Noninvasive Monitoring of Peripheral Perfusion in Critically Ill Patients

The evolution of medical knowledge over history happened more recently than advances in the art, industry and other sciences. The industrial revolution through the 18th and 19th centuries was bringing innovations and transforming life in America and Europe whereas it was widely accepted that diseases were the result of an imbalance in humours, and one of the conventional treatments to bring back the good healthy was draining blood through a phlebotomy (bloodletting) (1). Bloodletting was a common ‘cure for everything’ from ancient times until the nineteenth century. The practice gained wide acceptance in America in the eighteenth century with Dr. Benjamin Rush, who treated George Washington for acute laryngitis by draining one liter (nine pounds) of blood in less than 24 hours (2). George Washington died soon afterward. In that time, there was no knowledge of the association between loss of blood and circulatory shock. In fact, shock was still an abstract concept, usually described as ‘sudden vital depression’, ‘great nervous depression’, or ‘final sinking of vitality’. The history of hemodynamic monitoring overlaps with the history of shock and much of the history of shock relates to the history of traumatic shock. The term shock only came into clinical use with Edwin A. Morri, who began to popularize the term using it in his 1867 Civil War text, ‘A Practical Treatise on Shock After Operations and Injuries’ (3). Since then, the word shock started to be linked with the concept of cardiovascular collapse. In the same year, a British Surgeon named Jordan Furneaux wrote what it is known to be one of the first elaborate descriptions of abnormalities in peripheral perfusion during shock conditions (4). In his description, he emphasized the cold, clammy and mottle skin associated with high heart rate (Figure 1). The belief held by notable physicians of that time was that those alterations in peripheral perfusion during shock were the result of a disorder of the nervous system, known as ‘nervous collapse’. Despite these results, the final studies about neural regulation of cardiovascular function in shock did not occur until 1950s.