Abstract
The aim of this study was to compare the effects of different premedication protocols followed by a propofol/fentanyl TIVA on cardio-respiratory and hemodynamic changes in twenty-four dogs randomly divided into two groups (AMD-group: medetomidine, atropine and diazepam; AXD-group: xylazine, atropine and diazepam). Cardiorespiratory variables, acid-base indices, quality of sedation, induction, intubation and recovery were recorded throughout the experiment. Significant changes were observed for the pO2 level, which was increased in the AMDgroup from 90 min. (*P< 0.05) to 120 min. (**P< 0.01) of anesthesia. This can be explained by a reduction of the administration rate of propofol/fentanyl TIVA and oxygenation initiated due to excessively deep anesthesia detected by an anesthetsiologist, leading to improved ventilation and increased pO2. The pCO2 (*P < 0.05) reached more preferable values during the first 30 min. and pH (**P< 0.01) was significantly improved within the first 60 min. in the AXD-group thanks to less depressant effects of xylazine. Within the first 30 min. of anesthesia a significant heart rate difference between the groups was accompanied with significantly higher BP (hypertension) in the AXD-group (10 min. ***P< 0.001, 30 min. **P< 0.01). This points to the possibility of atropine application only in the case of a tendency to bradycardia followed by hypotension. It can be concluded that xylazine is a better option for the premedication of a propofol/ fentanyl TIVA in dogs undergoing a prolonged surgical intervention, in spite of the fact that lower sedation scores were attained. We have detected significantly less adverse cardio-respiratory and hemodynamic effects of xylazine, and a shorter recovery time when compared to medetomidine