BACKGROUND: Arterial pressure is the most commonly utilized guideline for the management of critically ill patients. However, the site of arterial pressure monitoring can impact the observed pressure. In patients undergoing cardiac surgery, peripheral arterial pressure can underestimate central aortic pressure and vasodilators magnify this phenomenon. There was also a large discrepancy between radial and femoral artery pressure in endotoxemic patients treated with vasopressors or hypothermic patients. We evaluated the effect of the continuous infusion of norepinephrine, the most commonly used vasopressor, on pressure and blood flow in both the brachial and femoral artery in dogs in normal condition. METHODS: Both the brachial and femoral arteries were cannulated for pressure monitoring and the other side arteries were exposed for the measurement of blood flow in 10 dogs. Two doses of norepinephrine (NE), 0.05 microgram/kg/min and 0.1 microgram/kg/min, were infused for 10 minutes each in sequence. Hemodynamic variables and blood flow were measured before the infusion of NE, and immediately after the infusion of the two doses of NE. RESULTS: NE increased both brachial and femoral arterial pressures with no difference between the two pressures. NE decreased blood flow in both brachial and femoral arteries even though cardiac output was maintained constantly which means NE caused the redistribution of blood flow. CONCLUSIONS: Unlike endotoxemic shock conditions or hypothermic vasoconstriction, NE didn't show different effects on pressure monitoring sites regardless of their diameter in normal condition. NE increased blood pressure and decreased blood flow in the same degree in both the brachial and femoral artery.