Relationships among Hematopoiesis, Blood Coagulation, Hemorrhage and Mortality in the Guinea Pig after Total Body X-Irradiation

Studies have been presented on blood, bone marrow, coagulation and their relation to mortality in guinea pigs exposed to 200, 400 and 600 r total body x-irradiation.

The initial responses of the blood and bone marrow were remarkably similar for the 3 doses of x-irradiation (ranging from LD₁₀ to LD₁₀₀). Marked differences among the dosages were noted in regeneration which occurred earliest after 200 r, later after 400 r and not at all after 600 r. Once started, regeneration was equally active after 200 and 400 r.

A coagulation defect, closely related to thrombocytopenia, was observed in the 6 to 13 day period following all doses of irradiation. An additional clotting defect, characterized by increases in the prothrombin time and heparin clotting time, was noted at 4 and 24 hours following all 3 doses of irradiation. The etiology of this defect requires further evaluation.

The pattern of hemorrhage, evaluated in various tissues by a semiquantitative scoring method, revealed that hemorrhage was most prominent in the 9 to 13 day period after exposure, and was closely related to thrombocytopenia. As the dose of x-ray increased, hemorrhage tended to become more protracted and severe and involved more organs. Hemorrhage disappeared rapidly as platelet formation returned in the recovery period. Hemorrhage was the chief factor in the severity and incidence of anemia after irradiation.