Norepinephrine is used to treat hypotension during shock, which indicates low cardiac output. The desired effect of norepinephrine is to increase cardiac output. The heart rate increases as a function of beta receptor stimulation, but this is not the desired effect. Systemic vascular resistance also increases in order to push blood back to the heart and other vital organs, but this is not the desired effect. Pulmonary vascular resistance is unaffected by norepinephrine.