Vatinoxan increases microcirculation in dogs anaesthetised with medetomidine-methadone-propofol-isoflurane for prescrotal castration – A randomized, clinical study

We investigated the impact of vatinoxan, a peripherally selective alpha₂-adrenoceptor antagonist, on oral mucosal and testicular surface microcirculation in dogs anaesthetised for prescrotal castration. Seventeen healthy, privately-owned dogs were randomly allocated to receive one of two intramuscular treatments: medetomidine 0.3 mg/m² + methadone 0.3 mg/kg (MM) or MM + vatinoxan 6 mg/m² (ZM). The dogs were then anaesthetised with propofol and isoflurane. Heart rates (HR) and mean arterial pressure (MAP) were recorded and microcirculatory variables quantified with real-time hybrid technology combining laser Doppler flow (LD-Flow) and reflectance spectroscopy for tissue haemoglobin oxygen saturation (Tissue-HbO₂). Measurements were obtained from both the oral mucosa and the exposed testicular surface during the procedure. Data were analysed with Wilcoxon's Rank Sum and Spearman correlation tests. Overall microcirculation was significantly higher for dogs in the ZM group: the median (range) for LD-Flow was 64 (21 - 461) and 297 (77 - 1558) perfusion units for MM and ZM (p < 0.001), whereas Tissue-HbO₂ was 71 (46 - 93) for MM and 88 (73-100) % for ZM, respectively (p < 0.001). No hypotension (MAP < 60 mmHg) was noted after either treatment. Moreover, HR was positively (p < 0.001), and MAP negatively (p < 0.001) associated with LD-Flow and Tissue-HbO₂. In conclusion, real-time assessment of oral mucosal microcirculation was easy and could be a valuable addition for monitoring tissue oxygen delivery in sedated and anaesthetised dogs. Vatinoxan markedly improved microcirculation in healthy dogs premedicated with medetomidine-methadone and anaesthetised with propofol and isoflurane.