Anaesthetic sparing effect of local anaesthesia of the ovarian pedicle during ovariohysterectomy in dogs.

OBJECTIVE

To evaluate the effect of local anaesthesia of the mesovarium on end-tidal isoflurane (Fe'(iso)) concentration and vital parameters during canine ovariohysterectomy.

STUDY DESIGN

Prospective, randomized, blinded study.

ANIMALS

Twenty client-owned dogs undergoing elective ovariohysterectomy. Mean age 1.7 (+/-0.53, SD) years and mean body weight 21 kg (+/-5.9, SD).

METHODS

Pre-medication was with intravenous acepromazine (0.02 mg kg(-1)) and methadone (0.1 mg kg(-1)). Anaesthesia was induced with propofol and maintained with isoflurane in oxygen. One group (n = 10) received local infiltration of the mesovarium with 0.5 mL lidocaine 2% and one group (n = 10) with 0.5 mL NaCl 0.9%. Heart (HR) and respiratory rates (fr), invasive mean arterial blood pressure (MAP) and Fe'(iso)were recorded. The Fe'(iso) was adjusted according to changes in HR, RR and MAP. Time points used for comparison were T1 (after induction of anaesthesia before surgery), T2 (after lidocaine infiltration of the mesovarium) and T3 (surgical manipulation of the ovaries). Data were analysed using a mixed model for repeated measurement anova and the Tukey adjustment. Results are presented as mean +/- SD; p < 0.05 was considered significant.

RESULTS

In both groups, HR and fr remained stable at the three time points. Mean values ranged from 84 to 94 beats minute(-1) and from 10 to 14 breaths minute(-1). The Fe'(iso) was significantly lower at T3 compared to T1 and mean values ranged from 0.95% to 1.24%. The mean arterial blood pressure was significantly higher at T3 compared to T1 and mean values ranged from 58 to 96 mm Hg. At none of the time points were there significant differences between the two groups for HR, fr, MAP or Fe'(iso).

CONCLUSION

Neither an isoflurane sparing effect nor a difference in autonomic response to surgery was demonstrated following local anaesthesia of the mesovarium.

CLINICAL RELEVANCE

There appeared to be minimal benefit from local anaesthesia of the mesovarium during this study.