Shionoya, Takuji

In experimental obstructive jaundice in rabbits, thrombosis is definitely delayed in the extracorporeal loop. White thrombi are laid down at the normal rate in many instances; in others there is a delay in deposition of platelets, while in still others cauliflower-like masses of platelets are rapidly deposited and tend to slow or even stop the blood stream before much fibrin is apparent. Fibrin deposits and formation of the red thrombus usually appear late in the experiment and often only at the ends of the collodion tubes. In vigorous animals, the thrombi rarely tend to obstruct and usually cease growing when they have made up the difference between the lumen of the glass tube and of the collodion tube. On the other hand, if the animal's general condition is poor and its circulation depressed, red thrombus forms more rapidly and tends to encroach progressively on the lumen until obstruction takes place. Even in such cases circulation through the loop persists for periods much longer than in the normal animal. Judging from the gross appearance of the thrombus the quantity and quality of fibrin seem deficient. Single injections of bile salts yield pictures similar to those seen in experimental obstructive jaundice. White thrombi are deposited but obstruction of the lumen is delayed because of inadequate formation of fibrin. The continuous intravenous injection of bile salts resulted in a progressive increase of the clotting time and in the level of bile acids of the blood. The state of the extracorporeal loop was likewise similar in many respects to that seen in obstructive jaundice. There was, however, a definite decrease in the size and numbers of white thrombi deposited on the collodion membrane. From the evidence presented it is obvious that the processes of blood coagulation and of thrombosis in the extracorporeal loop are definitely delayed in experimental obstructive jaundice and in animals that have received intravenous injections of bile salts. No attempt is made to explain the changes found in jaundice on the basis of the increased levels of bile acids in the blood although these experiments would indicate that such a possibility has not been ruled out.

1. Distilled water dialyzes through the collodion tube and causes hemolysis. Clotting of the hemolyzed blood in the collodion tube occurs later. 2. Bile salts accelerate the appearance and development of white thrombi in the heparinized animal. The masses of white thrombi are very loose, soft, fragile and easily broken into clumps of platelets. They are poor in fibrin or the fibrin is abnormal, since they have less retractility than those obtained from the use of physiologic sodium chloride solution or calcium chloride or serum. Despite the increase in number and size of white thrombi, normal clotting does not occur. 3. When the collodion tube is surrounded by 1 or 2 per cent d-glucose solution, tiny and numerous white thrombi appear as radiating figures. The masses of white thrombi are rather loose and fragile. The clotting time of the heparinized blood does not appear to be shortened. 4. When a 1 to 2 per cent solution of calcium chloride is used as the dialyzing fluid outside the collodion tube, or when it is injected into the circulation, the formation of white thrombi is accelerated. They grow very rapidly. In spite of the action of heparin, the white thrombi formed are not so fragile as when bile salts are placed outside of the collodion tube. Fibrin seems to form easily. Obstruction of venous cannula takes place speedily and if the clots in the cannula are not removed, the white thrombi in the collodion tube remain small and become red by sedimentation of red cells. 5. Intravenous use of 10 per cent solution of magnesium sulfate without heparin retards the coagulation of circulating blood and permits the blood to flow through the extracorporeal loop from three to four times as long as normal. The formation of white thrombi, as well as red, is retarded. Magnesium sulfate (1 per cent) in physiologic sodium chloride solution placed outside the collodion tube markedly retards the formation of white and red thrombi in the heparinized animal. Magnesium sulfate (10 per cent), 50 mg. for each kilo of body weight each hour, administered intravascularly in the heparinized animal definitely prevents the first stages of thrombosis, and consequently prevents clotting. 6. It is possible by the combined use of adequate amounts of magnesium sulfate and of heparin intravenously to prevent all stages of thrombus formation for from 1 to 3 hours.

The effects of environmental temperature on thrombosis in circulating blood were tested in the extracorporeal loop by the method previously described. Cold (7° to 15°C.) about the collodion tube retards the clotting of circulating blood. Obstruction of the arterial cannula occurs after from 15 to 25 minutes. Heat (40° and 55°C.) tends to hasten clotting; obstruction by red clot takes place after from 4 to 6 minutes and from 2 to 4 minutes, respectively. In the latter case no characteristic thrombus structure may be seen. These results were what might be expected. The formation of white thrombi occurs even under the influence of cold, and they continue to form and grow as long as the circulation continues. When the carotid artery is partially occluded and the blood stream slowed, after the injection of the anticoagulant, the blood has a tendency to form red thrombi on the foreign surface of the vascular loop. The thrombi are deposited chiefly in the arterial half of the apparatus, especially at the bottom of the arterial end of the collodion tube, just as in the case of Aschoff's sand experiments. In spite of incoagulability of heparinized blood, red clots, with interwoven fibrin bands, are found. Also very tiny white thrombi may form in other parts of the collodion tube. The effect of complete obstruction of the carotid artery and jugular vein on thrombus formation was studied after the use of anticoagulant. When the carotid artery is obstructed the formation of white thrombi is negligible and sedimentation of erythrocytes and deposition of fibrin appear throughout the apparatus; then the blood, at a standstill, clots very slowly. When the jugular vein is obstructed, dislodgment of platelet thrombi probably results from the pulsating movement, and sedimentation of erythrocytes follows, forming mixed thrombi. The dislodged white thrombi tend to gather in the bottom of the tubes of the widest caliber, especially in the collodion tube.

A new method has been described for the study in vivo of thrombus formation in blood circulating extracorporeally in an artificial loop. This method permits of control of many factors, and hence of intensive study of thrombus formation under many and varied conditions. It admits of separate study of the formation of white thrombi and of the deposition of fibrin, which may apparently be independent processes.

1. Effects of anticoagulants, heparin and hirudin, on extracorporeal thrombosis were studied in thirty-three experiments by means of the extracorporeal vascular loop. In spite of adequate single doses of the anticoagulants white thrombi are formed and obstruction to flow may follow in the course of time, but the formation of red thrombi is markedly retarded. 2. The new method throws some light on the mechanics of thrombosis. The influences of foreign surfaces, of irregularities on the surface of the vessels, of whirlpools and of eddying motion of the blood current and of slowing and of stagnation with consequent prolonged contact with foreign surfaces are demonstrated, and these are analyzed in respect to the laying down of platelets and leucocytes. 3. The structure of white thrombi formed after anticoagulant injection is almost identical with that described by Welch. In one respect, however, the present results appear to differ from his: the formation of fibrin is postponed and retarded, and hence the collections of platelets are deposited in greater amount.

Thrombus formation has been studied in normal rabbits with an experimental method of establishing extracorporeal circulation. In the normal animal circulation in the extracorporeal loop usually ceases in from 6 to 10 minutes, or at most, in very large and vigorous animals, in 25 minutes.1 Cessation of the circulation is due most frequently to obstruction of the venous cannula (sometimes of the arterial cannula) by a mass of white thrombi and secondary fibrin formation around it. The site of the clot is determined somewhat by the swiftness of the blood stream. In the collodion tube red mural thrombi are obtainable as a rule. They are flat and present a wide base resting on tiny white thrombi. After the complete obstruction of the circulation, the blood in the apparatus clots very rapidly. When the obstruction occurs very quickly either in the arterial or venous cannula, or when the blood stream is very slow, the clotting in the loop may occur before platelets are laid down in large numbers or before the formation of the white thrombi is evident. Mixed thrombi are found in the jugular vein, and have their inception in the white thrombi, in the cannula or from the injured intima. They extend in the direction of the blood flow.