Spectros

Real-Time Tissue Perfusion Monitors

about ischemia

 

 

Relevance

The final common pathway of nearly all death in the hospital is ischemia, namely an  inadequate delivery of oxygen to a part of the body. Global ischemia results in failure of multiple organs (brain, heart, liver and gut, lung), which is lethal. Local ischemia, such as cardiac ischemia or mesenteric (gut) ischemia leads to failure of one organ, which can often lead to permanent injury or death.

Mechanism

Ischemia is defined as an insufficient delivery of oxygen to a part of the body, caused by changes in cardiac output, changes in the distribution of blood oxygen content or flow, or by constriction or blockage of the blood vessels, or by changes in the need of the tissue for oxygen (such as during fever or certain drug reactions). 

Common causes of ischemia are:

Hypotension or shock (low blood pressure, e.g. in septic shock or heart failure)

Thromboembolism (blood clots which restrict the blood flow and force the blood to the certain regions of the body.)

Bradycardia or Tachycardia (abnormally slow or rapid beating of the heart)

Atherosclerosis (lipid-laden plaques obstructing the lumen of arteries)

Consequences

Since oxygen is carried to the organs by hemoglobin in red blood cells, insufficient blood supply causes tissue to become oxygen-starved. This can cause cell death and organ dysfunction.  In tissues that rapidly consume oxygen, such as heart and brain at normal body temperature, cell death due to severe ischemia can begin in as little as 3-5 minutes before becoming irreversible. Complete cessation of oxygenation of such organs for more than 20 minutes typically results in irreversible damage.

Ischemia is a feature of heart diseasestransient ischemic attackscerebrovascular accidents, ruptured arteriovenous malformations, and peripheral artery occlusive disease. The heart, the kidneys, and the brain are among the organs that are the most sensitive to inadequate blood supply.

Detection of ischemia

T-Stat uses visible light spectroscopy (VLS) to measure the oxygen content of hemoglobin at a micro-vascular level.  By analyzing the reflected white light from the tissue the T-Stat is able to assess the adequacy of oxygen delivery (blood flow) to specific tissues and organs. The T-Stat provides a continuous, non-invase and localized measurement, sensitive to regional and global ischemia.