Evaluation of the antinociceptive effect of NK-1 antagonist - maropitant, in different doses in dogs undergoing ovariohysterectomy - a prospective randomized clinical study.

To compare the antinociceptive effect of maropitant at different doses in female dogs undergoing ovariohysterectomy to evaluate postoperative analgesic requirements. In total, 45 healthy female dogs were randomly assigned to five groups (n = 9). All groups were given morphine and acepromazine for premedication, followed by induction with propofol and maintenance with sevoflurane. The control group (CG) were given a continuous rate infusion (CRI) of 1 mL/kg/hour of physiological 0.9% saline. The treatment groups were, an intravenous (IV) bolus of 1 mg/kg/ maropitant followed by a CRI of 50 (G50), 75 (G75), 100 (G100), and 200 µg/kg/hour (G200). Heart and respiratory rate, invasive arterial blood pressure, oxygen saturation, end-tidal carbon dioxide partial pressure, sevoflurane concentration, and temperature were evaluated. Rescue analgesia consisted of fentanyl, given when heart rate and blood pressure increased by > 20%. Postoperative pain was assessed by the Short Form Glasgow Composite Measure Pain Scale, and tramadol rescue analgesia was administered when the score was > 6. No significant differences in cardiorespiratory parameters, temperature or postoperative pain evaluation. Expired fraction of sevoflurane was significantly different between CG (2.11 ± 0.07), G50 (1.81 ± 0.07; p < 0.04) and G100 (1.81 ± 0.06; p < 0.03). Maropitant CRI administration during the perioperative period in female dogs undergoing ovariohysterectomy showed efficacy in lowering the anesthetic requirements of sevoflurane in G50 and G100; however, it was not sufficient to suppress the autonomic response to somatic and visceral nociceptive stimulation and did not demonstrate any evident effect on pain evaluation.