All of the following drugs increase cardiac output, except?
ExplanationAll of these catecholamines cause stimulation of β1 receptors, thus increasing cardiac contractility, but norepinephrine also has a very strong effect on α1 receptors, thus increasing afterload to such a degree that cardiac output may actually decrease after administration of this drug.
Cardiac output = Systemic blood pressure/Systemic vascular resistance
According to this formula, systemic vascular resistance (SVR) is inversely related to cardiac output; thus, an increase in the SVR may decrease the cardiac output. Other drugs have more effect on cardiac contractility than on SVR, and thus, cardiac output increases with their administration.
