The aim of this study is to evaluate the effect of continuous rate infusion of lidocaine on the bispectral index (BIS) in isoflurane-anesthetized calves maintained at a constant end-tidal concentration. Eight healthy male Holstein calves aged between eight and twelve month, distributed in two experimental groups lidocaine group (LG) and control group (CG) will be used. The animals will be premedicated with xylazine (0.05 mg kg-1 IV). Ketamine (2.0 mg kg-1 IV) and midazolam (0.1 mg kg-1 IV) for induction. The animals will be positioned in right lateral recumbency and anesthesia is maintained with isoflurane (1.3%) under controlled ventilation, which will be adjusted to a peak inspiratory pressure of 15 cm H2O and respiratory rate of 6 breath min-1. After 40 minutes, the animals of LG will receive a bolus of lidocaine (2 mg kg-1) folowed by a continous rate infusion of 100 mcg kg-1 min-1. In the control group (CG) the same methodology will be applied, substituting lidocaine for an equal volume of saline. BIS sensor will be applied in frontal-temporal position and their values measured for 1 minute in each moment, and the average of this period will be used. Measurements for BIS, electromyography (EMG), heart rate (HR), mean arterial pressure (MAP) and rectal temperature (RT) will be recorded at basal time (T0), after 10 minutes of xylazine administration (TX), before lidocaine or saline administration (T0), and then at 20-minutes intervals after treatment (T20 to T80). ETCO2 will be evaluated since T0. The BIS and EMG data will be submitted to One way ANOVA and the others variables to Repeated measures ANOVA following Bonferroni test (p< 0.05).
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