Quantitative Aspects of Blood Coagulation in the Generalized Shwartzman Reaction: 1. Effects of Variation of Preparative and Provocative Doses of E. Coli Endotoxin

Extract: The generalized Shwartzman reaction (GSR) is induced in rabbits by two properly spaced intravenous injections of bacterial endotoxin and is characterized by the occurrence of bilateral renal cortical necrosis. This report describes the quantitative changes in the coagulation mechanism in response to variation of preparative and provocative doses of E. coli endotoxin and of the interval between injections. It also correlates the coagulation changes with the pathologic findings of renal cortical necrosis. Renal cortical necrosis was induced in 34 of 49 (70 %) of rabbits using 0.100 mg/kg of endotoxin as the preparative (first) injection and 0.200 mg/kg 24 hours later as the provocative (second) dose. Four hours after the preparative injection white blood cells and platelets fell significantly while fibrinogen, prothrombin time, and Factors V and VIII fell slightly. At 24 hours all determinants except the platelets had recovered and the white cells, Factor V and fibrinogen had risen to significantly higher levels than baseline. Following the second (provocative) injection of endotoxin, a precipitous fall in all factors occurred. Maximal changes developed two hours after the second injection for white cells and platelets and by four hours for the coagulation factors; at this time kidneys show fibrin. By 48 hours all factors except the platelets had returned to 24 hour levels (table I). Rabbits given 0.100 mg/kg of endotoxin and normal saline 24 hours later did not develop cortical necrosis of kidneys or reduction in levels of any of the coagulation factors or platelets (table II). With 0.1 mg/kg of endotoxin as the preparative dose, the effect of variation in the provocative dose at 24 hours was studied. With 0.2, 0.1, 0.05 mg/kg provocation renal cortical necrosis was observed in 60-100 % of animals. Rabbits given 0.01 mg/kg of endotoxin, or saline, as the second injection did not develop the GSR. Coagulation changes were measured four hours after the provocative injections. With doses of endotoxin of 0.025 mg/kg and greater there was a significant fall in white cells, platelets and each of the coagulation factors measured. With 0.01 mg/kg there was a significant decrease in Factors II, V and VIII but no significant fall in white cells, platelets or fibrinogen. With saline all of the measured factors rose (table V). Changes in fibrinogen following different provocative doses are demonstrated in fig. 5. Renal cortical necrosis did not occur until a fall in fibrinogen of 66 mg/100 ml was produced. The effect of varying the preparative dose was studied. Groups of rabbits were given either saline, 0.001 mg/kg, 0.01 mg/kg or 0.1 mg/kg endotoxin preparation and all animals received 0.1 mg/kg endotoxin 24 hours later. With saline or 0.001 mg/kg endotoxin as preparation no GSR occurred. With a 10 and 100 fold increase in concentration of endotoxin the GSR was regularly produced. With saline preparation significant changes occurred only in white cells and platelets. A significant decline in all factors except Factor VIII was produced by preparation with 0.001 mg/kg endotoxin; the fibrinogen fell 89 mg/100 ml but no animal developed renal cortical necrosis. The inadequately prepared animal appeared able to tolerate an amount of fibrinogen conversion that would, in the properly prepared animal, result in renal cortical necrosis. In rabbits prepared with 0.01 mg/kg and 0.1 mg/kg of endotoxin significant changes occurred in all factors and renal cortical necrosis was produced (table VI). Rabbits were given 0.1 mg/kg endotoxin as preparation and a dose of 0.1 mg/kg was administered at 24 hours to one group of animals and at 48 hours in a second group. In the 24 hour group the GSR occurred in 10 of 13 animals; following endotoxin at 48 hours renal cortical necrosis was not produced in any of 18 rabbits. Changes in the coagulation mechanism four hours after provocation are shown in table VII and demonstrate that the fall was similar in both groups for all factors except fibrinogen. Fibrinogen decreased 178 mg/100 ml in animals given injections 24 hours apart but there was only a 70 mg/100 ml fall in the 48 hour group. The data suggest that by 48 hours after adequate preparation the RES has recovered to the degree that clotting intermediates are removed and significant amounts of fibrin are cleared thus preventing deposition in the kidneys and cortical necrosis. The interdependence of preparative and provocative doses of endotoxin was demonstrated. A dose of 0.01 mg/kg prepared the animal for subsequent provocation with 0.1 mg/kg; 0.1 mg/kg prepared animals for subsequent provocation with as little as 0.025 mg/kg. However, the combination of 0.01 mg/kg as preparation and 0.025 mg/kg as provocation did not result in cortical necrosis of the kidneys or in a fall of any of the coagulation factors (tables VIII and IX). Conclusions: In the presence of adequate preparation provocative doses of endotoxin capable of inducing cortical necrosis of the kidneys were always associated with significant consumption of all coagulation factors measured. With inadequate preparation, produced either by decreasing the preparative dose of endotoxin or by increasing the interval between injections, significant activation of the clotting system occurred but renal cortical necrosis did not develop. Speculation: The development of the generalized Shwartzman reaction, and, by inference, Shwartzman-like human syndromes, appears to require activation of the coagulation mechanism and the development of intravascular clotting. However, the degree of clotting induced by stimuli of known potency and the degree of fibrin deposition in the tissues are critically dependent upon the prior state of preparation of the animals, probably reflecting the functional adequacy of the reticulo-endothelial system.