What medical term is used to describe pallor in response to arterial blockage?

The term that specifically describes pallor in response to arterial blockage is indeed "pallor." Pallor refers to an unusual lightness of the skin color, which occurs when there is insufficient blood flow to the area, often due to arterial obstruction. This condition can lead the skin to appear pale or white.

When an artery is blocked, blood supply to the tissue can be compromised, resulting in a lack of oxygen and nutrients, which contributes to that paler appearance. The physiological mechanism behind this is the body’s response to the reduced perfusion; it attempts to conserve blood flow to vital organs, thus redirecting it away from the extremities or less essential areas, which leads to the visible paleness associated with pallor.

The other terms relate to different medical conditions. Chadwick’s Sign refers to a bluish discoloration typically seen in pregnancy due to increased blood flow to the cervix, while erythema indicates redness of the skin due to increased blood flow, and necrosis refers to tissue death, which would be a more severe consequence of prolonged arterial ischemia. Each of these terms corresponds to quite different physiological processes than pallor resulting from arterial blockage.