthesia (isofluorane), thus decreasing its undesirable effects systemically (3). The objective of the study is to evaluate the analgesic and anesthesiologic capacity of an opioid-free protocol using dexmedetomidine, alfaxalone, and lidocaine intra-operatively in female cats undergoing ovariectomy, comparing it with a standard protocol. The study is based on 30 subjects randomly assigned to experimental group 1 and standard group 2. Group 1 received administration of dexmedetomidine at 15 µg/kg IM and alfaxalone at 2 mg/kg IM for induction of anesthesia, followed by maintenance of anaesthesia in isofluorane and administration by continuous infusion (CRI) of dexmedetomidine at 1 µg/kg/h IV. Physiological parameters were measured for each patient during nine well-defined stages of surgery. Patients in standard group 2 received an additional dose of methadone at 0.1 mg/kg IM during anaesthesia induction and did not receive intraoperative dexmedetomidine CRI. Both groups received a dose of intra-ligamentous lidocaine during surgery before ovariectomy. The parameters recorded for both groups and the FGS resulted in the good outcome from both anesthesiological and analgesic point of view of the experimental group compared with the control group, demonstrating in fact the analgesic power of intraoperative dexmedetomidine and of the exsperimental protocol.