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Hemogasometry, hemodynamics and respiratory effects of different inspired fractions of oxygen in calves under sevoflurane anesthesia and mechanical ventilation


This research aims to establish the effects in hemodynamics, respiratory and blood gas between different inspired oxygen concentrations (FiO2 0.21, FiO2 0.6 and FiO2 > 0.95) in calves anesthetized by sevoflurane under controlled ventilation. Seven Holstein male calves, aged between six and twelve months, weighing 70-180 kilograms will be used. All animals will participate in all experimental groups and will be anesthetized four times, always respecting a minimum interval of seven days between each procedure. Initially each animal will be anesthetized for determining the individual minimum alveolar concentration (MAC) for sevoflurane. Sequentially, the animals will be induced to anesthesia with sevoflurane (8 V%), administered by mask with oxygen flow at 10 mL. kg-1. min-1 and immediately intubated with endotracheal tube and the inspired oxygen fraction adjusted as each experimental group, FiO2 0.21 (G21), FiO2 0.6 (G60) and FiO2 > 0.95 (G100). After intubation, all animals will be submitted to mechanical ventilation with intermittent positive pressure mode with a maximum inspiratory pressure initially set at 15 cm H2O and respiratory rate in seven movements per minute and adjusted later if necessary, in order to maintaining ETCO2 values between 40 and 45 mmHg. Anesthetic maintenance will be performed with sevoflurane, an expired concentration equivalent to 1.4 MAC, using the MAC previously determined in each individual. Observations of hemodynamic, respiratory and blood gas variables will be evaluated at 30 minutes intervals after the induction of anesthesia (M30, M60, M90, M120, M150 e M180, respectively). (AU)

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