Retraction

RETRACTION of a blood clot, the spontaneous separation of serum from the clot. The absence of retraction is one of the phenomena of the hemorrhagic syndrome in Werlhof's disease (see). Gaheim (Nauch), the first to note the absence of retraction in Werlhof's disease, associated it with a decrease in the number of blood platelets. Le Sourd and Pagniez experimentally came to the same conclusion. However, Achard and Aynod obtained good retraction in their experiments even in the absence of platelets. Glanzmann, Opitz, and Schober consider retraction a function of platelets, but not their quantity, but their quality. According to Glanzmann, retraction is caused by the enzyme retractozyme, produced by platelets. Levit and Schulman experimentally came to the conclusion that between the number of platelets and the volume of retracted serum there exists, although incomplete, but a clear parallel. They also pointed to the necessity of observing precise technique in determining retraction, since sometimes retraction depends on the diameter of the test tube, its position, and, according to Rozhansky, the properties of the vessel wall. Levit and Schulman propose the following technique: blood in the amount of 5-10 cm³ is drawn into a thoroughly washed and dried with alcohol and ether test tube with a diameter of 1.5-2 cm and is left for a day at room temperature. After a day, the amount of retracted serum is determined and its ratio to the volume of blood taken is calculated. This ratio is called the retraction index (R.I.); in normal conditions it is 0.3-0.5. It should be assumed that retraction expresses certain physicochemical properties of blood, which depend to some extent on the quantity and quality of platelets, on the concentration of salts (Aynod, Rozhansky) and possibly other factors. The absence of retraction is noted in the overwhelming majority of cases of Werlhof's disease, but in the literature there are isolated observations of the absence of retraction in other diseases: pleurisy, pneumonia, Bright's disease (Gaheim), diabetes, Banti's disease, leukemia, tuberculosis (Levit). The phenomenon of retraction has diagnostic significance only in combination with other symptoms of hemorrhagic diathesis.