Evaluation of acepromazine-induced hemodynamic alterations and reversal with norepinephrine infusion in standing horses.

The effects of norepinephrine (NOR) infusion on hemodynamic alterations induced with sedative doses of acepromazine (ACP) were evaluated. Infusion of NOR at 1 μg/kg body weight (BW)/minute for 15 min was administered to 5 standing horses 45 min (T45) after intravenous injection of ACP at 0.1 mg/kg BW. Systolic arterial blood pressure (SAP) and hemodynamic parameters were evaluated on the median artery. Parameters were evaluated every 5 min from 45 to 65 min (T65) at 75 (T75), 90 (T90), and 105 (T105) minutes after ACP administration, and the vessel's surface (SURF), diameter (DIAM), circumference (CIRC), peak systolic velocity (PSV), end diastolic velocity (EDV), mean velocity (MV), volumetric flow (VF) and resistivity index (RI) of the flow were calculated. Acepromazine induced hypotension and vasodilation with a significant rise in SURF, DIAM, CIRC, PSV, EDV, MV, and VF and a reduction in RI and SAP, which were significantly counteracted from T50 to T60 for EDV, VF, MV and RI, and to T65 for SAP, from T50 to T90 for CIRC and SURF and to T60 for DIAM. These findings demonstrate that a 1 μg/kg BW/minute NOR infusion can reverse ACP's vasodilatory effects, restoring hemodynamic parameters and blood pressure in horses.