OBJECTIVES

The aim of this study was to evaluate the anaesthetic recovery quality after sevoflurane anaesthesia in dogs. The clinical signs, anaesthetic recovery times, hypnotic component of the anaesthetic state measured by bispectral index and the autonomic nervous system reactivity (ANSr) measured by Anemon-I were studied. The influence of the kind of surgery on the anaesthetic recovery quality was also analyzed.

MATERIALS

10 dogs treated in Veterinary Teaching Hospital for several diseases were anaesthetized with sevoflurane to perform major surgery. Soft tissue surgery was performed in 5 dogs and orthopaedic surgery was performed in the other 5.

Dogs were premedicated with acepromazine (0.04 mg/kg), buprenorphine (0.01 mg/kg) and atropine (0.04 mg/kg). Anaesthesia was induced with sevoflurane (7-8 %) by facial mask. Sevoflurane was administered for maintenance, beginning at a concentration of 3 % to rapidly achieve minimal alveolar concentration (MAC 2.36). Once MAC was reached, the vaporizer setting was adjusted as needed to maintain a depth of anesthesia suitable for surgery. Depth of anesthesia during anaesthetic recovery was monitored by bispectral index. Changes of the autonomic nervous system reactivity (ANSr) were determined by Anemon index. Time for recovery from anaesthesia was determined by recording the following times: time of extubation, time of first movement, time of reflexes recovery. During recovery, SpO2, expired sevoflurane concentration, heart rate and respiratory rate were measured.

Results were calculated as mean ± SD. Recovery times were analyzed by use of one-way ANOVA, with surgical technique (orthopaedic surgery and soft tissue surgery) being the variable of interest. For all analyses, values of P < 0.05 were considered significant.

RESULTS

Heart and breath rate during the anaesthetic recovery did not change significantly. Heart rate was significantly higher (p<0.05) undergoing orthopaedic surgery. The Anemon index raised significantly (p<0.001) during the recovery of the reflexes in both groups from 66.0±14.4 (at the end of anaesthesia) to 100.4±18.0 (extubation). It can be said that in this period the animal had a significant sympathetic stimulation. Bispectral index also increased significantly from 54.4±14.9 (at the end of anaesthesia) to 95.8±2.5 (extubation).

Anaesthetic recovery times did not show significant differences between the two kinds of surgery. The mean recovery times for all animals were: time the dog recovered the palpebral reflex: 10.8±7.7 min, time of extubation: 16.6±7.9 min and time of first movement: 16.4±8.2 min.

CONCLUSION

The Anemon Index increased significantly during the anaesthetic recovery. This stage supposes, then, a stressful period during general anaesthesia. Monitoring of heart rate is not enough to evaluate stress during anaesthetic recovery.

Anaesthetic recovery after sevoflurane anaesthesia in dogs is fast and comfortable. No excitement or other complications were observed during this period. No significant differences were observed between groups (orthopaedic and soft tissue surgery) in regard to recovery times.