Cyanosis

CYANOSIS (from the Greek kyanos - blue), bluish discoloration of the skin coverings and accessible mucous membranes (nasal cavity, mouth and fauces, eye conjunctiva, etc.), a pathological symptom in various diseases accompanied by circulatory disorders. In terms of distribution and intensity, cyanosis can be very diverse. Cyanosis can be both general and local, affecting only certain areas. Cases of exceptionally strong, uniform cyanosis of the body are known, in which the color of the patient approaches a dark violet or even black color (see Blue disease). More often, cyanosis is observed mainly in certain areas of the body: on the extremities, tip of the nose, auricles. In such cases, they speak of acrocyanosis. Upon careful examination of cyanotic skin, it is possible to distinguish in some cases dilated branches of small blood vessels (veins), while in others the entire coloration of the skin has the character of a diffuse bluish-violet background. It should be noted that often to the cyanotic coloration are added brownish or yellowish tints, due to the formation and deposition in the skin of breakdown products of the blood pigment - biliverdin and bilirubin. As indicated, cyanosis is a symptom in various lesions of the circulatory system, and some of the forms of cyanosis mentioned above have their own special mechanism of development. In most cases, in diseases accompanied by significant venous congestion, such as emphysema, defects of the right heart (insuff. valv. tricuspidalis, stenosis art. pulmonaris and far-advanced stenosis of the mitral opening), there is a marked swelling of the large venous trunks and considerable dilation of the small veins and venous bends of the capillary loops with stagnant blood in them. Thus, the determining factor in the development of cyanosis in these diseases with right-heart insufficiency is the filling of the venous network with blood due to difficulty in blood outflow and the associated slowing of blood flow through the vessels. It must however be emphasized that in many cases cyanosis is observed in patients in whom, despite the most careful examination, it is impossible to detect any difficulty in the venous blood flow to the right heart, any filling of the venous network with blood, or even any slowing of blood flow. This includes, for example, cyanosis observed in insufficiency of the aortic valves, in collapses, in mountain sickness, in acute infections, and in clinically healthy people with low blood pressure. In these cases, cyanosis most often combines with pallor ('pale' cyanosis) and is most pronounced where the skin is thin and translucent, for example around the eyes and on the auricle. The origin of this type of cyanosis finds its explanation in the relative poverty of oxygen in the blood of these patients, in their anoxemia. Depletion of oxygen is especially sharply expressed in the venous blood, where the tension of O₂ sometimes drops to 50 or less volume percent (against 68- 44 O¹ 73% in normal). Anoxemia is caused primarily by increased utilization of O₂ in the tissues supplied with blood in insufficient quantities. Cyanosis from anoxemia is observed both with weakness of the right heart and sometimes with vascular and left-heart insufficiency of circulation (see also Circulation, Heart, general diagnosis).-The diagnostic value of cyanosis in general and of its individual types is extremely great, as it is an early and often very persistent symptom in diseases of the heart and other organs, preceding for a long time the visible insufficiency of circulation, the so-called decompensation. Local cyanosis usually accompanies circulatory disorders in a certain vascular area and makes it possible to judge the topographical difficulty of blood outflow. Local cyanosis is observed in thrombophlebitis, compression of large veins by tumors, ligatures, scars, etc., and quite easily disappears when the main CAUSE is eliminated.