The effects on cardio-respiratory and acid–base variables of a constant rate infusion of alfaxalone–HPCD in sheep

Alfaxalone in a 2-hydroxypropyl-β-cyclodextrin (HPCD) formulation is an intravenous (IV) hypnotic agent characterised by the stability of cardiorespiratory effects after a single-bolus administration. The objective of this study was to investigate the cardiovascular, respiratory, and acid–base effects of alfaxalone–HPCD administered during a continuous rate infusion in six Ripollesa sheep. After instrumentation, a 2 mg/kg IV bolus of alfaxalone followed by a continuous infusion of 10 mg/kg/h was administered to the sheep. Heart rate, arterial blood pressure, respiratory rate and arterial blood gases were recorded. Occasional side effects and time to standing were also noted.No significant changes were observed in arterial blood pressure, but during the infusion and the initial stages of recovery, a significant increase in heart rate occurred during the last 120 min of the study. Significant respiratory depression was detected during the infusion period and the first 15 min of recovery. This study showed that a constant rate infusion alfaxalone in un-premedicated sheep produced clinically acceptable haemodynamic results and a mild respiratory depression that may require intermittent positive pressure ventilation.