The Effect of Gamma Irradiation on the Cardiovascular System of the Rhesus Monkey

The usual division of the acute radiation syndrome into hematologic, gastrointestinal, and neurological subsyndromes (1) underemphasizes the importance of changes in the cardiovascular system of the animal at doses between 3000 and 5000 R. This dose range is usually included in the gastrointestinal syndrome. Personal clinical observation of irradiated monkeys and the published data from some of the human radiation accidents (2, 3) suggest that an important factor contributing to death is cardiovascular collapse. This may occur before overt gastrointestinal lesions with massive loss of fluid and electrolytes into the bowel lumen have developed and in the absence of any neurological signs. It is possible that the cardiovascular collapse is due to central nervous system damage, but the possibility of a direct effect on the cardiovascular system has not been excluded. Previous investigations have shown that supralethal doses of whole-body irradiation produce a decrease in the blood pressure either during or immediately after exposure (3-10). In the dog, after 1000 R of total-body irradiation where death is ultimately due to the gastrointestinal syndrome, mild hypotension develops immediately after irradiation. It is not associated with a significant change in either