Prothrombin Utilization in Radiation Injury

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Abstract
Twelve dogs were given 600 r, 2000 K.V.P., 1.5 mm., K.V.L. 4.3 mm. Pb, 15.0 (0.15) r/min., whole body radiation by the bilateral exposure technic. The following studies were performed serially: hematocrit, white blood cell count, platelet count, prothrombin concn. (Ware and Seegers), estimate of Ac-globulin (Ware and Seegers), whole blood clotting time, and prothrombin utilization (Buckwalter, Blythe, and Brinkhous). Eleven dogs died between the 9th and 15th post-irradiation day. The 12th dog lived through the 20th post-irradiation day, after which the studies were discontinued. Clinically and at autopsy, all of the dogs exhibited evidence of extensive diffuse hemorrhage. The typical pancytopenia was demonstrated in 8 of the dogs. A slight, terminal decrease in the concn. of prothrombin occurred in 4 of the dogs. No evidence was found for a deficiency of Ac-globulin. The results indicate that prothrombin utilization after this amt. of radiation approaches 0 from the 9th post-irradiation day to death. The whole blood clotting time became prolonged only after the utilization of prothrombin approached 0 and the platelet level had fallen below 50,000/cu. mm. At autopsy the blood clotted promptly after the vessels were cut and the blood was allowed to escape into the tissues. The presence of an anticoagulant is not necessary in order to explain the hemorrhagic syndrome of radiation injury. The occurrence of a profound pancytopenia, severe infections, increased capillary fragility with possible other vascular factors, and the changes attributable to these conditions would appear adequate to explain this syndrome. However, this results do not rule out the existence of a weak and, as yet, uncharacterized anti-coagulant.