The Microcirculation as a Therapeutic Target in the Treatment of Sepsis and Shock

Vanina S. Kanoore Edul, M.D.; Arnaldo Dubin, M.D., Ph.D.; Can Ince, Ph.D.

Disclosures

Semin Respir Crit Care Med. 2011;32(5):558-568. 

In This Article

Historical Perspective: The Discovery of the Microcirculation

The discovery of the circulation of the blood is an essential part of the history of medicine and has appeared in various forms throughout the ages until it was finally fully described. Knowledge about the circulation was very poor in ancient civilizations such as those of the Egyptians and Greeks. In the second century AD, Galen (AD 129–201) stated the following,

The blood flowed through the hepatic veins to the right ventricle of the heart where it passed through the sinus venarum and the two venae cavae. Then it went partly through the pulmonary artery into the lungs in order to nourish them, while another and very small part of it passed directly through invisible pores of the septum cordis into the left ventricle.

Here it was mixed with what he called the vital spirit and was carried by the aorta and its branches to all the organs of the body. The idea that there was a communication between the two ventricles was accepted by physicians for 14 centuries to come. In addition, there was the idea that blood continuously emanates from the liver and was continuously being replenished instead of being circulated as is now known. Venous blood was considered contaminated with soot that was expired through the lungs and that the vital spirit which was present in the air was actively sucked into the body. In this view of the cardiovascular system, diastole was considered the active cycle of the heart.[1]

The Spanish theologian Miguel Serveto, in his theological treatise on the reformation of Christianity (Christianisimi Restitutio, 1553) discussed the nature of the divine spirit. He claimed that this vital spirit had its origin in the left ventricle of the heart and that the lungs assisted greatly in its generation by purifying the blood that was taken from the pulmonary arteries, transferred to the pulmonary vein, and then poured into the left ventricle. This paragraph, together with the denial of the trinity, led to his imprisonment and his demise at the stake, along with his books, that same year. Finally, in 1628, Sir William Harvey made his exposition of the entire circulation and was credited with the discovery of the minor circuit of the circulation for the annals of medicine, although Harvey's appreciation of the function of the heart as a pump propelling the blood through the circulation remains controversial.[2]

However, 300 years before Harvey's discovery, an Arab physician had described in detail the pulmonary circulation. Ibn al Nafis (1210–1288), a philosopher, writer, and poet and one of the greatest physicians of his age, clearly described the pulmonary circulation.[3] He stated that the septum of the heart is not perforated as was believed but that the blood flows from the heart to the lungs and thence through the pulmonary veins to the left side of the heart.

The blood from the right chamber of the heart must arrive at the left chamber, but there is no direct pathway between them. The thick septum of the heart is not perforated and does not have visible pores as some people or Galen thought. The blood from the right chamber must flow through the vena arteriosa (pulmonary artery) to the lungs, spread through its substance, be mixed with air, pass through the arteria venosa (pulmonary vein) to reach the left chamber of the heart.

Ibn al-Nafis also described the anatomy of the lungs and was the first person to appreciate the coronary circulation: "The nourishment of the heart is from the blood that goes through the vessels that permeate the body of the heart." While describing the anatomy of the pulmonary vessels, Ibn al Nafis described that between the arterious vein (pulmonary artery) and the venous artery (pulmonary vein) "there might exist perceptible passages." This suggestion can probably be regarded as the first mention of the notion of a microcirculation in the history of medicine.[4]

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