Comparison of anaesthetic and analgesic effects of emulsified isoflurane used alone or combined with lidocaine and fentanyl in dogs

AIM: The objective of this study was to investigate the effects of a combination of emulsified isoflurane, lidocaine, and fentanyl (EI-L-F) compared with the efficacy of emulsified isoflurane alone (EI), a combination of emulsified isoflurane and lidocaine (EI-L) or emulsified isoflurane and fentanyl (EI-F) for anaesthetising dogs. METHODS: Eight mongrel dogs were anesthetised with EI (8 mL/kg/hour), EI-L (3 mg/kg/hour lidocaine and 6 mL/kg/hour of emulsified isoflurane), EI-F (1.5 μg/kg/hour fentanyl and 6 mL/kg/hour of emulsified isoflurane), and EI-L-F (5 mL/kg/hour of emulsified isoflurane, 1 μg/kg/hour of fentanyl and 2.4 mg/kg/hour of lidocaine). Each dog received all four treatments and there was a 15-day washout period between the treatments. The dogs' anaesthesia and analgesia scores and physiological parameters were determined before and 5, 10, 20, 30, 40, 50, 60, 70 and 80 minutes after the administration of anaesthetic agents. RESULTS: The dogs in each of the four groups became laterally recumbent within 1 minute. Respiration rate and heart rate increased (p<0.05) during the first 5 minutes of anaesthesia in all groups. Respiration rate in the EI-F-L group was higher (p=0.037) than other groups from 30 to 50 minutes. Heart rate was higher in the EI than EI-F-L group (p=0.018) from 10 to 20 minutes, then returned to near baseline. Arterial oxygen saturation decreased during the period of anaesthesia but was higher (p=0.032) from 10 to 50 minutes in EI-F-L group than in other groups. The total anaesthesia scores in the EI-L-F group were higher than the EI and EI-L groups (p<0.05). The mean time to body movement was 5 (SD 2), 5 (SD 2), 7 (SD 2) and 8 (SD 2) minutes for the EI, EI-L, EI-F and EI-F-L groups, respectively. The mean time to standing was 8 (SD 2), 9 (SD 2), 10 (SD 2) and 13 (SD 3) minutes for the EI, EI-L, EI-F and EI-F-L groups, respectively. No excitement was observed during recovery after anaesthesia. CONCLUSIONS: The EI-F-L combination that was used in this study provided an adequate anaesthesia effect in dogs, which was characterised by adequate analgesia and muscle relaxation without any complications.