Which of the following involves a reduction in oxygen delivery to tissues?

Ischemia specifically refers to a decrease in blood flow to a tissue, leading to a reduction in oxygen delivery. This can occur due to various factors, such as arterial blockage, which impairs the oxygen supply necessary for cellular metabolism and function. When tissues do not receive adequate oxygen, they can sustain damage, leading to a range of pathological conditions, including tissue necrosis if the ischemia is severe and prolonged.

In contrast, dyscrasia typically refers to an abnormal or pathological condition of the blood, often indicating a disorder of the blood components, which may indirectly affect oxygen delivery but does not directly describe a reduction in blood flow. Hypovolemia relates to a decreased volume of circulating blood, which can lead to reduced perfusion and oxygen delivery, but is more about overall blood volume rather than localized blood flow issues. Cellulitis is an infection of the skin and subcutaneous tissues and does not inherently involve a direct reduction in oxygen delivery to tissues in the way ischemia does.