Fentanyl or sufentanil continuous infusion during isoflurane anesthesia in dogs: clinical experiences

The objective of this study was to determine the cardiorespiratory and the clinical effects of a combination of fentanyl or sufentanil during isoflurane anaesthesia in dogs undergoing TPLO surgery. Twelve dogs were randomly assigned into 2 groups receiving IV fentanyl 4 µg kg-1 (FI) or sufentanil 0,5 µg kg-1 (SI), anaesthesia was induced with propofol and maintained with isoflurane in oxygen. The ETIso was kept at 1.3%, except when an excessive deep level of anaesthesia was noted. After induction, a continuous infusion of fentanyl (4 µg kg min-1) or sufentanil (0,5 µg kg min-1) was started. Breathing was spontaneous throughout the anaesthetic procedure or assisted/controlled when respiratory depression was noted (transient apnoea or ETCO2  60 mmHg). Infusion rate was adjusted according to modifications of clinical signs and cardiovascular parameters. Concomitant infusion of fentanyl or sufentanil and isoflurane in dogs provided a safe and stable plane of analgesia/anaesthesia, with good cardiovascular stability.