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

Objective To evaluate the dose of propofol needed for induction of anaesthesia following sedation of healthy dogs with medetomidine-vatinoxan-fentanyl (MVF) or medetomidine-fentanyl (MF), and evaluation of selected cardiovascular variables during maintenance with isoflurane. Study design A prospective randomized, controlled, blinded, clinical trial. Animals A total of 80 client-owned dogs (2–8 years old, 5–20 kg). Methods Dogs were premedicated intravenously with medetomidine (0.005 mg kg -1 ), vatinoxan (0.1 mg kg -1 ) and fentanyl (0.01 mg kg -1 ) (MVF, n = 40), or medetomidine (0.005 mg kg -1 ) and fentanyl (0.01 mg kg -1 ) (MF, n = 40). Anaesthesia was induced 10 minutes later with propofol and maintained with isoflurane in oxygen-air. Fentanyl was infused intravenously (0.01 mg kg -1 hour -1 ). Sedation score and dose of propofol was recorded. Respiratory frequency, heart rate (HR), mean arterial pressure (MAP, noninvasive), and rectal temperature (Trec), were recorded after induction (baseline) and at 10 minute intervals for 60 minutes (T10–T60). Incidence of hypotension (MAP < 60 mmHg) was recorded. Data were analysed using Mann-Whitney U-test, analysis of variance and Fisher’s exact test. Results Dogs given MVF required less propofol for induction [1.0 (0.5–3.8) mg kg -1 ] compared to MF [1.8 (0.7–4.0) mg kg -1 , p = 0.023]. At baseline, HR was significantly higher in MVF (80 ± 21 beats minute -1 ) compared to MF (60 ± 21 beats minute -1 , p = 0.025). Dogs given MVF had significantly lower MAP compared to MF throughout the observation period, with a higher incidence of hypotension (52%) compared to MF (5%, p < 0.001). Compared to baseline, Trec significantly decreased at T30–T60 with MVF and at T40–T60 with MF. Conclusions Premedication with MVF provided a greater propofol-sparing effect than MF. MVF followed by isoflurane and fentanyl should be used with caution due to lower MAP and greater incidence of hypotension.