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 1μg/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 1μ/kg BW/minute NOR infusion can reverse ACP's vasodilatory effects, restoring hemodynamic parameters and blood pressure in horses.