“…The administration of inotropic drugs, such as dobutamine or ephedrine, is one of the primary methods used to restore acceptable blood pressure in anaesthetized horses. The haemodynamic effects of dobutamine, a catecholamine with direct acting b 1 -, b 2 -, and a-adrenoceptor agonist activity (Ruffolo & Messick, 1985;Vernon et al, 1992), have been well characterized in the anaesthetized horse (Swanson et al, 1985). Dobutamine (2.5±5.0 mg/kg/min) increased oxygen delivery in ponies (Gasthuys et al, 1991) and horses (Dyson & Pascoe, 1990;Wertz et al, 1992) partly by increasing cardiac output and partly by increasing haemoglobin concentration.…”