Effect of Intratesticular Lidocaine on Isoflurane Requirements in Dogs Undergoing Routine Castration

Objectives: To evaluate the isoflurane sparing effect of intratesticular lidocaine administration in dogs undergoing castration.

Methods: Thirty dogs received a standardised anaesthetic regimen including systemic analgesia with intramuscular buprenorphine at a dose of 0·02 mg/kg and intravenous carprofen at a dose of 4 mg/kg. Dogs were randomly assigned to a lidocaine group receiving 1 mg/kg lidocaine into each testis or a control group receiving no lidocaine. Baseline physiological parameters were measured after 10 minutes at an end-tidal isoflurane concentration of 1·3%. End-tidal isoflurane concentration was altered throughout surgery to maintain these parameters within 10% of baseline and recorded at five time points. T0 was baseline, T1 was the start of surgery, T2 to T3 were clamping of the testicular pedicles and T4 was skin closure. End-tidal isoflurane concentrations were compared using analysis of variance and Bonferroni tests.

Results: Fifteen healthy dogs were included in each study group. End-tidal isoflurane concentration was significantly lower in the lidocaine group compared to the control group at T2 (P<0·01), T3 (P<0·01) and T4 (P<0·01).

Clinical Significance: Intratesticular lidocaine reduces isoflurane requirements in dogs undergoing castration.