Effects of medetomidine-vatinoxan-fentanyl or medetomidine-fentanyl premedication on propofol induction dose and mean arterial blood pressure in dogs anaesthetised with isoflurane.

MVF reduces propofol induction dose but markedly increases hypotension risk compared to medetomidine-fentanyl alone.

This prospective, randomised, controlled, blinded clinical trial evaluated the propofol-sparing effect and cardiovascular impact of adding vatinoxan (an alpha-2 adrenoceptor antagonist with peripheral selectivity) to a medetomidine-fentanyl premedication protocol in 80 healthy client-owned dogs undergoing isoflurane anaesthesia. Dogs (2–8 years, 5–20 kg) received either medetomidine-vatinoxan-fentanyl (MVF, n=40) or medetomidine-fentanyl (MF, n=40) intravenously, followed by propofol induction and isoflurane-fentanyl infusion maintenance. MVF significantly reduced the median propofol induction dose (1.0 mg/kg) compared to MF (1.8 mg/kg, p=0.023), demonstrating a meaningful propofol-sparing effect. However, MVF dogs exhibited significantly higher baseline heart rate (80 vs. 60 beats/min, p=0.025), consistent with vatinoxan's peripheral alpha-2 blockade attenuating medetomidine-induced bradycardia. Despite this, MAP was significantly lower in MVF dogs throughout the entire 60-minute observation period, and the incidence of clinically relevant hypotension (MAP <60 mmHg) was markedly higher in MVF (52%) versus MF (5%, p<0.001). Rectal temperature declined in both groups during maintenance, with MVF showing earlier onset of hypothermia. The authors conclude that while vatinoxan improves sedation depth and reduces propofol requirements, the combination of MVF with isoflurane and fentanyl infusion carries a substantially elevated risk of hypotension and should be used with caution, with vigilant haemodynamic monitoring and readiness to intervene.

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